Type B Vital Relays - Alstom

Corrective Maintenance
Table 6–11. Mechanical Test and Adjustment Procedure (Cont.)
Step
Procedure
8 If the bridge travel is not acceptable, adjust the bridge travel. Turn the armature
stop screw until the bridge travel measurement is within specification. The screw
must be locked tight in place by the lock nut provided.
Generally, operating values of a relay are easier to obtain when this air gap is
held to the minimum value.
9 Make and break openings for front and back contacts are measured by inserting
the proper thickness gauge between the adjustable residual screw and core
face.
• With the break gauge in place, all specified contacts are open.
• With the make gauge in place, all specified contacts are closed.
2 FRONT
CONTACTS
BACK CONTACT
10 Verify the contact opening measurements meet the specifications indicated in
the appropriate ED sheet.
11 If the contact opening measurements are not acceptable, bend the pressure
plate forcing the contact spring to the proper position to meet the acceptable
make and break values.
With the contact spring properly positioned, the stop plate is bent toward the
contact spring until it just touches the spring. Note that the spring bears against
the pressure plate and touches the stop plate.
If a pressure plate or stop plate is bent too far away from a contact spring, this
can be corrected by bending the plate to stop a little too near the spring and
then bend the plate away from the spring.
12 Use a pressure gauge to verify the contact pressure meets the specifications
indicated in the appropriate ED sheet.
When making contact pressure measurements, place the pressure as close to
the contact as possible (at the center of the extreme outer end of the spring) to
obtain a true reading. Back contact springs must move a minimum of 0.010 inch
from the stop plate; this measurement is taken at the end of the stop plate.
P1457, Rev. Nov/07 6–19 Alstom Signaling Inc.