ABC's of Spray Painting

ABC’s of Spray Painting $10.00 A-2928-A

ABC’s of Spray Painting Forward Table of Contents About this book….. Forward …..…………………..….2 While this book examines the spray finishing operation and its This book has been updated equipment from many viewpoints, several times from “The ABC’s of 1. Introduction ………………..3 there is still much more to be Spray Equipment,” originally learned to become truly proficient published by The DeVilbiss Surface Preparation………...3 at spray finishing. Company in 1954. It focuses on equipment and techniques for Paint Preparation……………3 spray finishing. The best way to become proficient at spray finishing is to 2. Air Atomizing Spray just do it! Many trade technical The format of the original book Guns………………………....4 and community colleges offer was question-and-answer. We Spray Gun Types ……….….4 courses in spray finishing, a great have retained that format in this way to improve your skills. edition. Part Identification and Function……………….……..6

Many of the “tricks” of the This book is organized around the Operation ……………..……..9 professional spray finisher involve major components of an air spray Maintenance ……….………11 paints and coatings. The system… spray guns, material manufacturers of these materials containers, hose, air control Troubleshooting …………...13 routinely publish complete books equipment, compressors, spray on these subjects. These booths, respirators and a short publications are available in section on general cleanliness and 3. Material Containers…...…16 specialty paint stores and will other sources of information. A provide you with considerable thorough understanding of the detail. Many of these books also material in this book - plus a lot of 4. Hose and Connections …18 contain information on techniques actual spray painting practice - for surface preparation. should enable you to handle just about any spray painting situation. 5. Air Control Equipment.….20

Another important source of information, particularly on Although we have made an effort 6. Respirators …….…….……22 equipment use and selection is to make this book as detailed and your local spray finishing as complete as possible, be aware equipment distributor. No book that the equipment and product 7. Air Compressors…….……23 could ever completely cover a systems used to illustrate points specialist’s in-depth knowledge of are entirely based on DeVilbiss equipment, techniques, technology. DeVilbiss is the 8. Spray Booths ……….…….25 maintenance and troubleshooting. world’s oldest and largest manufacturer of spray painting equipment, and has maintained Information is available from many this leadership since its founding resources on the subject of spray in 1888. finishing. It is our hope that this book will provide you with a start toward perfecting your finishing skills.

A recent addition to resources available to the spray finisher is the World Wide Web. Many manufactures are represented and question and answer forums are available. Please visit our websites . at www.devilbiss.com and www.binks.com.

2 1. Introduction Plastic parts may contain static you close, but for professional This book is about the selection, electricity from the molding results, use a viscosity cup. It is a use and maintenance of finishing process. This static attracts simple but very accurate way to equipment: spray guns, tanks, particles of dust and dirt. Eliminate measure the thickness of paint. cups, hoses, compressors, them by treating with “destatisiz- With the cup, you can thin or regulators, spray booths, ing” air using a special blow-off reduce the paint to the precise respirators, etc. It presumes that gun that imparts a neutral charge consistency required by the you are familiar with standard to the airflow. A chemical anti- manufacturer. surface preparation techniques static treatment is also available. that may be required before Always prepare paint in a clean, finishing actually begins. It also dust-free environment. Paint has a presumes a basic knowledge of remarkable ability to pick up dirt. Paint Preparation the many different types of paints Dirty paint will not only clog your and coatings available. Today’s finishes are extremely spray gun, but it will also ruin your complex chemical formulations. paint job. Get in the habit of Creating a perfect finish requires a They include both solvent and always pouring paint into the cup solid knowledge of surface waterborne types. Some may or tank through a paint strainer. preparation, finishes and spray require the addition of solvents to Paint is never as clean as it looks. painting equipment. The first two form the proper spraying viscosity. are extensively covered in many Others may simply require the other books. The manufacturers of addition of a second component at paints and coatings have gone to a prescribed ratio to obtain great length to publish information sprayable consistency. Many of on their new and existing them also have hardeners or other products. chemicals, added to them to But, even an extensive knowledge insure correct color match, gloss, of surface preparation techniques hardness, drying time or other and paint chemistry is not enough characteristics necessary to to assure a professional finish. produce a first class finish. Make The finish must be applied by a sure you are familiar with the spray gun, and all the variables of specific finish material data sheets its use must be mastered. accompanying each material. Do not mix materials from various The equipment necessary to apply manufacturers. Read and follow the finish Ð the spray gun, tank, directions carefully. cup, regulator, hoses, compressor, etc. Ð must all be All finish materials must also be matched to the job as well as to supplied with a Material Safety each other. That equipment must Data Sheet (MSDS). This data be used and maintained properly, provides information on proper with an appreciation of how and handling and disposal of why it works the way it does. materials. Many states require that MSDS be kept on file by the user. The moment of truth for any finish happens when the trigger is The first step is knowing the type pulled. This book focuses on that and color of paint the project moment. requires. With this determined, follow the manufacturer’s instruction for preparing it exactly. Surface Preparation If you have any doubts about how to proceed, don’t guess! Contact The surface to be finished should your paint supplier for help. be well cleaned before painting. If Improperly prepared paint will the paint manufacturer’s never produce a good finish! instructions call for it, the surface should be chemically treated. Use The chief characteristic that a blow-off gun and tack rag to determines the sprayablility of remove all dust and dirt. No paint and how much film may be amount of primer or paint will applied is its viscosity … or cover up a badly prepared consistency. Following the paint surface. manufacturer’s instructions will get 3 3 2. Air Atomizing Spray Guns Figure 4 shows a material con- Suction feed is easily identified by Introduction tainer some distance away from the fluid tip extending slightly be- The spray gun is the key its pressure feed gun. yond the face of the air cap, see component in a finishing system. It figure 2. The type of material feed system is a precision engineered and is also a way of classifying guns: manufactured instrument. Each type and size is specifically Suction Feed... draws material to designed to perform a certain, the gun by suction as in Figure 1. defined range of tasks. Gravity Feed... the material travels As in most other areas of finishing down, carried by its own weight work, having the right tool for the and gravity as in Figure 3. job goes a long way toward get- Pressure Feed... the material is ting professional results. fed by positive pressure as in Figure 2 - Suction Feed Air Cap This chapter will help you know Figure 4. which is the proper gun by review- Suction feed guns are suited to Guns may also be classified as ing the Conventional Air and High many color changes and to small either external or internal mix Volume/Low Pressure spray gun amounts of material, such as in depending upon the type of air designs commonly used in finish- automotive panel/bumper repairs cap. ing - suction feed, gravity feed and and "completes," touchup, or pressure feed. It will also review lower production operations. the different types of guns and 3. What is a suction feed gun? components within each design. A spray gun design in which a A thorough understanding of the 4. What is a gravity feed gun? stream of compressed air creates differences between systems will a vacuum at the air cap, providing This design uses gravity to flow allow you to select the right gun, a siphoning action. Atmospheric the material from the cup, which is to use it properly to produce a pressure on the material in the mounted above the gun, into the high quality finish and to con- suction cup forces it up the suction gun for spraying. No fluid pickup tribute toward a profitable finishing tube, into the gun and out the fluid tube is used, since the fluid outlet operation. tip, where it is atomized by the air is at the bottom of the cup. cap. The vent holes in the cup lid This cup has a vent hole at the top must be open. This type gun is SPRAY GUN TYPES of the cup that must remain open. usually limited to a one-quart, or It is limited to 34 ounce capacities 1. What is an air spray gun? smaller, capacity container and due to weight and balance. low to medium viscosity materials. An air spray gun is a tool which Gravity feed guns are ideal for uses compressed air to atomize small applications such as paint, or other sprayable material, automotive panel/bumper repairs and to apply it to a surface. and "completes," spot repair,or Air and material enter the gun for finishing in a limited space. through separate passages and They require less air than a suction are mixed at the air cap in a feed gun, and usually have less controlled pattern. overspray.

