Surface Preparation & Safety

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SURFACE PREPARATION & SAFETY

+ Surface Preparation & Safety

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Contents

v Introduction 1 Safety Monitoring and Remote Control Systems

3 OSHA’s Proposed Rule for Silica Hits the Streets By Alison B. Kaelin, CQA, ABKaelin, LLC

5 Shipyard Regulatory Update By Alison B. Kaelin, CQA, ABKaelin, LLC

10 On the Time Between Blasting and Priming 11 Safety Considerations for Abrasive Blasting Operations 15 Setting Up Air Blasting Equipment 19 Surface Preparation: Adventures in Frustration By Peter Bock, CorrLine International

Introduction

This eBook features articles from the Journal of Protective Coatings & Linings (JPCL) about surface preparation and safety. All information about the articles is based on the original dates of publication of these materials in JPCL. Please visit www.paintsquare.com for more articles on these and other topics.

Safety Monitoring and Remote Control Systems for Blasting in Shipyards

last cleaning is a critical process to remove mill scale, The Safety System Features slag, and pre-existing coatings on steel surfaces and to The complete safety system is composed of three sub-sys- prepare substrates for the subsequent application of a tems: the monitoring system for checking the blast worker’s protective coating. Dry abrasive blast cleaning is known safety, the remote control system of the blasting nozzle(s), Bto provide the best surface roughness for an ordinary and the special bone conduction ear-set system for voice organic or inorganic coating, although it is considered a very communications among workers and managers. Addition- dangerous process. ally, the safety system has a function to analyze the actual In shipyards, dry abrasive blast cleaning is especially dan- result of a blast cleaning job. gerous. Modern shipbuilding practice is to construct vessels as a series of “blocks,” coat these, and then join up to finish the build. Workers must contend with a very poor environ- In shipyards, dry ment because of a mist of paint debris, spent abrasive particles, noise, and the danger from blasting media traveling at abrasive blasting a high speed. Also, their work can involve moving through is especially dangerous. narrow access holes (600 mm x 800 mm hole) in the steel blocks. Moreover, blasters work alone for a long time. There The Safety Monitoring System is virtually no visibility inside these steel blocks during blast- The safety monitoring system features emergency call sig- ing, so developing a safety system for blast cleaning workers naling, sensing vibration data, and checking location data for is more essential than for many other types of projects. blast cleaning workers in the blasting cell. Basing a remote workers’ safety and contact system on When the worker with a 2.45GHz RFID active tag is work- wireless technology is more difficult to develop than such ing in the blasting cell, the safety system works as follows: a system for other work areas because of the possibility at information about working conditions is transmitted from shipyards of wireless data transmission errors by reflection, the active tag through a network to the monitoring system, refraction, and diffusion of the radio waves in the blasting where the manager can check workers’ safety using comput- area (cell). There are also technological limits in building er-analyzed emergency signal data with the workers’ loca- the safety system for shipyard job areas, but developments tion information. in IT (Information Technology) and RFID (Radio-Frequency The monitoring system consists of three functions to Identification) technology have made remote control safety check workers’ safety and to send the emergency signal to systems possible. the manager. First, it’s a function for storing and analyzing This article summarizes work carried out by Won-Jun information; second, it’s a function for monitoring workers’ Yun, Byung Hun Lee, and Dong-Min Kim of Hyundai Indus- location and their safety information; and third, it’s a func- trial Research Institute, Hyundai Heavy Industries, Co. Ltd. tion for sounding a buzzer and sending SMS (Short Mes- Korea, and Young-Shick Ro, School of Electrical Engineering, sage Service) to the manager. Also, it can give an alarm by University of Ulsan, Korea, into such a system. The summa- analyzing the vibration sensor on a worker, including direct ry will concentrate on the features of such a safety system, emergency calling. Finally, it can monitor remaining battery rather than on the technical aspects. capacity of the active tag and temperature of the working The summary is based on a presentation given at PACE conditions. 2010, the joint conference of SSPC and PDCA, held Feb. 7–10, 2010, in Phoenix, AZ. The full paper is published in the The Remote Control System for Blasting Nozzles Proceedings (www.sspc.org). The remote control of blasting nozzle(s) is integrated with

the safety monitoring system to cut compressed air when an Operation Procedure of the Safety System emergency situation occurs. Managers also can check the To confirm workers’ safety, there are three ways to check the blasting nozzle status and turn it off remotely using PC when emergency signals from workers in the blasting cell: sensing emergencies occur. The remote control system can control the active tag emergency call, analyzing a sensed danger the blasting nozzle valve directly after checking the condition signal automatically by vibration sensor, and using voice of blasting nozzles one by one or altogether. communication with a special bone conduction ear-set. The monitoring system can sense various emergencies, The Special Bone Conduction ring alarms, and send the information about the emergen- Ear-Set Communication cy to managers. After the manager checks the SMS or the The special bone conduction ear-set system with neck mi- emergency signal on the monitoring system, he or she crophone is necessary to communicate about blast working can reconfirm the worker’s safety by having a conversa- conditions in the cell with a person in the managing office. tion through the bone conduction ear-set. If an emergency Working conditions in the blasting cell and protective occurs, the blasting nozzles can be controlled remotely by a clothes for blast cleaning work are not conducive to easy manager. Also, actions can be taken for workers to be safely voice communication. So it is more difficult to communicate evacuated from the life-threatening emergency, as well as using normal methods inside the steel block. Thus, a special for the urgent rescue of nearby co-workers. Emergency sig- system that the worker can use while wearing a mask, ear- nals can be transmitted to all managers to prevent sudden plugs, and a helmet had to be developed. accidents and to inform them of the rescue process. For communication among workers and managers during This innovative safety system for workers blasting in ship- the blast cleaning job, the special voice communication yards allows managers to communicate with workers in real system using the existing infrastructure with TRS (Trunked time and thus also allows managers to properly distribute Radio System), which can communicate with a group, was the workload and make a contribution to the improvement in used. Workers wearing masks and earplugs can still listen productivity. with the aid of the bone conduction mechanism and speak using a neck microphone, which makes communication possible through the vibration of vocal cords. Because blast cleaning workers must pass through small access holes to work in the steel block, the developed system is small and has the added conveniences of portability and noise interception.

