available at all times. However, the compressor
and mechanism should be checked occasionally for
maintenance of pressure. When in good shape, the
air system will not lose more than two or three
pounds per hour (mechanism not operating), but
there is no need for alarm if the leakage exceeds
this figure somewhat, unless it becomes progres
sively worse.
·
The first place to check for air leaks is the intake
valve on the mechanism; a few operations of the
breaker may dislodge any foreign material which
may be lodged at the valve seat. If this does not
cure the leak, all air connections and joints should
be checked with soapy water. Then if the leak
still persists, it may be necessary to re-grind the
intake valve to its seat. However, this valve has
been carefully ground to its seat before leaving the
factory, and this operation will rarely be necessary.
The main cylinder must be reasonably free from
leaks in order not to lose power at the end of the
closing stroke. To this end, the main piston has
been provided with rings, and the piston shaft has
a packing gland where it passes through the top of
the cylinder casting. The packing gland may be
easily tightened, but this should not be necessary
for long periods of time since the packing material
is rather solid. Too much tightening here will, of
course, tend to put a drag on the breaker when
opening. The cylinder leaks may be observed by
energizing the closing circuit with the
"Y"
(cutoff)
relay blocked (breaker in the closed position), or
by operating the intake valve manually. If the
mechanism is in good condition, a small amount of
air may be felt at various points by an exploring
hand, but an unusual amount should be investi
gated. If the mechanism overtravels when the air
is applied in this manner, it is a reasonably good
12
indication that the leaks are not excessive. These
leaks are present only when the mechanism oper
ates; the air is sealed off positively by the intake
valve at all other times.
The throttle piston should be inspected for free
operation. It is returned to its restricting position
by a spring and if the piston becomes jammed in
the open position, the breaker would slam exces
sively in closing.
An instruction leaflet from the Westinghouse Air
Brake Co. is supplied with each compressor unit; it
should be used in conjunction with this instruction
book for overall maintenance of the mechanism and
compressor unit. It should be considered that this
instruction leaflet is primarily designed to recom
mend adequate maintenance for the compressor
equipment as normally used in such places as gas
oline stations, etc., where the compressor operates
very frequently for long periods of time. It is logical
that the equipment as used on these pneumatic
mechanisms would not require such a frequent
maintenance schedule since it operates relatively
little. The instruction leaflet accompanying the com
pressor should be used as a guide to maintenance
procedure, but our experience has indicated that
the period between inspections can be materially
increased. An adequate schedule can be best deter
mined in each individual case by experience but in
many cases it is likely that it can be set to coincide
with regular breaker inspections.
If there is any trouble in operation, the mecha
nism should be taken out of service at once and put
into proper condition. The circuit breaker is highly
dependent upon the proper functioning of the
mechanism which therefore should be kept in good
condition at all times.
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