Brian Ballew SA-ALCRIESM 450 Quentin Roosevelt Road Kelly AFB, TX

Transcription

1 230 LOX Opportunity ASSessm ents Brian Ballew SA-ALCRIESM 450 Quentin Roosevelt Road Kelly AFB, TX SA-ALCTTIESM has been examining and evaluating different Liquid Oxygen (LOX) cleaning technologies as part of an opportunely assessment to support SA-ALC Single Managers owning equipment that uses LOX or high pressure oxygen. The objective of this opportunely assessment is to find technologies that will work for particular equipment. Maintaining cleanliness in oxygen systems is vital. First, the system will be providing oxygen to a crew or passengers for breathing. Any contamination or residues left in the system will be inhaled, possibly poisoning the users of the oxygen. Therefore, a cleaner must be nontoxic. Secondly, hydrocarbon residues, on the order of 5 mg/ft2, can react with liquid or gaseous oxygen and cause a fire. This fire can burn through the tubing and spread to other aircraft systems or the structure. It is important to use a process that will completely remove manufacturing by products such as grease and oil in the tube, and will not leave hydrocarbon residues such as surfactants. Finally, all particulate residues must be flushed from the tube. A particle that contacts the side of a tube can provide enough energy to initiate a fire in the system, even without the presence of hydrocarbons. This requires measures to flush particles from the tube during cleaning and to prevent them from entering the tube after it is cleaned. Luf thansa Maintenance fa cilities TIESM participated in the NATO initiated Oxygen Systems Cleaning Team tour of Lufthansa's maintenance facilities in Hamburg and Frankfurt Germany. The team documented Lufthansa's CFC-free oxygen cleaning processes. Commercial aircraft use high pressure gaseous oxygen for emergencies. The cleaning requirements are the same for gaseous and high pressure oxygen. Lufthansa cleans their oxygen regulators in a heated alcohol bath followed by a purging with nitrogen gas. Tubing is precleaned with a steam cleaner

2 711 then cleaned either in a heated alcohol bath or by half filling the tube with alcohol and agitating. Both processes are followed by purging the tube with nitrogen gas then plugging the ends and bagging the tube. Gages are inspected prior to calibration. If they are contaminated in any way, they are discarded. If a gage fails the check, it is discarded. Walk around (portable) oxygen bottles are sandblasted and inspected for corrosion or cracks. The phosphate treatment used for surface preparation prior to painting is used to clean the bottle out. Lufthansa uses Krytox grease sparingly to minimize excess accumulations of the grease that will interfere with equipment function or make equipment difficult to clean. Lufthansa does not try (and cannot with their alcohol bath) to remove KrytOx from their equipment. If a part is being repaired, it is wiped off with a clean, lint free cloth and inspected for particles. If this is satisfactory, the part is considered clean. Lufthansa does not clean tubing in place on an aircraft. In the few instances that the oxygen system has been contaminated, all of the lines were replaced. NADEP Cherry Point TlESM participated in a tour of NADEP Cherry Point's oxygen cleaning f aci I ities. NADEP Cherry Point is implementing the inorganic Navy Oxygen Cleaner (NOC) to clean LOX and breathing oxygen equipment. Their cleaning process is straight forward, but a significant amount of quality assurance is required to ensure safety. Oxygen components are disassembled and inspected. Excessively dirty parts are precleaned with a solution of 50% NOC and 50% water, with a few ml of non-ionic detergent added to prevent spotting (this solution is not for final cleaning). The solution is applied with a spray bottle and scrubbed by hand and rinsed with warm tap water. - Final cleaning is performed in an ultrasonic tank, heated to 150F, for 5-10 minutes. After the parts are cleaned, they are rinsed with warm tap water followed by a rinse with demineralized water heated to 11OF. The parts are then dried with nitrogen. If the NOC dries on a surface, it will leave a chalky white residue.