others discussed in the proposal: abrasives such as mineral slags as well as sand, paints, concrete, portland cement, silicates, and soil. As part of the rulemaking, OSHA performed an extensive analysis entitled “Respirable Crystalline Silica—Health Effects Literature Review and Preliminary Quantitative Risk Assessment.” The available evidence indicated that employees exposed to respirable crystalline silica at concentrations well below the current PELs (of 100 and 250 µg/m3) have OSHA’S Proposed Rule an increased risk of lung cancer and silicosis. Occupational exposures to respirable crystalline silica also may result in the development of kidney and autoimmune diseases and in death from other nonmalignant respiratory diseases, includ- for Silica Hits the Streets ing chronic obstructive pulmonary disease (COPD). Summary of the Proposed Rules By Alison B. Kaelin, Among the aspects of the proposed rule that may be of inter- CQA, ABKaelin, LLC est to the coatings industry are the following. • Requirements to comply with applicable ventilation standards (e.g., 29CFR1926.57) for abrasive blast cleaning. While the ventilation standards have long been in place, they have n August 23, 2013, the U.S. Occupational Safety and not been fully implemented in many containment systems. Health Administration (OSHA) unveiled its long-expect- • Requirements for laboratory analysis of respirable silica ed proposed rule for protecting workers against respi- samples by an ISO 17025-accredited laboratory. rable crystalline silica. OSHA issued two versions of the • Construction industry exemption from exposure monitor- proposed rule, one for general industry and shipyards O ing for specific operations if engineering and work practice (1910/1915) and one specific to construction (1926). controls and respiratory protection are implemented. The proposed rule reduces the current permissible exposure • Options for establishing regulated areas or developing a limit (PEL) for general industry, shipyards, and construction written access plan (which appears to be very similar to the to 50 micrograms per cubic meter of air (µg/m3). The current worker protection plan required by the Lead Standard). PEL for general industry and shipyards is 100 µg/m3, and the • Addressing training requirements via the Hazard Communi- current PEL for construction is 250 µg/m3. cation Standard. Once published in the Federal Register, OSHA will accept The paragraphs in the proposed rule address similar topics comments for 90 days, as part of a rulemaking process. A (e.g., methods of compliance) of other comprehensive health hearing will be held in early March 2014, and the final rule standards. will be issued sometime after. The proposal and related in- The box on p. 53 gives a brief summary of the proposals formation can be read on https://www.osha.gov/silica/index. for General Industry and Shipyards and for Construction. html. The box highlights some similarities and differences be- While no conclusions on the actual requirements should tween the two proposals. be drawn based on a proposed rule, the proposed provisions do provide insight into likely approaches that will be con- Alison B. Kaelin, CQA, has more than 25 years of public sidered by OSHA when the final rule is issued. Employers health, environmental, transportation, and construction man- should consider the requirements of the proposed rule as agement experience in the coatings industry. She is the own- they apply to their operations, and plan how to implement er of ABKaelin, LLC, a Pittsburgh, the requirements when the rule is final. Background on PA-based provider of outsourced respirable crystalline silica, including its health effects, and a quality assurance, auditing, training, summary of the proposal follow. consulting, and related services Background to the protective coatings, construction, fabrication, and nuclear Silica is a compound composed of the elements silicon and industries. She is a certified quality oxygen (chemical formula SiOz). Respirable crystalline silica auditor, a member of SSPC, and a means airborne particles that contain quartz, cristobalite, NACE-certified coating inspector. and/or tridymite. The respirable portion is determined by a She was a 2012 JPCL Top Thinker, respirable-particle-size-selective sampling device. a 2012 JPCL Editor’s Award Winner, and an SSPC Technical The proposed rule estimates that exposures to crystalline Achievement Award winner in 2005. silica can occur in more than 30 major industries and operations. Silica can be present in the following materials and in (See table on next page)

Shipyard Regulatory Update ©iStockphoto/milarka What’s Happening with Enforcement, Regulation, By Alison B. Kaelin, CQA, and New OSHA Guidance Documents ABKaelin, LLC

his article reviews OSHA enforcement on shipyard ac- • Respiratory protection tivities and recent guidance on illumination and ventila- • Wiring design, protection, methods, components, and tion related to ship repairing, shipbuilding, and ship- equipment for general use breaking that fall under OSHA’s Standards for Shipyard • Guarding of deck openings and edges TEmployment (29 CFR 1915). It also discusses new OSHA • Welding and cutting (arc, gas, and oxygen-fuel) information on abrasive blasting hazards and potential Cal/ • Hazard communications OSHA Lead Standard changes that are applicable to shipyard • Toxic metals and many other industrial painting sectors. • Painting Shipyards are fixed facilities with dry docks and fabrication • Abrasive wheel machinery equipment capable of building a ship, defined as watercraft • Occupational noise typically suitable or intended for uses other than personal • Hand and portable powered tools and equipment or recreational. Activities of shipyards include the construc- • Confined space tion of ships, their repair, conversion and alteration, and the • Lighting production of prefabricated ship and barge sections. • Lockout/tagout OSHA Enforcement Summary OSHA Shipyard Fact Sheets Illumination Review of the most frequent OSHA citations for NAICS Code In November 2013, OSHA issued a Fact Sheet on Safe Light- 336611–Ship Building and Repairing from October 2012 ing Practices in the Shipyard Industry. It elaborated upon through September 2013, and OSHA’s enforcement data 29 CFR 1915.82, Subpart F, General Working Conditions: for NAICS 336611 and 29 CFR 1915, indicates the following Lighting, and provided the minimum lighting requirements areas of non-compliance resulting in citations. Areas are (Table 1). ordered from highest to lowest, and some similar areas were Note that the values in Table 1 differ from SSPC-Guide 12, grouped by the author. Guide for Illumination of Industrial Painting Projects, which

itime (1915) does not have specific ventilation requirements. OSHA General Industry Standard Ven- tilation standard (1910.94, Ventilation), published in the 1970s, established the first requirements for abrasive blast booths as (1) exhaust-ventilated to provide continuous air flow at all openings during blasting operations, (2) capable of preventing escape of abrasives into adjacent work areas, and (3) able to provide prompt clearance of dust when abrasive blasting ceases. The Industrial Ventilation: Manual of Recommended Practices, published by the American Conference of Governmental Industrial Hygienists, provided the basis for the design of blast booths for the stated purpose of “operator visibility and to control escape of contaminants into adjacent work areas.” It established the minimum air flows (60–100 feet per minute), trans- port velocities in ductwork (3,500 feet per minute), and design criteria with inward air flow exhausting to a remotely located dust collection system, as shown in Figure 1. SSPC-Guide 6, Guide for Containing Surface Preparation Debris Generated During Paint Removal Operations, relies on the Industrial Ventilation Manual criteria as

suggests that a higher level of lighting is required for work, Fig. 1: Typical blast booth surface preparation, and inspection activities. SSPC-Guide design 12 recommendations are shown in Table 2. Use of a portable light meter can help assess the adequacy Source: Reference 10.80.3 and 10.80.4; American of lighting. Be sure to use it frequently to re-verify that light- Conference of Govern- ing levels remain constant. Make sure your light meter is mental Industrial Hygien- ists, Abrasive Blasting capable of taking measurements in the range of your lights Room, 02-91, VS-80-01 and that it meets your accuracy needs. Most light meters have an accuracy range from 5% up to 18% and even higher. OSHA Ventilation in Shipyard Employment Guide A Shift in Approach? SECTION THROUGH TYPICAL ROOM Q = 60–100 cfm/ft2 of floor for downdraft with typical choice 80 cfm/ft2 OSHA 3639-04 2013: Ventilation in Shipyard Employment Q = 100 cfm/ft2 of wall for cross draft provides a review of basic principles of ventilation and Lower control velocities may be used depending on toxicity of the con- taiminant, object and blasting media, and the size of the blasting room. provides methods for selection, installation, and use of venti- Notes: 1. The above ventilation is for operator visibility and to lation systems to reduce contaminants during shipyard oper- control escape of contaminants into adjacent work areas. 2. Operator in an abrasive blasting room is required to wear ations. While it primarily focuses on confined and enclosed appropriate NIOSH-certified respiratory protection. spaces, it provides guidance applicable to any industry. 3. For rotary tables, use 200 cfm/ft2 of total opening (taken without curtains). Unlike General Industry (1910) and Construction (1926), Mar- 4. For blasting cabinets, see VS–80–02.

