Model M5120B-10M Relief Valve

10-1200 PSIG Relief Valve


Circle Seal Controls Model M5120B-10M Relief Valve

Catalog literature: Relief Valves Catalog.pdf Acrobat DC

The Circle Seal Controls model M5120B-10M relief valve provides a combination of absolute leak-proof sealing when closed and virtually maintenance-free dependability in a relatively small, lightweight package.

How it Works


  • Zero leakage: to 95-98% of cracking pressure
  • Positive reseat: reseals dead tight only slightly below the cracking pressure
  • Accurate set pressure: valves can be pre-set to required cracking pressure
  • Adjustable: interchangeable springs permit change of crack pressure range; tamper-proof adjustment inside of valve
  • Excellent flow characteristics: lift ring poppet design allows high flow rates with minimum amount of pressure rise
  • No chatter: chatter eliminated through use of friction damping device; damping bars prevent poppet from over-travel at initial cracking thrust; damping load is proportional to spring load
  • Minimal maintenance: fluid is not throttled across the seal, which, combined with soft seat and poppet design, prevents seat and seal erosion
  • Versatile: vent-to-atmosphere or inline connections; various materials for both body and seals; sizes ranging from 1/8″ to 1-1/4″; PED certifications and CE marking available for most models

Technical Data:

  • Configuration: Popoff with manual override
  • Cracking pressure: 10-1200 PSIG
  • Body material: Brass
  • Seal material: Teflon
  • Connection: 1-1/4″ MNPT
  • Temp range: -100 to +400F


  • Handle type: Ring (for cracking pressures up to 450 psig); Lever (for cracking pressures above 450 psig)
  • “B” & “H” dimensions (diameter / hex): 2.00″
  • “E” dimension (length) for cracking pressures between 10-450 psig: 6.95″
  • “M” dimension (length) for cracking pressures between 451-2400 psig: 10.42″

M5120B-10M Relief Valve