U.S. Department of Labor
Process: Surface Preparation and Preservation
The three predominant spray methods used in shipyard employment include high-pressure, airless, and high volume low pressure (HVLP) systems. Not one method is better than the other, but preferences may be determined based on the desired outcome and facility resources. Regardless of which type of system is used, similar hazards exist with all.
Typical high-pressure conventional spray painting occurs when paint is applied to an object through the use of an air-pressurized spray gun. The air gun has a nozzle, paint basin, and air compressor. When the trigger is pressed, the paint mixes with the compressed air stream and is released in a fine spray. Normally, a manual operation method is used in vessel spraying where the air-gun is held by a skilled operator, about 6 to 10 inches (15–25 cm) from the object, and moved back and forth over the surface, each stroke overlapping the one previous to ensure a continuous coat.
Airless spraying systems are powered by a high-pressure pump, ranging in pressure from 300 to 7,500 pounds per square inch. This method allows coatings to better penetrate pits and crevices, applies a uniform thick coating, and reduces the number of coats needed to be applied. Also, airless pumps have the versatility to be powered by a range of different types of motors such as electric, compressed air (pneumatic) or hydraulic.
HVLP systems deliver air at a much higher volume, but with a much lower pressure so that more of the paint or coating ends up on the surface instead of in the air. There are two different types of HVLP spray gun systems; conversion high-volume low-pressure system and turbine air system. The first utilizes traditional air compressor equipment and accessories, but at a much lower pressure (approximately 25 pounds per square inch), while air turbine systems operate from an air turbine instead of an air compressor, delivering an extremely high volume of air at very low pressure (about 4 to 6 pounds per square inch).
Hazards and Control Measures
During spray painting operations, paint is forced into the atmosphere under pressure through a restricted opening. The breakup of a liquid into small particles to produce a fine mist is known as atomization. The atomization of paint increases the surface area of the liquid. Although this method is favored for painting large areas in a fairly short amount of time and, in some cases, using less product than with brush or roller applications, two primary hazards exist -- worker exposure to toxic or hazardous substances and fires or explosions.
While the use of highly toxic coatings has been greatly reduced over the years, the potential for workers to become exposed to compounds in excessive concentrations still exists. Workers performing spray paint operations are at a higher risk for respiratory exposure to these toxic vapors than with brush or roller applications. Exposure occurs when the paint becomes airborne -- not only increasing coverage of surface area, but the rate of release of toxic vapors into the atmosphere. This is especially true in a confined space. OSHA standards specify permissible exposure limits (PELs) for workers (29 CFR Part 1915, Subpart Z). However, OSHA recognizes that many of its PELs are outdated and inadequate for ensuring protection of worker health. This has been demonstrated by the reduction in allowable exposure limits recommended by many technical, professional, industrial, and government organizations, both inside and outside the United States. To provide employers, workers, and other interested parties with a list of alternate occupational exposure limits that may serve to better protect workers, OSHA has annotated the existing Z-Tables with other selected occupational exposure limits (Permissible Exposure Limits – Annotated Tables). Where adequate engineering and administrative controls are infeasible to control worker exposure to toxic or hazardous substances, employers must provide workers with the appropriate PPE for the work activity being performed (29 CFR Part 1915.152).
During the handling of highly volatile paints, workers face, eyes, head, hands, and all other exposed parts must be protected (29 CFR 1915.35(b)(9)). To prevent skin contact, an appropriate protective suit and gloves should be worn. Safety goggles, glasses, or face shields must be worn to prevent paint or coatings from coming into contact with workers' eyes. During spray paint operations, a full face respirator or loose fitting hood respirator can also serve as effective eye protection.
