ABC’s of SPRAY FINISHING Equipment & Techniques For Spray Finishing

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www.carlisleft.com About this book….. While this book examines the spray This book has been updated several Table of Contents finishing operation and its times from “The ABC’s of Spray equipment from many viewpoints, Equipment,” originally published by Forward …..…………………..….2 there is still much more to be The DeVilbiss Company in 1954. It 1. Introduction ...... 3 learned to become truly proficient at focuses on equipment and spray finishing. techniques for spray finishing. Surface Preparation...... 3 Paint Preparation...... 3 Solvent Selection...... 3 The best way to become proficient The format of the original book was at spray finishing is to just do it! question-and-answer. We have 2. Air Atomizing Spray Guns 5 Many trade technical and retained that format in this edition. Spray Gun Types...... 5 community colleges offer courses in Part Identification and spray finishing, a great way to Function...... 7 improve your skills. This book is organized around the Operation...... 10 major components of an air spray Maintenance ...... 12 system…spray guns, electrostatic Troubleshooting...... 14 Many of the “tricks” of the applicators, material containers, hose, professional spray finisher involve air control equipment, compressors, 3. Electrostatic Spray paints and coatings. The spray booths, respirators and a Process...... 17 manufacturers of these materials short section on general cleanlines Definition ...... 17 routinely publish complete books on and other sources of information. Electrostatic Processes/ these subjects. These publications A thorough understanding of the Equipment ...... 18 are available in specialty paint material in this book—plus a lot of Operating Safely...... 20 stores and will provide you with actual spray painting practice— considerable detail. Many of these should enable you to handle just 4. Material Containers ...... 23 books also contain information on about any spray painting situation. techniques for surface preparation. 5. Hose and Connections ....25

Although we have made an effort to 6. Air Control Equipment .....27 Another important source of make this book as detailed and as information, particularly on complete as possible, be aware that 7. Respirators ...... 29 equipment use and selection is your the equipment and product systems local spray finishing equipment used to illustrate points are entirely 8. Air Compressors ...... 30 distributor. No book could ever based on DeVilbiss, Ransburg and completely cover a specialist’s in- Binks technology. DeVilbiss, Ransburg, 9. Spray Booths ...... 31 depth knowledge of the equipment, and Binks are three of the world’s 10. Diaphragm Pumps...... 34 the techniques, the maintenance oldest and largest manufacturer of and troubleshooting. spray paint equipment, and have 11. High Pressure Spraying ..36 maintained this leadership since its founding in 1888. Information is available from many 12. H.P. Spray Guns...... 37 resources on the subject of spray finishing. It is our hope that this book 13. Two Ball Piston Pumps....38 provides you with a start toward 14. H.P. Equipment Setup ...... 39 perfecting your finishing skills. 15. Four Ball Piston Pumps ..40 A recent addition to resources 16. Circulating Systems ...... 41 available to the spray finisher is the World Wide Web. Many 17. H.P. Troubleshooting ...... 43 manufactures are represented and question and answer forums are available. Please visit our website at www.carlisleft.com

2 This static attracts particles of dust precise consistency required by the and dirt. Eliminate them by treating manufacturer. with “destatisizing” air using a This book is about the selection, use Always prepare paint in a clean, and maintenance of finishing special blow-off gun that imparts a neutral charge to the airflow. dust-free environment. Paint has a equipment: spray guns, tanks, cups, remarkable ability to pick up dirt. hoses, compressors, regulators, Dirty paint will not only clog your spray booths, respirators, etc. It spray gun, but it will also ruin your presumes that you are familiar with Paint Preparation paint job. Get in the habit of always standard surface preparation Today’s finishes are extremely pouring paint into the cup or tank techniques that may be required complex chemical formulations. through a paint strainer. Paint is before finishing actually begins. It They include both solvent and never as clean as it looks. also presumes a basic knowledge of waterborne types. Some may the many different types of paints require the addition of solvents to and coatings available. form the proper spraying viscosity. Solvent Selection – Creating a perfect finish requires a Others may simply require the Electrostatic Finishing solid knowledge of surface addition of a second component at a preparation, finishes and spray prescribed ratio to obtain sprayable Research engineers have been painting equipment. The first two are consistency. Many of them also working for more than thirty years on extensively covered in many other have hardeners or other chemicals, a continuing development of electro- books. The manufacturers of paints added to them to insure correct static coating processes and and coatings have gone to great color match, gloss, hardness, drying equipment, as well as techniques length to publish information on their time or other characteristics and service to further improve the new and existing products. necessary to produce a first class high efficiency of this process. These finish. Make sure you are familiar techniques can be quite useful for But, even an extensive knowledge with the specific finish material data paint formulators by providing better of surface preparation techniques sheets accompanying each wraparound; higher quality finishes and paint chemistry is not enough to material. Do not mix materials from requiring less touch-up and, increasing assure a professional finish. The various manufacturers. Read and paint film build. This information is a finish must be applied by a spray follow directions carefully. gun, and all the variables of its use guide to solvent selection to improve must be mastered. All finish materials must also be electrostatic sprayability. supplied with material Safety Data The equipment necessary to apply sheets (MSDS). This data provides Controlled Paint Resistivity - the finish – the spray gun, tank, cup, information on proper handling and A Factor in Formulation regulator, hoses, compressor, etc. – disposal of materials. Many states It has been determined that coating must all be matched to the job as require that MSDS be kept on file by formulations for electrostatic well as to each other. That the user. application, in addition to meeting equipment must be used and customer requirements for durability, maintained properly, with an The first step is knowing the type drying time, gloss, etc., should have appreciation of how and why it and color of paint the project an electrical resistance within a works the way it does. requires. specified range for best atomizing The moment of truth for any finish With these determined, follow the characteristics and electrical happens when the trigger is pulled. manufacturer’s instruction for deposition. This book focuses on that moment. preparing it exactly. If you have any doubts about how to proceed, don’t Electrical resistivity is a characteristic guess! Contact your paint supplier which must be built into the paint Surface Preparation for help. Improperly prepared paint formulation. It has generally been will never produce a good finish! The surface to be finished should be found that most materials can be well cleaned before painting. If the The chief characteristic that adjusted to have suitable resistance paint manufacturer’s instructions call determines the sprayablility of paint and still meet other requirements. for it, the surface should be and how much film may be applied, We have found that no single, chemically treated. Use a blow-off is its viscosity … or consistency. simple characteristic or adjustment gun and tack rag to remove all dust Following the paint manufacturer’s provides optimum sprayability for and dirt. No amount of primer or instructions will get you close, but any given coating. However, paint will cover up a badly prepared for professional results, use a adjustment of paint resistivity surface. viscosity cup. It is a simple but very through appropriate selection of accurate, way to measure the solvents improves many paints that Plastic parts may contain static thickness of paint. With the cup, you otherwise could not be sprayed electricity from the molding process. can thin or reduce the paint to the efficiently by the electrostatic process. 3 optimum ranges will usually improve dispersed resin is also beneficial. its sprayability. Most paints of high pigment volume Solvent Classification for A specific selection should be based concentration and paints where the Electrostatic Usage on the best compromise to obtain binder is highly nonpolar, such as Solvents may be classified as POLAR the desired resistivity, viscosity, flow bodied linseed oil, styrenated alkyds, or NONPOLAR. For our purposes, rate, evaporation rate, cost, and other lacquers based on hydrocarbon resins the differences in polarity between conventionally considered factors. (like cyclized rubber or butylene different solvents provides a means copolymers), and long oil alkyds, to adjust the total resistivity of a Evaporation Rates vs. may be improved by solvent adjustment, paint mixture. Electrostatic Equipment Used but the possible upgrading of these All Ransburg No. 2 Process disk materials by this method is limited. NONPOLAR Solvents normally do equipment requires slower Preliminary Ransburg research seems not improve sprayability. These formulations than normally used for to indicate that the use of concentrated solvents include the aliphatic and conventional hand air guns. The larger additives with paints of these types aromatic hydrocarbons, chlorinated disk diameter and higher the speed of offers a better prospect for sprayability solvents, and the turpentines. rotation, the slower the evaporation improvement. rates should be made. No. 2 Process The addition of POLAR Solvents bells require paints in about the same compatible with the basic coating evaporation range as for conventional material often improves electrostatic air guns, while the No. 2 Process sprayability. Polar solvents include handguns require still faster solvents. the ketones, alcohols, glycol ethers, esters, and nitroparaffins. Because of complex interactions of solvents, resins, and binders, it may Viscosity Guide happen that a solvent of a certain The initial trial paint formulation polarity will reduce the mixture should be of high viscosity (preferably resistance more than an equal exceeding 50 seconds on a No. 4 amount of a second solvent which Ford cup) so that the reduced formula has a higher polarity. As these will have satisfactorily high solids reactions are not always predictable, content after solvent additions. the adjustment of resistivity is It is usually best to adjust viscosity necessarily a guide trial-and-error after resistivity, since viscosity is a procedure. less critical factor for electrostatic sprayability. Coating Material Guide Short oil length alkyd vehicles, with Resistance Adjustment by small amounts of high polarity Solvent Selection modifying resins like amino resins, Nonpolar solvents may be used as epoxy, or phenolic, respond well to extenders to vary paint viscosity or the adjustment of resistivity by solvent flow properties without seriously addition. changing the electrical resistance of the mixture. An exception occurs Air-dry lacquers and similar fast drying with paints that are of low resistivity, materials usually contain so much for example vinyl solutions or nitro- polar solvent that their resistivity is cellulose materials. The conductivity below the desired range. In such of these special mixtures may some- cases, incorporating the maximum times be reduced to a usable factor allowable quantity of nonpolar dilutant by the addition of nonpolar solvents. (example: the substitution of esters for ketones) will improve sprayability. Generally, the additions of solvent of highest polarity will give the greatest Organosols dispersed in hydrocarbons electrical resistance reduction to a can be improved by thinning just mixture’ solvents of intermediate before use with the polar solvents polarity provide intermediate resist- of high solvency. Reduction long ance reductions, etc. The adjustment before use with polar solvents of of paint resistivity to the specified low solvency and swellability for the

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2. Air Atomizing Spray Guns Introduction 2. What are the types of air spray guns? Siphon feed is easily identified by The spray gun is the key component the fluid tip extending slightly beyond in a finishing system. It is a precision Air spray guns may be classified in the face of the air cap, as shown in engineered and manufactured various ways. One way is by the Figure 2. instrument. Each type and size is location of the material container: specifically designed to perform a certain, defined range of tasks. Figure 1 shows a gun with a cup attached below it. As in most other areas of finishing work, having the right tool for the job Figure 3 shows a gun with a cup goesalong way toward getting attached above it. professional results. Figure 4 shows a material container Figure 2 - Siphon Feed Air Cap This chapter will help you know some distance away from its which is the proper gun by reviewing pressure feed gun. Siphon feed guns are suited to the Conventional Air LVMP The type of material feed system is many color changes and to small (TransTech) and High Volume/Low also a way of classifying guns: Pressure spray gun designs amounts of material, such as in commonly used in finishing—siphon Siphon Feed... draws material to the touchup or lower production oper- feed, gravity feed and pressure feed. gun by siphoning as in Figure 1. ations. It will also review the different types Gravity Feed... the material travels of guns and components within down, carried by its own weight and each design. gravity as in Figure 3. 4. What is a gravity feed gun? This design uses gravity to flow the A thorough understanding of the Pressure Feed... the material is fed material from the cup, which is differences between systems will by positive pressure as in Figure 4. mounted above the gun, into the gun allow you to select the right gun, to Guns may also be classified as for spraying. No fluid pickup tube is use it properly to produce a high either external or internal mix. used, since the fluid outlet is at the quality finish and to contribute bottom of the cup. toward a profitable finishing 3. What is a siphon feed gun? operation. This cup has a vent hole at the top A spray gun design in which a of the cup which must remain open. stream of compressed air creates a It is limited to 32 ounce capacities vacuum at the air cap, providing a SPRAY GUN TYPES due to weight and balance. siphoning action. Atmospheric 1. What is an air atomizing spray pressure on the material in the siphon Gravity feed guns are ideal for small gun? cup forces it up the pickup tube, applications such as spot repair, into the gun and out the fluid tip, detail finishing or for finishing in a Air atomizing spray guns are where it is atomized by the air cap. limited space. They require less air available in three types: Conventional, The vent holes in the cup lid must be than a siphon feed gun, and usually Low Volume Medium Pressure open. This type gun is usually limited have less overspray. [LVMP (TransTech)] and High to a one-quart, or smaller, capacity Volume Low Pressure (HVLP). container. Conventional air spray guns pass virtually all the input pressure to the air cap. HVLP reduces the air pressure internallyto a much lower pressure (10 PSI atomizing pressure). LVMP is higher pressures than HVLP but substantially lower than conventional. LVMP is nearly as efficient as HVLP but will render a finish much closer to conventional.

