EvaluationsDuring the evaluations, the CHP coatings removal process demonstrated several significant advantages over other removal techniques:
- Low Blast Pressure. Blast pressures typically range from 20-35 pounds per square inch (psi), depending on the coating system and substrate material. At these low pressures, coatings can be successfully removed without damaging the substrate.
- Reduced Waste Generation. The CHP media can be recycled, on average, between five to 10 times before it is spent. The media actually performs optimally after the first few cycles, as it breaks down and forms its sharply defined edges.
- Drop-In Replacement. The process can be used in standard light abrasive equipment. It also can be considered as a drop-in replacement for many plastic media blasting (PMB) systems, as it meets MIL-P-85891 for Type VII media.
- Environmental Stewardship. CHP is 100% organic, non-toxic, and biodegradable. In addition, the CHP coatings removal process meets DoD environmental, pollution prevention and toxic chemical use reduction requirements.
- The U.S. Navy (Naval Station Mayport, Naval Air Depot [NADEP] Jacksonville, FL, Naval Submarine Base [NSB] Kings Bay, GA Trident Refit Facility [TRF])
- The U.S. Air Force (Robins Air Force Base [AFB], FL)
- The National Aeronautics and Space Administration (NASA) (Kennedy Space Center, FL, Acquisition Pollution Prevention [AP2]).
- Radar domes (radomes)
- Aircraft speed brakes
- Helicopter blades
- Propeller spinner caps
- Passive Counter Measure System (PCMS) radar-absorbing material, surface ship life raft shells
- NASA Shuttle panels
Materials TestedAs part of the evaluation, project stakeholders contributed materials to be subjected to the CHP removal process. These materials included the following items:
- A P-3 Orion aircraft radome panel was provided by NADEP Jacksonville. The P-3 radome is composed of a polyester fiberglass substrate and was coated with a MIL-PRF-23377 epoxy primer and a MIL-PRF-85285 polyurethane topcoat (see Figure 3). Currently hand sanding and chemical stripping techniques are used to remove coatings from P-3 radomes. During the CHP evaluation, the coatings were removed at a rate of 12 square feet per four (ft2/hr), with no resulting substrate damage (see Figure 4). It is estimated that 34 hours of sanding/chemical stripping per radome could be replaced by seven hours of CHP coatings removal.
- MK-92 surface ship radome panels were provided by SERMC, Naval Station Mayport. The radome is composed of a honeycomb fiberglass substrate (single honeycomb layer on the upper portion of the radome and a double-layered honeycomb on the lower portion of the radome) (see Figure 5). An enamel coating was deposited on the substrate. Coatings on the MK-92 radome are currently removed via hand sanding. During the CHP evaluation, the coatings were removed at a rate of approximately 32 ft2/hr, with no resulting substrate damage (see Figure 6). It is estimated that 62 hours of hand sanding per radome could be replaced by eight hours of CHP coatings removal.
- A SH-60B Blackhawk helicopter blade was provided by the AIMD at Naval Station Mayport. The blade was composed of a titanium, fiberglass, and carbon graphite matrix composite substrate and the coating system consisted of polyurethane. On one section of the blade the coatings were removed to the primer at a rate of 29 ft2/hr, and on a separate section the coatings were removed to the substrate at a rate of nine ft2/hr, with no resulting substrate damage in either case (see Figure 7). At the AIMD, hand sanding is used to remove coatings from small sections of the blades (i.e., approximately 2 ft2). At the AIMD alone, it is estimated that a two-hour hand sanding job per blade could be replaced by five minutes of CHP coatings removal. Significantly greater savings may be realized at both U.S. Army depots and U.S. Navy aviation repair facilities, where most helicopter blade maintenance and overhaul is completed and where hand sanding is used extensively.
- Several sections of Type 3R PCMS radar-absorbing material were provided by SERMC, Naval Station Mayport. With the CHP process, average coatings removal rates of 35 ft2/hr were achieved, with no resulting damage to the tiles (see Figure 8).
- A F-18 Hornet antenna cover was provided by NADEP Jacksonville. The antenna cover is composed of an epoxy fiberglass substrate and is coated with an epoxy primer and polyurethane topcoat. During the evaluation, the topcoat was removed at a rate of 11 ft2/hr, with no visual damage to the component (see Figure 9).
- A C-130 Hercules propeller spinner cap was provided by Robins AFB. The spinner cap is composed of a fiberglass substrate with an electrical wire matrix embedded inside. The coating system consists of white surface PM 8-W-5 primer and a polyurethane erosion resistant topcoat. During the evaluation, the coatings were removed from the substrate at an average rate of 10 ft2/hr, with no resulting substrate damage (see Figure 10). It is estimated that 16 hours of hand sanding per spinner cap could be replaced by one hour of CHP coatings removal.
Pursuing ImplementationFollowing the proof-of-concept evaluation, the team completed a cost analysis to quantify the potential cost savings that could result from replacing the current removal processes with CHP. The data were provided by the respective stakeholders and Midvale Environmental Technologies, and they included labor, material and utility costs. The analysis indicated that implementing the CHP coatings removal process could result in cost avoidances from $20,000 to more than $1.5 million annually, depending on the throughput of the components.
For more information, contact Bob Tierney, Naval Station Mayport, FL, 904,270,6730, ext. 204, firstname.lastname@example.org; or Brad Biagini, Concurrent Technologies Corp., National Defense Center for Environmental Excellence, 814.269.2840,email@example.com.
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