Type B Vital Relays - Alstom

Corrective Maintenance
Table 6–11. Mechanical Test and Adjustment Procedure (Cont.)
Step
Procedure
13 If the contact pressure is not acceptable, manually adjust the pressure plate and
stop plate.
PRESSURE
PLATES
STOP
PLATES
Contact pressure is created by contact follow resisted by the pressure plate.
Contact follow is the total movement of the heel contact caused by the armature
bridge raising the pusher (not affected by pressure or stop plates). Armature
springs (heel contact spring) are adjusted with a down pressure before
assembling the pusher.
The adjustment of the contact group consists of positioning the pressure plate
and stop plate on each stationary spring to ensure the correct amount of contact
follow.
Armature springs on all groups are adjusted with a down pressure.
14 Using a pressure gauge at the adjustable residual screw, check the pressure
required to just raise the bridge stop screw from its stop. Compare pressure
value to the requirements indicated on the ED sheet. Adjust if necessary.
ADJUSTABLE RESIDUAL SCREW
P1457, Rev. Nov/07 6–20 Alstom Signaling Inc.