Air and material enter the spray gun through separate passages, and are mixed at the air cap in a controlled Figure 1- Siphon Feed Gun with Figure 3- Gravity Feed Gun with pattern. attached cup attached cup 5 2. Air Atomizing Spray Guns HVLP, or High-Volume/Low Pro Tip: Type Viscosity Fluid Atomizing Type When using a gravity feed system, Feed (#2Zahn) Oz/Minute Pressure Production Pressure, uses a high volume of air downsize the tip one size from siphon. Siphon upto24 10-12 40-50 Low (typically between 15-26 CFM) If the siphon system calls for a .070”, Gravity upto24 10-12 30-40 Low delivered at low pressure (10 PSI or use a .055 or .062”” Pressure upto29 20-24 50-60 High less at the air cap) to atomize paint HVLP upto29 14-16 10 High into a soft, low-velocity pattern of 5. What is a pressure feed gun? particles. Table 1 In this design, the fluid tip is flush In most cases, less than 10 psi is with the face of the air cap (see Fig- 6. What is an external mix gun? needed in order to atomize. ure 5). The material is pressurized in This gun mixes and atomizes air and Proper setup utilizes no more fluid a separate cup, tank or pump. The fluid outside the air cap. and air pressure than is needed to air pressure forces the material produce the required quality and a through the fluid tip and to the air It can be used for applying all types of materials, and it is particularly flow rate that will meet production cap for atomization. desirable when spraying fast drying requirements. paints such as lacquer. It is also As a result, far less material is lost in used when a higher quality finish is overspray, bounceback and desired. blowback than with conventional air spray. This is why HVLP delivers a dramatically higher transfer efficiency (the amount of solids applied as a percent of solids sprayed) than spray systems using a higher atomizing pressure.

The HVLP spray gun resembles a standard spray gun in shape and operation. Models that use high Figure 6 - External Mix Gun inlet pressure (20-80 psi) and 7. What is an internal mix cap? convert to low pressure internally within the spray gun are called This gun mixes air and material HVLP conversion guns. inside the air cap, before expelling them. Some HVLP models, particularly It is usually used where low air those using turbines to generate pressures and volumes are air, bleed air continuously to available, or where slow-drying minimize back-pressure against materials are being sprayed. the air flow of the turbine. Figure 4 - Typical Pressure Feed Gun A typical example is spraying flat The air cap design is similar to that with remote tank wall paint, or outside house paint, of a standard spray gun, with a This system is normally used when with a small compressor. variety of air jets directing the large quantities of material are to be atomizing air into the fluid stream, Internal mix guns are rarely used for atomizing it as it leaves the tip. applied, when the material is too finishing when a fast-drying material heavy to be siphoned from a is being sprayed, or when a high HVLP is growing in popularity and container or when fast application is quality finish is required. new environmental regulations are required. Production spraying in a requiring it for many applications. manufacturing plant is a typical use of a pressure feed system HVLP can be used with any low-to-medium solids materials that can be atomized by the gun, including two-component paints, urethanes, acrylics, epoxies, enamels, lacquers, stains, primers, etc.

Figure 7 - Internal Mix Gun Figure 5 - Pressure Feed Air Cap 8. What is HVLP?

6 2. Air Atomizing Spray Guns PART IDENTIFICATION FUNCTION 12. What are the advantages of e) volume of air in cubic feet per minute (cfm) and pressure in pounds 9. What are the principal parts of a the multiple jet cap? per square inch (psi) available spray gun? This cap design provides better atomization of more viscous See the DeVilbiss or Binks spray materials. gun catalog for the proper selection of air cap / fluid tip / needle It allows higher atomization combinations and typical uses. pressures to be used on more viscous materials with less danger of split spray pattern. 14. What is the function of the It provides greater uniformity in fluid tip and needle? pattern due to better equalization of They restrict and direct the flow of air volume and pressure from the material from the gun into the air cap. stream. The fluid tip forms an It also provides better atomization internal seat for the tapered fluid for materials that can be sprayed needle, which reduces the flow of Figure 8 - The Anatomy of a Spray Gun with lower pressures. material as it closes. (see Figure 11) 10. What happens when the The amount of material that leaves trigger is pulled? the front of the gun depends upon the viscosity of the material, the The trigger operates in two stages. material fluid pressure and the size Initial trigger movement opens the of the fluid tip opening provided air valve, allowing atomizing air to when the needle is unseated from flow through the gun. the tip. Further movement of the trigger Fluid tips are available in a variety of opens the fluid needle, allowing fluid sizes to properly handle materials of material to flow. When the trigger is various types, flow rates and released, the fluid flow stops before viscosity’s. the atomizing air flow. Figure 10 - External Mix Air Cap This lead/lag time in the trigger operation, assures a full spray pattern when the fluid flow starts. It 13. How should an air cap be also assures a full pattern until the selected? fluid flow stops, so there is no coarse atomization. The following factors must be con- sidered:

11. What is the function of the air a) Type, viscosity and volume of cap? material to be sprayed The air cap (see Figure 10) directs b) size and nature of object, or compressed air into the fluid stream surface, to be sprayed (Multiple, or to atomize it and form the spray larger, orifices increase ability to Figure 11 - The Fluid Tip and Needle pattern. (see Figure 9) atomize more material for faster painting of large objects. Round Tapered Blunt 15. What is the nozzle Fewer, or smaller, orifices usually combination? require less air, produce smaller spray patterns and deliver less In practice, the air cap, fluid tip, material. These caps are designed needle and baffle are selected as a for painting smaller objects and/or unit, since they all work together to using slower speeds. produce the quality of the spray pattern and finish. These four items, c) material feed system used - as a unit, are referred to as the pressure, siphon or gravity nozzle combination. Figure 9 - Types of Spray Patterns d) size of fluid tip to be used (Most There are various styles of caps to air caps work best with certain fluid produce different sizes and shapes tip/needle combinations.) of patterns for many applications. 7 2. Air Atomizing Spray Guns Pressure Feed 16. What are the standard fluid tip 17. How are fluid tip and needle Material Flow Tip sizes and flow rates? sizes identified? Viscosity Rate Size The standard sizes, corresponding DeVilbiss and Binks fluid tips and #2 Zahn fluid tip opening dimensions and flow needles are identified by the letters upto23sec Low .0425"/1.1mm rates are: or numbers stamped on the tip and 23-28sec Med .055"/1.4mm the needle. 28-48sec High .070"/1.8mm The identification letters on these over48sec High .086"/2.2mm Conventional Air Spray components should match. See the Table 4 Fluid Tip Flow Rate/ appropriate DeVilbiss/Binks spray I.D. Material gun catalog for the proper selection NOTE: Viscosity conversion charts Pressure Feed Systems of fluid tip and needle combinations. are available to convert one viscosity .028"/.7mm up to 12 oz/min cup reading to another from any .0425"/1.1mm up to 20 oz/min material or equipment supplier. .055"/1.4mm up to 30 oz/min 18. What fluid tip and needle (2) The physical size of the object to .070"/1.8mm over 30 oz/min combination sizes are most be painted must also be considered. .070"/1.8mm porcelain enamel common? .086"/2.2mm heavy body materials As a general rule, use the largest .110"/2.75mm heavy body materials .042/1.1mm, .055/1.4mm and possible spray pattern consistent Siphon Feed Systems .070/1.8mm are most commonly with the object size. Remember that .070"/1.8mm up to 12 oz/min used. The .070/1.8mm size is used different air caps deliver various .062"/1.6mm up to 10 oz/min for siphon feed, while .055/1.4mm pattern characteristics. This can Gravity Feed Systems and .062/1/6 are used for gravity reduce both spraying time and the .055"/1.4mm up to 30 oz/min Feed. For pressure feed the most number of gun passes. .062/1.6mm up to 30 oz/min common tips are .042/1.1mm, (3) The next consideration in Table 2 .05 5/1.4mm and .070/1.8mm, evaluating nozzle combinations is the speed with which the finish will be applied, and the desired level of HVLP / LVMP 19. How are nozzle combinations quality. Fluid Tip Flow Rate/ selected? For speed and uniform coverage, I.D. Material Five basic considerations are in- Pressure Feed Systems choose a nozzle combination which volved in selecting the nozzle com- produces a pattern as wide as .0425"/1.1mm up to 10 oz/min bination: .055"/1.4mm up to 14 oz/min possible. .070"/1.8mm up to 20 oz/min type and viscosity of material For finish coat work, quality is the .086"/2.2mm over 20 oz/min being sprayed Siphon Feed Systems deciding factor. Choose a nozzle .086"/2.2mm up to 9 oz/min physical size of object being combination which produces a fine .070"/1.8mm up to 8 oz/min finished atomization and a smaller pattern Gravity Feed Systems size, thereby giving greater .055"/1.4mm up to 12 oz/min desired speed/finish quality application control. .062"/1.6mm up to 12 oz/min gun model being used (4) The model of the gun itself will Table 3 limit the selection of nozzle available air volume (cfm) and combination. pressure (psi) from compressor For a siphon feed gun, there are two (1) The type and viscosity of the nozzle types available which are material being sprayed is the suitable for finishing operations. first factor to consider. These nozzles have fluid tip Rule of thumb openings of .070"/1.8mm to Optimum fluid pressures are 8-20 Rule of thumb .086"/2.2mm, and are designed to psi. Pressures greater than this The lower the viscosity of the handle viscosities up to 28 seconds generally indicate the need for a material, the smaller the I.D. of the in a No. 2 Zahn Viscosity Cup. larger fluid tip size. fluid tip. For a pressure feed gun, the amount of material discharged depends upon material viscosity, the inside diameter of the fluid tip, the length and size of hose and the pressure on the material container or pump.

8 2. Air Atomizing Spray Guns If the fluid tip opening is too small, Tips are made of the following 24. What is the fluid needle the paint stream will be too high. If metals: adjustment? the fluid tip opening is too large, you a) 300-400 grade stainless steel for This adjustment controls the travel of will lose control over the material both non-corrosive and corrosive the fluid needle, which allows more discharging from the gun. materials b) Carboloy inserts for or less material through the fluid tip. For most HVLP guns, the paint flow extremely abrasive materials See Figure 8. shouldn't exceed 16 oz. per minute. With pressure feed systems, the For recommended flow rates for fluid delivery rate should be adjusted each fluid tip size, consult the . 23 What is viscosity? by varying the fluid pressure at the DeVilbiss or Binks catalog. The viscosity of a liquid is its body, pressure pot. Use the fluid (5) Available air supply is the last or thickness, and it is a measure of adjustment knob for minor and/or factor to consider. its internal resistance to flow. Vis- temporary flow control. This will cosity varies with the type and extend the life of the fluid needle and Pressure feed air caps consume temperature of the liquid. Any tip. between 7.0 and 26.0 CFM, reference to a specific viscosit depending on air pressure applied. If y measurement must be accompanied your air supply is limited, because of an undersized compressor, or many by a corresponding temperature 25. What are the components of specification. siphon and gravity feed systems? other air tools are in use at once, the gun will be starved for air, producing Viscosity is usually measured in Typical siphon and gravity feed incomplete atomization and a poor poise and centipoise (1 poise=100 systems consist of; a siphon feed or finish. centipoise). The most common gravity feed spray gun with cup, an measurement used to determine air compressor (not shown), a viscosity in finishing is flow rate combination filter/air regulator and 20. What are the criteria for (measured in seconds from a Zahn, air hoses. (See Figure 12) selectingapressure feed nozzle? Ford or Fisher Viscosity Cup). While the fluid discharge in ounces Viscosity conversion may be per minute fromasiphon feed gun accomplished by consulting a is relatively stable (largely because it viscosity conversion chart. is determined by atmospheric Different viscosity cup sizes are pressure), the fluid discharge from a used for different thicknesses of pressure feed gun depends more materials. Each cup has a precision upon the size of the inside diameter hole at the bottom of the cup. Use a of the fluid tip and the pressure on smaller or larger hole in the cup the paint container or pump. The depending on the thickness of the larger the opening, the more fluid is material. discharged at a given pressure. Viscosity control is an extremely If the fluid tip ID is too small for the important and effective method to amount of material flowing from the maintain application efficiency and gun, the discharge velocity will be too high. The air, coming from the air quality consistency. Always measure viscosity after each batch of material cap, will not be able to atomize it properly causing a center-heavy is mixed and make sure material temperature is the same, normally pattern. 70° to 90° F. If the fluid tip opening is too large, Figure 12 - Siphon Feed and Gravity Consult your coatings Technical material discharge control will be Feed System Components Data Sheet for temperature lost, often resulting in a split pattern. recommendations. OPERATION The fluid tip/air cap combination 26. How is siphon and gravity must be matched to each other and feed equipment hooked up for to the job at hand. Spray gun 23. What is the spreader adjust- operation? catalogs include charts to help you ment valve? match them properly. Connect the air supply from the A valve for controlling the air to the compressor outlet to the filter/air horn holes which regulate the spray regulator inlet. pattern from maximum width down 21. Of what metals are fluid tips to a narrow or round pattern. Connect the air supply hose from the made? (See Figure 8) air regulator outlet to the air inlet on the spray gun. 9 2. Air Atomizing Spray Guns After the material has been reduced when the gun is held 8" from the (6) If the material is spraying too to proper consistency, thoroughly surface). heavily and sagging, reduce the mixed and strained, pour it into the material flow by turning in the fluid cup and attach the cup (siphon adjusting screw (clockwise). feed) or attach the cup and fill with Remember, proper setup utilizes no the coating (gravity feed). more fluid and air pressure than is needed to produce the required quality and a flow rate that will meet 29. How are siphon and gravity production requirements. feed systems initially adjusted for spraying? 28. What are the components of a pressure feed system? (1) Spray a horizontal test pattern Figure 14 – Fluid Adjustment Screw (air cap horns in a vertical position). A pressure feed system consists of; Hold the trigger open until the paint (3) With the fluid adjusting screw a pressure feed spray gun, a pres- begins to run. There should be even open to the first thread, and the air sure feed tank, cup or pump, an air distribution of the paint across the pressure set at approximately 30 psi, filter/regulator, appropriate air and full width of the pattern. (see Figure make a few test passes with the gun fluid hoses and an air compressor. 13). The fan control knob is normally on some clean paper. If there are See Figure 16 adjusted fully counter-clockwise. If variations in particle size- specks the distribution is not even but is and/or large globs - the paint is not symmetrical a different fluid tip may atomizing properly (see Figure 19). help. If the pattern is not (4) If the paint is not atomizing symmetrical, there is a problem with properly, increase the air pressure either the air cap or the fluid slightly and make another test pass. tip/needle that must be corrected. Continue this sequence until the Refer to the Troubleshooting Section paint particle size is uniform for examples of faulty patterns to help diagnose your problem.