2. What are the types of air spray guns? Air spray guns may be classified in various ways. One way is by the location of the material container: Figure 1 shows a gun with a cup attached below it. Figure 1- Suction Feed Gun with Figure 3 shows a gun with a cup attached cup attached above it. Figure 3- Gravity Feed Gun with attached cup

4 2. Air Atomizing Spray Guns (Cont’d)

Type Viscosity Fluid Atomizing Type 8. What is HVLP? Feed (#2 Zahn) Oz/Minute Pressure Production A DeVilbiss Pro Tip: Suction up to 24 10-12 40-50 Low HVLP, or High-Volume/Low When using a gravity feed system, Gravity up to 24 10-12 30-50 Low Pressure, uses a high volume of 12-24 downsize the tip one size from suction. Pressure up to 29 50-60 High air (typically between 15-26 CFM) If the suction system calls for a .070”, delivered at low pressure (10 PSI use a .055” or .063” or less at the air cap) to atomize paint into a soft, low-velocity 6. What is an external mix air pattern of particles. 5. What is a pressure feed gun? cap? In many cases, less than 10 psi is In this design, the fluid tip is flush This gun mixes and atomizes air needed in order to atomize. with the face of the air cap (see and fluid outside the air cap. Proper setup utilizes no more fluid Figure 5). The material is It can be used for applying all and air pressure than is needed to pressurized in a separate cup, types of materials, and it is produce the required quality and a tank or pump. The pressure forces particularly desirable when flow rate that will meet production the material through the fluid tip spraying fast drying paints such as requirements. and to the air cap for atomization. basecoat and lacquer. It is also As a result, far less material is lost used when a high quality finish is in overspray, bounceback and desired. blowback than with conventional air spray. This is why HVLP delivers a dramatically higher transfer efficiency (the amount of paint that adheres to the substrate compared to the amount of paint sprayed) than spray systems using a higher atomizing pressure. The HVLP spray gun resembles a standard spray gun in shape and Figure 6 - External Mix Gun operation. Models that use high inlet pressure (35-80 psi) and convert to low pressure internally 7. What is an internal mix cap? within the spray gun are called This cap mixes air and material HVLP conversion guns. inside the air cap, before expelling Some HVLP models, particularly them. those using turbines to generate Figure 4 - Typical Pressure Feed Gun with remote pot It is normally used where low air air, bleed air continuously to pressures and volumes are minimize back- pressure against This system is normally used available, or where slow-drying the air flow of the turbine. when large quantities of material materials are being sprayed. are to be applied, when the The air cap design is similar to material is too heavy to be A typical example is spraying flat that of a standard spray gun, with siphoned from a container or wall paint, or outside house paint, a variety of air jets directing the when fast application is required. with a small compressor. atomizing air into the fluid stream, atomizing it as it leaves the tip. Production spraying in a Internal mix caps are rarely used manufacturing plant or fleet for finishing when a fast-drying HVLP is growing in popularity and refinishing operation is a typical material is being sprayed, or when new environmental regulations are use of a pressure feed system a high quality finish is required. requiring it for many applications. HVLP can be used with a wide variety of materials, including two-component paints, urethanes, acrylics, epoxies, enamels, lacquers, stains, primers, etc.

Figure 5 - Pressure Feed Air Cap Figure 7 - Internal Mix Air Cap 5 5 2. Air Atomizing Spray Guns (Cont’d) PART IDENTIFICATION There are various styles of caps to c) material feed system used FUNCTION produce different sizes and (pressure, suction or gravity) shapes of patterns for many 9. What are the principal parts d) size of fluid tip to be used applications. of a spray gun? (most air caps work best with certain fluid tip/needle Spreader Needle Adjustment Packing Valve combinations) 12. What are the advantages of the multiple jet cap? e) volume of air in cubic feet per Fluid Air Adjustment Cap minute (cfm) and pressure in Screw This cap design provides better pounds per square inch (psi) avail- atomization of more viscous Fluid able. Tip materials. Fluid Needle See the DeVilbiss spray gun It allows higher atomization catalog for proper selection of air Air pressures to be used on more Valve cap / fluid tip / needle viscous materials with less danger combinations and typical uses. of split spray pattern. It provides greater uniformity in Figure 8 - Spray Gun Anatomy pattern due to better equalization 14. What is the function of the of air volume and pressure from fluid tip and needle? the cap. 10. What happens when the They restrict and direct the flow of material from the gun into the air trigger is pulled? It also provides better atomization for materials that can be sprayed stream. The fluid tip includes an The trigger operates in two with lower pressures. internal seat for the tapered fluid stages. Initial trigger movement needle, which reduces the flow of opens the air valve, allowing air to material as it closes. (see Figure flow through the gun. 11). Further movement of the trigger The amount of material that pulls the fluid needle from its seat leaves the front of the gun at the fluid tip, allowing fluid depends upon the viscosity of the material to flow. When the trigger material, the material fluid is released, the fluid flow stops pressure and the size of the fluid before the air flow. tip opening provided when the needle is unseated from the tip. This lead/lag time in the trigger operation assures a full spray Figure 10 - Multiple Jet External Mix Fluid tips are available in a variety pattern when the fluid flow starts. Air Cap of sizes to properly handle It also assures a full pattern until materials of various types, flow the fluid flow stops, so there is no rates and viscosity. coarse atomization. 13. How should an air cap be selected? The following factors must be con- 11. What is the function of the air sidered: cap? a) type, viscosity and volume of The air cap (see figure 10) directs material to be sprayed compressed air into the fluid stream to atomize it and form the b) size and nature of object, or spray pattern. (see Figure 9) surface to be sprayed (multiple, or larger, orifices increase ability to Round Tapered Blunt atomize more material for faster painting of large objects). Fewer, or smaller orifices usually Figure 11 - The Fluid Tip and require less air, produce smaller Needle spray patterns and deliver less material. (These caps are designed for painting smaller objects and/or using slower speeds) Figure 9 - Types of Spray Patterns 6 2. Air Atomizing Spray Guns (Cont’d)