the basis of its ventilation requirements for abrasive blast- (4) There is no need to collect the air contaminant. ing containments. In industrial field painting, it generally If we apply the four factors to industrial painting and abra- involves bringing duct work to the face of the containment sive blast cleaning in the construction, marine, or shipyard system or just inside the containment wall and having air industries, where the quantity of contaminants are high and inlets generally across from them, mimicking the design of a non-uniform and many of which are toxic, it would suggest blast booth (Fig. 2). that LEV may be more appropriate than dilution ventilation. This type of venti- LEV is “an industrial ventilation system that captures lation is considered and removes emitted contaminants before dilution into the dilution ventilation ambient air of the workplace.”1 While we typically associate (general exhaust LEV with vacuum shrouds and vacuum attachments, LEV can ventilation), which is include placement of one or more exhaust air ducts in the “a form of exposure immediate vicinity of where the exposure is occurring. LEV control that involves is frequently used in the shipbuilding industry and is the rec- providing enough air ommended method when workers are exposed to hazardous in the workplace to di- chemicals, when a large amount of dust or welding fumes Fig. 2: Efficient method of supplied lute the concentration are generated, or during cold weather when increased heat- ventilation (forced air) with system of airborne contam- ing costs from the use of dilution ventilation is a concern. away from tank opening. Source: Edward J. Willwerth, Atlantic inants to acceptable The Shipyard Guide suggests that using ventilation in an Environmental & Marine Services levels.”1 exhaust mode and placing the ductwork where contami- The Shipyard nants are released in the air by the operation is an effective Guide states that both method in capturing the generated contaminants and greatly general dilution ventilation and local exhaust ventilation reduces exposure to workers in a space (Fig. 2). (LEV) at the source are suitable for controlling exposures. Table 3 (excerpted from Ventilation in Shipyard Employ- However, it states that local exhaust ventilation is typically ment), suggests that LEV may be more appropriate for abra- preferred and more effective. sive blast cleaning. The Shipyard Guide also states that dilution ventilation While the preference for LEV may be specific to shipyards, involves the reduction of contaminants being generated all industries should evaluate the hazards and unique char- in the space through the introduction of clean outdoor air (through air inlets) and removal of the contaminants through a dust collector. It notes that sometimes, this can cause a supply and exhaust imbalance that positively or negatively pressurizes the space or results in short circuiting (when only a small portion of the space is ventilated). The Shipyard Guide depicts dilution ventilation as inefficient, requiring a lot of air and air movement to reduce the level of hazardous contaminants. The Shipyard Guide also suggests that four factors should be considered before using dilution ventilation for protecting worker health. (1) The quantity of contaminant released should be relatively low and uniform. (2) Workers should be located far away from the contaminant source. (3) The toxicity of the contaminant must be low.

acteristics of the work area to which their employees are • Slags can contain trace amounts of toxic metals such as exposed and consider all methods for reducing exposures. arsenic, beryllium, and cadmium. When working with materials covered by comprehensive The fact sheet also suggests that when performing abra- health standards (such as lead) which require the use of sive blasting to reduce worker hazards from materials, one engineering controls for the purpose of reducing worker needs to use nearly identical controls as one would for lead exposures to as low as feasible, LEV may be more in line or other toxic metals, including engineering controls (e.g. with the definition of an engineering control, which focuses containment and ventilation), work practices (hand and body on elimination or reduction of the hazard at the source. PPE and hygiene), and respiratory protection. Some other observations made in the fact sheet include: Duct Work • recommending the use of alternative, less toxic blasting Whether you use dilution or local exhaust ventilation, an materials such as sponge, baking soda, or dry ice; integral part of the system is the ductwork. The Shipyard • keeping coworkers away from the blaster; Guide is consistent with the guidance provided in SSPC’s • cleaning and decontaminating tarps and other equipment C3 Course, and SSPC-Guide 16, Guide to Selecting Dust at the worksite; and Collectors, and states that consideration should be given to • scheduling blasting when the least number of workers are the type and length of the hose and layout of duct work to at the site. ensure the greatest amount of air flow. Take a look at your abrasive blast cleaning operations and As the length of hose or ductwork increases, the amount materials and consider what equipment, processes, materi- of air moved decreases due to frictional losses. Therefore, als, or worker changes may be necessary to reduce worker the shortest length of hose or ductwork should be used. exposures to abrasive blasting material hazards. Equally important is the amount of bends or turns in Are We Closer to Revising the Cal/osha Lead Standard? the ductwork. A greater number of bends or turns greatly In April 2011, the California Department of Health/Occupa- decreases the volume of air moved. Try to keep the hose as tional Lead Poisoning Prevention Program (OLPPP) began straight as possible. To put this in perspective, one sharp providing information to support revisions to the 30-year-old 90-degree bend in a 20-inch-diameter duct is equivalent to Cal/OSHA Construction Lead Standard based on more recent adding 46 additional feet to the length of the ductwork. health-based scientific evidence. OLPPP suggests that the When we install ductwork through manways, small open- following changes are necessary. ings, and other limited egress areas, it may impede entry/ • Provide medical surveillance, blood lead level (BLL) exit. The Shipyard confined space standard requires that if testing, annual blood pressure measurements, and question- ventilation ductwork blocks access to a confined space, then naires to all employees likely to be exposed to lead. all workers must be provided with airline respirators, and • Increase frequency of medical surveillance of BLLs and a person must be stationed outside the space to maintain further increases if above 10 µg/dL. communication and to aid in the event of an emergency. The • Remove employee from lead exposure at or above 30 µg/ Guide suggests a saddle be used in these cases. A saddle is dL or if two successive blood lead concentrations measured a piece of equipment that allows entry/exit without remov- over a four-week interval are at or above 20 µg/dL. ing the duct work. • Return employee to work when two blood lead tests taken Abrasive Blasting Hazards four weeks apart are less than 15 µg/dL. OSHA released a new fact sheet in November 2013, titled, • Lower Permissible Exposure Limit (PEL)/Action Level (AL) Protecting Workers from the Hazards of Abrasive Blasting which reflect new medical/toxicological information on Materials. It outlines the following abrasives and likely chronic and low-level health effects. health effects. • Conduct regular testing of surfaces in eating areas and • Silica sand (crystalline) can cause silicosis, lung cancer, change areas and clean more frequently when lead is found. and breathing problems in exposed workers. Establish a quantitative limit for lead on surfaces and specify • Coal slag and garnet sand may cause lung damage similar sample collection and analysis methods. to silica sand (based on preliminary animal testing). • Provide quarterly employee training. Training should maxi- • Copper slag, nickel slag, and glass (crushed or beads) also mize the use of participatory and hands-on methods. have the potential to cause lung damage. • Post warning signs in areas where lead is present. • Steel grit and shot have less potential to cause lung dam- • Define and require minimum engineering and work prac- age. tice controls unless the employer can demonstrate that such

controls are not feasible. References • Do not allow certain high-risk work 1. OSHA Technical Manual. practices. In October 2013, the California Department of Public About the Author Health (CDPH) made a recommendation to Cal/OSHA for a Alison B. Kaelin, CQA, has more than 25 years of public new PEL based on the low level health effects literature and health, environmental, transportation, and construction man- new modeling of the relationship between air lead levels and agement experience in the coatings industry. blood lead levels. She is the owner of ABKaelin, LLC, a pro- CDPH used an updated version of the original model used vider of OSHA training, quality assurance, by OSHA to develop the General Industry Standard for lead auditing, consulting, and related services and challenged the model using actual BLL and mortality to the protective coatings, construction, data obtained over the last 20 years. The modeling and the fabrication, and nuclear industries. conclusions support the overwhelming body of recent scien- Kaelin is a certified quality auditor and tific evidence indicating the health impacts of very low BLL NACE-certified coating inspector. She was a 2012 JPCL Top exposures ranging from 5–10 µg/dL. The modeling focused Thinker, a 2012 JPCL Editor’s Award Winner, and an SSPC on two issues. Technical Achievement Award winner in 2005. At SSPC 2014, • Estimate the amount of lead in workplace air inhaled by she was presented the inaugural Women in Coatings Impact workers without respirators that would result in BLLs of 5, Award. She is a JPCL contributing editor. 10, 15, 20, and 30 µg/dL over a 40-year working lifetime. • Estimate the time it would take for a worker’s BLL to come down to 15 µg/dL from a higher level once the worker is removed from workplace lead exposure. The modeling arrived at the following conclusions. To keep almost all workers’ (95%) BLLs below 5 µg/dL over their working lifetime, the amount of lead in the air the worker is exposed to must not be above 0.5μµg/m3 averaged over an 8-hour workday. The model also shows that the amount of lead in a worker’s blood climbs very fast in the first few years of workplace exposure and then climbs much more slowly in the remaining years. Even though a worker’s BLL does not climb much during the remaining years, lead levels in the bones continue to increase. The lead in the bones is slowly released into the blood throughout a worker’s lifetime. The model also estimates the time it may take for a worker’s BLL to come down to a BLL of 15 µg/dL, after removal from workplace exposure. The CDPH concluded that based on available scientific evidence adverse health effects begin to emerge at BLLs of 10 µg/dL and likely lower. Modeling suggests that in order to maintain BLLs of 10 µg/ dL over a working lifetime in 95% of workers, the air concentration of lead must not exceed 2.1 µg/m3 as an 8-hour TWA average or to maintain a BLL of 5 µg/dL a PEL of 0.5 µg/m3 as an 8-hour TWA average. Cal/OSHA is expected to introduce a final rule by the end of this year. Industry professionals expect medical removal levels to be established at 15–20 µg/dL and a PEL of approximately 20 µg/m3 as an 8-hour TWA average.