Figure 16 - Pressure Feed System Components 29. How is equipment hooked up for pressure feed spraying?

Even Distribution Connect the air hose from the air regulator to the air inlet on the gun. Figure 15- Test Patterns Connect the mainline air hose to the Figure 13 - Horizontal Test Pattern (5) If the pattern seems starved for air inlet on the tank, cup or pump. material, and the fluid adjusting CAUTION: Do not exceed the (2) If the pattern produced by the screw is open wide (to the first container's maximum working above test appears normal, rotate thread), the atomization air pressure pressure. the air cap back to a normal may be too high, or the material may spraying position and begin spray- be too heavy. Recheck the viscosity Connect the fluid hose from the fluid ing. (Example - a normal pattern with or reduce the air pressure. outlet on the tank to the fluid inlet on a #30 air cap will be about 9" long the gun.

10 2. Air Atomizing Spray Guns 30. How is the pressure feed gun 6 If using HVLP, using an “Air Cap guns) from the surface being adjusted for spraying? Test Kit”, verify that the air cap sprayed. pressure in not above 10 psi if Open spreader adjustment valve for 34. What is the proper technique required by a regulatory agency. maximum pattern size. (see figure 8) for spray gun stroke and triggering? Open fluid adjustment screw (counter clockwise) until maximum The stroke is made with a free arm needle travel is achieved. Opening motion, keeping the gun at a right beyond that point will lessen the angle to the surface at all points of internal spring tension and leakage the stroke. at the fluid tip may result. Triggering should begin just before the edge of the surface to be sprayed is in line with the gun . 31 How is the pressure feed gun nozzle. The trigger should be held balanced for spraying? fully depressed, and the gun moved in one continuous motion, until the 1 Using control knob on fluid other edge of the object is reached. regulator, set fluid pressure at 5 to The trigger is then released, shutting 10 psi. Figure 17 – Air Cap Test Kit off the fluid flow, but the motion is continued for a few inches until it is 2 Using control knob on air reversed for the return stroke. regulator, set air atomization After establishing the operating pressure at 30-35 psi. pressures required for production When the edge of the sprayed object and finish quality, develop a is reached on the return stroke, the Pressure Standardization program 3 Spray a test pattern (fast pass) on trigger is again fully depressed and a piece of paper, cardboard, or for your finish room to follow. the motion continued across the wood. From that test pattern, 32. What is a pressure object. determine if the particle size is small standardization program? Lap each stroke 50% over the enough and uniform throughout the After establishing air and fluid preceding one. Less than 50% pattern to achieve the required finish overlap will result in streaks on the quality. If particle size is too large or pressures that meet required quality and production, record the data to finished surface. Move the gun at a is giving too much texture in the constant speed while the trigger is finish, turn the atomization pressure be used for that application for future reference. (see figure 18) pulled, since the material flows at a up in 3 to 5 psi increments until constant rate. particle size and texture of finish is acceptable. Another technique of triggering is Booth # ______referred to as "feathering." 4 Spray a part with these settings. If Material Sprayed ______Feathering allows the operator to you are not able to keep up with the Application ______limit fluid flow by applying only production rate required or if the Viscosity ______partial trigger travel. finish is starved for material, Fluid Temperature ______. increase the fluid pressure (or use a Spray Gun Model ______35 What happens when the gun is larger capacity fluid tip) with the fluid Air Cap _____ Fluid Tip ____ arced? regulator control knob in 2 to 4 psi Air Pressure ______Arcing the stroke results in uneven increments until required wet Fluid Pressure ______application and excessive overspray coverage is accomplished. at each end of the stroke. When the tip is arced at an angle 45 degrees 5 Remember, as you turn up the from the surface (see figure 19), Figure 18 – Pressure fluid pressure the particle size will approximately 65% of the sprayed Standardization Chart increase. Once the coverage material is lost. required is obtained, it will be necessary to re-adjust the 33. How should the spray gun be atomization pressure in 3 to 5 psi held? increments as explained in step 3 to It should be held so the pattern is insure required particle size and perpendicular to the surface at all finish texture is achieved. times. Keep the gun tip 8-10 inches (air spray guns) or 6-8 inches (HVLP

11 2. Air Atomizing Spray Guns nearly flat, surfaces should be fluid passages by directing stream sprayed. into an approved, closed container. All containers used to transfer Remember to overlap the previously flammable materials should be sprayed areas by 50% to avoid grounded. (Be sure to comply with streaking. local codes regarding solvent When painting very narrow surfaces, disposal.) you can switch to a smaller gun, or Then, remove the air cap, clean it as cap with a smaller spray pattern, to previously explained and replace it avoid readjusting the full size gun. on the gun. The smaller guns are usually easier to handle in restricted areas. Wipe off the gun with a solvent- soaked rag, or if necessary, brush A full size gun could be used, the air cap and gun with a fiber however, by reducing the air pres- brush using clean-up liquid or sure and fluid delivery and triggering thinner. properly. To clean a pressure feed gun with MAINTENANCE remote cup or tank, turn off air sup- 37. How should the air cap be ply to cup or tank. Release material cleaned? pressure from the system by opening relief valve. Remove the air cap from the gun and immerse it in clean solvent. Material in hoses may be blown Blow it dry with compressed air. back. Lid must be loose and all air pressure off. Keep gun higher than If the small holes become clogged, container, loosen air cap and trigger soak the cap in clean solvent. If gun until atomizing air forces all Figure 19 - Spray Techniques reaming the holes is necessary, use material back into the pressure a toothpick, a broom straw, or some 36. What is the proper spraying vessel. sequence and technique for other soft implement. (see figure 20) A gun cleaner may be used for finishing applications? Cleaning holes with a wire, a nail or either type of gun. This is an en- Difficult areas, such as corners and a similar hard object could closed box-like structure (vented) permanently damage the cap by edges, should be sprayed first. Aim with an array of cleaning nozzles enlarging the jets, resulting in a directly at the area so that half of the inside. defective spray pattern. spray covers each side of the edge or corner. Guns and cups are placed over the nozzles, the lid is closed, the valve is Hold the gun an inch or two closer energized, and the pneumatically than normal, or screw the spreader controlled solvent sprays through the adjustment control in a few turns. nozzles to clean the equipment. Needle travel should be only partial by utilizing the "feathering" The solvent is contained, and must technique. Either technique will be disposed of properly. reduce the pattern size. Some states' codes require the use Figure 20 - Cleaning the Air Cap If the gun is just held closer, the of a gun cleaner, and it is unlawful to stroke will have to be faster to com- 38. How should guns be cleaned? discharge solvent into the pensate for a normal amount of A siphon or pressure feed gun with atmosphere. material being applied to smaller attached cup should be cleaned as After cleaning a spray gun in a gun areas. follows: cleaner, be sure to lubricate as When spraying a curved surface, Turn off the air to the gun, loosen indicated in Figure 22. keep the gun at a right angle to that the cup cover and remove the fluid surface at all times. Follow the tube from the paint. Holding the tube curve. While not always physically over the cup, pull the trigger to allow possible, this is the ideal technique the paint to drain back into the cup. to produce a better, more uniform, Empty the cup and wash it with finish. clean solvent and a clean cloth. Fill it After the edges, flanges and corners halfway with clean solvent and spray have been sprayed, the flat, or it through the gun to flush out the 12 2. Air Atomizing Spray Guns 40. What parts of the gun require lubrication? (Figure 22) The A fluid needle packing, the B air valve packing and the C trigger bearing screw require daily lubrication with a non-silicone gun lube. The D fluid needle spring should be coated lightly with petroleum jelly or a non-silicone grease (ie. Lithium). Lubricate each of these points after every cleaning in a gun washer!

Figure 21` - Using a Hose Cleaner Use a hose cleaner to clean internal passages of spray guns and fluid hose. This device incorporates a highly efficient fluid header, which meters a precise solvent/air mixture. The cleaner operates with compressed air and sends a finely - Figure 22 - Lubrication Points atomized blast of solvent through the fluid passages of the hose, the spray gun, etc. This simple, easy to use cleaner speeds up equipment cleaning and saves solvent. Savings may be as much as 80%. It also reduces VOC emissions. (Be sure that both the hose cleaner and gun are properly grounded.) Where local codes prohibit the use of a hose cleaner, manually backflush the hose into the cup or tank with solvent and dry with compressed air. Clean the container and add clean solvent. Atomization air should be turned off during this procedure. Pressurize the system and run the solvent through until clean. (Be sure to comply with local codes regarding solvent dispersion and disposal.) Clean the air cap, fluid tip and tank. Reassemble for future use. 13 2. Air Atomizing Spray Guns Problem Cause Correction

Fluid leaking from packing nut 1. Packing nut loose 1. Tighten, do not bind needle 2. Packing worn or dry 2. Replace or lubricate

Air leaking from front of gun 1. Sticking air valve stem 1. Lubricate 2. Foreign matter on air valve or 2. Replace or lubricate seat 3. Worn or damaged air valve or 3. Replace seat 4. Broken air valve spring 4. Replace 5. Bent valve stem 5. Replace 6. Air valve gasket damaged or 6. Replace missing

Fluid leaking or dripping from 1. Packing nut too tight 1. Adjust front of pressure feed gun 2. Fluid tip or needle worn or 2. Replace tip and needle with damaged lapped or matched sets 3. Foreign matter in tip 3. Clean 4. Fluid needle spring broken 4. Replace 5. Wrong size needle or tip 5. Replace 6. Dry packing 6. Lubricate

Jerky, fluttering spray Siphon and Pressure Feed 1. Material level too low 1. Refill 2. Container tipped too far 2. Hold more upright 3. Obstruction in fluid passage 3. Backflush with solvent 4. Loose or broken fluid tube or 4. Tighten or replace fluid inlet nipple 5. Loose or damaged fluid tip/seat 5. Adjust or replace 6. Dry or loose fluid needle packing 6. Lubricate or tighten nut Siphon Feed Only 7. Material too heavy 7. Thin or replace 8. Contained tipped too far 8. Hold more upright 9. Air vent clogged 9. Clear vent passage 10. Loose, damaged or dirty lid 10. Tighten, replace or clean coupling nut 11. Dry or loose fluid needle packing 11. Lubricate or tighten packing nut 12. Fluid tube resting on cup bottom 12. Tighten or shorten 13. Damaged gasket behind fluid tip 13. Replace gasket

14 2. Air Atomizing Spray Guns Problem Cause Correction Top or bottom-heavy spray 1. Horn holes plugged 1. Clean, ream with non-metallic pattern* 2. Obstruction on top or bottom of point (ie. Toothpick) fluid tip 2. Clean 3. Cap and/or tip seat dirty 3. Clean

1. Right or left-heavy spray pattern* 1. Left or right side horn holes 2. Clean, ream with non-metallic plugged point (ie. Toothpick) 2. 2. Dirt on left or right side of fluid 3. Clean tip

*Remedies for the top, bottom, right, left heavy patterns are: 1. Determine if the obstruction is on the air cap or fluid tip. Do this by making a solid test spray pattern. Then, rotate the cap one-half turn and spray another pattern. If the defect is inverted, obstruction is on the air cap. Clean the air cap as previously instructed. 2. If the defect is not inverted, it is on the fluid tip. Check for a fine burr on the edge of the fluid tip. Remove with #600 wet or dry sand paper. 3. Check for dried paint just inside the opening. Remove paint by washing with solvent.

