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Non-Return Series

Check Valve / NRV

Poppet type, spring loaded check valves that allow flow in one direction and seal tight against reverse flow — female, male and tube end connections, rated up to 10000 PSI.

Stainless steel poppet type check valves (NRV)
Up to 10000 PSIWorking pressure*
Product Overview

Poppet Type Check Valves (NRV)

A check valve, or non-return valve, lets fluid pass in one direction only. In the Kalpataru poppet design, inlet pressure lifts a spring-loaded poppet off its seat once it exceeds the set cracking pressure. When flow stops or reverses, the spring and back pressure drive the poppet onto a soft O-ring seat for a tight, repeatable shut-off.

The valves protect pumps, compressors, instruments and upstream equipment from backflow, and prevent cross-contamination between lines. Bodies are machined from bar stock, with a clear flow-direction arrow marked on every valve.

  • Prevents reverse flow
  • Selectable cracking pressure
  • Soft seat, bubble-tight reseal
  • Works in any orientation
  • Viton, Buna-N or PTFE seals
  • Flow arrow on every body
Request a Quote View Dimensions
Pipe Connections1/4" to 1" NPT / BSP
Tube OD1/8" to 1" & 3 mm to 25 mm
Max Working Pressure3000 / 6000 / 10000 PSI
MaterialsSS 304 / 316 / 316L, Brass, Alloys
01
Types

Check Valve Types

FF
Non return valve female x female

Female × Female NRV

Female NPT / BSP threads on inlet and outlet. Screws directly onto nipples, pump outlets or valve ends and is the most common pattern for pipe-threaded instrument and utility lines.

  • End Conn.TOD / FPT / MPT
  • Tube OD1/8" to 1" OD (Fractional)
    3 mm to 25 mm OD (Metric)
  • Thread1/8" to 2" NPT (Taper); BSPP / BSPT / ISO / Metric on request
  • Test PressureUp to 10000 psi
  • Seal RingViton / Neoprene / Silicon
  • MOCSS 316, 304 / Brass / Alloy 400, 600, C276 / CS
  • Model No.MOC*-NRV-IN*-OUT*
MF
Male x female non return valve illustration

Male × Female NRV

Male thread on one end, female on the other, so the valve screws straight into a port and accepts the next component without an extra nipple — a shorter, lighter assembly with one fewer joint.

NPT / BSP M × FCompact
OD
OD x OD non return valve illustration

OD × OD NRV

Double ferrule compression tube ends on both sides for direct installation in instrument tubing runs, from 1/8" to 1" and 3 mm to 25 mm OD. No threaded adapters are needed.

Tube × TubeDouble ferrule
PRV
Pressure relief valve

Pressure Relief Valve

Spring-loaded valve that opens at a set pressure to relieve excess line pressure and protect instruments and tubing.

  • End Conn.TOD / FPT / MPT
  • Tube OD1/4" to 1" OD (Fractional)
    6 mm to 25 mm OD (Metric)
  • Thread1/8" to 1" NPT (Taper); BSPP / BSPT / ISO / Metric on request
  • Set PressureAs per specification
  • Seal RingViton / Neoprene / Silicon
  • MOCSS 316, 304 / Brass / Alloy 400, 600, C276 / CS
  • Model No.MOC*-PRV-IN*-OUT*
02
Specifications

Technical Specifications

ProductCheck Valve / Non-Return Valve — Poppet Type, Spring Loaded
Process & Instrument Connection1/4", 3/8", 1/2", 3/4", 1" NPT / BSP & others on request
Fractional Tube OD1/8", 1/4", 3/8", 1/2", 3/4", 1"
Metric Tube OD3, 6, 8, 10, 12, 16, 20, 25 mm
End ThreadsNPT (ASME B1.20.1), BSP / BSPP (ISO 228), BSPT (ISO 7) & others on request
Max Working Pressure3000 / 6000 / 10000 PSI (207 / 414 / 690 bar) depending on model and material
Cracking Pressure1/3, 1, 10, 25 PSI typical; other values on request
Seat / SealSoft O-ring seat — Viton (FKM), Buna-N (NBR) or PTFE
Body MaterialsSS 304, SS 316, SS 316L, Brass, Inconel, Monel, Hastelloy C
OptionsOxygen service cleaning, NACE MR0175 / ISO 15156 materials, PMI, TPI
TestingCracking & reseal check, hydrostatic shell test, reverse-flow leak test
CertificatesEN 10204 3.1 material certificate, test certificate, third party inspection on request
03
Materials

Material Grades

Stainless Steel

SS 304 SS 316 SS 316L

Nickel Alloys

Monel 400 Inconel 600 Inconel 625 Hastelloy C-276

Copper Alloys

Brass C36000

Seat & Seal Materials

O-ring Viton (FKM) O-ring Buna-N (NBR) Seal PTFE
MaterialUNS No.Bar StockForgings
SS 304S30400ASTM A479 / A276ASTM A182 F304
SS 316S31600ASTM A479 / A276ASTM A182 F316
SS 316LS31603ASTM A479 / A276ASTM A182 F316L
Monel 400N04400ASTM B164ASTM B564
Inconel 600N06600ASTM B166ASTM B564
Inconel 625N06625ASTM B446ASTM B564
Hastelloy C-276N10276ASTM B574ASTM B564
BrassC36000ASTM B16—
04
Material Charts