Due to the wide range of chemical hazards involved in coating operations, a "one type fits all" approach for protection does not exist. Employers should consult with the manufacturer, or look to the manufacturer's SDS, to determine the best type of material that will prevent exposure (Appendix A to Subpart I of Part 1915 – Non-Mandatory Guidelines for Hazard Assessment, Personal Protective Equipment (PPE Selection, and PPE Training). The same determination should be made with gloves, as not all gloves will provide an equal level of protection from the particular coating being used. In some cases, barrier creams may be an appropriate method of protection.
OSHA requires that workers wear respirators when working with paints and tank coatings mixed with or dissolved in volatile, toxic, or flammable solvents, even when mechanical ventilation is in use (29 CFR 1915.35(a) and (b)). During exterior paint spraying operations with paints dissolved in volatile, toxic, or flammable solvents, workers must be protected by a suitable filter cartridge type respirator (29 CFR 1915.35(b)). In confined spaces, tanks or compartments, airline (or supplied-air) respirators must be used during spraying operations with paints mixed with toxic vehicles or solvents (29 CFR 1915.35(a)). The air supplied to airline or supplied-air respirators must be tested and determined suitable for human consumption. Compressed breathing air shall meet at least the requirements for Grade D breathing air described in ANSI/Compressed Gas Association Commodity Specification for Air, G-7.1-1989, (29 CFR 1910.134(i)(1)(ii)).
Respirators are also required along with mechanical ventilation regardless of whether the work area is large and well-ventilated (29 CFR 1915.35(a)(1)(i) through (iii) and (b)(1)). Filter respirators are required during brush applications of paints with toxic solvents in confined spaces or in other areas where there is limited ventilation (29 CFR 1915.35(a)(2)). Workers entering such compartments for a limited time must also be protected by filter respirators (29 CFR 1915.35(b)(13)).
For operations involving the use of materials containing hazardous substances, such as cleaning solvents and isocyanate-containing epoxy and polyurethane coatings, ventilation must be used to remove the vapor at the source and to dilute the concentration of vapors in the space to a safe level (29 CFR 1915.32(a)(2)). If vapors cannot be diluted to a safe concentration, suitable respiratory protection in accord with the requirements of 29 CFR 1915, Subpart I must also be worn, as well as suitable clothing and equipment to provide skin and eye protection (29 CFR 1915.32(a)(3)).
Personal hygiene is also an important aspect to keeping workers safe. Effective hand washing practices after the application of paints and coatings will help to reduce possible ingestion of toxic chemicals. Employers must train workers on the importance of washing both hands and face, following the application of paints and coatings, at the end of the workshift and before eating, drinking or smoking, to minimize the risk of ingestion of hazardous substances (29 CFR 1915.88(e)(3)).
Organic coatings, adhesives and resins are often dissolved with highly toxic, flammable and explosive solvents with flash points below 80°F. When the potential exists for paints or coatings to produce a flammable atmosphere, employers must follow the safety precautions provided in 29 CFR 1915.36 and 29 CFR 1915.35(b). Sufficient exhaust ventilation must be used when working with such materials to keep the concentration of solvent vapors below 10% of the lower explosive limit (LEL) (29 CFR 1915.35(b)(1)). A competent person must conduct frequent tests to ascertain the concentration of solvent vapors. If the concentration of solvent vapors reaches or exceeds the LEL, painting must stop and the area evacuated. If the concentration does not fall when painting is stopped, the employer must supply additional ventilation to bring the concentration to an acceptable level (29 CFR 1915.35(b)(2)). Exhaust ducts must be discharged to an area away from other work areas and sources of possible ignition. The employer must conduct periodic testing of the exhaust and surrounding areas (around the vessel or dry dock) to ensure that the exhausted vapors are not accumulating (29 CFR 1915.35(b)(4)).
Only certain types of equipment are permitted for use in and around work areas where highly toxic, flammable and explosive solvents with flash points below 80°F are present. All motors and associated control equipment must be explosion proof and properly maintained and grounded (29 CFR 1915.35(b)(5)). Also, fans must have non-sparking blades, and portable air ducts made up of non-sparking materials (29 CFR 1915.35(b)(5)). It is important to remember that while a ventilator may have a non-sparking fan it may not meet the requirements to be considered explosion-proof.