15. What is the nozzle combination? Rule of thumb Rule of thumb Optimum fluid pressure is 8-20 psi. The lower the viscosity of the In practice, the air cap, fluid tip, Pressures greater than this material, the smaller the I.D. of the needle and baffle are selected as generally indicate the need for a fluid tip. a unit, since they all work together larger fluid tip size. to produce the quality of the spray pattern and finish. These four items, as a unit, are referred to as Material Production Tip the nozzle combination. 17. How are fluid tip and needle Viscosity Rate Size sizes identified? #2 Zahn up to 23 sec Low 1.1 mm 16. What are standard fluid tip DeVilbiss fluid tips and needles are identified by the letters 23-28 sec Med 1.4 mm sizes and flow rates? stamped on the tip and the 28-48 sec High 1.8 mm The standard sizes, corresponding needle. over 48 sec High 2.2 mm fluid tip opening dimensions and The identification letters on these flow rates are: components should match. See NOTE: Viscosity conversion the appropriate DeVilbiss spray Plus Technology charts are available to convert one (High Efficiency) gun catalog for the proper viscosity cup reading to another Tip Size Max. Flow Rate selection of fluid tip and needle from any material or equipment Gravity Feed combinations. 1.2 mm/.047" 6 oz./min. supplier. 1.3 mm/.051" 7 oz./min. 1.4 mm/.055" 8 oz./min. 1.5 mm/.059" 9 oz./min. (2) The physical size of the object 1.6 mm/.062" 10 oz./min. to be painted must also be 1.8 mm/.070" heavy-bodied material 18. What fluid tip and needle combination sizes are most considered. As a general rule, use Suction Feed 1.6 mm/.062" 9 oz./min. common? the largest possible spray pattern 1.8 mm/.070" 12 oz./min. consistent with the object size. 1.0, 1.1, 1.4 and 1.8 are most Pressure Feed Remember that different air caps 1.0 mm/.039" 10 oz./min. generally used. The 1.4 and 1.6 deliver various pattern 1.4 mm/.055" 16 oz./min. or heavy-bodied material combination is used for gravity characteristics. This can reduce feed, while 1.6 and 1.8 are used both spraying time and the HVLP Technology for suction feed. For pressure feed number of gun passes. Tip Size Max. Flow Rate the most common tips are 1.1mm and 1.4mm. (3) The next consideration in Gravity Feed 1.2 mm/.047" 4 oz./min. evaluating nozzle combinations is 1.3 mm/.051" 5 oz./min. the speed with which the finish will 1.4 mm/.055" 6 oz./min. 1.5 mm/.059" 7 oz./min. 19. How are nozzle be applied and the desired level of 1.6 mm/.062" 8 oz./min. 1.8 mm/.070" heavy-bodied material combinations selected? quality. Suction Feed 1.8 mm/.070" 6 oz./min. Five basic considerations are in- For speed and coverage, choose 2.0 mm/.078" 7 oz./min. a nozzle combination which 2.2 mm/.086" 8 oz./min. volved in selecting the nozzle produces a pattern as wide as Pressure Feed combination: 1.1 mm/.042" 12 oz./min. possible. 1.4 mm/.055" 16 oz./min. type and viscosity of material or heavy-bodied material being sprayed When quality is the deciding Conventional Air Spray factor, choose a nozzle physical size of object being combination which produces fine Tip Size Max. Flow Rate finished/fan pattern size atomization and a smaller pattern Gravity Feed size, thereby giving greater 1.2 mm/.047" 6 oz./min. desired speed/finish quality 1.3 mm/.051" 7 oz./min. application control. 1.4 mm/.055" 8 oz./min. 1.5 mm/.059" 9 oz./min. gun model being used 1.6 mm/.062" 10 oz./min. (4) The model of the gun itself will 1.8 mm/.070" heavy-bodied material available air volume (cfm) and limit the selection of nozzle Suction Feed pressure (psi) from combination. 1.6 mm/.062" 9 oz./min. 1.8 mm/.070" 12 oz./min. compressor For a DeVilbiss suction feed gun,

Pressure Feed (1) The type and viscosity of the there are several nozzle types 1.1 mm/.042" 12 oz./min. available which are suitable for 1.4 mm/.055" 16 oz./min. material being sprayed is the or heavy-bodied material first factor to consider. finishing operations. These

