Model HP524B-2M Relief Valve

150-575 PSIG Relief Valve


Circle Seal Controls Model HP524B-2M Relief Valve

Catalog literature: Relief Valves Catalog.pdf Acrobat DC

The Circle Seal Controls model HP524B-2M Relief Valve is a small, durable valve for use on pressure lines and pressure vessels of all types. It is bubble-tight at normal operating pressure, cracks accurately and repeatedly at a preset pressure to pass adequate flow with minimal pressure rise. It offers exceptional performance characteristics in service with virtually all gases and liquids.

How it Works


  • Zero leakage: up to 95-98% of cracking pressure
  • Increased sealing efficiency: as pressure increases, the resilient o-ring seal is forced against the metal poppet up to the cracking pressure
  • Cracking pressure accuracy: valves can be pre-set to required cracking pressure; 100% seat leakage tested
  • Tamper-proof adjustment: adjustable only from the inlet side for safety against tampering; permits precise setting for the most exacting system requirements
  • Sticking eliminated: poppet head provides metal seat on the low pressure side of the seal, which limits squeeze on the resilient o-ring; prevents water and dirt from entering the valve
  • Long, maintenance-free service: parts will not wear out in normal service; overhaul, if necessary, is quickly made by replacing the resilient o-ring seal
  • Variations: vent-to-atmosphere or inline connections; various materials for both the body and seals; PED certifications and CE marking available for most models


  • System overpressure protection
  • Storage tanks
  • Freon recovery systems
  • Medical equipment
  • Refrigeration & heating equipment
  • Measuring & dispensing pumps
  • Communications equipment
  • Process control instruments
  • R&D pilot plants

Technical Data:

  • Configuration: Popoff
  • Cracking pressure: 150-575 PSIG
  • Body material: Brass
  • Seal material: Silicone
  • Connections: 1/4″ MNPT
  • Temp range: -70 to +450F


  • “A” dimension (height): 1.17″
  • Hex dimension (across flats): 0.625″

HP524B-2M Relief Valve