TM 55-203
the triple valve and the rate of brake pipe reduction. If
valve, leaky main piston packing ring, leaky auxiliary
the triple valve is dry and gummy or the brake pipe is
reservoir tube, and broken graduating spring.
reduced at too rapid a rate through leakage or
(2) Air leaks
otherwise, quick action is almost sure to result.
(a) A blow from the triple valve exhaust indicates a
(b) A broken retarding spring permits the triple
leak either from the brake pipe or the auxiliary reservoir.
valve piston to move to retarded release position,
To determine which, cut out the brake by closing the
causing a slow release of the brake.
brake pipe branch pipe cutout cock. If the brake applies
c. Valve Buzzing. A type K triple valve in good
and the blow stops, it indicates a leak from the brake
condition will not continuously buzz. A continuously
pipe If the blow continues and the brake does not apply,
buzzing valve indicates that the emergency valve is
it indicates a leak from the auxiliary reservoir.
leaking, in which case there will be a blow at the triple
(b) An auxiliary reservoir blow is caused by a leaky
valve exhaust. This may sometimes be remedied by
slide valve, triple valve body gasket, or the auxiliary
jarring the triple valve lightly near the emergency valve.
reservoir tube. A leaky slide valve usually will cause a
Should this not stop the blow, apply the brake in
blow when the triple valve is in either release or
emergency by parting the hose and opening the angle
application position, while a leaky body gasket or
cock quickly; then release the brake by connecting up
auxiliary reservoir tube will cause a blow only when the
the hose and repeat the operation, if necessary. This
triple valve is in release position.
may dislodge the dirt and allow the valve to seat
(c) A brake pipe blow is caused either by a leak by
properly. If the valve cannot be forced to its seat, the
the emergency valve or the check valve case gasket.
defect should be reported for correction.
(d) A leaky main piston packing ring may prevent
the brake from applying on a light reduction on a long
train or if applied it may prevent a proper release.
(3) Broken springs
(a) A broken graduating spring may cause
undesired quick action depending upon the condition of
Section VI. SPECIAL-PURPOSE EQUIPMENT
8-26. Air Strainer and Wasp Excluder
a. General. The 3/8-inch OB-1 strainer with choke and
wasp excluder may be encountered on freight cars built
for foreign service and other special-purpose cars. It is
8-27.
Combined Brake Cylinder and Auxiliary
connected with the triple valve exhaust by a short pipe
Reservoir
nipple and takes the place of the pressure retaining
a. General. The auxiliary reservoir has a choke
valve and pipe described in paragraph 8-21g. The
plug inserted in the tube leading to the brake cylinder.
purpose of the device is to choke the brake cylinder
The purpose of the choke is to nullify the quick-action
exhaust and provide for a longer release time after a
feature. In other respects, this reservoir and the brake
release has been started.
This device, however,
cylinder are the same as those described elsewhere in
exhausts all the air pressure at the reduced rate. The
this manual. Piston travel less than 7 inches or more
strainer curled hair cleans the air and protects the choke
than 9 inches must be adjusted to approximately 8
from being clogged. A wasp excluder located in the
inches.
strainer opening to the atmosphere insures a clear
passage.
b. Operation. The operation of this equipment is
the same as that described in paragraph 8-16 except
b. Components. The 3/8-inch OB-1 air strainer
when the brake pipe pressure is suddenly reduced to
with choke and wasp excluder consists of a strainer
cause emergency quick action, as described in
body tapped for a 3/8-inch pipe, perforated brass plate,
curled hair which cleans the air, and a choke fitting
flow of brake pipe air to the brake cylinder. It, therefore,
which holds the choke and wasp excluder. The OB-1
prevents quick action from being passed to adjoining
strainer is connected to the triple valve exhaust pipe by
equipment. Consequently, in a train of special-purpose
a cap, thus the path of the exhaust air is through the
equipment, the brake pipe reduction will not be at an
cap, strainer hair, choke, and wasp excluder to the
emergency rate throughout the train on account
atmosphere.
8-56
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