Center-heavy spray pattern 1. Fluid pressure too high for 1. Balance air and fluid pressure atomization air (pressure feed) Reduce spray pattern width 2. Material flow exceeds air cap’s capacity 2. Thin or reduce fluid flow 3. Spreader adjustment valve set too low 3. Adjust 4. Atomizing pressure too low 5. Material too thick 4. Increase pressure 5. Thin to proper consistency Split spray pattern 1. Fluid adjusting knob turned in 1. Back out counter clockwise to too far achieve proper flow 2. Atomization air pressure too 2. Reduce at regulator high 3. Fluid pressure too low (pressure 3. Increase fluid pressure feed) 4. Change to a larger tip

15 2. Air Atomizing Spray Guns Problem Cause Correction Starved spray pattern 1. Inadequate material flow 1. Back fluid adjusting screw out to first thread or increase fluid pressure 2. Low atomization air pressure 2. Increase air pressure and (siphon feed) rebalance gun

Unable to form round spray 1. Fan adjustment stem not 1. Clean or replace pattern seating properly

Dry spray 1. Air pressure too high 1. Lower air pressure 2. Material not properly reduced 2. Reduce to proper consistency (siphon feed) 3. Gun tip too far from work 3. Adjust to proper distance surface 4. Gun motion too fast 4. Slow down

Excessive overspray 1. Too much atomization air 1. Reduce pressure pressure 2. Gun too far from surface 2. Use proper gun distance 3. Improper technique (arcing, 3. Use moderate pace, parallel gun speed too fast) to work surface

Excessive fog 1. Too much, or too fast-drying 1. Remix properly thinner 2. Too much atomization air 2. Reduce pressure pressure

Will not spray 1. No pressure at gun 1. Check air lines 2. Fluid pressure too low 2. Increase fluid pressure at tank (internal mix cap with pressure tank) 3. Fluid tip not open enough 3. Open fluid adjusting screw 4. Fluid too heavy (siphon feed) 4. Reduce fluid or change to pressure feed 5. Internal mix cap used with 5. Change to external mix air siphon feed cap 6. Pressure feed cap/tip used 6. Use suction feed cap/tip with siphon feed

16 3. Electrostatic Spray Processes PRINCIPLES OF With a typical electrostatic spray gun, charge immediately, and since like ELECTROSTATICS a charging electrode is located at charges repel each other, newly the tip of the atomizer. The electrode driving charged particles or droplets Introduction receives an electrical charge from a will tend to be repelled from spots Electrostatic spray finishing power supply. The paint is atomized that are already coated and attracted combines the mechanical process as it exits past the electrode, and to the remaining areas of bare metal. of atomization with the distributive the paint particles become ionized Similarly, particles and droplets that effects of electrical attraction (pick up additional electrons to were propelled beyond the grounded and repulsion to achieve a highly become negatively charged) object will tend to curve in around be- efficient product finishing operation. hind it, thus giving the “wrap-around” The degree to which electrostatic and recess penetration effects associ- Atomization is achieved in liquid force influences the path of paint ated with electrostatic spray finishing. systems by air, airless, air-assisted, particles depends on how big they and rotary apparatus. The coating are, how fast they move, and other If, however, a metallic or otherwise material is brought into contact with forces within the spray booth such electrically conductive object is in or through the immediate vicinity of as gravity and air currents. Large the vicinity which is NOT properly highly charged electrodes. As this particles sprayed at high speeds electrically grounded, an entirely occurs, a considerable level of have great momentum, reducing the different process can occur. Initially, electrical charge is transferred either influence of the electrostatic force. because it is an electrically neutral by direct contact or by passage A particle’s directional force inertia condition, it will attract the charged through a highly ionized zone near can be greater than the electrostatic particles or droplets of coating the applicator tip (which can be used field. Increased particle momentum material. However, as more and more up to 100 kV), to the particles or can be advantageous when painting coating material arrives and shares its droplets of coating material. Since all a complicated surface, because charge with the object, the electrical the particles or droplets are similarly the momentum can overcome the charge will build up in the object charged and since like charges Faraday cage effect — the tendency because there is no pathway to repel one another. Pattern in an for charged paint particles to deposit ground, turning the object into a static electrostatic spray process tends only around the entrance of a cavity. electricity “battery”. Eventually, and to be larger and more evenly distrib- in many cases, this can mean just uted than that of a non-electrostatic On the other hand, small paint a few seconds, enough electrical process. This increases the ease particles sprayed at low velocities charge can accumulate in the and efficiency. have low momentum, allowing the object that a spark can be generated electrostatic force to take over and between it and the nearest ground When a metallic object, which is attract the paint onto the workpiece. surface. Or, similarly, an ungrounded electrically neutral or grounded This condition is acceptable for metallic object can simply retain its is present, the electric field is simple surfaces but is highly electrical charge for an indefinite time established between the charging susceptible to Faraday cage until a grounded surface is brought electrodes of the applicator and the problems. An electrostatic system near enough for a spark to occur. grounded object which, in this case, should balance paint particle This grounded surface can be a is the item we wish to coat. The velocity and electrostatic voltage to swinging conveyor hook or an electrically charged particles or optimize coating transfer efficiency. operator reaching out to touch the droplets of coating material are charged object. Likewise, a spark attracted via the electric field toward Since the object is grounded through can occur between the electrostatic the grounded object in much the its hanger and conveyor back to device and itself and a grounded same way that iron filings are electrically neutral earth, the charge object if the electrodes or other high attracted to a magnet. As the does not accumulate in the metal voltage portion of the device are particles or droplets come in contact of the object, allowing it to continue placed or brought too close to ground. with the grounded object, they to accept more charges from newly begin to dissipate their electrical arriving particles or droplets of charges with the metal of the object. coating material. Since the particles or droplets do not shed all of their

17 3. Electrostatic Spray Processes conductivity to prevent the charge from ELECTROSTATIC shorting to ground. PROCESSES/EQUIPMENT

Operating Electrostatics Safely The electrostatic application of Electrostatic finishing is safe if the atomized materials was developed to equipment is maintained properly enhance finish quality and improve and safety procedures are followed. transfer efficiency. All items in the work area must be grounded, including the spray booth, Presently, there are seven types conveyor, parts hangers, application of electrostatic processes for spray Faraday Cage Effect equipment (unless using conductive/ application: waterborne coatings), and the spray • Electrostatic air spray atomization Electrostatic Advantages operator. • Electrostatic high-volume, The main benefit offered by an low-pressure (HVLP) atomization electrostatic painting system is As electrical charges come in contact • Electrostatic airless atomization transfer efficiency. In certain with ungrounded components, the • Electrostatic air-assisted applications electrostatic bells can charges can be absorbed and stored. airless atomization achieve a high transfer efficiency This is known as a capacitive charge • Electrostatic electrical atomization exceeding 90%. This high efficiency build up. Eventually, enough charge is • Electrostatic rotary-type translates into significant cost built up so that when the ungrounded bell atomization savings due to reduced overspray. item comes within sparking distance • Electrostatic rotary-type A phenomenon of electrostatic of a ground, and is charge as a spark. disk atomization finishing known as “wrap” causes Such a spark may have enough some paint particles that go past energy to ignite the flammable vapors Regardless of the electrostatic finish- this workpiece to be attracted to the and mists that are present in the ing systems, each has its advantages back of the piece, further increasing spray area. and limitations. What may be suitable transfer efficiency. for one situation may not be suitable An ungrounded worker will not know in another. Increased transfer efficiency also that the capacitive charge has been reduces VOC emissions and absorbed until it is too late. Workers What is Electrostatic Air lowers hazardous waste disposal should never wear rubber- or cork- Spray Atomization costs. Spray booth cleanup and soled shoes, which can turn them Electrostatic air spray uses an air cap maintenance are reduced. into ungrounded capacitors. Special with small precision openings that shoe-grounding devices are available. allows compressed air to be directed Coating Application If workers are using hand-held guns, into the paint for optimum atomiza- Any material that can be atomized they should grasp them with bare tion. Electrostatic air spray is the most can accept an electrostatic charge. hands or with gloves with cut-outs widely used type of atomization in Low-, medium-, and high-solids for fingertips and palms that allow the industry today due to its control solvent borne coatings, enamels, adequate skin contact. and versatility. Electrostatic air spray lacquers, and two-component coatings provides very high transfer efficiency can be applied electrostatically. Proper grounding of all equipment by utilizing the electrostatic charge to that is not used for the high-voltage wrap paint around edges and capture The various types of electrostatic process is essential. Grounding straps overspray that would have been un- systems can apply coatings regard- should be attached to equipment and usable waste. Standard electrostatic less of their conductivity. Waterborne connected to a known ground. A quick air spray provides transfer efficiencies and metallic coatings can be highly inspection of all equipment, includ- in the 40 to 75% range depending on conductive. Solvent-borne coatings ing conveyors and part hangers, can the type of material and application. tend to be nonconductive. Any metallic reveal improper grounding. coatings can contain conductive metal What is Electrostatic HVLP particles. These metallic coatings must Good housekeeping can pay divi- Spray Atomization be kept in circulation to prevent a short dends. Removing paint build up from Electrostatic HVLP spray utilizes the circuit in the feed line. As high volt- parts hangers can help ensure that same atomization characteristics age is introduced into the system, the workpieces are grounded. Unground- as electrostatic air spray technol- metal particles can line up to form a ed objects, such as tools and con- ogy with slight modifications. When conductive path. System modifications tainers, should be removed from the using air HVLP, the pressure of the may be required because of coating finishing area. compressed air at the air cap must be reduced to a range of 0.1 to 10 psi. 18 3. Electrostatic Spray Processes Transfer efficiency is greater when Electrostatic Air-Assisted transfer efficient spray gun process using HVLP spray to lower the Airless Atomization in the industry today. The ultrasoft particle velocity and atomize the Electrostatic air-assisted airless forward velocity of the spray pattern material thus causing less waste spray technology uses the airless achieves transfer efficiencies and blow-by of material. Some spray principle to atomize the fluid of nearly 100% on most products. electrostatic equipment can be easily at reduced fluid pressure with This high transfer efficiency converted or transformed between assisted atomizing air to aid in spawned the industry of painting air spray and HVLP spray technology reducing pattern tailing and affect and refurbishing machinery and by simply changing four parts. HVLP pattern shape. Air-assisted airless furniture in place. spray technology helps meet stringent spray technology offers some of EPA codes requiring reduced VOCs the desirable characteristics of both Electrostatic Rotary- and waste. Electrostatic HVLP spray airless spray and air spray; the Bell-Type Atomization provides transfer efficiencies in the desirable characteristics being An electrostatic bell atomizer is a 40 to 80% range depending on the medium to high delivery rates, ability high-speed rotary bell that uses type of material and application. to spray heavy viscosities at low centrifugal force and mechanical velocities, and high transfer efficiency. shearing to atomize material and efficiently transfer material from the bell edge to the target being painted. The bell is used on a turbine motor where the pattern is carefully directed by the use of compressed air, introduced to the pattern at the edge of the bell cup. The compressed air gives the material forward velocity to aid in penetrating recessed areas. The bells are usually mounted stationary, reciprocated or on robots to coat products on straight line This is where atomization takes place! conveyors. The bells may also be Air cap and fluid tip design are the key factors positioned on both sides of the in atomization and transfer efficiency. conveyor. Rotary-bell-type atomiza- tion provides transfer efficiencies in the 60 to 85% range. Electrostatic Electrical Atomization Air Spray Atomization Technology Electrostatic electrical atomization Electrostatic Rotary- is accomplished by using a rotary Disk-Type Atomization bell on the end of a gun to evenly An electrostatic rotary-disk atomizer What is Electrostatic Airless dispense paint to the edge of the is a high-speed rotary atomizer that Spray Atomization bell. Once the coating material uses centrifugal force along with Electrostatic airless spray technology reaches the edge of the bell it is mechanical shearing to atomize utilizes the principle of fluid at high introduced to an electrical charge. coating material and efficiently pressures (500-5,000 psi) atomizing The electrical charge at the sharp transfer the material from the disk through a very small fluid nozzle edge (approximately 100 kV) edge to the target being painted. orifice. Size and shape of the spray causes paint of a medium electrical The disk is used in an omega shape pattern, along with fluid quality is resistance range (0.1 to 1 megohms) loop conveyor to coat the product. controlled by the nozzle orifice. to disperse onto the product. The Disks may be mounted stationary Airless spray technology evolved pure electrical application is a slightly and tilted (up to 45°) to coat small after air spray to aid in faster slower process than an air spray parts of 12 in. or less, or mounted application rates using higher or air-assisted airless technology on reciprocating arms to coat parts delivery and heavier viscosities and requires a rotational type spray up to 40 ft. in height but generally on larger parts. paint technique, due to the bells no wider than 4 ft. in width. The disk spray pattern, but is the most produces transfer efficiencies in the 70 to 95% range.