Additionally, in cases where liquid solvents, paint and preservative removers, and paints or coatings are capable of producing a flammable atmosphere, the below control requirements and hazard solutions must be taken.
Liquids/substances with flashpoints 80°F and above
- Hot work must not be performed in the space or adjacent spaces during painting operations (29 CFR 1915.14(a)(1)(i)).
- Rags soaked with solvents must be kept in covered metal containers (29 CFR 1915.36(a)(3) and 29 CFR 1915.81(a)(5)).
- Paints, thinners, and solvents must be kept in fire-resistant covered containers when not in use (29 CFR 1915.81(a)(5)).
- Smoking and open flames must be prohibited in the area (29 CFR 1915.36(a)(1)).
- Arcing and sparking equipment and tools must not be used (29 CFR 1915.36(a)(1)).
- Equipment that may generate static electricity (e.g., ventilation systems) must be grounded and bonded. (29 CFR 1915.35(a)(4)).
- Only explosion-proof lights must be used (29 CFR 1915.36(a)(4)).
- Adequate ventilation must be maintained in storage, mixing, and transfer areas (29 CFR 1915.36(a)(2)).
- Frequent tests must be required during painting operations to determine if air concentrations are below 10 percent of the LEL (29 CFR 1915.36(a)(2)).
- Suitable firefighting equipment must be immediately available (29 CFR 1915.36(a)(6)).
- 30-gallon drums and containers of flammable or toxic liquids must be placed in an area where they will not be subject to physical damage (29 CFR 1915.173(d)).
- 55-gallon drums containing flammable or toxic liquids must be surrounded by dikes or pans (29 CFR 1915.173(e)).
- Power and lighting cables must be inspected by a competent person to verify that the insulation is in excellent condition and free of all cracks and worn spots, that lines are not overloaded, and that they are suspended with sufficient slack to prevent undue stress or chafing. The competent person must ensure there are no electrical connections within 50 feet of paint the operation (29 CFR 1915.36(a)(5))1.
- Spills of solvents should be cleaned up immediately.
Liquids/substances with flashpoints below 80°F
- Sufficient exhaust ventilation must be provided to keep the concentration of solvent vapors below 10 percent of the lower explosive limit (LEL). Frequent tests must be made by a competent person to ascertain concentrations (29 CFR 1915.35(b)(1)).
- If the concentration exceeds 10 percent of the LEL, work must be stopped and the compartment evacuated until the concentration falls below 10 percent of the LEL (29 CFR 1915.35(b)(2)).
- Ventilation must be continued after painting is complete until the space or compartment is gas free. (29 CFR 1915.35(b)(3)).
- Exhaust ducts must discharge clear of working areas and away from sources of possible ignition (29 CFR 1915.35(b)(4)).
- Periodic tests must be conducted by the Shipyard Competent Person to ensure the exhausted vapors are not accumulating in other areas within or around the vessel or dry dock (29 CFR 1915.35(b)(4)).
- All motors and control equipment must be explosion proof, and fan blades and portable air ducts non-ferrous (29 CFR 1915.35(b)(5)).
- All footwear worn during painting operations must be non-sparking (29 CFR 1915.35(b)(9)).
- PPE must not produce static electrical sparks (29 CFR 1915.35(b)(9)).
- No matches, lighted cigarettes, cigars, pipes, cigarette lighters, or ferrous articles are allowed into the work area (29 CFR 1915.35(b)(10)).
- All solvent drums taken into the compartment where painting operations are being performed must be placed on nonferrous surfaces and grounded to the vessel (29 CFR 1915.35(b)(11)).
- All metallic parts of paint spraying equipment must be grounded and bonded to the vessel (29 CFR 1915.35(b)(12)).
