5.
PRESSURIZATION/DEPRESSURIZATION. The limiting pressurization/
depressurization rates must be known and provision for adherence to these
limits designed into the chamber systems.
a. Pressurization. The pressurization rate for hyperbaric chambers will
vary from a few feet per minute to the higher rates required for submarine
escape training. Design pressurization rates for chambers intended for
treatment of decompression sickness should be 100 feet per minute from 0 to
165 feet seawater pressure.
b. Depressurization. Design depressurization rates should be in
accordance with the diving decompression schedules listed in the U.S. Navy
Diving Manual (Reference (3)). Normally, the capability for very slow
depressurization is required, 4 feet per hour being a typical rate. The
control system design should incorporate automatic mode to relieve the
chamber operator at the slow rates.
Section 2.
AIR SYSTEMS
1. COMPRESSED AIR SYSTEMS. Compressed air systems are used mainly in
recompression chambers, experimental air diving, and air saturation diving
hyperbaric complexes. This section discusses the basic elements of an air
system as shown schematically in Figure 6-9.
2.
INTAKE AIR FILTER. Regardless of how clean the atmospheric air is at
the point of compressor suction, the air must be filtered to prevent
contamination and unnecessary wear in the compressor. Under local
contamination, such as exhaust of an internal combustion engine near the
suction filter, the compressor or the engine must be shut down. In cases
where an emergency diesel generator is installed in the facility, an
electrical interlock which will shut down the compressor when the generator
starts is desirable.
Air intakes should be located in the open, well above ground level and sited
as far as possible from equipment which emit impurities. Hoods, screens,
and/or filters should be used to protect the intake from rain, hail, and
other wind-borne debris.
Compressor manufacturers will supply requirements for pressure drop through
intake piping and filtering. The manufacturer will also provide the maximum
length and size of intake piping recommended so as not to damage the
compressor. If this information is not supplied by the manufacturer, it is
recommended that the pressure drop not exceed 3 inches of water. A dry type
intake filter is recommended over all other types, an oil bath type is
prohibited.
3. COMPRESSOR. The air compressor should have the required output flow
capacity and discharge pressure of compressed air at an acceptable air purity
with good reliability and low maintenance.
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