Troubleshooting guide

34
www.bendix.com 1-800-AIR-BRAKE (1-800-247-2725)
R-8P
™
Relay Valve
R-12P
™
Relay Valve
Typical Converter Dolly Components
The R-8P
™
and R-12P
™
pilot relay valves are special
purpose relays designed specifically for use on trailers
and converter dollies. These 0 p.s.i. crack and
differential relays speed up brake application signals to
provide an equal or balanced pressure signal to all trailer
and dolly brakes on double and triple trailer
combinations. By maintaining the same application
signal across the entire train of trailers these pilot
operated relay valves aid in achieving overall vehicle
brake balance and stability.
The SV-1
™
synchro valve is a remote mounted air
operated, ON-OFF control valve. It is used to control
air from a remote supply, has a set opening and closing
pressure and can be used to delay or sequence the
action of other pneumatic devices. Use of the SV-1
™
valve in dolly or towing trailer system prevents
automatic application of the towing (lead) trailer or
dolly emergency brakes in the event a breakaway occurs
with the towed (rear) trailer. The SV-4
™
synchro
valves work similarly to the SV-1
™
synchro valves, and
are used on trailer converter dollies to minimize the
possibility of false charging.
The RE-6NC
™
relay emergency (non-charging)
valve is used in Dolly Systems and replaces the
conventional RE-6
™
valve. The RE-6NC
™
valve is similar
to the RE-6
™
valve but is designed to prevent direct
filling of the dolly reservoir through the RE-6NC
™
valve.
It is generally used in conjunction with the PR-3
™
pressure protection and single check valve to provide
rapid dolly brake release.
The PR-3
™
reservoir control valve is the
combination of a PR-4
™
pressure protection valve and
a single check valve. This valve may be used in a variety
of applications, however the most common is in the
converter dolly brake system where it functions to delay
filling of the reservoir until pressure in the supply air
line exceeds 75 psi and to prevent pressure loss due
to a failure in the trailer being towed.
The PP-1
™
control valve is commonly mounted to
the frame and used as a brake release valve. Pushing in
the PP-1
™
valve releases the dolly’s parking brake and
allows it to be moved. Since the dolly uses its own
supply air to park, once it’s moved, pulling out the
PP-1
™
valve button re-parks the dolly.
RE-6NC
™
Relay
Emergency Valve
SV-1
™
Synchro Valve
PR-3
™
Reservoir
Control Valve
Trailer/Converter Dolly Brakes
Converter Dolly systems also widely use
DC-4
™
double-check valves (see page 14),
and TR-3
™
inversion valves (see page 27).
SV-4
™
Trailer
Release
Valve
PP-1
™
Control
Valve