19 3. Electrostatic Spray Processes Operating Electrostatic Manual equipment operators will The directed conduction of the Coating Systems Safely be grounded through the equipment electric charge through its array of as long as it is being held in contact wires, cables, and equipment is Personnel Grounding with the bare skin. As soon as the accompanied by a variety of stray equipment is released from direct electrical charges passing through General (skin) contact with the operator, the air by various means such as air *The integrity of the system ground other grounding methods becomes ionization; charged particles in the MUST be inspected regularly and necessary. air and radiated energy. Such stray maintained. charges may be attracted to any The operator SHOULD NOT conductive material in the spray It is simple, but VITAL to be sure wear insulating gloves! Special area. If the conductive material does that all objects in an electrostatic conductive gloves may be used not provide a safe drain to electrical coating area are grounded (reference and are recommended. ground, which will allow the charge NFPA-33). to dissipate as fast as it accumulates, * If insulating (cloth or rubber) it may store the charge. When its 1. Inspect all grounded wires daily. gloves are worn, both palms electrical storage limit is reached, Look for good, firm joints at all MUST be cut out to allow bare or when it is breached by external points of connection (paint pots, skin contact with the equipment! circumstances (such as the approach flow regulators, booth wall, power This allows the operator to of a grounded object or person, supply, etc.). Look for breaks change the equipment from one or one at lower potential), it may in the ground wire. Repair any hand to the other. discharge its stored charge to the defect IMMEDIATELY! nearest ground. If there is no safe * If gloves are worn for chemical path to ground (such as a ground 2. Inspect all conveyor apparatus safety, grounding wrist straps wire) it may discharge through the (hooks, hangers, etc.) daily. If may be connected from the air as a spark. A spark may ignite there is any accumulation of dried operator’s wrist to the applicator the flammable atmosphere of a spray coating material on any of these assembly. area. The hazard area extends from objects, remove it before using the point of origin up to as much them! All persons in the spray area as a twenty foot radius. See the must be grounded at ALL times! NFPA-33 for definition and limitations 3. Inspect the floor daily for of “hazard area”. excessive accumulation of dried This may be accomplished safely coating material (or other by the use of conductive soled It is a simple, but vital matter to be residue). If there is any, remove it! shoes, disposable conductive boots, sure that ALL conductive objects or personnel grounding straps. within the spray area are grounded. Safe grounding is a matter of proper This will include such items as, equipment maintenance, proper spray but are not limited to: cabinets, technique, and good housekeeping. Equipment Grounding benches, housings, ladders, bases, containers, stands, people, Daily inspection of grounding General and product. apparatus and conditions, however, In electrostatic coating systems, the will help prevent hazards that are flow of high voltage power from the ALL of which are not by design, caused by normal, daily operations. power supply to the atomizing head insulated from ground MUST of the applicator is insulated from be connected directly and Personnel grounding is the most ground and isolated from all other INDIVIDUALLY to true earth ground. difficult area of electrical hazard functions and equipment. When the Resting on a concrete floor or control. Most people do not realize voltage reaches the atomizer, it is being attached to a building column what excellent capacitors they are. transferred to the coating material may not always be sufficient ground. In a very short time, without proper where, by introducing a (normally) In order to provide the best ground grounding, the human body can negative charge, it causes the connection possible, always attach a build enough static charge to atomized fluid to seek the nearest ground wire to the terminal indicated cause dangerous spark discharge. (normally) positive ground. In a by the ground symbol and then to a Therefore, ALL persons in an properly constructed and operated proven, true earth ground. Always electrostatic coating area MUST be system, that ground will be the target check ground connections for grounded at ALL times! object. integrity. Some items, such as rotators and paint stands, may be

20 3. Electrostatic Spray Processes supported on insulators, but all to the aluminium hook, the standard flammable fluid from one container components of the system up to assembly has 15 feet of aircraft to another, both containers MUST the insulator MUST be grounded. cable and a solderless connecter be properly connected to a proven for mounting. One assembly should ground first and then to each other. It is recommended that ground wires be conveniently located at each Personnel executing such a transfer be made of No. 18, bare, stranded station. After the high voltage is must also be grounded. An appropri- wire (minimum). Where possible, use off and the atomizer has stopped, ate number of ground hook assem- larger wire. the hook should be touched to the blies are included with systems that atomizer hub or applicator housing require them. If your installation is Where items are mounted directly momentarily to dissipate any residual no longer equipped with the device, on structural components such as charge. It should then be hooked to replacements may be purchased building columns, the ground the applicator housing. (15946) or fabricated according to. connection MUST still be made. In many cases the structural DO NOT allow the hook or its cable component may be painted or coated to touch the working edge of a disk NO. 2 Hand Applicator with an insulating material, and or bell atomizer. This edge is critical On-Site Painting in many cases the equipment will to good atomization and should be painted. These coatings are ALWAYS be protected from any For over 50 years the No. 2 Process insulating. The ground connection contact that might cause even the hand applicator has been the must be as perfect as possible. slightest damage. For overhead most widely used tool by on-site applicators it may be necessary painting industry for the refinishing to suspend the cable with a spring of office furniture, office panels, Applicator Grounding or other elastic material in order lockers, school furniture, and dozens General to prevent edge contact. Most of other items. Waterborne Fluid Supply Enclosures WARNING: The high voltage include an insulated paint stand plus Quite often we are asked about MUST be OFF and GROUNDED a grounded chain link enclosure, the dangers and possible damage before any direct personal and a gate that is equipped with a to computers, phone systems, or contact is made with equipment. limit switch, switch trip, warning light electronically keyed security systems and control box. The enclosure is when electrostatic painting is done Procedures to be followed for safely also equipped with a standard ground nearby. conducting electrostatic coating hook assembly to ground the paint operations are outlined in “Operating supply when personnel are inside of Concerning those types of applications, Your Electrostatic Coating System the enclosure. the following facts should be noted: Safely” section in this Service Manual. Personnel entering an insulated fluid 1. The No. 2 Process hand Electrostatic systems depend on high supply enclosure MUST FIRST be applicator is not electromagnetic. voltage to atomize coating material sure that the system is NOT operating It is electrostatic (much like the and deposit it on the target object. and that the Warning Light is OFF! static from carpets or wool and During operation, the system is at After entering the enclosure, the synthetic clothing), and works high voltage. Personnel must ground hook must be attached at an output of 100 kilovolts at NEVER attempt any direct contact to the paint supply BEFORE any 30-50 microamperes current with the equipment UNTIL the high personal contact is made. The draw (100 microamperes voltage is OFF, the atomizer has ground hook MUST be attached maximum short circuit current). STOPPED rotating and the ground during all service and above all, hook has been attached to the during the addition of fluid to the *Grounding of all conductive objects applicator or paint supply as supply container! When leaving the near an electrostatic spray applicator indicated. The ground hook cable enclosure remove the ground hook is of utmost importance. MUST be secured to a proven, true and close and secure the gate. The earth ground and readily accessible warning light MUST be ON whenever 2. Unlike x-rays, “electrostatics” to the applicator or paint supply. the system is operating. does not go “through” objects.

3. Some computers and phone A ground hook is designed to be used Ground MUST be maintained during systems are now shielded by the with disk or bell atomizers or with the addition of fluid to any supply manufacturer against outside insulated fluid suppliers. In addition container! Whenever transferring static.

21 3. Electrostatic Spray Processes 4. If the static shielding of the unit 6. Computer software such as 9. When painting any type of is unknown, the keyboard, CPU tapes, disks, diskettes, etc., electrical control panel or (central processing unit) and its should be removed from inside console it is generally not known cable preferably should be and the immediate surrounding if all pushbuttons, switches, removed from the immediate area of any enclosures that are meters or pilot lights are properly painting area for protection of to be painted. grounded. In view of this, it is the device. If this is not feasible desirable to cover all of these they should be completely 7. Lightning or electrostatic voltage items with aluminum foil, which wrapped in aluminum foil that is sparking into an A.C. circuit can is grounded to the panel or grounded to an earth ground. create “spikes” or electromag- another earth ground. This will create a “Faraday cage” netic pulse (EMP) that can around the computerized device. cause unpredictable damage 10. All on-site painting companies to electronic hardware. should have adequate liability 5 Electrical sparks of all types insurance to protect them in the create an R.F. energy (radio 8. Surge suppressors are available event or any real or perceived frequency) that may radiate that may help protect appliances damage as a result of their through the air and enter into from “spikes” of current if the operations. electronic circuits. The resulting suppressor is in the A.C. line damage is unpredictable. supplying the appliance. In view of the above unknown and possible uncontrolled conditions, Ransburg does not recommend the electrostatic painting of computer cabinets, consoles or painting in close proximity to these devices.

22 4. Material Containers The rate of fluid flow is controlled Introduction by increasing or decreasing the air All spray painting systems - from pressure in the tank. the smallest brush to the most sophisticated finishing system- must have containers to hold the A typical pressure feed tank material being applied. consists of; A the shell, B a clamp-on lid, C the fluid tube, D Material container types and sizes the fluid header, E regulator, F vary considerably, depending on gauge, G a safety relief valve, and the kind of spraying system being H agitator. used. Pressure feed tanks are available This chapter will discuss these A B with either top or bottom fluid containers, their particular applica- Figure 1 - Cup Attachment Styles outlets, and with various tions, their construction and main- accessories. tenance. 5. What capacity does a pressure feed cup have? 1. What are material containers? A pressure feed cup can have a one or two quart capacity. Any container which serves as a material supply reservoir for the Anything larger is considered a spray gun. These containers are pressure feed tank, which may be usually made of metal or plastic positioned some distance from the with capacities of 1/2 pint or more. gun. 2. What are the types of material containers? There are three common types of cups which attach to the gun itself: Siphon, Gravity and Pressure. There are also remote pressure cups and tanks, which are located away from the gun. See Page 4 for types of guns and systems. 3. Where are cup container used? Cup containers are typically one Figure 3 - Pressure Feed Tank quart or less, and are used where relatively small quantities of 7. Where are pressure feed material are being sprayed. tanks recommended? 4. How are material feed cups Figure 2 - Regulated 2 Qt. Pressure feed tanks provide a attached to lid assemblies? Pressure Cup practical, economical method of material feed to the gun over Cups are attached using a lid 6. How do pressure feed tanks extended periods of time. assembly (sometimes called a cup work? attachment) that either clamps A They are mostly used in or screws B onto the cup Pressure feed tanks are closed continuous production situations, container. (see Figure 1) Some lid containers, ranging in size from because the material flow is assemblies are detachable from about two gallons to 60 gallons. positive, uniform and constant. They provide a constant flow of the gun, while others are integral Tanks can be equipped with parts and do not detach from less material, under constant pressure, to the spray gun. agitators (see Figure 3) that keep expensive models. the material mixed and in The tank is pressurized with clean, suspension. regulated, compressed air, which forces the fluid out of the tank through the fluid hose to the gun.

