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Safety Relief Valve

Model / MPN: 646B-2-3/8-52CP4 | NSN: 4820-01-227-1011
ITAR Registered seal

A valve designed to automatically release excessive pressures. It is actuated by static pressure upstream of the valve and is used as a safety valve or relief valve, and may be set to close at a predetermined pressure. It is not designed for regulation of continuously fluctuating loads. It may be inline or cartridge (manifold) design. Excludes valve (1), relief, pressure and temperature.

Product Details
NATO Stock Number
Sold in multiples of
1 EA
Thread Direction
Right-hand all ends
Flow Control Device
Bonnet Type
Inside screw
Bonnet Attachment Method
Maximum Operating Temp
225.0 degrees fahrenheit single response
Connection Style
G46b plain (pipe) 2nd end
Connection Style
G9 plain, optional en (pipe) 1st end
Valve Operation Method
Connection Type
Threaded external pipe 2nd end
Connection Type
Threaded internal pipe 1st end
Adjustable Pressure Range
+10.0 to 50.0 pounds per square inch
Maximum Operating Pressure
3600.0 pounds per square inch single response
Thread Size
0.375 inches all ends
Rubber synthetic seat
Steel comp 303 body
Steel comp 303 flow control device
Media For Which Designed
Air 1st response
Media For Which Designed
Hydraulic fluid, mineral base 2nd response
Style Designator
C1 angle
Thread Series Designator
Npt all ends

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646B-2-3/8-52CP4 Cross Reference
  • 646B-2-3/8-52
  • 646B-2-3/8-52