HIGH AND MEDIUM PRESSURE WATER PAINT STRIPPING PROCESSES
High and medium pressure water blast systems are used for paint stripping surfaces with low-volume water streams at pressures ranging from 3,000 to 15,000 psi (medium pressure operations), and from 15,000 to 55,000 psi (high-pressure operations). The medium pressure systems may be augmented with blast water additives and/or surface treatments. For example, sodium bicarbonate may be added to the water stream, or environmentally compliant chemicals may be applied to painted surfaces prior to water blasting. High-pressure systems typically use pure water streams. With both medium and high-pressure water systems, specialized nozzles can be used to achieve effects ranging from a relatively gentle, layer-by-layer removal of organic paints to removal of metal flame spray coating and other tough, tightly adherent coatings. The process water, paint, and residue are collected by the effluent-recovery system for filtering the paint and residue, removing leached ions (copper, cadmium, lead, etc.), microparticulates, chlorides, sulfates, nitrates, and other contaminants. The water is passed through a coalescing tank to remove oils and film, a through charcoal filter, microfilters and, finally, a deionization system to ensure that the water is Type IV or better deionized water. The recovered deionized water is recycled back into the process.
Currently, WR-ALC at Robins AFB uses a medium pressure water system (12,000 - 15,000 psi). The system is used for coating removal on the C-5, C-130, and F-15 aircraft and also some off-aircraft components. The system is used with either a non-hazardous air pollutant chemical remover, sodium bicarbonate blast media, or by itself depending on the coating being removed.
Use of high and medium pressure water paint stripping as a replacement for chemical paint strippers results in the following compliance benefits:
Compliance benefits include: 1) reduced recordkeeping and reporting requirements under the Clean Air Act Title V Operating Permits Program, NESHAPs Program, and SARA programs, 2) reduced administrative burden associated with hazardous waste (i.e., tracking, plans, reports, training), and 3) reduced administrative burden associated with OSHA (i.e., training and recordkeeping).
The compliance benefits listed here are only meant to be used as a general guideline and are not meant to be strictly interpreted. Actual compliance benefits will vary depending on the factors involved, e.g. the amount of workload involved.
No material compatibility problems have been documented for use of high and medium pressure water processes to de-paint metallic surfaces. However, according to Mr. Randy Ivey, Materials Engineering (WR-ALC/TIEDM) medium and high-pressure water streams can damage composite and honeycomb thin skinned materials. The use of specific chemicals to augment medium pressure water processes must be evaluated on a case-by-case basis.
|Safety and Health:||
Proper design, operation, and maintenance of the equipment is required for its safe use. Proper personal protective equipment is also recommended.
Consult your local industrial health specialist, your local health and safety personnel, and the appropriate MSDS prior to implementing this technology.
capital cost for high and medium pressure water processes will vary considerably,
depending upon the process and its application. Capital costs for medium
pressure systems range from $40,000 to $70,000 and capital costs for high-pressure
systems range from $850,000 to $1,500,000. According to PRO-ACT, the cost
of water is an integral part of the process and potential savings due to
recycling and elimination of surface washing following chemical paint stripping.
Annual Operating Cost Comparison for High Pressure Water Paint Stripping and Chemical Paint Stripping
Click Here to View an Active Spreadsheet for this Economic Analysis and Enter Your Own Values. To return from the Active Spreadsheet, click the reverse arrow in the Tool Bar.
Medium pressure water paint removal is an approved process in T.O.1-1-8. However, use of this process requires approval by the engineering authority of the specific Weapon System manager and Equipment Item Manager. High-pressure water paint removal systems are not recommended by the Air Force corrosion Program Office and technical guidance for the process is not provided. Use of this process must be approved by the engineering authority of the specific Weapon System Manager and Equipment Item manager.
For Air Force applications, high and medium pressure water paint stripping must not be used on any aircraft or weapon systems without the knowledge and approval of the appropriate system manager, office(s) having engineering authority on the specific airframe(s) and the Air Force Corrosion Program Office.
|Points of Contact:||
Air Force Corrosion
Prevention and Control Office
The following is a list of high and medium pressure water system vendors. This is not meant to be a complete list, as there may be other manufacturers of this type of equipment.