7 7 2. Air Atomizing Spray Guns (Cont’d) nozzles have fluid tip openings atomize it properly causing a Viscosity conversion may be ranging from .062” to.086", and center-heavy pattern. accomplished by consulting a are designed to handle viscosities viscosity conversion chart. If the fluid tip opening is too large, up to 28 seconds in a No. 2 Zahn material discharge control will be Viscosity Cup. lost. 23. What is the spreader adjust- For a DeVilbiss pressure feed The fluid tip/air cap combination ment valve? gun, the amount of material must be matched to each other discharged depends upon material and to the job at hand. Spray gun A valve for controlling the air to viscosity, inside diameter of the catalogs include charts to help you the horn holes which regulate the fluid tip, length and size of hose, match them properly. spray pattern from maximum width and pressure on the material down to a narrow or round pattern container or pump. (see figure 8). If the fluid tip opening is too small, 21. Of what metals are fluid tips the paint stream velocity will be made? too high. If the fluid tip opening is 24. What is the fluid needle too large, you will lose control over Tips are made of the following adjustment? metals: the material discharging from the This adjustment controls the gun. a) 300-400 grade stainless steel distance the fluid needle is For most HVLP guns, the paint for both non-corrosive and allowed to retract from its seat in flow shouldn't exceed 16 oz. per corrosive materials the fluid tip, which allows more or less material through the fluid tip minute. For higher flow rates, b) Carboloy inserts for extremely (see figure 14). consult the DeVilbiss HVLP Spray abrasive materials Gun catalog. With pressure feed systems, the (5) Available air supply is the last fluid delivery rate should be factor to consider. 22. What is viscosity? adjusted by varying the fluid pressure at the pressure pot. Use The viscosity of a liquid is its body, Pressure feed air caps consume the fluid adjustment knob for minor or thickness, and it is a measure between 7.0 and 25.0 CFM, and/or temporary flow control. of its internal resistance to flow. depending on design. If your air This will extend the life of the fluid Viscosity varies with the type and supply is limited, because of an needle and tip. undersize compressor, or many temperature of the liquid. Any other air tools are in use at once, reference to a specific viscosity measurement must be the gun will be starved for air, 25. What are the components of accompanied by a corresponding producing incomplete atomization suction and gravity feed temperature specification. and a poor finish. systems? The most common measurement used to determine viscosity in Typical suction and gravity feed 20. What are the criteria for finishing is flow rate (measured in systems consist of: a suction feed selecting a pressure feed seconds from a Zahn, Ford, Fisher or gravity feed spray gun with cup, nozzle? or other viscosity cup). an air compressor (not shown), a combination filter/air regulator and While the fluid discharge in Different viscosity cup sizes are air hoses (see figure 12). ounces per minute from a suction available. Each cup has a hole at feed gun is relatively stable the bottom, specified to an exact (largely because it is determined size. Use a viscosity cup that is by atmospheric pressure), the fluid designed to handle the time range discharge from a pressure feed of the materials in use. Viscosity gun depends more upon the size control is an extremely important of the inside diameter of the fluid and effective method to maintain tip and the pressure on the paint application efficiency and quality container or pump. The larger the consistency. Always measure opening, the more fluid is viscosity after each batch of discharged at a given pressure. material is mixed and make sure material temperature is the same, If the fluid tip ID is too small for the normally 70û to 80û F. amount of material flowing from the gun, the discharge velocity will Viscosity recommendations may be too high. The air, coming from be given in poise and centipoise the air cap, will not be able to (1 poise=100 centipoise). 8 2. Air Atomizing Spray Guns (Cont’d) that must be corrected. Refer to particle size- specks and/or large the Troubleshooting Section for globs - the paint is not atomizing examples of faulty patterns to help properly (see figure 15). diagnose your problem. (4) If the paint is not atomizing properly, increase the air pressure slightly and make another test pass. Continue this sequence until the paint particle size is relatively uniform.

Figure 12 - Suction Feed and Gravity Feed System Components Uneven distribution

OPERATION 26. How is suction and gravity feed equipment hooked up for Figure 13 - Horizontal Test Pattern operation? (2) If the pattern produced by the Connect the air supply from the above test appears normal, rotate compressor outlet to the filter/air the air cap back to a normal regulator inlet. spraying position and begin spray- Connect the air supply hose from ing. (Example - a normal pattern Even Distribution the air regulator outlet to the air with a conventional or #2000 HVLP inlet on the spray gun. air cap will be about 10-11" long Figure 15- Test Patterns when the gun is held 8" from the After the material has been re- (5) If the pattern seems starved for duced to proper consistency, thor- surface). material, and the fluid adjustment oughly mixed and strained into the screw allows full needle travel, the cup, attach the gun to the cup fluid tip may be too small or the (suction feed) or pour material into material may be too heavy. attached cup (gravity feed). Recheck the viscosity or increase the size of the fluid tip and needle (6) If the material is spraying too 27. How are suction and gravity heavily and sagging, reduce the feed systems initially adjusted material flow by turning in the fluid for spraying? adjusting screw (clockwise). Figure 14 Ð Fluid Adjustment (1) Spray a horizontal test pattern Remember, proper setup utilizes Screw (air cap horns in a vertical no more fluid and air pressure position). Hold the trigger open than is needed to produce the until the paint begins to run. There (3) With the fluid adjusting screw required quality and a flow rate should be relatively even open to the first thread,(see figure that will meet production distribution of the paint across the 14) and the air pressure set at requirements. full width of the pattern. (see approximately 30 psi, or for HVLP Figure 13). Adjust the pattern 10 psi at the air cap. Make a test width with the spreader pass (move the spray gun 3 times adjustment valve. If distribution is the normal speed) with the gun on not even, there is a problem with some clean paper, cardboard or either the air cap or the fluid tip wood. If there are varations in 9 9 2. Air Atomizing Spray Guns (Cont’d) 28. What are the components of Open spreader adjustment valve a pressure feed system? for maximum pattern size(see figure 8). A pressure feed system consists of: a pressure feed spray gun, a Open fluid adjustment screw until pressure feed tank, cup or pump, the first thread is visible (see an air filter/regulator, appropriate figure 14). air and fluid hoses, and an air compressor (see figure 16). 31. How is the pressure feed gun balanced for spraying?

1) Using control knob on fluid Figure 17 Ð Air Cap Test Kit regulator, set fluid pressure at 5 to 10 psi. After establishing the operating 2) Using control knob on air regulator, pressures required for production set air atomization pressure at 25-50 and finish quality, develop a psi or for HVLP 10 psi at the air cap. Pressure Standardization program for your finish room to follow. 3) Spray a test pattern (fast pass) on a piece of paper, cardboard, or wood. From that test pattern, 32. What is a Pressure determine if the particle size is Standardization Program? small enough and relatively After establishing air and fluid uniform throughout the pattern to pressures that meet required qual- achieve the required finish quality ity and production, record the data (see figure 15). If particle size is to be used for that application for too large or is giving too much future reference. (see figure 18) texture in the finish, turn the atomization pressure up in 3 to 5 Booth #: ______psi increments until particle size and texture of finish is acceptable. Material Sprayed ______4) Spray a part with these Application ______settings. If you are not able to keep up with the production rate Viscosity ______required or if the finish is starved Fluid Temperature ______Figure 16 - Pressure Feed System for material, increase the fluid Components pressure with the fluid regulator Spray Gun ______control knob in 2 to 4 psi Air Cap ______Fluid Tip ___ increments until required wet 29. How is equipment hooked coverage is accomplished. Note: Air Pressure ______up for pressure feed spraying? A larger capacity fluid tip may be Fluid Pressure ______required. Connect the air hose from the air regulator to the air inlet on the 5) Remember, as you turn up the gun. fluid pressure the particle size will Figure 18 Ð Pressure Standardization increase. Once the coverage Chart Connect the mainline air hose to required is obtained, it will be the air inlet on the tank. necessary to re-adjust the CAUTION: Do not exceed the atomization pressure in 3 to 5 psi 33. How should the spray gun container's maximum working increments as explained in step 3 be held? pressure. to insure required particle size and It should be held so the pattern is Connect the fluid hose from the finish texture is achieved. perpendicular to the surface at all fluid outlet on the tank to the fluid times. inlet on the gun. 6) If using HVLP, using an “Air Cap Test Kit” verify that the air Keep the gun tip 8-10 inches (air cap pressure is not above 10 psi, if spray guns) or 6-8 inches (HVLP 30. How is the pressure feed required by a regulatory agency guns) from the surface being gun adjusted for spraying? (see figure 17). sprayed.