3 Quality Assurance procedures can be accomplished in the shop and the laboratory. Shop procedures are to inspect the solution for particles, foaming and proper ph. The laboratory Quality Assurance process is to filter a prepared sample through a teflon filter and compare the weight of the residue to the weight of residue from the freshly prepared solution before it was used. If the batch is out of specification, it is discarded. LOX Crossfeed TlESM participated in the LOX Crossfeed, held at Tinker AFB, 15 Jun 95. There were many presentations from the Navy, Air Force, NASA and industry. The Navy's Navy Oxygen Cleaner (NOCI was discussed in detail both by NAVSEA and NADEP Cherry Point. Both of these presentations emphasized the need for quality checks on the cleaning processes. New solvents, such as HCFC-225, which are potential replacements for CFC-113 were also discussed. These solvents do have potential, but are not withuut drawbacks such as cost, health questions and potential regulations. The Air Force gave a brief review of the trip to Lufthansa. The difficulty of cleaning gages with anything but CFC-113, was another topic of interest. Some locations will continue to use CFC-113 for the foreseeable future. NASA is buying gages with tubes that can be opened to simplify cleaning, although these gages are more expensive. Wilford Hall Hospital TIESM visited the Wilford Hall Medical Center (WHMC) at Lackland AFB to see how their oxygen system is maintained. They convert LOX into oxygen onsite. WHMC's oxygen system is operated at 50 psi. Every three months the oxygen systems in the wings of the hospital are checked for proper pressure. This check is made with a gage calibrated inhouse. If a faulty gage is found, it is discarded and replaced. If an operator suspects a gage is wrong, it is checked in their maintenance shop, and if it is faulty the gage is replaced. New pressure gages are checked in the shop to ensure they are correctly calibrated. The shop uses a desk top calibration unit specifically designed for hospital needs. This unit is returned to the manufacturer every year for maintenance. Only 232

4 777 very expensive gages used for hyperbaric medicine are sent to a PMEL for maintenance. Regulators and flow meters are repaired inouse. The solvent used to clean these parts is ethyl alcohol. SA-ALC/LAP Tubing Shop The LAP tubing shop bends stock tubing to necessary shapes for LOX as well as for other fluids. A part of this process is to use oils to lubricate a mandrel inserted in the tube to maintain its shape. These oils must be removed from the tube before it is installed on the aircraft. The LAP Tubing Shop uses a perchloroethylene vapor degreaser to remove the contaminants from the tubes. Perchloroethylene is LOX compatible. However, it is an EPA 17 chemical and its use does incur disposal costs. Air quality specialists at Brooks AFB were contacted about possible health affects for the crew. In their opinion, as long as the perchloroethylene and its residues are completely removed, there will be no problem. LAP has discovered no problems with their tubing. Alternatives exist, specifically, LoxCLEAN Systems Inc, in San Diego, manufactures equipment that plugs into both ends of a tube and can clean it to LOX standards, using the Navy's NOC cleaner. SA-ALC/EM, LAP and TIESM are working to purchase and install this equipment. LAP Hydrostatic Shop The LAP Hydrostatic Shop is responsible for maintenance of the LOX equipment on the C-5. There work on LOX equipment mainly consists of removal of equipment that is sent to other locations for repair. They will tighten fittings and perform routine maintenance if necessary. They clean fittings with alcohol and blow dry them to remove any residue. As a side note, this shop does not even have authorization to use CFC-113. Precision Measurement Equipment Laboratory (PMEU shop at Kelly AFB I toured the PMEL gage cleaning area. Gages are brought into the area as part of the calibration interval determined by Aerospace Guidance and

5 3?L Metrology Center. The gage is not cleaned, rather freon is pumped through it to remove residues that might contaminate the calibration equipment. The gage is "cleaned" in just that way. The gage is attached to a piece of equipment that pumps CFC-113 through the bourdon tube of the gage. The freon is checked under a black light, when no florescence is seen (an indication of oil) the gage is declared clean. Approximately 6 oz of freon is needed to accomplish this. After the gage is "cleaned," it is calibrated. If the gage is acceptable, the gage is returned to service. If not, it is thrown away, as all but a few gages can be opened to adjust them. Conclusions There are alternatives for cleaning LOX and high pressure oxygen systems. The solution, as in all pollution prevention solutions, depends on what you are trying to accomplish. When cleaning LOX or high pressure oxygen equipment, compatibility and common sense is the key. Questions to ask before making a change. Why clean the part? Is your final cleaning process going to leave a residue that will be incompatible? Can you measure the residue? Is the part worth cleanjng? Can it be thrown away? Can a gage be calibrated without removing it? Is it best to continue with using CFC-113? SA-ALC is asking these questions about the equipment we manage. In some instances there may be process changes that are simple to accomplish and implement. In some cases, the changes may be difficult to incorporate. There may be even a few processes that will remain the same. Whatever the particular solution for a particular item will be, we are committed to give the best answer. The replacements will be made in the appropriate system TOS or new general series TOs that will cover entire classes or similar equipment that requires LOX or high pressure oxygen systems cleaning.

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