On the Time between Blasting and Priming

How long can a blasted surface be left before priming under different and vary from job to job. In Jordan, for example, oxidation temperatures/relative or orange rust may not occur for several hours or days, but humidity environments? in UAE, you can probably expect to see rust break through in few hours, depending on the time of the day or night. It is almost impossible to state the effect of time, tem- Editor’s Note: Problem Solving Forum questions are posted perature, and humidity on all blast-cleaned surfaces. On any on the free daily electronic newsletter, PaintSquare News, given job, the answer must be the sole responsibility of the on behalf of JPCL. Responses are selected and edited to inspector, who conducts on-site checks of the conditions conform to JPCL style. To subscribe to PaintSquare News, go to www.paintsquare.com/psn/. such as the following: • Place of work From Lee Edelman • Air temperature—minimum and maximum CW Technical Service • Relative humidity Always attempt to prime the prepared surfaces before the • Dew point specified surface preparation starts degrading. Most speci- • Steel temperature fications will address this practice. Humidity and dew point • Necessary ventilation should be monitored throughout the process, so that when • Type of weather, such as sunlight, rain, wind speed, and humidity or dew points exceed what the specification al- direction lows, there should not be any painting activities. These on-site checks must be done at least three times per If the prepared surface has degraded, most specifications shift. The inspector should have the sole right to determine will require reblasting to the specified degree of surface the time without deviating from the specification. preparation. From Remko Tas From Richard D. Souza Futuro SRL Stoncor Middle East LLC As a curiosity, flash rust did not occur for 10 days in a dry cli- How long a blast-cleaned surface can remain uncoated is not mate at an altitude of 4,000 m (13,000 ft) in Bolivia, hundreds the issue; rather, the highest criterion is the steel tempera- of kilometers away from the influence of saltwater and con- ture: It should always be at least 3 degrees C (5 F) higher tamination from industry-generated air pollution. We could than the calculated dew point temperature. This margin of still safely paint the interior of the tank in one shot, achieving safety is sufficient for all type of coatings. a high efficiency. A common scenario is that the contractor blasts all day long; experiences problems with the compressor or oth- From Lubomir Jancovic er piece of equipment; and as a result of the equipment MSPLUB Inc. problems, lets the newly blasted steel sit a long time before You have to prime the blasted surface of steel within eight coating. But the standard requires that the surface to be hours. Otherwise, blasting was for nothing. If the relative painted must meet the cleanliness criteria set by the client or humidity is more like 60%, you have to prime the surface consultant. These criteria supersede every other judgment within four hours.

Editor’s Note: This Applicator Training Bulletin is an update of an original article written by Walter Shuler, certified safety professional and safety ©iStockphoto/ZooCat consultant; Jeff Theo, Service Painting Compa- ny; and Mike McGinness, Custom Process Sys- tems. The article was originally published in the June 1998 issue of Protective Coatings Europe (PCE) and was updated for this issue by Dan Safety Considerations O’Malley, Manager of the Environmental, Health, and Safety Group; and Stan Liang, Director of for Abrasive Blasting Operations Health and Safety; KTA-Tator, Inc.

he Occupational Safety and Health Administration ant that you understand what they are and observe the (OSHA) writes and enforces regulations that govern proper safety precautions. The hazards of abrasive blasting safety and health practices in the work place, with many include, but are not limited to: pertaining to cleaning and painting operations. Most • dust, Tof these regulations are very specific about how to • noise, and do a job safely. Their purpose is not to make our job more • equipment. difficult, but to make it safer. These regulations have been developed over many years through studies on how and Dust why accidents happen, and following these written proce- The dust produced by abrasive blasting is a very serious dures and regulations should ensure that we don ‘t make the health hazard. Dust results from the breakdown of abra- same mistakes that have injured others in the past. sives and the pulverizing of surface coatings, rust, millscale, This article will review some of the general requirements and other materials on the steel surface being blasted. The of regulations on abrasive blasting and explain how they can individual dust particles vary in size from 1 micron (1⁄25,000- help increase job safety. inch) to 1,000 microns (1⁄25-inch) in diameter. Dust larger than 10 microns may be visible and settles quickly. Dust Hazards of Abrasive Blasting smaller than 10 microns, called respirable dust, is invisible, When you blast clean surfaces with abrasive driven by air, remains suspended in the air for a longer period of time, you have to deal with several hazards to your health and and can pass through the respiratory system’s defenses and safety. Some of these hazards can be lethal, so it is import- settle in the small air sacs in the lung called alveoli.

such as lead, arsenic, cadmium, and hexavalent chromium. One of the most common toxic metal hazards encountered in the removal of a coatings system is lead, a toxic metal that can damage the body’s blood-forming, nervous, urinary, and reproductive systems. Lead also accumulates in the body; thus, exposure to small doses over long periods of time can cause great harm. Exposure to toxic metals can also directly affect the skin. Metals such as hexavalent chromium can irritate the skin or cause an allergic reaction. Other metals can have an irritant effect on the respiratory tract, such as pulmonary edema (fluid build-up in the lungs) caused by severe cadmium dust exposure. Entry can also occur via ingestion, typically caused by poor hygiene practices such as eating, drinking, and smoking in the work area. To determine the specific toxic metals likely to be present in a coatings system, paint chip samples should be collected from representative areas of the structure. The metals that the samples should be analyzed for would depend on a number of considerations, such as the type of structure and the type of coatings system being evaluated. Sometimes, toxic metal content can be determined based on historical knowl- edge of the coatings system being evaluated. Toxic metals can also be present in the virgin abrasive blast media, such as crystalline silica in silica sand abrasive. However, dust-containing crystalline silica also can be produced during other abrasive blasting activities, such as surface preparation of concrete. A study published in the September 2006 issue of the Journal of Occupational and Environmental Hygiene indicated that elevated exposure to ©iStockphoto/tolgabayraktar crystalline silica exposure also can result when it is present in the coatings system being removed.1 The Safety Data Sheet should be consulted to determine Dust of this size cannot be dissolved by the lung fluids. what metals may be present in the abrasive blast media. Because the lung cannot break down or cast out the par- Recently, OSHA has begun requiring abrasive manufacturers ticles, it does the next best thing in its defense program, to list toxic metals in their products, even if they are present which is to isolate the intruder by building a thick, fibrous only in trace amounts. Arsenic is commonly found in steel tissue around it. When too much of this tissue develops, the grit and coal slag abrasives, while beryllium is commonly lung is said to be “fibrotic,” or in a condition of fibrosis. found in coal slag abrasives. The routes of entry and the associated health effects de- When there is exposure to toxic dust, the primary con- pend on the chemical and physical properties of the dust. If cern is to control respiratory exposure. Respiratory protec- the dust is soluble in water and respirable in size, it can enter tion must comply with the OSHA Respiratory Protection the alveoli, pass through the walls of the alveoli in the lungs, Standard (29 CFR 1926.103). This standard requires feasible and enter the bloodstream. Once in the bloodstream, dust engineering and work practice controls to be employed be- can be transported rapidly throughout the body and damage fore respiratory protection is used by workers. Engineering various organ systems. controls include ventilated abrasive blasting containments Other health hazards may be present in the dust pro- and considering alternatives to abrasive blasting, such as duced by the abrasive blasting process. These hazards can vacuum-shrouded power tools, water jetting, and chemical result from the removal of coatings containing toxic metals stripping. Job rotation is an example of a work practice con-

