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Fisher™ Type H800 Relief Valves
Type H800 relief valve is a compact, lightweight, direct-operated relief valve.
It is used primarily between a pneumatic instrument and its supply pressure regulator to limit the instrument supply pressure to 50 psig / 3,4 bar should the supply pressure regulator fail open.
Fisher™ Type H800 Relief Valves


Body Size and End Connection Style
1/4 NPT
Flow Coefficient
Wide-Open Cg: 55
Km: 0.79
Maximum Allowable Inlet (Relief) Pressure
250 psig / 17.2 bar
Relief Pressure Range
Non-adjustable, start-to-discharge between 39 to 44 psig / 2.7 to 3.0 bar
Reseat Pressure
35 psig / 2.4 bar or higher
Temperature Capabilities
-20 to 150°F / -29 to 66°C
Approximate Weight
5 ounces / 140 grams
Additional Technical Data
For additional technical information, contact your local Sales Office or refer to technical documentation.


  • Application Dependability
  • Easy Installation
  • Economical
  • Tamper-Resistant


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