10 2. Air Atomizing Spray Guns (Cont’d) 34. What is the proper technique to produce a better, technique for spray gun stroke more uniform, finish. and triggering? After the edges, flanges and cor- The stroke is made with a free ners have been sprayed, the flat, arm motion, keeping the gun at a or nearly flat, surfaces should be right angle to the surface at all sprayed. points of the stroke. Remember to overlap the previ- Triggering should begin just ously sprayed areas by 50% to before the edge of the surface to avoid streaking. be sprayed. The trigger should be When painting very narrow sur- held fully depressed, and the gun faces, you can switch to a smaller moved in one continuous motion, gun, or cap with a smaller spray until the other edge of the object is pattern, to avoid readjusting the reached. The trigger is then full size gun. The smaller guns are released, shutting off the fluid usually easier to handle in restrict- flow, but the motion is continued ed areas. for a few inches until it is reversed for the return stroke. A full size gun could be used, however, by reducing the air pres- When the edge of the sprayed sure and fluid delivery and trigger- object is reached on the return ing properly. stroke, the trigger is again fully depressed and the motion continued across the object. MAINTENANCE Lap each stroke 50% over the 37. How should the air cap be preceding one. Less than 50% cleaned? overlap will result in streaks on the finished surface. Move the gun at Remove the air cap from the gun a constant speed while the trigger Figure 19 - Spray Techniques and immerse it in clean solvent. If is pulled, since the material flows necessary, use a bristle brush to at a constant rate. clean dried paint. Blow it dry with compressed air. Another technique of triggering is 36. What is the proper spraying referred to as "feathering." sequence and technique for If the small holes become Feathering allows the operator to finishing applications? clogged, soak the cap in clean limit fluid flow by applying only Difficult areas, such as corners solvent. If reaming the holes is partial trigger travel. and edges, should be sprayed necessary, use a toothpick, a first. Aim directly at the area so broom straw, or the specially that half of the spray covers each designed cleaning needle and handle from a Professional Spray 35. What happens when the gun side of the edge or corner. is arced? Gun Cleaning Kit. Hold the gun an inch or two closer Arcing the stroke results in uneven than normal, or screw the Cleaning holes with a wire, a nail application and excessive over- spreader adjustment control in a or a similiar hard object could spray at each end of the stroke. few turns. Needle travel should be permanently damage the cap by When the tip is arced at an angle only partial by utilizing the "feath- enlarging the jets, resulting in a of 45 degrees from the surface ering" technique. Either technique defective spray pattern. (see figure 19), approximately will reduce the pattern size. 65% of the sprayed material is lost. If the gun is just held closer, the stroke will have to be faster to compensate for a normal amount of material being applied to smaller areas. When spraying a curved surface, keep the gun at a right angle to that surface at all times. Follow Figure 20 - Cleaning the Air Cap the curve. While not always physi- cally possible, this is the ideal 11 11 2. Air Atomizing Spray Guns (Cont’d) 38. How should guns be The solvent is contained, and Clean the container and add clean cleaned? must be disposed of properly. solvent. Atomization air should be turned off during this procedure. Some states' codes require the A suction or pressure feed gun Pressurize the system and run the use of a gun cleaner, and it is un- with attached cup should be solvent through until clean. (Be lawful to discharge solvent into the cleaned as follows: sure to comply with local codes atmosphere. Turn off the air to the gun, loosen regarding solvent dispersion and the cup cover and remove the fluid After cleaning a spray gun in a disposal.) gun cleaner, be sure to lubricate tube from the paint. Holding the Clean the air cap, fluid tip and as indicated in Figure 22. tube over the cup, pull the trigger tank. Reassemble for future use. to allow the paint to drain back into the cup. Empty the cup and wash it with 39. What parts of the gun clean solvent and a clean cloth. require lubrication? (Figure 22) Fill it halfway with clean solvent The fluid needle packing A, the air and spray it through the gun to B flush out the fluid passages by valve packing and the trigger directing stream into an approved, bearing screw C require daily closed container. All containers lubrication with a non-silicone/non- used to transfer flammable petroleum gun lube. materials should be grounded. (Be The fluid needle spring D should sure to comply with local codes be coated lightly with petroleum regarding solvent disposal). jelly or a non-silicone grease (ie. Then, remove the air cap, clean it Lithium). as previously explained. Clean Lubricate each of these points outside of fluid tip and baffle area, after every cleaning in a gun and replace air cap on the gun. washer! Wipe off the gun with a solvent soaked rag, or if necessary, brush C A the air cap and gun with a fiber brush using clean-up liquid or thinner. To clean a pressure feed gun with Figure 21 - Using a Hose Cleaner remote cup or tank, turn off air supply to cup or tank. Release Use a hose cleaner to clean material pressure from the system internal passages of spray guns by opening relief valve. and fluid hose. This device D incorporates a highly efficient fluid Material in hoses may be blown header, which meters a precise back. The lid must be loose and solvent/air mixture. The cleaner B fluid pressure off. Keep gun higher operates with compressed air and than container, loosen air cap and sends a finely - atomized blast of trigger gun until atomizing air solvent through the fluid passages forces all material back into the of the hose, the spray gun, etc. pressure vessel. This simple, easy to use cleaner A gun cleaner may be used for speeds up equipment cleaning Figure 22 - Lubrication Points either type of gun. This is an en- and saves solvent. Savings may closed box-like structure (vented) be as much as 80%. It also with an array of cleaning nozzles reduces VOC emissions. (Be sure inside. that both the hose cleaner and Guns and cups are placed over gun are properly grounded.) the nozzles, the lid is closed, the valve is energized, and the Where local codes prohibit the use pneumatically controlled solvent of a hose cleaner, manually sprays through the nozzles to backflush the hose into the cup or clean the equipment. tank with solvent until clean and dry with compressed air.

