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 Section 4 OPERATION OF COMPRESSED AIR DISTRIBUTION SYSTEMS
1 SAFETY PRECAUTIONS.
1.1 Explosion Hazards. Although compressed air at all pressures can be
dangerous, high-pressure systems are especially so. Serious explosion
possibilities exist in compressed air systems whenever high-pressure air is
suddenly admitted into pockets or dead ends which are at or near atmospheric
pressure. The air temperature in the confined space is increased to the
ignition point of any flammable material that may be present. This
autoignition or diesel action has been the cause of serious explosions that
r e s u l t e d in loss of life and complete destruction of facilities. Such an
explosion can create shock waves that travel throughout the compressed air
system and may possibly cause explosions at remote points. Under such
c o n d i t i o n s , a small quantity of oil residue, or even a small cotton thread,
m a y be sufficient to cause ignition.
1.2 Preventive Measures. As a safeguard against explosions in high-pressure
compressed air systems, a number of precautions should be taken.
(a) Use of Slow-Opening Valves. These valves are used in pocketed
spaces such as lines to gauges and regulators to prevent a sudden pressure
rise in these spaces.
( b ) Elimination of Flame Arrestors. Flame arrestors. sometimes used to
prevent flame propagation in pipelines, s h o u l d not be installed in high-
-pressure air systems as they may create additional hazards.
( c ) Pipe Coloring. H i g h - p r e s s u r e air lines
a r e identified with a
painted light gray band and adjoining light green
arrowhead pointing in the
n o r m a l flow direction. These markings are placed
o n high-pressure air lines
at each point where piping enters or emerges from
a wall and immediately
a d j a c e n t to all valves, regulators, check valves,
s t r a i n e r s , and other
components
( d ) Location of Equipment. High-pressure air storage and dryer
c y l i n d e r s are isolated from other facilities as a precaution against damage
t h a t could result from the rupture of the cylinders.
(e) System Tests. Before putting a high-pressure compressed air system
i n t o operation, the required testing of DM-3.5, Design Manual, Compressed Air
and Vacuum Systems, must be accomplished by competent personnel with an
e n g i n e e r responsible for safety.
2 STARTUP INSPECTION. Before placing a new compressed air distribution
system in service, or after a major overhaul to an existing system, make sure
t h e following requirements are fulfilled.
(a) System meets all applicable requirements as stated in the approved
specifications.
( b ) A p p l i c a b l e f i e l d t e s t s , as described in NAVFAC DM-3.5, Design
Manual, Compressed Air and Vacuum Systems, and section 3, paragraph 1.2 have
b e e n satisfactorily completed.
5-12
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