23 4. Material Containers 8. When is an agitator used in a When abrasive or corrosive pressure feed tank? materials are being sprayed, the tank shell is coated or lined with a When the material being used has special material, oracontainer filler or pigment that must be kept insert is used. in motion to keep its particles in proper suspension. An agitator can be hand, air or electrically 13. What are container inserts? driver They are liners that are placed 9. What isasingle regulated inside the tank to hold the tank? material, keeping it from direct This is a pressure feed tank with contact with the tank walls. They one air regulator controlling only are made of disposable the pressure on the material in the polyethylene. tank. Using inserts reduces tank An extra-sensitive regulator is cleaning time and makes color available for use with lower fluid changeover easier. They also flow and/or lower viscosity allow multiple batches of material material where precise control is to be mixed in advance. needed. You may want to consider stainless steel “Inner containers” when using ceramics or corrosive materials. Another option to consider is Figure 5 - Double Regulated Tank putting the coating container directly into the tank if room allows. Be sure that the tank 11. What are code and non-code “pickup tube” does not touch the pressure tanks? bottom of the coating container Code tanks are manufactured to inserted into the tank. rigid standards as specified by the American Society of Mechanical Engineers. (ASME) Each step of 14. When would you use a manufacture is closely controlled, bottom outlet tank? and welding of the shell is (1) When you are using more certified. Code tanks are designed viscous materials. to withstand pressures up to 80 or 110 psi. (2) When continuous, steady pressure is required, such as Non-code tanks are normally when feeding plural component restricted to3gallons in size or proportioning equipment. less. Due to the type of construction, non-code tanks are (3) When you wish to use all the Figure 4 - Single Regulated Tank rated at 80 psi or less. material in the tank and you are not using an insert. 10. What isadouble regulated tank? 12. What materials are used to 15. What would I use if I have construct pressure feed tanks? This is a pressure feed tank difficulty accurately setting equipped with two air regulators. The smaller, non-code, light-duty lower fluid pressures? One provides regulation for the air tanks are made of plated steel and An extra-sensitive regulator is pressure on the material in the have lower inlet pressure available for use with lower fluid restrictions. tank (thereby controlling fluid flow and/or lower viscosity flow). The other controls The heavy-duty, ASME-code materials where precise control atomization air pressure to the tanks are made of galvanized or is needed. spray gun. 300 series stainless steel. They also have pressed or stainless steel lids with forged steel clamps. 24 5. Hoses&Connections The tube is the interior flexible 5. What sizes of air hose are Introduction artery that carries air or fluid recommended? material from one end of the hose The various types of hose used to The hose from the regulator to a carry compressed air and fluid to the other. gun or tank should be a minimum material to the spray gun are The reinforcement adds strength of 5/16" ID. Tools requiring more important parts of the system. to the hose. It is located between air may need 3/8" ID hose or Improperly selected or maintained the tube and cover, and it can be larger. hose can create a number of many combinations of materials problems. This chapter will review and reinforcement design. Its the different kinds of hose and design determines pressure Type Length Size fittings in use, provide guidance in rating, flexibility, kink and stretch selecting the proper types for the resistance and coupling retention. Air Tools 0' - 10' 1/4" ID job and cover the maintenance of hose. The cover is the outer skin of the General 10' - 20' 5/16" ID hose. It protects the reinforcement 1. What types of hose are used from contact with oils, moisture, Purpose 20' - 50' 3/8" ID in spray painting? chemicals and abrasive objects. 50' - 100' 1/2" ID There are two types; air hose - The cover protects the used to transfer compressed air reinforcement, but does not 0' to 20' 5/16" ID from the air source to the gun, and contribute to hose performance. fluid hose - used only in pressure HVLP 20' - 50' 3/8" ID feed systems to transfer the 50' - 100' 1/2" ID material from its container to the Hose color coding spray gun. Figure 3 - Recommended air RED or TAN .....air and water (NOTE: Do not use air hose for hose sizes solvent-based materials.) 6. What is pressure drop? GREY ...... air w/static ground This is the loss of air pressure due BLACK ...... low pressure fluid to friction (caused by air flow) between the source of the air and TAN ...... conductive the point of use. As the air travels through the hose or pipe, it rubs 3. What type of tube is used in against the walls. It loses energy, fluid hose? pressure and volume as it goes. Since the solvents in coatings 7. How can this pressure drop would readily attack and destroy be determined? ordinary rubber compounds, fluid At low pressure, with short lengths hose is lined with special nylon of hose, pressure drop is not solvent-resistant material that is particularly significant. As impervious to common solvents. pressure increases, and hose is lengthened, the pressure rapidly drops and must be adjusted. 4. What sizes of fluid hose are recommended? All air hose is subject to pressure loss or drop. For example, 1/4" Type Length Size pressure drop is 1 psi per foot and 5/16" is 1/2 psi per foot. This General 0' - 20' 1/4" ID pressure loss may result in poor Figure 1 - Basic Hose atomization. Construction Purpose 10' - 35' 3/8" ID 35' - 100' 1/2" ID Too often, a tool is blamed for 2. How is hose constructed? malfunctioning, when the real Binks/DeVilbiss hose is a 100' - 200' 3/4" ID cause is an inadequate supply of performance designed compressed air due to an combination of three components; Figure 2 - Recommended fluid undersized ID hose. Tube, Reinforcement and hose sizes A B C For optimum spray gun results, Cover. the following is recommended: up to 20 ft - 5/16" I.D. only over 20 ft - 3/8" I.D. 25 5. Hoses & Connections 8. How are hoses maintained? Care should be taken when selectingaquick, detachable air Hoses will last a long time if they connection. Due to design, most are properly maintained. Q.D. connections result in Be careful when dragging hose significant pressure drop. This can across the floor. It should never be adversely affect spray guns with pulled around sharp objects, run higher consumption air caps such over by vehicles, kinked or as HVLP. otherwise abused. Hose that ruptures in the middle of a job can ruin or delay the work. Proper hose cleaning techniques are covered on Pages 11 and 12. The outside of both air and fluid hose should be occasionally wiped down with solvent. At the Figure 4 - Threaded-Type end of every job, they should be Connection stored by hanging up in coils. 12. What isaquick-disconnect type connection? 9. What kinds of hose fittings are This is a spring-loaded, available? male/female connection system Permanent, crimp type or reusable that readily attaches and detaches fittings are used to connect hoses by hand. No tools are required. to air sources or to spray equipment.

10. What kinds of hose connections are available? Although there are many different styles, the two most common are the threaded and the quick-disconnect types. Remember that elements added to any hose, such as elbows, connectors, extra lengths of hose, etc., will cause a pressure drop. On HVLP systems, quick-disconnects must have larger, ported openings to deliver proper pressure for atomization. Because of normal pressure drop in the devices, they are not recommended for use with HVLP.

11. What isathreaded- type connection? This is a common swivel-fitting type that is tightened with a wrench.

Figure 5 - Quick-Disconnect Type Connection 26 6. Air Control Equipment Air control equipment comes in a Regulators are used in lines Introduction wide variety of types, but it already equipped with an air The control of the volume, the basically all performs one or more filtration device. pressure and the cleanliness of of the following functions; air Air regulators are available in a filtering/cleaning, air pressure the air entering the spray gun are wide range of cfm and psi of critical importance to the regulation/indication and air capacities, with and without distribution through multiple performance of the system. pressure gauges and in different outlets. Following some key installation degrees of sensitivity and principles will help decrease the accuracy. risk of contaminants. For example, 4. How does an air filter work? They have main line air inlets and it’s important to use the right size regulated or non-regulated air air compressor for your It filters out water, oil, dust and dirt outlets. application. An overworked air before they get on your paint job. compressor can produce a Air entering the filter is swirled to significant amount of dirt and oil. remove moisture that collects in Additionally, proper piping is very the baffled quiet zone. 6. How is an air filter/regulator installed? important to help prevent Smaller impurities are filtered out condensation from forming within Bolt the air filter/regulator by a filter. Accumulated liquid is A the line and contaminating the air securely to the spray booth. (see carried away through either a supply. Figure 2) manual or automatic drain. This chapter examines the various This location makes it convenient types of equipment available to to read the gauges and operate perform these control functions. the valves. Install the filter/ regulator at least 25 feet from the (B) compressed air source. Install 1. What is air control the (C) takeoff elbow on top of the equipment? (D) main air supply line. Any piece of equipment installed Piping should slope back toward between the air source and the the compressor, and a (E) drain point of use that modifies the leg should be installed at the end nature of the air stream. each branch, to drain moisture from the main air line. Use piping of sufficient I.D. for the 2. Why is air control equipment volume of air being passed, and necessary? the length of pipe being used. Raw air, piped directly from an air source to a spray gun, is of little use in spray finishing. Raw air Minimum Pipe Size Recommendations* contains small, but harmful, quantities of water, oil, dirt and Compressor Main Air Line other contaminants that will alter HP CFM LENGTH SIZE the quality of the sprayed finish. Raw air will likely vary in pressure 1 1/2 - 2 6-9 Over 50' 3/4" and volume during the job. 3-5 12-20 Up to 200' 3/4"

There will probably be a need for Figure 1 - Air Filter Over 200' 1" multiple compressed air outlets to 5-10 20-40 Up to 100' 3/4" run various pieces of equipment. 100' - 200' 1" Any device, installed in the air line, 5. What is an air regulator? which performs one or more of This is a device for reducing the Over 200' 1 1/4" these functions, is considered to main line air pressure as it comes 10-15 40-60 Up to 100' 1" be air control equipment. from the compressor. Once set, it 100' - 200' 1 1/4" maintains the required air pressure with minimum Over 200' 1 1/2" 3. What are the types of air fluctuations. control equipment? Table 1

27 6. Air Control Equipment *Piping should be as direct as will not condense out into solid possible. If a large number of particles. fittings are used, larger I.D. pipe Check the following: should be installed to help overcome excessive pressure a) Drain filter, air receiver and air drop. line of accumulated moisture. b) Be sure the filter is located at least 25 feet from the air source. c) Main air line should not run adjacent to steam or hot water piping. d) Compressor air intake should not be located near steam outlets or other moisture-producing areas. e) Outlet on the air receiver should be near the top of the tank. f) Check for damaged cylinder head or leaking head gasket, if the air compressor is water cooled. g) Intake air should be as cool as possible.

Figure 2 – Air/Filter Regulator Installation 9. What causes excessive pres- sure drop on the main line gauge of the filter/regulator? 7. How often should the a) The compressor is too small filter/regulator be drained of to deliver the required air accumulated moisture and dirt? volume and pressure for all It depends largely on the level of tools in use. system use, the type of filtration in b) The compressor is not the air system, and the amount of functioning properly. humidity in the air. c) There is leakage in the air line For average use, once-a-day or fittings. drainage is probably sufficient. d) Valves are partially opened. For heavily-used systems, or in high humidity, drainage should e) The air line, or piping system, occur several times daily. is too small for the volume of air required. Refer to Table 1, Some units drain automatically Page 20. when moisture reaches a predetermined level.

8. What steps should be taken if moisture passes through the filter/regulator? Since moisture in the spray gun atomization air will ruinapaint job, it must be removed from the air supply. When the compressed air temperature is above its dew point temperature, oil and water vapor 28 7. Respirators provide the necessary respiratory usually used in finishing Introduction protection when using materials operations with standard Spray finishing creates a certain that are not suitable for organic materials. (not suited for paints amount of overspray, hazardous vapor respirators. containing isocyanates). vapors and toxic fumes. This is The visor/hood style provides a true, even under ideal conditions, greater degree of coverage to the and there is no way to avoid it head and neck of the operator. entirely. Both styles require a positive Anyone near a spray finishing supply of clean, breathable air as operation should use some type of defined by OSHA (Grade D). respirator, or breathing apparatus. This chapter covers various types of equipment for this use.

1. What is a respirator? A respirator is a mask that is worn Figure 3 - Organic Vapor over the mouth and nose to Respirator prevent the inhalation of overspray 6. What is a dust respirator and fumes and vapor. where is it used? Dust respirators are sometimes 2. Why is a respirator used in spray finishing but, in most necessary? applications, they are Figure 1 – Positive Pressure unsatisfactory. (see Figure 4) For two reasons: Visor/Hood First...some type of respiratory protection is required by OSHA/ NIOSH regulations. Second...even if it wasn't a requirement, common sense tells you that inhaling overspray is not healthy. Overspray contains toxic particles of paint pigments, harmful dust Figure 4 - Dust Respirator and vapor. Exposure to any of the above is a potential health risk. These respirators are equipped with cartridges that remove only Depending on design, a respirator solid particles from the air. They can remove some, or all, of these have no ability to remove vapors. dangerous elements from the air around a spray finishing operator. They are effective, however, in Figure 2 – Positive Pressure Mask preliminary operations such as Respirator sanding, grinding and buffing. 3. What types of respirators are 5. What is an organic vapor used by spray finishing respirator and where is it used? NOTE: operators? This type of respirator, which There are three primary types; the covers the nose and mouth, (see Before using any respirator, air-supplied respirator, the organic Figure 3) is equipped with a carefully read the manufacturer’s vapor respirator and the dust replacement cartridge that Safety Precautions, Warnings and respirator. removes the organic vapors by Instructions. Many respirators are chemical absorption. not suitable for use with isocyanates, asbestos, ammonia, Some are designed with a prefilter pesticides, etc. 4. What is an air-supplied to remove solid particles from the respirator? air before it passes through the This type is available in both chemical cartridge. mask and visor/hood styles. Both The organic vapor respirator is 29 8. Air Compressors piston type compressor is the 5. What isasingle stage Introduction more commonly used. compressor? All air tools, spray guns, sanders, This is a piston-type compressor etc., must be supplied with air with one or more cylinders, in 3. How doesapiston-type which is elevated to the higher which air is drawn from the pressures and is delivered in compressor work? atmosphere and compressed to its sufficient volume. The air This design elevates air pressure final pressure withasingle stroke. compressor compresses air for through the action of a use in this equipment and is a All pistons are the same size, and reciprocating piston. As the piston major component of a spray they can produce up to 125 psi. moves down, air is drawn in painting system. This chapter will through an intake valve. As the examine the various types piston travels upward, that air is available. 6. Where are single stage compressed. Then, the compressors used? Compressed air is measured on now-compressed air is discharged the basis of the volume supplied through an exhaust valve into the The application of this compressor per unit of time (cubic feet per air tank or regulator. is usually limited toamaximum minute, or cfm) at a given pressure of 100 psi. It can be used Piston type compressors are pressure per square inch (psi), above 100 psi, but above this available with single or multiple referred to as delivery. pressure, two stage compressors cylinders in one or two-stage are more efficient. Displacement is the output of air models, depending on the volume by a compressor at zero pressure, and pressure required. or free air delivery. 7. What isatwo-stage compressor? 1. What is an air compressor? A compressor with two or more cylinders of unequal size in which An air comp ressor is a machine air is compressed in two separate designed to raise the pressure of steps. air from normal atmospheric pressure to some higher pressure, The first (the largest) cylinder as measured in pounds per compresses the air to an square inch (psi). While normal intermediate pressure. It then atmospheric pressure is about Figure 1 - Piston Type Air exhausts it into a connecting tube 14.7 pounds per square inch, a Compressor called an intercooler. compressor will typically deliver air at pressures up to 175 psi. 4. How doesarotary screw From there, the intermediate compressor work? pressurized air enters the smaller When selectingacompressor: cylinder, is compressed even Rotary screw compressors utilize more and is delivered toastorage Rule of thumb two intermeshing helical rotors in tank or to the main air line. The cubic feet per minute a twin bore case. Air is delivered by an electrically compressed between one convex Two stage compressors can powered2stage industrial air and one concave rotor. Trapped deliver air to over 175 psi. compressor is 4 times the motor's volume of air is decreased and the They are normally found in horse power rating. (CFM=4xHP) pressure is increased. operations requiring compressed air of 125 psi or greater.