trol. Note that job rotation is not permitted by OSHA in all Noise cases (if workers are exposed to hexavalent chromium, for Most forms of abrasive blasting create the hazard of noise instance). If such a control is used, a written schedule must exposure, which will vary depending on the blasting condi- be developed and followed. tions. Regardless of the nature, excessive amounts of noise Respiratory protection may only be used after engineer- may require personal hearing protection for blasters and ing and work practice controls are employed and workers other workers in the general area. Depending on the size of are still exposed above the OSHA Permissible Exposure the equipment, the material being blasted, and the location Limit (PEL) for a given toxic dust. Employers must select, of the blasting operation, noise levels can range from about use, and maintain respirators in accordance with a written 90 decibels to more than 110 decibels. OSHA’s limit for noise program (the elements of which are specified by OSHA in depends on the duration of exposure. For an eight-hour shift the Respiratory Protection Standard). of continuous exposure, the limit is 90 decibels. Personal Blasters typically use a Type CE or helmet-type airline hearing protection should then be recommended if the level respirator. Workers in the vicinity of the blasting area, such and exposure time of the workers exceed the OSHA stan- as pot tenders and lookouts, are required to wear respiratory dard. Noise protection must reduce exposure to below the protection. Workers engaged in clean-up operations should OSHA limit. also be equipped with respiratory protection. These workers Note that some abrasive blasting hoods already provide are usually assigned a half-mask, air-purifying respirator some degree of noise protection, but the manufacturer’s with high-efficiency cartridges (labeled as N, R, or P 100). specifications should be checked to see if the degree of noise However, workers cleaning up abrasive blasting debris when reduction will be adequate. When there is any question blasting is still in progress (as is often the case when recycla- about the existing levels (meaning a noise survey is needed) ble grit is used) may need a higher level of protection. Such or the adequacy of hearing protection, a health and safety workers may need to wear the same type of respirator as the professional should be consulted. blasters, as their exposure levels are likely to be similar. The National Institute of Occupational Safety and Health Equipment (NIOSH) conducts research on health issues in the work The equipment used in abrasive blasting operations can place, and one of its main functions is to test and certify create physical hazards that require certain precautions. The industrial respiratory protection equipment. All respiratory following are some examples of equipment commonly used protection equipment used in the workplace must be ap- during the abrasive blast cleaning process and the respective proved by NIOSH. precautions that should be taken during their use. Respiratory protection should continue to be worn after • “Deadman” control: This is usually a spring-loaded control blasting as long as dust-laden air remains. Respirable dust located near the nozzle end of the blast hose. When de- in an abrasive blasting booth or containment can remain pressed, it starts the flow of high-pressure air and abrasive. suspended for long periods of time after blasting is finished. When released, it stops the flow. Deadman controls can be This time period is largely dependent on the effectiveness of either pneumatic (air-operated) or electric. In either case, the ventilation system, unless the work is performed out- the control must be kept depressed by the operator for the doors. system to work. This prevents a nozzle from blasting the A health and safety professional should review all proj- operator or nearby workers with abrasive if dropped. Always ects that require abrasive blast cleaning to determine what verify that there is a Deadman control and that it is operable precautions, if any, should be taken to eliminate the hazard before any work is performed. of chemical exposure. Examples of these precautions include • Hoses: Hoses are subject to severe abrasion from the disposable clothing, boots, gloves, respiratory protective high-pressure air and abrasive that moves from the pressure devices, and hygiene practices. Hygiene facilities that can be vessel to the nozzle. Ruptures can cause serious injury. Metal required by OSHA include hand wash stations and showers. piping carrying abrasive also deteriorates rapidly. Hoses and OSHA requires provision of a hand wash station when work- piping should be inspected on a regular basis and repaired ers may come into contact with toxic materials. Whether or or replaced periodically as necessary. Hose and pipe cou- not showers are mandatory depends on which OSHA stan- plings also should be inspected regularly. Blast hose cou- dard is applicable. If workers are exposed to lead, showers plings should be wired together and whip checks should be are required when exposures exceed the PEL. used. Whip checks are safety cables that restrain movement

of the hose should the coupling connection become compro- Summary mised. When performing abrasive blasting, safety considerations • Pressure vessels: Pressure vessels for compressed air or must be given to hazards including dust, noise, and equip- abrasive under pressure should be checked regularly be- ment. Once the hazards are determined, procedures for cause they are also subject to abrasion and deterioration be- personnel protection can be developed. In addition to being yond that of normal pressure vessels. Pressurized abrasive provided with personal protection, workers must be properly tanks must have a removable plate for internal inspection. trained in the use, inspection, and maintenance of equip- All vessels must conform to American Society of Mechani- ment. cal Engineers (ASME) boiler and pressure vessel codes. Procedures to control exposure to health and safety • Valves: All valves and rubber valve parts are subject to hazards must conform to the OSHA regulations that govern wear and should be inspected and replaced periodically. blasting operations. Additional regulations from state or • Fill ports: Pressure vessels for abrasive blasting should local jurisdictions may be in force. Twenty-three states have have a funnel-shaped input that is easily accessible to the their own version of OSHA, and their regulations are at least operator so that strain caused by lifting bags of abrasive is as strict and, in some cases, stricter than federal OSHA regu- avoided. lations. • Hoseline grounding: Nozzles should be grounded because This article should not be considered a comprehensive the air and abrasive can create enough friction to develop a analysis of abrasive blasting health and safety. When there substantial charge of static electricity. This is most important is any doubt about the nature of the hazard or how to protect while working inside tanks or in other areas where there is workers, assistance should be obtained from a health and potential for explosion. safety professional, typically someone who is a Certified • Personal protective equipment: In addition to respiratory Industrial Hygienist or a Certified Safety Professional or pos- and noise protective equipment, blasters should wear ap- sesses a degree from a related field of study. parel to prevent damage to their skin from abrasive blasting and ricochet. Such apparel includes safety footwear or References: toe guards, coveralls, leather or rubber capes, and gloves. 1. Meeker, John D., Pellegrino, Anthony, and Susi, Pam, Pant and sleeve cuffs should be secured with tape or other “Comparison of Occupational Exposures Among Painters suitable fasteners. These clothing rules are most difficult Using Three Alternative Blasting Abrasives.” Journal of to enforce during hot weather, but despite the discomfort, Occupational and Environmental Hygiene, Volume 3, Issue 9 they still must be enforced. Protective equipment should be (September 2006): pp. D80–84. inspected daily and repaired or replaced as necessary. Clean storage areas should be provided for respiratory protection and protective apparel. It is most important that blasters receive proper training in the use of personal protective equipment.

Setting Up Air Abrasive Blast Equipment

Editor’s Note: This Applicator Training Bulletin is an update of a previous article written by Joe Fishback of Custom Blast Services Inc. It was first published in the November 1989 JPCL and has been updated for this issue Fig. 1: Blast pot by Bill Corbett and Stan Liang of KTA-Tator, Inc. Courtesy of Axxiom Manufacturing

Air compressors are generally identified by output capaci- n air abrasive blast equipment system is composed of ty, such as 250 CFM, 325 CFM or 750 CFM. CFM means cubic several major components, including the following. feet per minute, which is how the volume of pressurized air • Air Compressor is measured. The power to run a compressor is usually pro- • Blast Pot (Pressure Blast Tank) vided by an internal combustion engine (gasoline or diesel) A• Abrasive (Blast Media) or by an electric motor. Selection of a power unit is generally • Blast Nozzle dictated by the area where blasting is to be done or by the • Moisture Trap availability of utilities. • Deadman Switch Before starting the compressor, remember to: • Blast Hood • check the engine oil level; • Interconnect Hoses • check the coolant level; and Let’s take a look at each to see how they work together to • check the belts and hoses for leaks or defects. provide an efficient abrasive blast system. Blast Pot Air Compressor The blast pot (Fig. 1, p. 17) is a coded pressure vessel gen- The air compressor provides high-pressure air for the blast- erally referred to as a pressure blast tank (PBT). Because it ing operation. This machine takes in atmospheric air at 14.7 is a pressure vessel, it must have a stamp on it showing that psi and compresses it to a pressure several times higher, it has been pressure tested. The PBT is further identified by usually about 120 psi. The heat generated through compres- size. For example, it may be called a 6-ton PBT or a 6-sack sion is somewhat dissipated by an air intercooler. The air pot (based on silica sand), referring to the amount of abra- then passes through moisture and oil separators to make it sive it can hold. During operation, the blast pot is pressur- dry and oil-free as it exits the compressor. ized and feeds abrasive into the air stream.

