Operation & Maintenance Instruction
Page 20 of 24
August, 2003
4225-50, S.6
7.7.18 Using only finger and thumb pressure, position the
sealing bead of the diaphragm (6) into the diaphragm bead
groove on the top cover mounting face of the body (49).
7.7.19 Install a NEW 1
1
/
16
" O.D. ring gasket (3) into its
groove in the top cover (2).
7.7.20 Insert two guide pins into two diagonally opposite
threaded holes of the body (49). Using the pins as guides,
position the cover assembly (2, 3) onto the body (49). In the
remaining two threaded holes, tighten by hand, two
1
/
2
" x 1
3
/
4
"
hex head cap screws (1). Remove the two guide pins and
install the other two
1
/
2
" x 1
3
/
4
" hex head cap screws (1). Torque
all four cap screws between 35 and 55 foot-pounds.
7.7.21 Limiting Valve, Back Flow Check Valve
7.7.22 Using a foam-tipped swab applicator, evenly spread
a light coating of Triple Valve Oil, Wabtec Corporation
Specification M-07611-20 (AAR Specification M-912) around
the collar on each end of the spring cage (41).
7.7.23 Install the piston return spring (40) into the spring
cage (41), then install the cage with spring (41, 40) as a unit
into the body (49) so that the spring (40) goes over and around
the end of the shaft of the piston (16), which has already
been installed.
7.7.24 Position a NEW diaphragm (44) onto the brake
cylinder limiting valve stem (45) so that the flat surface of the
diaphragm, which shows the part number, faces away from
the stem towards the threaded end.
7.7.25 Using #2 Silicone Grease, Wabtec Corporation
Specification M-07680-02, lubricate the surfaces of two NEW
o-rings (47, 46). Also lightly lubricate the o-ring grooves on
the shaft of the stem (45) and the bearing surfaces of the
piston bushing in the body (49).
7.7.26 Install the spring, stem and diaphragm (45 to 48)
into the body (49), o-ring end first. Be sure that the bead of
the diaphragm (44) is properly seated in its groove in the
body (49). Use finger pressure to seat the bead.
7.7.27 Install the diaphragm follower (43) and brake cylinder
limiting valve spring (42) into the body (49) so that it seats on
the diaphragm follower (44).
7.7.28 Install a NEW back flow check valve (37) and
the check valve spring (36) into the proper cavity of the
body (49).
7.7.29 Install a NEW 2" flange fitting gasket (39), a NEW
2" O.D. ring gasket (35) and a NEW
11
/
16
" O.D. ring gasket
(38) into their grooves in the bottom cover (34).
7.7.30 Carefully position the bottom cover assembly (34,
35, 38 and 39) on the body (49) making sure that all gaskets
and assemblies of the body are properly in place. Secure
the bottom cover (34) to the body (49) by installing four
1
/
2
" x
1
1
/
4
" hex head screws (33). Equally torque the screws
between 35 and 55 foot-pounds.
7.7.31 Accelerated Service Release Valve
7.7.32 Install a NEW accelerated release check valve (30)
into the service portion filling piece (31).
7.7.33 Install the check valve spring (29) into the filling piece
(31) so that it seats on the check valve (30), then install the
spring seat (28) to retain the parts in place.
7.7.34 Place a NEW filling piece gasket (32) and the service
portion filling piece (31) in position on the body (49).
7.7.35 Apply a light coating of #2 Silicone Grease, Wabtec
Corporation Specification M-07680-02, to the surfaces of a
NEW
1
/
4
" O.D. o-ring (26). Also lightly lubricate the o-ring
groove on the service accelerated release valve plunger (25)
and the bearing surfaces of the plunger bushing of the filling
piece.
7.7.36 Install the NEW lubricated
1
/
4
" O.D. o-ring (26) into
its groove on the short end of the service accelerated release
valve plunger (25), then install the plunger with o-ring (26, 25)
into the filling piece (31), longer end of the plunger first.
7.7.37 Using the Accelerated Release Valve Piston Spanner
Wrench, as shown in Figure 10, to hold the service
accelerated release valve piston (24), install a NEW
diaphragm (23) onto the piston (24) so that the part number
on the diaphragm faces away from the piston toward the
threaded end.
7.7.38 Install the diaphragm follower (22) and lightly coat
the threads of the service accelerated release valve piston