12 2. Air Atomizing Spray Guns (Cont’d) 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. Clean 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. Dry packing 1. Lubricate front of pressure feed gun 2. Packing nut too tight 2. Adjust 3. Fluid tip or needle worn or 3. Replace tip and needle with damaged lapped set 4. Foreign matter in tip 4. Clean 5. Fluid needle spring broken 5. Replace 6. Wrong size needle or tip 6. Replace

All Feed Systems Jerky, fluttering spray 1. Loose or damaged fluid 1. Tighten or replace tip/seat 2. Dry packing or loose fluid 2. Lubricate packing or tighten needle packing nut packing nut 3. Material level too low 3. Refill 4. Container tipped too far 4. Hold more upright 5. Obstruction in fluid passage 5. Backflush with solvent 6. Loose or broken fluid tube or 6. Tighten or replace fluid inlet nipple

Suction Feed Only 7. Material too heavy 7. Thin or reduce 8. Air vent clogged 8. Clear vent passage 9. Loose, damaged or dirty lid 9. Tighten, replace or clean coupling nut 10. Fluid tube resting on cup 10. Tighten or shorten bottom 11. Damaged gasket behind fluid 11. Replace gasket tip

13 13 2. Air Atomizing Spray Guns (Cont’d) Problem Cause Correction Top or bottom-heavy spray 1. Horn holes plugged 1. Clean, ream with a toothpick, broom pattern* straw or the specially designed 2. Obstruction on top or bottom cleaning needle and handle from a of fluid tip Professional Spray Gun Cleaning Kit 3. Cap and/or tip seat dirty 2. Clean

3. Clean

Right or left-heavy spray 1. Horn holes plugged 1. Clean, ream with a toothpick, broom pattern* 2. Dirt on left or right side of fluid straw or the specially designed tip cleaning needle and handle from a Professional Spray Gun Cleaning Kit 2. Clean

*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.

1. Fluid pressure too high for 1. Balance air and fluid pressure Center-heavy spray pattern atomization air (pressure feed) Increase 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

1. Fluid adjusting knob turned in Split spray pattern too far 1. Back out counter-clockwise to 2. Atomization air pressure too increase flow high 2. Reduce at regulator 3. Fluid pressure too low (pressure feed) 3. Increase fluid pressure 4. Fluid tip too small 4. Change to larger tip

14 2. Air Atomizing Spray Guns (Cont’d) 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 (suction 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 3. Gun too far from surface and select correct 4. Gun motion too fast temperature solvent 3. Adjust to proper distance 1. Too much atomization air 4. Slow down Excessive overspray pressure 2. Gun too far from surface 1. Reduce pressure 3. Improper technique (arcing, gun speed too fast) 2. Use proper gun distance 3. Use moderate pace, keeping gun parallel to work surface 1. Too much, or too fast-drying Excessive fog solvent 2. Too much atomization air 1. Remix with correct pressure temperature solvent 2. Reduce pressure

1. Pressure feed cap/tip used Will not spray with suction feed 2. No pressure at gun 1. Use suction feed cap/tip 3. Fluid needle not retracting 4. Fluid too heavy (suction feed) 2. Check air lines 3. Open fluid adjusting screw 4. Lower fluid viscosity or change to pressure feed

15 15 3. Material Containers

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

16 16 3. Material Containers (Cont’d) the material mixed and in atomization air pressure to the 12. What materials are used to suspension. spray gun. construct pressure feed tanks? The smaller, non-code, light-duty tanks are made of plated steel and 8. When is an agitator used in a have lower inlet pressure pressure feed tank? restrictions. When the material being used has The heavy-duty, ASME-code filler or pigment that must be kept tanks are made of galvanized or in motion to keep its particles in 300 series stainless steel. They proper suspension. An agitator also have plated or stainless steel can be hand, air or electrically lids with forged steel clamps. driven. When abrasive or corrosive materials are being sprayed, the 9. What is a single regulated tank shell is coated or lined with a tank? special material, or a polyethylene tank liner is used. This is a pressure feed tank with one air regulator controlling only the pressure on the material in the 13. What are tank liners? tank (see figure 4). They are inserts that are placed inside the tank to hold the material, keeping it from direct contact with the tank walls. They are made of disposable polyethylene. Using liners reduces tank cleaning time and makes color changeover Figure 5 - Double Regulated Tank and cleanup easier.

11. What are code and non-code pressure tanks? Code tanks are manufactured to rigid standards as specified by the American Society of Mechanical Engineers. (ASME) Each step of manufacture is closely controlled, and welding of the shell is certified. Code tanks are designed to withstand pressures up to 110 psi. Non-code tanks are normally Figure 4 - Single Regulated Tank restricted to 3 gallons in size or less. Due to the type of construction, non-code tanks are 10. What is a double regulated rated at 80 psi or less. tank? Note: This is a pressure feed tank The A.S.M.E. code, as it relates to pressure vessels attached to spray gun nozzles, is primarily concerned equipped with two air regulators with the use of flammable materials and also covers (see figure 5). applications where a tank is used in an OSHA-regulated environment. To comply with OSHA regulations, if you One provides regulation for the air are using a flammable material at greater than 15 PSI and your local fire department has adopted NFPA 33, pressure on the material in the you must use an A.S.M.E. code tank. Refer to NFPA tank (thereby controlling fluid 33, standard for spray application using flammable or flow). The other controls combustible materials. 17 17 4. Hoses & Connections The tube is the interior flexible 5. What sizes of air hose are Introduction artery that carries air or fluid recommended? The various types of hose used to material from one end of the hose 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" I.D. 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 fittings in use, provide guidance in Type Length Size rating, flexibility, kink and stretch selecting the proper types for the resistance and coupling retention. 0' - 10' 1/4" ID job and cover the maintenance of hose. The cover is the outer skin of the General 10' - 25' 5/16" ID hose. It protects the reinforcement from contact with oils, moisture, Purpose 25' - 50' 3/8" ID 1. What types of hose are used solvents and abrasive objects. 50' - 100' 1/2" ID in spray painting? The cover protects the reinforcement, but does not 0' to 25' 5/16" ID There are two types: air hose - contribute to hose performance. used to transfer compressed air HVLP 25' - 50' 3/8" ID from the air source to the gun, and 50' - 100' 1/2" ID fluid hose - used only in pressure DeVilbiss hose is color-coded: feed systems to transfer the Figure 3 - Recommended air material from its container to the RED or TAN..... air and water hose sizes spray gun. (NOTE: Do not use air hose for GREY...... air w/static ground solvent-based materials.) 6. What is pressure drop? BLACK ...... low pressure fluid This is the loss of air pressure due to friction (caused by air flow) 3. What type of tube is used in between the source of the air and fluid hose? the point of use. As the air travels Since the solvents in coatings through the hose or pipe, it rubs would readily attack and destroy against the walls. It loses energy, ordinary rubber compounds, fluid pressure and volume as it goes. hose is lined with special solvent-resistant nylon material that is impervious to common 7. How can this pressure drop solvents. be determined? At low pressure, with short lengths of hose, pressure drop is not 4. What sizes of fluid hose are particularly significant. As recommended? pressure increases, and hose is Type Length Size lengthened, the pressure rapidly drops and must be adjusted. General 0' - 25' 1/4" ID All air hose is subject to pressure Purpose 25' - 50' 3/8" ID loss or drop. For example, 1/4" pressure drop is 1 psi per foot and Figure 1 - Basic Hose 50' - 100' 1/2" ID 5/16" is 1/2 psi per foot. This Construction pressure loss may result in poor Figure 2 - Recommended fluid atomization. hose sizes 2. How is hose constructed? Too often, a tool is blamed for malfunctioning, when the real DeVilbiss hose is a performance cause is an inadequate supply of designed combination of three compressed air due to an components: Tube A, undersized I.D. hose. Reinforcement B and Cover C. 18 18 4. Hoses & Connections (Cont’d) Care should be taken when For optimum spray gun results, 11. What is a threaded- type selecting a quick-disconnect air the following is recommended: up connection? connection. Due to design, most to 25 ft - 5/16" I.D., over 25 ft - Q.D. connections result in 3/8" I.D. This is a common swivel-fitting significant pressure drop. This can type that is tightened with a adversely affect spray guns with wrench.(see figure 4). higher consumption air caps such 8. How are hoses maintained? as HVLP. Hoses will last a long time if they are properly maintained. Be careful when dragging hose across the floor. It should never be pulled around sharp objects, run over by vehicles, kinked or 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 is a quick-disconnect type connection?

