A slightly higher purity standard than that in Table 12-7 has been
established for the atmosphere of a saturation diving complex. This
requirement is presented in Table 12-9.
The most comprehensive list of contaminants which must be considered, if
there is any possibility that they may be present, is contained in BUMED
INSTRUCTION 6270.3, Exposure Limit Values for Health Hazardous Air
Contaminants (see Reference (3)).
3.
PIPING AND GAS STORAGE SYSTEMS. The procedures for cleaning piping and
gas storage systems can be very simple such as continuous steam flushing for
several hours, through flushing with hot water and a non-ionic household
detergent or brush scrubbing with hot soapy water. These simple procedures
are particularly applicable to conventional recompression chambers which do
not go deeper than about 200 feet. These procedures can be used for deeper
systems, bearing in mind that they must pass the final gas purity test.
Systems can be flushed as a continuous circuit or taken apart and cleaned as
separate pieces. After cleaning has been completed, the piping and gas
storage systems must be thoroughly dried. This drying of a system is more
difficult than it may appear because a piping system contains many small
recesses in which liquids can be trapped and from which the drying takes
place very slowly. In general, a recompression chamber can be dried in about
10 to 20 hours by a slow flow of warm, dry, clean air. If available, dry
nitrogen can be used but it is no better than dry clean air. The drying can
be speeded up by pulling a vacuum on the system and then gently warming the
hardware with something like a hot air gun.
4.
OXYGEN HIGH PRESSURE AND HIGH CONCENTRATION SYSTEMS. Cleaning systems
which will contain oxygen under high pressure or in concentrations greater
than 30 percent by volume is altogether different from cleaning a breathing
air system. It is essential that all traces of combustible substances be
removed from the oxygen system by one of the standardized methods of cleaning
for oxygen service.
5.
CLEANING STANDARDS AND SPECIFICATIONS. There are many standards and
specifications which give very detailed procedures for cleaning and testing
for cleanliness level of gas systems which are to be used for Naval breathing
gas and oxygen piping. The fabricator and user are advised to critically
select the method which will best meet the needs of his system. A few of the
many standards and specifications are listed below:
BUSHIPS 9230.12 Oxygen and Nitrogen Piping Systems, Cleaning, and
Inspection of
MIL-STD-767 Cleaning Requirements for Special Purpose Equipment,
Including Piping Systems
MIL-STD-1246 Product Cleanliness Levels and Contamination Control
Program
MIL-STD-1330 Cleaning and Testing of Oxygen and Nitrogen Gas Piping
Systems
MIL-STD-1359 Cleaning Methods and Procedures for Breathing Oxygen
Equipment
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