the compressed air continues to cool, additional moisture condenses in the bull hose. This remaining moisture is trapped by the moisture separator just before it enters the PBT. This trapping is done either with a centrifuge-style separator or with a replaceable filter element-style separator. Generally, it is necessary to leave an air bleed valve open in the bottom of the moisture trap when blasting to allow the moisture to be expelled. Deadman Switch The deadman switch (Fig. 2), either pneumatic or electrical, Fig. 2: Multi-colored deadman switches. Courtesy of SAFE allows the blaster to have remote control over the pressur- Systems, Inc. ization of the blast hose. With pneumatic operation, this is accomplished when pressure through the deadman switch Abrasive (Blast Media) closes the air control valve and opens an escape valve. This While not usually thought of as abrasive blast equipment, prevents air from entering the PBT and at the same time, not much happens to the surface without the abrasive. it depressurizes the PBT. Electrically operated systems use Abrasives are generally categorized as expendable (one-time pinch valves to stop the flow in the blast hose. With electri- use) or recyclable (multiple uses). The type, size, shape and cally controlled systems, the PBT is always pressurized when hardness of the abrasive all affect productivity as well as the the bull hose is connected and pressurized. depth and shape of the surface profile or anchor pattern. The The primary purpose of the deadman switch is safety. It cleanliness of the abrasive is just as important as the clean- provides a means to stop the discharge of abrasive from the liness of the compressed air used to propel the abrasive. A nozzle when a safety hazard arises. The fact that it allows the vial test is performed on new or recycled abrasive prior to blaster to start and stop work at his discretion is a secondary use. The abrasive is tested for oil according to ASTM D7393 purpose. and conductivity according to ASTM D4940. According to the SSPC standards, abrasives cannot contain any visible oil and Blast Hood cannot have a conductivity that exceeds 1,000 µS. The blast hood (Fig. 3) is a piece of safety gear that provides a degree of comfort to the blaster as well. This hood is gen- Blast Nozzle erally a reinforced plastic shell with a replaceable skirt that The blast nozzle is a small but important piece of the blasting covers the torso of the blaster. It has a double-faced shield of equipment. It is the last item to exert influence on the blast clear plastic for eye protection and an air feed line to provide media. Nozzles are identified by their shell composition, their positive pressure under the hood. The positive air pressure lining composition, the size of the orifice and length (for ex- under the hood prevents the entrance of harmful blasting ample, aluminum shell with tungsten lining, size #7, short). dust and abrasive. Air coolers are also available. If the air is The orifice size number relates to the size in 1⁄16-inch units coming from a diesel compressor, an air purifier and carbon (#7 = 7⁄16-inch). The size of the nozzle has a bearing on the monoxide monitor are required. amount of air and abrasive used and on the amount of work completed. The larger the size of the nozzle, the greater the Hoses consumption of supplies. Nozzles are chosen for the work to Hoses vary in size depending on the work to be performed, be performed. available air capacity, distance to work area and other considerations. Moisture Trap The first in the sequence is the bull hose. This is generally The moisture trap is a device that allows the compressed a short hose — less than 50 feet long, with an internal diam- air to shed water. As the air is compressed, heat is gener- eter (ID) of approximately 2.5 inches or less that provides ated. As this hot air passes through the heat exchanger to passage of air from the compressor to the PBT. lower the air temperature, water in suspension (humidity) is The next hose is an air-line with an approximate ID of 0.75 condensed. Generally, a compressor is fitted with a moisture inches or less that provides air first to a moisture trap and trap. This first trap catches most of the water. However, as then to the blast hood. The section between the moisture

trap and the hood is smaller, down to 0.25-inch ID. Control hoses can be down to 0.20-inch ID and are generally duplex (dual-line) hoses. They run from the control valve on the PBT to the deadman switch and back to complete the circuit when the blaster is ready to commence work. Includ- ed here is the electrical wiring necessary if the deadman is electrically operated. It generally operates from a 12-volt DC source such as the compressor power unit’s DC system. The last hose in the circuit is the blast hose. It is a thick- wall, wire-reinforced hose designed and constructed to contain the high-pressure air (up to 120 psi) and abrasive mixture that moves from the PBT to the blast nozzle. The blast hose is constructed in three layers: an inner wearing lining, a conductive layer and an outer wrapping. Abrasive passing through a blast hose builds up static electricity. The conductive layer is needed so the whole system can be grounded. As a general rule, the hose should be three times the ID of the nozzle orifice; ideally, 1.25 inches to 1.5 inches for optimum production. Setting Up the System With the major sub-assemblies identified, we can now set up our blasting equipment. Position the compressor upwind from the work area so that airborne grit does not enter the cooling or air intake systems. The compressor should be level so that the oil and moisture separators can function efficiently. The power unit’s lubrication system also depends on the compressor being level. After fluid levels (oil, coolant and fuel) have been verified and topped off, the compressor is ready to start. Fig 3: Blast hood The bull hose should be laid out with no kinks and a min- Courtesy of Bullard imum of bends. Prior to making connections at the compressor and PBT, the sealing gaskets should be examined the hose for the deadman switch. The fittings on the ends of for tears, cracks or other sealing problems. As soon as the this hose are brass, male/female and threaded. It is neces- connectors have interlocked, a safety pin or wire should be sary to use the proper-sized wrench to prevent damage to inserted to prevent accidental separation of the joint. If this the brass hex surfaces. As the hose is installed, care should separation should occur, there is great potential for per- be taken to lay the hose parallel to the blast hose. The sonnel or property damage as the hose whips around. The control line should also be secured to the blast hose by tape hose should be examined for damaged locking lugs, missing or other means to minimize possible damage to this less du- gaskets, soft spots, torn covers or other damage. rable hose. This is important because air leaks in the control If any defects are observed, consideration should be given line will not allow the control valve to pressurize the PBT and to replacement of the worn or damaged part. If all appears thus no blasting takes place. The threaded fittings should be in good condition, make the connections at the compressor tightened securely but not over tightened. and PBT moisture trap. Now, go back to the air source for connection of an air-line The next step is to lay out the blast hose utilizing the same to feed the small moisture trap for hood atmosphere. These inspection procedures used for the bull hose and fittings. If fittings are usually 0.75-inch crow’s foot, quick-disconnect all is in good shape, connect the selected nozzle and pin all fittings. Inspection of hose gaskets and locking lugs is once fittings. again necessary. Be certain to pin all quick-disconnect crow’s When the blast hose connection is complete, you can run feet.