9. What types of hose fittings are This is a spring-loaded, male/ available? female connection system that readily attaches and detaches by Permanent, crimp type or reusable hand. No tools are required (see fittings are used to connect hoses figure 5). to air sources or to spray equipment.

10. What types 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 (high flow) to deliver proper pressure for atomization. Because of normal pressure drop in these devices, most are not recommended for use with HVLP.

Figure 5 - Quick-Disconnect Type Connection 19 19 5. Air Control Equipment 3. What are the types of air Regulators are used in lines Introduction control equipment? already equipped with an air The control of volume, pressure filtration device. Air control equipment comes in a and cleanliness of the air entering wide variety of types, but it Air regulators are available in a a spray gun are of critical basically all performs one or more wide range of cfm and psi importance to the performance of of the following functions; air capacities, with and without the system. filtering/cleaning, air pressure pressure gauges and in different Following some key installation regulation/indication and air degrees of sensitivity and principles will help decrease the distribution through multiple accuracy. risk of contaminants. For example, outlets. They have main line air inlets and it’s important to use the right size regulated or non-regulated air air compressor for your outlets. application. An overworked air 4. How does an air filter work? compressor can produce a significant amount of dirt and oil. It filters out water, oil, dust and dirt 6. How is an air filter/regulator Additionally, proper piping is very before they get on your paint job. installed? important to help prevent Air entering the filter is swirled to remove moisture that collects in condensation from forming within Bolt the air filter/regulator A the baffled quiet zone. the line and contaminating the air securely to the spray booth wall supply. Smaller impurities are filtered out near the operator. (see Figure 2) by a filter. Accumulated liquid is This chapter examines the various This location makes it convenient carried away through either a types of equipment available to to read the gauges and operate manual or automatic drain. 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 leg point of use that modifies the should be installed at the end of nature of the air. each branch, to drain moisture from the main air line.

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

20 20 5. Air Control Equipment (Cont’d) *Piping should be as direct as Check the following: possible. If a large number of a) Drain air filter, air compressor fittings are used, larger I.D. pipe tank, and air line of accumulated should be installed to help moisture. overcome excessive pressure drop. b) Be sure the air 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 compressor tank 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 Ð Air/Filter Regulator Installation 7. How often should the 9. What causes excessive pres- filter/regulator be drained of sure drop on the main line accumulated moisture and dirt? gauge of the filter/regulator? It depends largely on the level of a) The compressor is too small system use, the type of filtration in to deliver the required air the air system, and the amount of volume and pressure for all humidity in the air. tools in use. For average use, once-a-day b) The compressor is not drainage is probably sufficient. functioning properly. For heavily-used systems, or in c) There is leakage in the air line high humidity, drainage should or fittings. occur several times daily. d) Valves are partially opened. Some units drain automatically e) The air line, or piping system, when moisture reaches a is too small for the volume of predetermined level. air required. Refer to Table 1, Page 20.

8. What steps should be taken if moisture passes through the filter/regulator? Since moisture in the spray gun atomization air will ruin a paint job, it must be removed from the air supply. When the compressed air temperature is above its dew point temperature, oil and water vapor will not condense out into solid particles.

