Axelson CRBBM Relay
Manual or Automatic Reset Relays
OPERATION: 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 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.
The CRBBM and CRBBM-1 Relays are identical with the
exception that the -1 body is drilled and tapped for panel mountings. All other parts of the assembly are interchangeable.
TECHNICAL DATA:
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
DESIGN OVERVIEW:
The relay is normally-closed fast block and bleed valve which may be manually operated or be programmed to automatically reset 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.
APPLICATION: 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.
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