The hood atmosphere line is the last hose to be hooked To assure the quality of cleaning, two important checks up. This hose has brass screwed fittings similar to those on should be made. The first is a compressed air cleanliness the control line. The same care in hook-up should be exer- test, also known as a white rag or blotter test. This test cised, with particular attention to preventing entry of debris. determines if the blast air is free of moisture and oil as it Now, with all hoses connected to their respective fittings, is delivered to the nozzle. The abrasive valve is closed to you are ready for pressurized air. Close all air outlet valves prevent abrasive from entering the air stream. A white rag on the compressor. Press the shutdown bypass button or blotter (called an “absorbent collector”) fastened to a as well as the start button. The compressor should start rigid backing is then positioned in the air stream within 24 and run. After the temperature moves up to the operating inches of the nozzle. A non-absorbent collector such as rigid temperature, it is time to press the service air switch. At this transparent plastic may also be used. After a minimum of time the air pressure gauge should register approximately one minute, the collector is removed and examined for oil or 110–120 psi. If the reading is higher or lower, adjustments moisture contamination. If evidence of oil is present on the should be made before beginning the blasting operation. collector, adjustments must be made to the system, possibly When the compressor stabilizes at working air pressure, by service personnel from the supplier of the compressor. slowly open the valve to furnish hood atmosphere air. After The second test measures nozzle pressure. This measure- the quality (oil and contaminant-free) and quantity of this air ment is taken with a needle pressure gauge. The needle are verified, slowly open the valve for the bull hose. There is inserted into the blast hose in the direction of air and should be no air escape except at the moisture trap bleeds. abrasive flow. This insertion takes place close to the nozzle If air leaks are present, they should be repaired. The PBT can with both the air and the abrasive flowing. Nozzle pressure is now be filled with abrasive. read directly on the face of the gauge. Optimum blast nozzle The blaster should be clothed with sturdy shoes or boots, pressure should be approximately 100 psi for productive heavy pants, a long-sleeved heavy shirt and leather gloves work. Pressures lower or higher than 100 psi may improve for protection from bounce-back of abrasive. When the blast- productivity depending on the abrasive being used. er has been properly suited up, he or she can check opera- With proper setup of equipment and a thorough knowl- tion of the blast equipment. He or she does this by opening edge of good safety practices, your job should be safe and the deadman valve to pressurize the PBT and thus force trouble-free. a quantity of abrasive to enter the air stream to the blast hose. Adjustments in the amount of abrasive delivered to the nozzle can be made with an abrasive valve located close to the bottom of the PBT. Enough abrasive to do the work should be delivered, but not so much as to slow the impact or choke the blast hose or nozzle.

Surface Preparation: No, it’s just not good enough. Adventures in Frustration You’ll have to reblast. Abrasive blasting structural beams for a coastal petrochemical By Peter Bock project. All photos courtesy of CorrLine International Mobley Industrial Services Inc.

hese are dreaded words a contractor hates to hear, (SSPC-SP 5/NACE No. 1) reads as follows: whether they come from a third-party inspector or from “2.1 White Metal Blast Cleaned Surface: A white metal the contractor’s own QA/QC manager. Abrasive blasters blast cleaned surface, when viewed without magnification, have been hard at work all morning. Just before lunch- shall be free of all visible oil, grease, dust, dirt, mill scale, Ttime the blasters shut down. The spent blasting grit and rust, coating, oxides, corrosion products and other foreign the old coating (and rust) blasted from the surface have been matter.” hurriedly gathered and removed, the blasted surface blown That should be easy and straightforward — it’s white or down or vacuum cleaned to remove blasting dust, and the it isn’t. But it’s not always that simple. The standard states inspector summoned. that the the surface needs to be white “when viewed without The inspector or QA/QC person is not the bad guy — he magnification.” Does that mean the inspector has a right to or she is simply following his or her interpretation of the get his nose half an inch from the blasted surface, or should project specification and the industry standards used to write he view it from a more “normal” range? How visible are the specification. If there has not been sufficient discussion the “visible” contaminants and foreign matter? What about and agreement about standards and interpretation during non-visible contaminants? the pre-bid and pre-job conferences, the QA/QC person, the “2.1.1: Acceptable variations in appearance that do not third-party inspector and the contractor’s site superintendent affect surface cleanliness as defined in Paragraph 2.1 include may have significantly different opinions of what meets the variations caused by type of steel, original surface condition, project surface preparation specification. thickness of the steel, weld metal, mill or fabrication marks, This article discusses potential ambiguities in visual heat treating, heat-affected zones, blasting abrasives, and surface preparation standards and provides insight into differences because of blasting technique.” preventing disagreements between owners, inspectors and Acceptable “white metal” prepared steel surfaces may contractors, and avoiding delays and costly reblasting. in fact be several shades of gray, some of them because of abrasive blasting, some of them in spite of it, and “white SSPC-SP 5/NACE No. 1, White Metal Blast Cleaning metal” is a somewhat of a misnomer. Surface preparation standards are almost entirely visual. “7.4: Immediately prior to coating application, the entire SSPC’s definition of a “White Metal Blast Cleaned” surface surface shall comply with the degree of cleaning specified...

vacuumed or blown down again and — the dread of dreads — the inspector has to be called back to re-inspect. In the meantime, other previously acceptable areas of blasted surface may have deteriorated, so from a practical viewpoint, if the inspector turns down a portion, reblasting or at least resweeping the entire shift’s work is often the most cost-effective option. White Metal Blast Cleaning, is usually specified only for tank and vessel lining and for critical exterior surfaces. The costs and the perfection required are too high for most coating projects and SSPC-SP 10/ NACE No. 2, “Near White Metal Blast Cleaning,” or SSPC SP-6/NACE No. An area of staining — or discolor- 3, “Commercial Blast This blaster is using medium-grade garnet abrasive to obtain ation — in SSPC-SP 10 blast. a Commercial Blast Cleaned surface (SSPC-SP 6) and a 2-to- Does it pass or fail? Cleaning,” are specified 3-mil anchor profile. instead. “Near White Metal Blast Cleaning” allows 5 percent of a “unit area” of Any visible rust that forms on the surface of the steel after abrasive blasted steel surface to be less than white metal blast cleaning shall be removed by recleaning…” and “Commercial Blast Cleaning” allows for 33 percent. For If the inspector thinks that the job has not been done well both standards the less-than-white areas can have only “ran- enough, the contractor will have to reblast the unaccept- dom staining” consisting of “light shadows, slight streaks or able areas. Because the contractor has already set up for minor discolorations caused by stains of rust, stains of mill painting to ensure no more deterioration “immediately prior scale, or stains of previously applied coating.” to coating application,” all that effort is wasted. Blasting A “unit area” is defined as a 3-inch-by-3-inch square. equipment has to be brought back in, spent abrasive has to Therefore, if an inspector finds a 3-inch-square area in which be once again gathered and removed, the surface has to be more than 3 square inches are randomly stained, the area fails “Commercial Blast.” The math is easy; the stains are not. When is a Stain Not a Stain? Although the SSPC Protective Coatings Glossary defines a stain as “An area of a surface which, when compared to adjacent areas, has an equal surface profile but is discolored (usually darker) with a material having no apparent volume;” upon visual assessment, confusion remains about what constitutes a stain versus actual rust or mill scale left on the surface. How light, slight or minor do the “light shadows, slight streaks or minor discolorations” specified in SSPC-SP 6/NACE No. 3, Paragraph 2.1 have to be to pass, especially since the following paragraph (2.1.1) of the specification allows the same steel color variations as for “White Metal?” Beam end area has been blasted to a "Near White Metal" Just as for “White Metal Blast,” “Near White Metal” finish (SSPC-SP 10). and “Commercial Blast” require that “immediately prior to

