Axelson CRBBM Relay
With control (actuator) supply connected to the supply pressure inlet and no
instrument pressure at pilot pressure inlet, control pressure is blocked at the
supply pressure inlet and the supply pressure outlet is open to the exhaust
ports (radial holes in body). When instrument pressure is applied to the pilot
pressure inlet of the relay, it acts against the relay piston, shifting it to an
open position. This allows control pressure to pass from the supply
pressure inlet through supply pressure outlet to open the SSV safety
valve. It will remain in the position until instrument pressure is bled
from the pilot pressure inlet. Once the PSHL blocks and bleeds pressure
from the pilot pressure inlet, the relay spring will force the relay piston
downward to its block and bleed position, blocking control pressure at the
supply pressure inlet and opening the supply pressure outlet to exhaust,
allowing the SSV safety valve to close.
The CRBBM Relay will remain closed
until instrument supply is readmitted to the pilot pressure inlet. Once
instrument pressure is readmitted to the pilot pressure inlet, the relay will
shift automatically to its open position.
Maximum Working Pressure: 250 psi
Pilot Pressure: 35 to 150 psi*
Length: 7 1/4 in.
Connections: 1/4 NPT
Weight: 2 3/4 lbs.
Material: All corrosion resistant
The relay is normally-closed fast block and bleed
valve which may be manually operated or be programmed to
automatically resent or to require manual rest and provide a
means to manually override the safety system. Applications
of pilot pressure allows supply pressure to pass from inlet port
to outlet port. When the the pilot pressure is removed, the
relay shuts off the supply pressure and back bleeds quickly.
The figure to the right illustrates a typical application for
the relay. In this application, the relay is utilized to
separate the higher control pressure from the lower pressure
instrument supply and to provide a means of fast bleeding the
SSV Safety valve actuator pressure which is not possible through
the smaller orifices of the PSHL sensor. It provides the
means to manually override the PSHL sensor to hut in and lock
out the system once the SSV safety valve is closed.
APPLICATION FOR CRBBM RELAY