2. What types of compressors are most common in spray 8. What are the benefits of two finishing operations? stage compressors? There are two common types; the Two stage compressors are piston-type design and the rotary usually more efficient. They run screw design. cooler and deliver more air for the Because most commercial spray power consumed, particularly in finishing operations consume the over-100 psi pressure range. large quantities of compressed air Figure 2 – Rotary Screw Air at relatively high pressures, the Compressor

30 9. Spray Booths 4. What is a dry filter type spray Introduction booth? Containing the overspray and This booth draws overspray- keeping it out of the air and off contaminated air through other objects is an important replaceable filters and vents the consideration in a spray finishing filtered air to the outside. operation. This chapter looks at the primary method of controlling It is the most common type of overspray in the spray booth. It booth for most industrial discusses various types of booths applications. and details periodic maintenance. It is used for spraying low-volume, slower-drying materials, and is not affected by color changes. 1. What is a spray booth? A compartment, room or enclosure of fireproof construction; built to confine and exhaust overspray and fumes from the operator and finishing system. There are various models available, designed for particular spray applications. Figure 2 - Waterwash Type Spray Booth Consult the National Fire Protection Association (NFPA) pamphlet #33 and the O.S.H.A. requirements for construction specifications.

2. What are the benefits of a spray booth? Figure 1 - Dry Filter Type Booth A well-designed and maintained spray booth provides important 5. What is a waterwash type booth? advantages: Figure 3 - Automotive Downdraft Dry It separates the spraying A waterwash booth (see figure 2) Filter Booth operation from other shop actually washes the -contaminated overspray air with a cascade of activities, making the spraying, as 6. What is an exhaust fan? well as the other operations, water, and traps the paint solids. Fewer paint particles reach the cleaner and safer. A typical exhaust fan (see figure outside atmosphere to harm the 4) consists of a motor, a multiple It reduces fire and health hazards environment. blade fan, pulleys and belts. It by containing the overspray. Waterwash booths are generally removes overspray from the spray It provides an area that contains used when spraying more than 15 booth area. residue, making it easier to keep gallons of material a day. Contemporary exhaust fans are clean. It also keeps both the carefully designed to prevent operator and the object being overspray from coming into sprayed cleaner. contact with the drive mechanism. In a booth equipped with adequate Blades are made of non-sparking and approved lighting, it provides metal, and they move the better control of the finish quality. maximum volume of air-per-horsepower against resistance such as exhaust 3. What types of spray booths are stacks, filters, etc. (See NFPA there? pamphlet #33.) There are two; the dry filter type and the waterwash type.

31 9. Spray Booths (d) Coat the inside of the booth withastrippable, spray-on 10. What does an air covering. When the overspray replacement unit do? on it becomes too thick, strip The volume of air exhausted from and recoat. a spray booth is often equal to (e) Periodically check the lighting three or more complete air inside the booth, and replace changes per hour. weak or burned out bulbs. Under such conditions, the Improper lighting can cause the temperature may become irregular operator to apply a poor finish. and uncomfortable. Excessive dust may become a problem. 12. What routine maintenance To prevent these conditions, does a waterwash type booth sufficient "make-up" air must be Figure 4 – Exhaust fan require? introduced to compensate for the exhausted air. (a) Compounding of the water in 7. What is air velocity? this type unit is essential. The air replacement unit Employ only booth treatment Air velocity inafinishing operation automatically supplies this is the term used to describe the chemicals in accordance with "makeup" air - both filtered and suppliers' recommendations. speed of air moving through the heated - to eliminate the problems empty spray booth. The ph of the water should be of air deficiency. between8and 9. (b) Maintain the water level at the 8. What effect has air velocity on proper setting per spray booth efficiency? manufacturers' specifications. Air must move through the booth (c) Check the tank for paint with sufficient velocity to carry away overspray. buildup on the bottom, check the pump strainer to keep it Too low a velocity causes poor, clean and clear, check the air even potentially dangerous washer chamber and the working conditions, especially nozzles in the header pipe. If when the material contains toxic the nozzles are plugged, the elements. It also increases overspray will encroach on the maintenance costs. wash baffle section, fan and stack. Too high a velocity wastes power Figure 5 - Air Replacement Unit and the energy required to heat (d) Periodically check the float make-up air valve for proper operation. 11. What routine maintenance Flood the sheet to be sure 9. What is a manometer? does a dry type spray booth there is a uniform flow over the It is a draft gauge which indicates require? entire surface. when paint arrestor filters or intake (a) The continuous flow of air filters are overloaded. (e) Keep the booth interior and through the booth eventually exhaust stack free from. loads the filters with dirt and Some states and local codes overspray and dirt requireamanometer gauge on overspray. Periodically, inspect accumulation. each bank of filters to comply with and replace them with OSHA regulations. multistage filters, designed for spray booth use. Single-stage furnace filters will not do the job (b) Monitor the manometer readings daily, and know what a normal reading should be. (c) Keep the booth free of dirt and overspray. Floors and walls should be wiped down after every job. Pick up scrap, Figure 5 - Manometer newspapers, rags, etc. 32 9. Spray Booths 13. What checks can be used to assure good results from a spray booth? a) Keep the interior of the booth clean b) Maintain and replace intake and exhaust filters when necessary. c) Caulk all seams and cracks where dirt might enter

)d Maintain and clean all equipment used in the booth e) Keep operators' clothing clean and lint-free. f) Perform routine maintenance above on a scheduled basis

33 10. Diaphragm Pumps Introduction 2. What is meant by priming Ball Check A the pump? Remains closed due to pressure Diaphragm pumps can serve in the right hand chamber. several purposes in a spray Before setting working fluid system. The can be used as a pressures, start an empty pump Ball Check B transfer pump to move coatings by slowly opening the air Opens to allow fluid in the right from one container to another pressure valve (or regulator) to hand chamber to exit the pump (ie. drum to a pressure pot). the air motor. When the pump no longer cycles (full of coating), set Ball Check C In many cases larger diaphragm the fluid pressure to the working Remains closed due to pressure pumps can be used in a paint pressure. in the upper portion of the pump supply room to supply pressure to low pressure spray guns If the air motor receives full Ball Check D either in a dead-end system or a working pressure with an empty Opens to allow fluid to be circulating system. fluid section, the fluid section siphoned from the material contains air and will initially run container. They may also be used in the at high speed with no lubrication. spray booth to siphon directly This will increase the risk of When the connecting rod causes out of a container supplying low damaging the fluid section. both diaphragms to move to the pressure coatings to the spray left, the four ball check behave in gun. If required the coating could 3. How doesadiaphragm a direction opposite to the be returned to the source in a pump work? above. circulating system. Refer to Figure 2 4. How do I troubleshoot a diaphragm pump air motor?

Freezing Motor Air exhausting from the pump tends to freeze (stall) motor High humidity and/or cycle rate Fix: Pipe exhaust away from pump

Dirt or debris in air supply Dirt can plug internal ports & shear air motor o-rings Fix: Install air filtration

Oils in air supply Improper or excess Figure 1 Figure 2 lubrication can cause air motor o-rings to swell and We will assume the pump in stall the pump figure 2 is primed and the Fix: Following manufacturers 1. How are diaphragm pump recommendation for pressures determined? connecting rod at its maximum leftward movement and the lubrication pump is ready to move to the Diaphragm pumps are normally Water in air supply a 1:1 ratio. The maximum right. When fluid is called for, Water can wash out factory pressure would be limited by the both diaphragms begin to move to the right via the rod installed lubricant, leading to pump design (ie. 100 psi) or by pump failure the available pressure to the connecting them. The four Fix: Install proper filtration pump. ball/seat valves behave as follows:

34 10. Diaphragm Pumps Product discharged from air Pump will not prime or meet exhaust when idle delivery requirements Check for diaphragm rupture Suction line blocked or Check tightness of undersized, clogged ball diaphragm nut seats Suction line too long Pump blows air out main air Suction line pulling material exhaust when idle too far above top of fluid Check “U” cups on spool in level major valve Check valve plate and insert Air bubbles in product discharge for wear Check connections of Check sleeve and “O” ring suction plumbing on diaphragm Check “O” rings between connecting rod intake manifold and fluid Check “O” ring on piston for caps wear Check tightness of diaphragm nut 6. How do I troubleshoot a diaphragm pump wet section? Low output volume Check air supply Leaking Clamps Check for plugged outlet Old/worn clamps do not hose produce a good seal Pump mounted in vertical Leaking material can be an position? environmental issue Check for pump cavitation - Note: Most pumps use Suction pipe minimum 1/2” bolted construction rather and non-collapsible. than clamps and are less Cavitation will occur when prone to leakage the material is exiting the pump faster than it can be Clogged Checks drawn in. Checks cannot seat Check all intake & suction properly. Fluid will be joints - Must be airtight reduced or eliminated Use Teflon tape or sealant if Fix: Clean or replace check necessary assembly Check for sticking or improperly seating check Fluid Compatibility valves. Incompatibility can reduce life of pump Danger: Aluminum pumps may violently react with materials containing HHC (Hologenated Hydrocarbon) solvents, ie. Carbon Tetrachloride.

Under Sizing Pump cannot meet application requirements - shorter pump life. Undersizing typically causes high cycle rates.

35 11. High Pressure Spraying Introduction minute, L.P. equipment in ounces per minute. Use the appropriate protection High pressure spray equipment Plugging Tips device as listed in the coating’s will typically use between 300 and Due to the small opening in the Material Safety Data Sheet 4000 psi of fluid pressure. Low fluid tip, plugging is not (MSDS) pressure equipment (air spray and uncommon in H.P. equipment. HVLP) typically use 5-30 psi. Treatment and prevention for When high volume applications plugging may be found in the Warning: and heavy film builds are called troubleshooting section of this INJECTION HAZARD for, high pressure equipment manual. excels. Heat may be required for high Spray from the gun, hose leaks, or solids coatings ruptured components can inject Airless and air assist airless spray When using today’s higher solid fluid into your body and cause guns are used in high pressure materials, heating of the material extremely serious injury, including finishing. Also required is a pump to lower the viscosity may be poisoning or the need for capable of delivering the required to achieve the amputation. pressures required for high atomization required. Splashing fluid in eyes or on skin pressure guns. Not For Fine Finish can also cause a serious injury. The atomization capabilities of Other equipment concerns are H.P. equipment will not allow it to Fluid injected into the skin might hoses, regulators, filters, heaters obtain an automotive finish. look like just a cut, but is a serious and any other equipment that is Acceptability will depend on the injury and should be treated as subjected to the pressures being finish standards of the product such. used and must be rated to handle being sprayed as well as the GET IMMEDIATE MEDICAL the pressure. characteristics of the coating. ATTENTION. INFORM THE PHYSICIAN WHAT TYPE OF 1. What are the advantages of Safety High Pressure Finishing? MATERIAL WAS INJECTED. 3. What are the safety Do not point the spray gun at Speed of Application concerns with H.P. anyone or any part of the body. Due to the high flow rates, H.P. equipment equipment will be considerably Do not put fingers or hand over the spray tip. faster than L.P. equipment Skin Injection Improved Transfer Efficiency H.P. equipment has the capability Do not stop or detect fluid leaks Little or no air in the spray of injecting coating into fingers, witharag, hand, body or glove. pattern hands, etc. Do not usearag to blow back Sprays Most Coatings fluid. THIS IS NOT AN AIR Follow all safety instructions Cost for high volume and high SPRAY GUN. film build applications included with the equipment. Use tip guards and trigger locks where Be sure the trigger operates safely 2. What are the disadvantages appropriate before spraying. of High Pressure Finishing? Engage the gun safety when not Supporting Equipment spraying. Safety issues must be addressed. Insure that all supporting More training is required. equipment is rated for the ALWAYS RELIEVE THE Limited equipment flexibility. pressures that could be PRESSURE WHENEVER Unlike low pressure equipment, generated. Use the maximum WORKING ON THE SPRAY cup guns, feathering the trigger pump pressure as a guide. GUN. and pattern adjustment are not Tighten all fluid connections available Respirators before operating equipment. Higher Initial Costs H.P equipment must be able to Check all hoses, tubes, and handle the higher pressures used. couplings daily. Replace all worn, In addition, pumps are required to damaged, or loose parts generate the pressures. immediately. Not For Small Quantities H.P. equipment flow rates are generally rated in gallons per Figure 1 36 12. Airless and Air Assist Airless Guns Introduction High pressure spraying requires the use of spray guns that can 114-01506 .015 4” – 6” withstand the pressures 114-01508 .015 6” – 8” associated with the pressures 114-01510 .015 8” – 10” delivered via piston pumps. 114-01512 .015 10” – 12” 114-01514 .015 12” – 14” Airless and Air Assisted Airless 114-01516 .015 14” – 16” are currently available in both 114-01518 015 16” – 18” manual and automatic models. Table 1 – Sample .015 tips Some models may have maximum pressures below the pressures the Figure 2 – Incomplete pumping system may deliver. 3. How does an airless gun Atomization Consult your distributor to operate? determine your pump An airless spray gun uses high 1. What is an airless gun? hydraulic fluid pressure An airless gun uses high hydraulic generated by a pump. The fluid pressure to force coating through is forced through a small a small elliptical shaped orifice to elliptical shaped orifice (fluid tip atomize. or fluid nozzle) to generate the pattern.

