SD-03-42
Service Data
Formerly SD-56
(FSCM 06853)
RE-6 RELAY EMERGENCY VALVE
Figure 1.
DESCRIPTION
The Relay Emergency Valve is normally used in trailer
braking systems. It is a dual function valve, combining
the functions of a relay valve and an emergency valve.
The relay function is identical to that of a relay valve
serving the trailer air brake system as a remote
controlled brake valve Control (service) pressure from
the towing vehicle is routed through the trailer service
line and on to the relay portion of the valve. The
emergency function of the valve automatically applies full
trailer reservoir air pressure to the trailer chambers when
the trailer supply pressure falls below a pre-determined
minimum.
For ease of service, the valve features an "insert"
cartridge consisting of the inlet/exhaust valve and
emergency piston. Removal of the insert can usually be
accomplished without line removal.
The RE-6 Relay Emergency Valve may be flanged or
reservoir mounted, and identified, convenient porting
locations of delivery, service, emergency (supply) and
reservoir ports are provided.
Figure 2.
OPERATION (STANDARD TRAILER INSTALLATION)
INITIAL CHARGING
When the tractor is connected to a trailer and the service
and emergency lines are opened (via the tractor
protection system) the valve permits charging the trailer
reservoir to approximately the same air pressure as that
of the tractor reservoirs. Under initial charge conditions,
the valve applies trailer service air chambers as the
trailer emergency line Is charged. The application is
continued until the trailer supply (emergency) line is
charged to 60-65 psi at which time the application is
automatically released. The trailer reservoir continues to
be charged to full operating pressure.
SERVICE APPLICATION
During normal, service braking operation, the valve
serves as a relay valve, synchronizing tractor service
(application) air pressure with trailer service (application)
air pressure as the service foot brake valve on the tractor
is operated. If the tractor is equipped with a trailer hand
control (TC) valve, the trailer brakes can also be applied
independently of the tractor brakes
8-5