21 21 6. Respirators 4. What is an air-supplied air before it passes through the Introduction respirator? chemical cartridge. Consult with appropriate safety This type is available in both mask The organic vapor respirator is personnel or “Industrial Hygienist” and visor/hood styles. Both normally used in finishing opera- if in doubt as to the suitability of a provide the necessary respiratory tions with standard materials (not particular respirator before using protection when using materials suited for paints containing it. Respirators may not provide that are not suitable for organic isocyanates). protection against eye and skin vapor respirators. absorption of chemicals. The visor/hood style provides a Spray finishing creates a certain greater degree of coverage to the amount of overspray, hazardous head and neck of the operator. vapors and toxic fumes. This is true, even under ideal conditions. Both styles require a positive supply of clean, breathable air as Anyone near a spray finishing defined by OSHA (Grade D). operation should use some type of respirator, or breathing apparatus. Figure 3 - Organic Vapor This chapter covers various types Respirator of equipment for this use. 6. What is a dust respirator and where is it used? 1. What is a respirator? Dust respirators are sometimes A respirator is a mask that is worn used in spray finishing but, in most over the mouth and nose to applications, they are prevent the inhalation of overspray unsatisfactory. (see Figure 4) fumes and vapor. Figure 1 Ð Positive Pressure 2. Why is a respirator Visor/Hood necessary? For two reasons: First...some type of respiratory protection is required by OSHA/ Figure 4 - Dust Respirator NIOSH regulations. These respirators are equipped Second...even if it wasn't a with cartridges that remove only requirement, common sense tells solid particles from the air. They you that inhaling overspray is not have no ability to remove vapors. healthy. They are effective, however, in Overspray contains toxic particles preliminary operations such as of paint pigments, harmful dust sanding, grinding and buffing. and, in some cases, vapor fumes which can be harmful to your NOTE: health. Figure 2 Ð Positive Pressure Before using any respirator, Depending on design, a respirator Mask Respirator carefully read the manufacturer’s can remove some, or all, of these 5. What is an organic vapor Safety Precautions, Warnings and dangerous elements from the air respirator and where is it used? Instructions. Many respirators are around a spray finishing operator. not suitable for use with This type of respirator, which isocyanates, asbestos, ammonia, covers the nose and mouth, (see pesticides, etc. 3. What types of respirators are Figure 3) is equipped with used by spray finishing replaceable cartridges that operators? remove organic vapors by chemical absorption. There are three primary types; the air-supplied respirator, the organic Some are designed with pre-filters vapor respirator and the dust to remove solid particles from the respirator. 22 22 7. Air Compressors piston type compressor is the 5. What is a single 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 which is elevated to higher 3. How does a piston-type which air is drawn from the pressures and delivered in compressor work? atmosphere and compressed to its sufficient volume. The air This design elevates air pressure final pressure with a single stroke. compressor compresses air for through the action of a use in this equipment and is a reciprocating piston. As the piston All pistons are the same size, and major component of a spray moves down, air is drawn in they can produce up to 125 psi. painting system. This chapter will through an intake valve. As the examine the various types piston travels upward, that air is available. compressed. Then, the 6. Where are single stage Compressed air is measured on now-compressed air is discharged compressors used? the basis of volume supplied per through an exhaust valve into the The application of this compressor unit of time (cubic feet per minute, air tank or regulator. is usually limited to a maximum or cfm) at a given pressure per Piston type compressors are pressure of 125 psi. It can be used square inch (psi), referred to as available with single or multiple above 125 psi, but above this delivery. cylinders in one or two-stage pressure, two stage compressors Displacement is the output of air models, depending on the volume are more efficient. by a compressor at zero pressure, and pressure required. or free air delivery. 7. What is a two-stage compressor? 1. What is an air compressor? A compressor with two or more An air compressor is a machine cylinders of unequal size in which designed to raise the pressure of air is compressed in two separate air from normal atmospheric steps. 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 200 psi. From there, the intermediate 4. How does a rotary screw pressurized air enters the smaller When selecting a compressor: compressor work? cylinder, is compressed even more and is delivered to a storage Rule of thumb Rotary screw compressors utilize tank or to the main air line. The cubic feet per minute two intermeshing helical rotors in delivered by an electrically a twin bore case. Air is Two-stage compressors can powered 2 stage industrial air compressed between one convex deliver air to over 175 psi. compressor is 4 times the motor's and one concave rotor. Trapped They are normally found in horse power rating. (CFM=4xHP) volume of air is decreased and the operations requiring compressed pressure is increased. 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 at relatively high pressures, the Figure 2 Ð Rotary Screw Air Compressor 23 23 7. Air Compressors (cont’d) 9. Is there anything else to know, about air compressors? Because this book mainly focuses on spray guns, it provides only basic coverage of air compressors and how they operate. There is much more to know: How to select the proper equipment in terms of size, delivery, etc. Compressors may be portable or stationary and there are different models to meet a variety of needs.

24 24 8. Spray Booths

Introduction 3. What types of spray booths are there? Containing the overspray and keeping it out of the air and off There are two; the dry filter type other objects is an important and the waterwash type. consideration in a spray finishing operation. This chapter discusses various types of booths and 4. What is a dry filter type spray details periodic maintenance. booth? This booth draws overspray- 1. What is a spray booth? contaminated air through replaceable filters and vents the A compartment, room or filtered air to the outside. enclosure of fireproof construction; built to confine and exhaust It is the most common type of overspray and fumes from the booth for most industrial and operator and finishing system. automotive applications. Figure 2 - Waterwash Industrial Type Spray Booth There are various models It is used for spraying low-volume, available, designed for particular slower-drying materials, and is not spray applications. Spray booths affected by color changes. may be partially enclosed (figures 1 & 2) or totally enclosed (figure 3). Consult the National Fire Protection Association (NFPA) pamphlet #33 and the O.S.H.A. requirements for construction specifications. Figure 3 Ð Automotive Downdraft Dry Filter Booth

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

25 25 8. Spray Booths (Cont’d)

stage filters, designed for spray booth use. Single-stage furnace filters will not do the job. (b) Monitor the manometer reading daily, and know what a normal reading should be. (c) Keep the booth free of dirt and overspray. Floors and walls Figure 5 - Manometer should be wiped down after every job. Pick up scrap, 10. What does an air newspapers, rags, etc. replacement unit do? (d) Coat the inside of the booth The volume of air exhausted from with a strippable, spray-on Figure 4 Ð Exhaust fan a spray booth is often equal to covering. When the overspray 7. What is air velocity? three or more complete air on it becomes too thick, strip changes per hour. and recoat. Air velocity in a finishing operation is the term used to describe the Under such conditions, the (e) Periodically check the lighting speed of air moving through the temperature may become irregular inside the booth, and replace empty spray booth. and uncomfortable. Excessive weak or burned out bulbs. dust may become a problem. Improper lighting can cause the To prevent these conditions, operator to apply a poor finish. 8. What effect does air velocity sufficient "make-up" air must be have on spray booth efficiency? introduced to compensate for the exhausted air. 12. What routine maintenance Air must move through the booth does a waterwash type booth with sufficient velocity to carry The air replacement unit require? away overspray. automatically supplies this (a) Compounding of the water in Too low a velocity causes poor, "makeup" air - both filtered and this type unit is essential. even potentially dangerous heated - to eliminate the problems Employ only booth treatment working conditions, especially of air deficiency and airborne chemicals in accordance with when the material contains toxic contaminants. suppliers' recommendations. elements. It also increases The ph of the water should be maintenance costs. between 8 and 9. Too high a velocity wastes power (b) Maintain the water level at the and the energy required to heat proper setting per make-up air. manufacturers' specifications. (c) Check the tank for paint 9. What is a manometer? buildup on the bottom, check the pump strainer to keep it It is a draft gauge that indicates clean and clear, check the air when paint arrestor filters or intake washer chamber and the filters are overloaded. (see figure nozzles in the header pipe. If 5) Figure 6 - Air Replacement Unit the nozzles are plugged, the Some states and local codes overspray will encroach on the require a manometer gauge on wash baffle section, fan and 11. What routine maintenance each bank of filters to comply with stack. OSHA regulations. does a dry type spray booth require? (d) Periodically check the float valve for proper operation. (a) The continuous flow of air Flood the sheet to be sure through the booth eventually there is a uniform flow over loads the filters with dirt and the entire surface. overspray. Periodically, inspect and replace them with multi- 26 26 8. Spray Booths (Cont’d)

(e) Keep the booth interior and exhaust stack free from overspray and dirt accumulation.

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.

27 27 NOTES

28 NOTES

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