U.S. Department of Labor
Process: Surface Preparation and Preservation
Work Processes Used in Surface Preparation and Preservation
Surface preparation, paint, and other protective coatings used in shipbuilding and ship repair pose a hazard to workers. Potentially harmful substances can enter the body through inhalation, ingestion, and contact with the eyes or skin. Surface preparation requires pre-planning and evaluation of the area for potential hazards before beginning work.
Employers must assess the work activity and, where necessary, implement engineering controls or provide workers with the appropriate personal protective equipment (PPE) (e.g., gloves, respirators, protective clothing, hearing protection) to prevent exposure to such harmful substances (29 CFR 1915, Subpart I). A Shipyard Competent Person (SCP), Certified Industrial Hygienist (CIH), or Certified Marine Chemist (CMC) may be needed to help evaluate hazards and recommend PPE. Surface preparation and preservation work performed in enclosed or confined spaces presents additional hazards and should be assessed with particular attention on those hazards.
Typical surface preparation and preservation operations include:
- Abrasive Blasting - This is the most common surface preparation technique used to remove old paint and other surface materials such as rust, mill scale, dirt, and salts. This method is usually conducted during vessel fabrication (e.g., on piping, steel plates and steel members used in structural assemblies, and other miscellaneous materials) and during maintenance and repair operations that include blasting and painting the ship's hull, and interior tanks and spaces. During abrasive blasting activity, there is a potential for workers to be struck by rebounding abrasive blast material (for example, sand, metal or slag) and be exposed to toxic dust from abrasive blast material and coatings (such as silica, paint and grease) being removed. Further, workers may be at risk for possible falls as a result of pressure surges in the hose line, tripping over equipment (such as hoses), and poor visibility. This is particularly a concern when workers are conducting abrasive blasting from elevated work surfaces, such as scaffolding. Static electricity and elevated noise levels are also hazards that workers could be exposed to during abrasive blasting operations.
- Hydro-Blasting - This is a cavitating (bubble-producing) high-pressure water jet stripping system that uses an engine-driven high-pressure pump, a large volume of water, high-pressure hose, and a gun equipped with a spray nozzle. The high-pressure water stream can reach as high as 50,000 psi, and the water can contain added abrasives to further assist with removing hard coatings from metal substrates. Some systems (e.g., robotically driven) reuse (recirculate) the water for additional blasting by automatically removing the paint chips or stripped materials from the water. Similar to abrasive blasting, use of this system may expose workers to elevated noise levels, falls, and toxic or hazardous substances in coatings. Further, this process may produce hazardous waste which would require compliance with applicable local, state, and Federal environmental regulations.
- Chemical Stripping - This is a coating removal method involving the use of organic (e.g., methylene chloride-based solutions) and inorganic (e.g., caustic soda solutions) strippers, often immersing small parts in dip tanks containing the solution. Parts are then rinsed to remove any stripping solution residue. Potential hazards include: inhalation of toxic vapors and skin or eye contact with liquids produced through reactions between the cleaner and the material being removed.
- Thermal Stripping - The use of a flame or a stream of superheated air to heat and soften hardened coatings (such as paint), allowing for easy removal. While useful for small parts, this method is labor intensive and not suitable for heat-sensitive surfaces. Workers could be exposed to fumes and smoke. A fire watch and/ or hot-work permit may be required when conducting this type of operation.
- Mechanical Stripping - The use of needle guns, chipping hammers, sanders, and grinders to remove coatings from small parts and surfaces. While some power tools may be equipped with dust collection systems, generally hazardous levels of paint waste and airborne particulate may be emitted. High noise, flying particles, and sparks produced when grinding are concerns for workers engaged in this activity. When performed from elevated work surfaces, such as scaffolding, workers have the potential risk for falls.
- Painting - The application of paint through brush, roller, and spray methods. Depending on which paint application method is used, there is a potential for workers to be exposed to toxic materials and flammable or explosive mists, particulates, and vapors. When performed from elevated work surfaces, such as scaffolding, workers have the potential risk for falls.