test-blasted areas done as part of the contractor bid qualification or pre-job qualification, there should be a general agreement between the owner, contractor and third-party inspector. In advance of the project, a decision should be reached about what constitutes acceptable visual appearance of the prepared surfaces in order to conform to the specification standard. Inspection of the day’s surface preparation work should be an opportunity for agreement, not a source of frustration, confusion and conflict. After a commercial or near white blast of aged steel in a refinery or chemical plant environment (especially at a coastal location where high humidity and salt in the air are almost constant), it is often difficult to determine whether stains the inspector finds are allowable, or a result of degradation of the blasted surface. Newly-blasted support beam unit has flash rusted badly after an unexpected rain shower. According to the inspector, the most straightforward way to tell is to let the blasted area sit a while and see if the staining gets worse. From the contractor’s perspective, this can be perceived as an expensive way for the inspector to force a reblast. Using an agreed-upon visual comparison standard up front can help to avoid disagreement. SSPC-PA 17 Procedure for Determining Conformance to Steel Profile/ Surface Roughness/Peak Count Requirements Testing of a dry-abrasive-blasted surface for specified anchor profile can be a non-visual, quantifiable test. The traditional visual “comparator” test has been superseded by the use of profile replica tape, or of depth micrometer testing of the profile. Both replica tape and depth micrometer testing are quantitative measurements, but they measure only small samples of the entire prepared surface. The number of Light flash rusting on steel dry blasted to SSPC-SP 10. This area needs to be reblasted. required anchor profile tests should follow standards as a minimum or should be specified and agreed upon at the pre- job conference. Depth micrometer testing is highly accurate, coating application, the entire surface shall comply with the but measures only one pit per reading, so multiple groups degree of cleaning specified. Any visible rust that forms on of readings must be done to assure accuracy. The project the surface of the steel after blast cleaning shall be removed specification should clearly state the type and frequency of by recleaning…” But are the stains the inspector is finding blast profile tests required. on newly blasted “Near White Metal” or “Commercial” steel If newly-abrasive-blasted steel could be stabilized as it from before blasting, or are they new turning or rerusting of was blasted and without degradation, the inspector could the steel? inspect it and pass or fail the actual preparation work itself, rather than the preparation that has subsequently been Get the Picture affected by environmental conditions. Visual comparison standards for acceptable quality of The presence of salts on “White Metal” blasted steel sur- dry-abrasive-blasted surfaces (SSPC VIS 1) should be avail- faces has been known since before coating inspectors were able at the job site and should have been discussed and assigned CIP numbers. When the author was first learning agreed on at the pre-bid and pre-job conferences. Whether the offshore oil field maintenance painting business in the using available photographic standards, or digital photos of late 1970s, there was already a primitive test for salt residue

surface or more. The project specification should include the specific method to be used for testing for soluble salts. It may also include the number, frequency and location of tests. There is also a “visual” component — structures tend to corrode unevenly; verification tests have often shown widely varying results, indicating that surface contaminants are unevenly distributed on the prepared surface, tending to cluster or aggregate. This accounts for the phenomenon that some areas of the same abrasive blasted surface tend to flash rust faster and more severely than others. Both the equipment owner and a seasoned third-party inspector may have experience indicating where the structure being prepared will tend to corrode, that is, where the previous coating system failed the earliest or most exten- sively. Salt tests should be specified to be taken at precise areas which are expected to have the highest levels of resid- Moderate flash rusting on steel dry blasted to SSPC-SP 10. ual non-visible contaminants. Without such specificity, there may be disagreement. contamination on newly-blasted-steel surfaces. The original Wet surface preparation methods like wet-abrasive blast- field “salt test” consisted of licking the newly-blasted steel. ing or UHP water washing remove some non-visible contam- At that time the blasting medium was silica sand, and the inants, but the wet prepared steel surface can quickly flash steel looked clean “when viewed without magnification,” so rust as it dries. There are methods of inspecting a flash-rust- licking it was safe and sanitary, but you could always taste ed surface after wet preparation, but these are also entirely the salt. And, of course, the spot you licked immediately visual and are even more subjective than the “staining” flash rusted. Then the contractor painted over all that salt, described in SSPC-SP 6/NACE No. 3 or SSPC-SP 10/NACE because there was no cost-effective way of removing it. No. 2. The most common method of delaying flash rusting on SSPC Guide 15 dry-abrasive-blasted steel is dehumidification — reducing Field Methods for Extraction and Analysis of Soluble Salts relative humidity over the newly-blasted surfaces to a level on Steel and Other Nonporous Substrates where an electrolytic cell does not exist and flash rusting Since then, much more sanitary and quantifiable tests have cannot occur. been developed for measuring salt residues left on new- Dehumidification (DH) for the interior of a roofed tank ly-blasted surfaces. Different types of salt test procedures being dry-abrasive-blasted is relatively simple. There are few measure different groups of salts and it should be noted that and relatively small openings, and the steel sides and floor test results may vary, depending on the test method used. contain air and hold heat. Exterior structures can be scaffold- All the tests have in common the facts that they are expen- ed and tented with plastic sheeting to allow for DH, but such sive (anywhere from $10 to $40 for the test kit itself, exclud- tenting can be leaky and requires more DH to accomplish the ing the cost of the measuring device) and they are slow, originally desired results. In either case, the cost of running typically taking 10 to 30 minutes per test. All of the salt tests the DH system continuously can be very expensive, and if are also handicapped by two other factors: first, they mea- the DH is stopped for any reason, the blasted steel can quick- sure only a tiny area of the blasted surface, typically about ly flash rust. one one-hundredth of one percent, which is then assumed to An alternative and less expensive method of controlling be uniformly representative of the entire prepared surface, flash rusting after dry-abrasive blasting is the use of a and secondly, they do not specifically measure iron sulfides waterborne inhibitor chemical which changes the pH of left on the surface, and these are one of the primary causes the abrasive-blasted steel or leaves a thin residual coat on of flash rerusting. the blasted surface, or both. The inhibitor chemical can be A salt test measures salt concentration on two-to-four sprayed onto the newly-blasted surface immediately after square inches of the prepared surface and the test results blasting is completed or it can be used as a part of a wet- will be representing several hundred square feet of prepared abrasive-blast process.

Use of an inhibitor chemical allows a contractor some Whichever method is used, determination of the speci- time to finish abrasive blasting and cleanup, allows the fied level of surface preparation is predominantly a visual inspector time for a thorough inspection, and in some cases, process. To prevent disagreements, delays, frustration and allows abrasive blasting to continue for several shifts before costly reblasting; the end user, contractor and third-party in- shutting down, inspecting, and coating or lining the pre- spector should agree on visual acceptance standards before pared surfaces. surface preparation begins. The best way to reach agree- Inhibitors are frequently used during maintenance work ment is to use “visual” samples, preferably photos of accept- where the owner or inspector requires “Near White Metal” able surface preparation samples, available to all parties at appearance, but blasting and coating application cannot be the job site. done quickly enough to prevent flash rusting. The process is not recommended by paint companies but is frequently used About the Author in the oil and petrochemical maintenance areas. Peter Bock is vice president and technical service manager The dried inhibitor film is visually transparent. oT the for CorrLine International in Sugar Land, Texas. He is a U.S. inspector’s eye, the steel appears to be “Commercial” or Air Force veteran and has degrees “Near White Metal Blast,” (whatever the original standard from Tulane University and the and quality of blast), so it fulfills the visual standard. University of Northern Colorado. A third, relatively new method for controlling flash rust Bock has 37 years of experience with on abrasive-blasted steel is a proprietary waterborne pas- sales, management and technical sivation process. Unlike inhibitors, which must be applied service in oilfield and petrochemi- before any flash rusting occurs, the passivation process cal heavy-duty coatings in the U.S., claims to remove flash rust, restoring prepared steel to its Canada, Mexico, Venezuela, Indone- “White Metal” stage. Visual inspection and salt testing after sia, and Taiwan. He has experience the passivation process are the same as for newly dry-abra- with on- and offshore production, sive-blasted steel. drilling and workover rigs, shipyard work, natural gas and LNG, pipelines, terminals, refineries, and chemical plants. Conclusion He is a specialist in elevated temperature systems and CUI Surface preparation is the first and sometimes the most mitigation. JPCL important part of a successful industrial coating or lining project. Unfortunately, specification standards for surface preparation are almost entirely visual and can be somewhat subjective. After dry-abrasive-blast-surface preparation, properly prepared surfaces can quickly degrade from their initial state on completion of blasting, and need to be quickly inspected, approved and coated. Field-usable salt contamination tests can determine the presence of non-visible contaminants on visually-acceptable, prepared surfaces, but the tests available today are expensive, slow, and measure too small of a percentage of the prepared surface to be completely reliable. Flash rusting of a newly-abrasive-blasted surface can be prevented by dehumidification, which keeps humidity at the bare steel surface below a level where it can act as an electrolyte, by the use of inhibitors, or by a steel passivation process.