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Home > Hy-Lok Fluid System Products > Valves > Check & Relief Valves
Check & Relief Valves
Check valves, also known as clack valves or one-way valves, are an inexpensive yet effective solution to controlling back flow in high and low pressure fluid systems. Available in a wide range of sizes and cracking pressures, our mechanical check valves can handle up to 6,000 psi and temperatures up to 600°F.

We maintain a large inventory of instrument check valves, including welded check valves, compact check valves, ball check valves, high pressure check valves, and adjustable check valves. End connection options include male / female NPT, Hy-Lok tube fittings, and metal gasket & O-ring face seals. Hy-Lok offers stainless steel check valves brass check valves, and alloy 400 check valves.


700 Series Check Valves
  • Pressure rating to 3,000 psi (207 bar) at 70°F (21°C).
  • Temperature rating from -10°F to 375°F (-23°C to 191°C) with Viton O-ring seat standard.
  • O-ring provides leak tight shut-off.
  • Back stopped poppet design prevents the spring from being over-stressed.
  • Variety of springs are available for the cracking pressure in the range from 1/3 psi to 100 psi.
  • Wide range of body sizes allows Cv choices from 0.16 to 8.8.
  • Suitable for gas and liquids.
  • Variety of end connections include male/female NPT, ISO, BSP threads and female Hy-Lok tube fittings.
  • Body Material is standard in 316 stainless steel and brass.

700H High Pressure Check Valves
  • Pressure rating to 6,000 psi (413 bar) at 70°F (21°C).
  • Temperature rating from -10°F to 400°F (-23°C to 204°C) with Viton seat standard.
  • O-ring poppet design for replaceable high integrity seal.
  • Tight shut-off and accurate cracking pressure.
  • Cracking pressure includes 1/3, 1, 5, 10, and 25 psi.
  • Maximum flow design allows Cv choices from 0.67 to 4.7.
  • Suitable for gas and liquids.
  • Special applications are available in sour gas and fluorocarbon free.
  • Size range from 1/8" to 1" tubing and pipe.
  • Variety of end connections include male/female NPT, ISO, BSP threads and female Hy-Lok tube fittings.
  • Body Material is standard in 316 stainless steel.

CVA Adjustable Check Valves
  • Pressure rating up to 3,000 psi (207 bar) at 70°F (21°C)
  • Temperature rating from -10°F to 375°F (-23°C to 191°C) with Viton seat standard.
  • One piece body construction
  • Wide range of cracking pressures
  • Ease of adjustment
  • Size range 1/4" & 1/2" pipe.
  • Body material is 316 stainless steel and Brass.

RV Series: Relief Valves
  • Pressure rating to 3,000 psi (207 bar) at 70°F (21°C) for RV1 low pressure
  • Temperature rating from -10°F to 400°F (-23°C to 204°C) with Viton seat standard.
  • Standard 4.8mm (0.19in) orifice.
  • Cracking pressure range from 10 psi to 250 psi for RV1 and from 225 psi to 6,000 psi for RV2 series.
  • One spring adjustable over entire cracking pressure range for RV1 series.
  • Compact design for small space installation.
  • Cracking pressure adjustable externally.
  • Lock wire capability to maintain pressure relief setting.
  • Size range from 1/4" to 1/2" tubing and pipe.
  • Variety of end connections include male/female NPT, ISO, BSP threads and female Hy-Lok tube fittings.
  • Body material standard in 316 stainless steel.

RV2 Series: Relief Valves
  • Upto 6,000 psi (413 bar) at 170°F (21°C) for RV2 high pressure.
  • Temperature rating from -10°F to 400°F (-23°C to 204°C) with Viton seat standard.
  • Standard 4.8mm (0.19in) orifice.
  • Cracking pressure range from 225 psi to 6,000 psi for RV2 series.
  • One spring adjustable over entire cracking pressure range for RV1 series.
  • Compact design for small space installation.
  • Cracking pressure adjustable externally.
  • Lock wire capability to maintain pressure relief setting.
  • Size range from 1/4" to 1/2" tubing and pipe.
  • Variety of end connections include male/female NPT, ISO, BSP threads and female Hy-Lok tube fittings.
  • Body material standard in 316 stainless steel.

  • 701 Series Check Valves
  • Pressure rating to 3,000 psi (207 bar) at 70°F (21°C).
  • Temperature rating from -10°F to 375°F (-23°C to 191°C) with Viton O-ring seat standard.
  • O-ring provides leak tight shut-off.
  • Back stopped poppet design prevents the spring from being over-stressed.
  • Variety of springs are available for the cracking pressure in the range from 1/3 psi to 100 psi.
  • Wide range of body sizes allows Cv choices from 0.16 to 8.8.
  • Suitable for gas and liquids.
  • Variety of end connections include male/female NPT, ISO, BSP threads and female Hy-Lok tube fittings.
  • Body Material is standard in 316 stainless steel and brass.


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