Chemical & Mechanical Properties

GradeCMnSiPSCrNiMoOthers
SS 3040.082.001.000.0450.03018.0–20.08.0–10.5—N 0.10
SS 3160.082.001.000.0450.03016.0–18.010.0–14.02.0–3.0N 0.10
SS 316L0.0302.001.000.0450.03016.0–18.010.0–14.02.0–3.0N 0.10
Monel 4000.302.000.50—0.024—63.0 min—Cu 28.0–34.0, Fe 2.5
Inconel 6000.151.000.50—0.01514.0–17.072.0 min—Fe 6.0–10.0, Cu 0.50
Inconel 6250.100.500.500.0150.01520.0–23.058.0 min8.0–10.0Nb+Ta 3.15–4.15, Fe 5.0
Hastelloy C-2760.0101.000.080.040.0314.5–16.5Balance15.0–17.0W 3.0–4.5, Fe 4.0–7.0
Brass C36000————————Cu 60.0–63.0, Pb 2.5–3.7, Fe 0.35, Zn Bal.
Values in weight %. Single values are maximum unless stated. Limits as per the applicable ASTM bar stock specification.
GradeTensile Strength (MPa, min)Yield Strength 0.2% (MPa, min)Elongation (%, min)Hardness (max)
SS 30451520540201 HB
SS 31651520540217 HB
SS 316L48517040217 HB
Monel 40048017035—
Inconel 60055024030—
Inconel 62582741430—
Hastelloy C-27669028340—
Brass C36000338–469*124–310*18–53*—
Annealed condition. *Brass values are typical ranges depending on temper and bar diameter.
GradeDensity (g/cm³)Melting Range (°C)Key Characteristic
SS 3048.001400–1450General corrosion resistance, economical
SS 316 / 316L8.001375–1400Molybdenum for chloride & pitting resistance
Monel 4008.801300–1350Sea water, hydrofluoric acid service
Inconel 6008.471354–1413High temperature oxidation resistance
Inconel 6258.441290–1350High strength, crevice corrosion resistance
Hastelloy C-2768.891325–1370Severe oxidising & reducing chemicals
Brass C360008.50885–900Free machining, water & air service
05
Dimensions

Cracking Pressure, Size & Seal Tables

Cracking Pressure Options

Nominal Cracking PressurePSIbarTypical Use
1/3 PSI0.330.02Low pressure gas, purge and vent lines where minimal pressure loss is needed
1 PSI10.07General instrument air, water and light oil lines
10 PSI100.69Pump and compressor discharge, positive shut-off against back pressure
25 PSI251.72Chemical injection, preventing siphoning and free-flow through dosing pumps

Size vs Orifice

Pipe Size (NPT / BSP)Tube OD (Fractional / Metric)Orifice (mm)Orifice (in)
—1/8" / 3 mm2.40.094
1/4"1/4" / 6 mm, 8 mm4.80.188
3/8"3/8" / 10 mm6.40.250
1/2"1/2" / 12 mm9.50.375
3/4"3/4" / 16 mm, 20 mm12.70.500
1"1" / 25 mm15.90.625

Parts & Materials of Construction (SS 316 Valve)

No.PartStandard MaterialNotes
1Inlet BodySS 316 (ASTM A479)Threaded or tube end
2Outlet BodySS 316Flow arrow marked
3PoppetSS 316Guided for straight seating
4SpringSS 302 / SS 316Sets the cracking pressure
5Poppet O-ringViton (FKM)Buna-N or PTFE optional
6Body SealViton (FKM)Seals the body joint

O-ring / Seal Temperature Limits

Seal MaterialTemperature Range (°C)Good ForAvoid
Viton (FKM)-23 to 204Hydrocarbons, fuels, oils, most acidsKetones, amines, hot water / steam
Buna-N (NBR)-34 to 121Petroleum oils, hydraulic fluids, water, airOzone, strong acids, aromatic solvents
PTFE-54 to 204Almost all chemicals, solvents, oxygen serviceApplications needing very low leak rates at low pressure
Typical industry values for reference only. Cracking pressure tolerance, orifice and seal limits depend on model and media. Final dimensions are confirmed on the approved drawing for your order.
06
Applications

Where Our Check Valves Are Used

Pump & Compressor Discharge

Chemical Injection & Dosing

Instrument Air & Purge Lines

Hydraulic Circuits

Sampling & Analyser Systems

Gas Distribution Lines

Oil & Gas Wellheads

Water Treatment Skids

07
Why Kalpataru

Features & Advantages

One-Way Protection

Stops reverse flow that can damage pumps and instruments or contaminate upstream lines.

Soft Seat Shut-off

The O-ring seated poppet reseals tightly even at low back pressure, where metal seats tend to weep.

Choice of Cracking Pressure

Springs selected from 1/3 PSI to 25 PSI to match the duty, from low pressure purge gas to dosing pump outlets.

Full Traceability

Heat numbers are marked on bodies and recorded against mill certificates, with PMI and TPI available on request.

08
FAQ

Frequently Asked Questions

What is cracking pressure?
Cracking pressure is the minimum difference between inlet and outlet pressure at which the poppet starts to lift and flow begins. Below this value the valve stays closed. A higher cracking pressure gives firmer shut-off but a larger pressure drop.
Can the check valve be installed vertically?
Yes. Because the poppet is spring loaded, the valve works in horizontal, vertical-up or vertical-down lines. Always install it so the flow-direction arrow on the body points the way the fluid should travel.
Which O-ring material should I select?
Viton suits most hydrocarbons, oils and acids up to about 204 °C. Buna-N is an economical choice for water, air and hydraulic oil up to about 121 °C. PTFE is used where chemical compatibility is critical or for oxygen service. Tell us the media and temperature and we will recommend the seal.
Is a check valve a substitute for an isolation valve?
No. A check valve prevents reverse flow but is not a positive isolation device for maintenance. Use a needle or ball valve upstream or downstream when a line must be isolated.
09
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Need Check Valves for Your Project?

Share the end connections, cracking pressure, seal material, working pressure and quantity — we will quote with material certificates and delivery schedule.

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