2. What do I need to know to choose an airless fluid tip?

The following will determine Figure 3 – Air Assist pattern size and atomization,: An air cap similar to a Fluid tip orifice shape conventional or HVLP spray gun Fluid tip orifice area is added to a high pressure Fluid viscosity spray gun, thus the name Air Fluid pressure Assist Airless. Set the pressure on the assist air is set high Fluid tips for airless guns are enough to eliminate the tails. sized based on an equivalent Figure 1 – Airless Spray Gun (see figure 3) circular opening. As an example, a .015” opening can take on many 4. What is an air assist different shapes, thus different airless gun? pattern sizes and atomization levels. For example, Table 1 When air airless gun (see Figure shows 7 different .015 fluid tips 4) is set up with pressures under available for one model of an 2000 psi, the possibility of airless spray gun. incomplete atomization The shape of the opening is the increases. The net result is a variable that determines the pattern that has “tails” at the top pattern size. and bottom. If sprayed with such a pattern, one would see a stripe An additional note: The larger at the top and bottom of each pattern sizes are the result of a tip pass (see figure 2). Figure 4 – Air Assist Gun opening that is more slender than the shorter pattern tip. This will give a larger pattern size at the expense of more frequent tip plugging and shorter tip life.

37 13. Two Ball Piston Pumps Two Ball Piston Pumps It is generally recommended that the During the upstroke, the lower ball (B) maximum usable pressure is raises allowing coating to enter the Introduction approximately 60-70% of the lower portion of the fluid section. maximum pump pressure. A spray Coating in the upper portion of the gun that requires 1000 psi of fluid fluid section is pushed out of the pressure would need approximately outlet. The upper ball (A) remains an 18:1 pump (60% times 1800 psi closed. (see to Figure 2) would give 1080 psi of working pressure. During the downstroke, the lower ball Other factors that influence ratio remains closed. The upper ball is selection include: forced open allowing coating from the Gun distance from pump (pressure lower portion of the pump to enter the drop) upper portion pushing coating out of Circulation requirements (if used) the outlet. Viscosity of material Size of fluid tip in gun If the pump is designed properly, 50 Pipe layout percent of the pumps output will be delivered on each stroke. (one 3. What is meant by priming the upstroke, one downstroke). Note that pump? with most2ball pumps all of the coating siphoned into the pump for the Before setting working fluid pressures, complete cycle enters the fluid section start an empty pump by slowly on the upstroke. opening the air pressure valve (or Figure 1 – Two Ball Piston Pump regulator) to the air motor. When the pump no longer cycles (full of 5. What is the purpose of the Wet coating), adjust the regulator to set the Cup? A pump is required to generate the fluid pressure to the working pressure. pressures required for airless and air Lubrication for the upper packings is assist airless spray guns,. If the air motor receives full working provided byalubricant added to the pressure with an empty fluid section, “Wet Cup” at the upper portion of the The most common pump used to the fluid section contains air and will fluid section. This cup is not designed supply high pressure spray guns is an initially run at high speed with no to contain solvent. Solvent will air driven two ball piston pump. lubrication. This will increase the risk evaporate, leaving the upper packings of friction/heat damaging the packings without lubricant. Throat Seal 1. How are piston pump pressures and/or fluid section. Lubricant (TSL) should be used in the determined? wet cup. 4. How does a Two Ball Fluid Pump ratios are determined by the Section work? 6. What is meant by cavitation? size of the piston in the air motor compared to the size of the piston in The fluid section is connected to the A pump has little difficulty pushing the fluid section. air motor. As the air motor moves up material through the outlet into the (1 stroke) it brings the displacement piping or tubing system. The maximum pump pressure rod up. As the air motor moves down, available from a pump is the ratio of it pushes the displacement rod down. If the pump cannot bring material into the pump multiplied by the maximum the pump as fast as it pushes it out, a air inlet pressure as stated in the cavity or void is created in the input pump literature. area. This could result if the material is highly viscous or the siphon tube is As an example, considerapiston undersized or not airtight pump with an 8” air motor anda2” fluid section.

8” = 50.24 square inch area 2” = 3.14 square inch area

50.24/3.14 = 16:1 ratio

If the pump hadamaximum air inlet pressure of 100 psi, the maximum fluid pressure the pump could generate is 1600 psi.

2. What ratio do I need for my spray gun? Figure 2 – 2 Ball Fluid Section 38 14. High Pressure System Setup – Dead End 6. Drop Line regulator Introduction Allows for regulation to the required 4. What safety issues should be pressure of the spray gun. addressed in a high pressure Proper setup of high pressure system? equipment is necessary not only for efficient operation of the equipment, 2. What parameters in a “dead end” 1. All components in the systems but safe operation as well. system should be of concern? must be rated to handle the maximum pressure the pump Airless and Air Assist Airless may be 1. Use only components that can could generate. supplied by a dead-end system or a handle the pressures in the circulating system. system. This includes all 2. Avoid the possibility of any components in figure 1 as well as portion of the body being near the Following are instructions for a dead- hoses, guns, fittings, etc. fluid tip whenever there is a end system. 2. Fluid lines must be sized chance of fluid leaving the tip. If adequately to prevent large you inject your skin with coating, 1. How do I set up a simple (dead- pressure losses seek medical help immediately. end) high pressure system? 3. When using coating materials that “settle out” or high viscosity 3. If the gun is equipped with a Refer to Figure1for a typical “dead materials that need to be heated, trigger safety, engage it when the end” high pressure system. a circulating system may be a gun is not in use. better option. 1. 2 Ball Piston Pump 4. If the gun is equipped with a tip Available in range of approximately 3. How fast or slow should my guard (duck bill), do not remove 11:1 to 60:1 pump be cycling? it. 2. Filter/Regulator for Pump air motor The air motor of a piston pump needs Most pumps give a flow rate per to be supplied with clean, dry air cycle as well as a flow rate for 60 3. Surge tank (pulsation chamber) cycles. A flow rate of 15 cycles per Eliminates pulsation that happens minute will keep maintenance to a when the piston changes direction minimum. As you increase cycle 4. Dual Fluid Filters speed, maintenance cost will increase Prevents the line from being shut as well. down when it is time to clean the filter 5. Fluid pressure gauge If you undersize a pump, high cycle Monitors the fluid pressure in the main rates and high maintenance costs will line be the result.

Figure 1 – Dead End High Pressure System

39 15. Four Ball Pumps

Introduction

During the down stroke: Ball checks (D) and (A) open. Ball (A) allows fluid to exit while ball (D) allows fluid to enter the pump. Ball checks (B) and (C) remain closed.

During the up stroke: Ball checks (B) and (C) open. Ball (B) allows fluid to exit while ball (C) allows fluid to enter the pump. Ball checks (D) and (A) remain closed.

Figure 1 – Four Ball Piston Pump

A four ball pump generally is used ina“pump house” or “paint kitchen” for delivering lower pressures a long distance or high flow rates.

Pressures tend to be much lower than 2 ball pumps and are often regulated down at the point of use for air atomized spray guns.

1. What ratios are available inafour ball pump.

Due to the larger fluid section, a very large air motor would be required to achieve the typical pressures achieved with two ball pumps. Using the same air motors used in two ball pumps, Figure 2- Four four ball pumps typically top at Ball Fluid Section about a 7:1 ratio.

2. How does the fluid section of a four ball pump work?

A four ball piston pump fluid section contains four ball checks that alternate open and closed during up and down strokes (refer to figure 2).

40 16. Circulating Systems 2. How does a circulating By putting a back pressure Introduction system work? regulator in the system we create a dam that allows some fluid to A circulating system delivers fluid While some circulating systems return to source but set up a from the pump to the spray gun can get very complex, refer to partial blockade (back pressure) to and back to the pump. (see figure figure 1 for a very basic circulating allow material to flow to the spray 1). system gun.

You should consider a circulating The coating leaves the fluid The general sequence for system: section of the pump and travels adjusting a back pressure through hoses, pipes, etc. to the regulator is: 1. When multiple stations need spray gun. the same coating. 1. Set the regulator to insure 2. When you want to put a paint A valve or tee at the spray drop that the spray guns have heater in the system (to line returns a portion of the adequate operating reduce viscosity without material back to the pump on a pressure. adding solvents). return line. 2. Adjust for proper flow rate 3. When you have problems with 3. Adjust for proper pump the solids ofacoating “settling The materials may return to the speed out”. pump inlet or into the material container. 1. What flow rates are used in a Circulating system? 3. What is a back pressure regulator? Typical flow rates for solvent based materials are one foot per Referring to figure 1, imagine the second (60 feet/min). back pressure regulator (3) removed from the system and the Typical water based materials use piping is straight through back to one half foot per second (30 the pump. feet/min). There would be no reason for the material to flow to the spray gun Consult your Product Data Sheet as the path of least resistance for or your coating supplier for the material is back to the pump. recommendations for your coating.

5

5. Fluid Pressure Regulator w/gauge and standpipe/riser tube

Figure 1 – Circulating System

41 16. Circulating Systems 4. What other components are used in a circulating system?

Downstream Fluid Regulators: For controlling pressure at each spray gun

Surge Tanks/Chambers: For suppressing the “wink” or pulse in the system, induced by the pump changing direction during the cycle

Heaters: For decreasing viscosity without adding solvent and maintaining a constant viscosity

Filters: For removing contaminants and preventing plugging gun fluid tips and spray defects. Note: Filters are located in the pressure side of the system.

Strainers: For removing “trash” prior to entering the pump. Note: Strainers are located on the non-pressure portion of the system, normally on the end of the pump pick-up tube.

Drum Lifts/Elevators: Allows the pump and drum lid to be raised to facilitate replacement of the drum.

Agitator: Keeps material in suspension in the drum/container.

42 17. High Pressure Troubleshooting

Introduction Fluid Section Problems

Problems arising in a high No Material at outlet pressure pumping system can (Pump continually cycles) range from something as simple Check material supply as a plugged fluid tip to a runaway pump. Material on one stroke only. (fast down stroke) 2 Ball Service literature that Lower ball not properly seating accompanies your equipment is highly recommended reading. Material on one stroke only. (fast upstroke) 1. What problems can I have Worn or damaged seals with my high pressure system? Material leakage from solvent cup Plugged airless tips: Worn or improperly adjusted Caution: At a minimum, lock the upper packings. trigger before working on a high pressure airless fluid tip. If Air bubbles in product discharge possible, remove the pressure to Siphon kit improperly installed. the gun. (not air tight) Be cautious when cleaning the tip orifice. Use only Material on one stroke only. recommended tools to clean a (fast up or down stroke) 4 Ball plugged tip. One of lower balls not properly seating. Runaway Pump

When the material supply “runs Air Motor Problems out”, the pump will cycle at maximum speed. Air leakage out of main exhaust A “runaway” detecting valve can Worn Insert be installed in the air line Replace Insert between the air motor and the Worn valve plate & pin assy regulator to prevent pump Replace plate & assy. damage. Check your pump Damaged piston assy. accessory catalog for runaway Replace piston assy. valve options.

Defective Spray Patterns

Airless: Replace or clean the tip

Air Assist Airless: Rotate the air cap 180 degrees. If the pattern changes, clean or replace the air cap. If the pattern did not change, clean or replace the fluid tip.

43 ABC’s of SPRAY FINISHING

Equipment & Techniques For Spray Finishing

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