Static electricity during spray painting operations may be generated in ventilation or air moving equipment, and is a potential source of ignition in the presence of flammable substances. Electrical equipment rated for the specific flammable environment (i.e., explosion proof), and bonding and grounding of equipment are engineering controls that must be used to reduce the risk of ignition in the presence of flammable gases or vapors (e.g., from paints, cleaning agents, or other flammable liquids) (29 CFR 1915.35(b)(5) and (b)(12)). Prior to entry, a competent person must test the space to determine the concentration of flammable vapors and gases within the space (29 CFR 1915.12(b)). Explosion proof ventilation equipment (electrically rated for the specific flammability or explosion hazards) must be provided by the employer to maintain the concentration of flammable vapors and gases below 10% of the LEL before workers are permitted to enter the space (29 CFR 1915.12(b)(2)).
The following static electricity safety requirements apply where paints are dissolved in highly flammable liquids or gases, such as methane, acetylene, gasoline, acetone, or alcohols:
- All air-moving equipment or devices and metallic components, including ductwork, capable of generating a source of ignition through static electric discharge, must be electrically bonded to the structure of the vessel or vessel section or, in the case of land-side spaces, grounded to prevent an electric discharge in the space (29 CFR 1915.13(b)(11) and 29 CFR 1915.35(a)(4)).
- Motors and associated control equipment must be properly maintained and grounded (29 CFR 1915.35(b)(5)).
- Use only non-sparking paint buckets, spray guns and tools. Metal parts of paint brushes and rollers must be insulated (29 CFR 1915.35(b)(6)).
- Erect staging (scaffolds) in a manner that ensures it is non-sparking (29 CFR 1915.35(b)(6)).
- Ensure the proper use of required PPE (29 CFR 1915.35(b)(9), (b)(13) through (14)).
Amputations, lacerations, burns, and loss of eye-sight are additional hazards associated with spray painting operations. Such injuries may result from contact with high-pressure painting equipment, uncontrolled high-pressure hoses, and air leaks. OSHA requires that compressed-air hoses and connections be inspected before use. Visually damaged and unsafe hose must not be used (29 CFR 1915.131(h)). The following are some recommended solutions to avoid such hazards:
- Control access to the area of operation.
- Maintain high-pressure spray equipment according to the manufacturer's instructions.
- Use paint pots with appropriate pressure regulators or ratings.
Waste Management and Prevention
When spray paint operations are completed, the paint lines are typically flushed with a solvent to remove the coating from the line. Often the cleaning solvent can be as hazardous, or more hazardous as the coating being removed. The precautions discussed previously in regard to fire and explosion, as well as exposure protection for workers, must be followed. This includes limiting ignition sources, providing ventilation as necessary, and using appropriate PPE to prevent contact, inhalation or ingestion of the material. Also, grounding and bonding must be used to eliminate a potential ignition source.
Further, all waste materials need to be disposed of in accordance with local, state, and federal regulations.
1 On vessels, 29 CFR Part 1910, Subpart S is applicable when shore-based electrical installations provide power for use aboard vessels (e.g., the power from the electrical system comes from shore or from portable electrical generators), but does not apply to a vessel's permanently installed electrical systems. Under that standard, when determining what connections are safe or unsafe in or near paint operations, each must be evaluated based on the class of location in which they are intended to be used and the ignitable or combustible properties of the specific gas or vapor present (29 CFR 1910.307(c)(2)). The National Electrical Code, NFPA 70, lists and defines hazardous gases, vapors, and dusts by "Groups" characterized by their ignitable or combustible properties, and also contain guidelines for determining the type and design of equipment and installations that are approved for a specific hazardous (classified) location. Examples of such design principles and equipment characteristics may include the use of positive pressure ventilation, as well as explosion proof, non-incendive, intrinsically safe, and purged and pressurized equipment.
F-18, F-19, F-20, F-21, F-22, F-23