What is a check valve and how does it work?

A check valve (also called non-return valve or NRV) is a one-way valve that allows fluid to flow in one direction only and automatically prevents reverse flow (backflow). It works without any external actuation – the flowing fluid opens the valve, and when flow stops or reverses, gravity or back-pressure closes it. Check valves protect pumps from reverse rotation, prevent contamination of clean water supplies, and stop water hammer in pipelines.

What are the types of check valves?

Main types of check valves: (1) Swing Check Valve – disc swings on a hinge pin, low pressure drop, for horizontal lines, per BS 1868 / API 6D. (2) Dual Plate (Wafer) Check Valve – two semi-circular plates spring-loaded, compact wafer design, per API 594. (3) Piston/Lift Check Valve – disc lifts off seat, for vertical or horizontal lines, per BS 5352. (4) Tilting Disc Check Valve – disc tilts on pivot, fast closing, reduces water hammer. (5) Non-Slam Check Valve – spring-assisted, prevents water hammer. (6) Ball Check Valve – ball seats against opening, for small sizes and viscous fluids.

What is the difference between swing check valve and dual plate check valve?

Swing check valve: Single disc on hinge, full bore opening, lowest pressure drop, needs space for disc to swing, slower closing (risk of water hammer), best for steady flow. Dual plate (wafer) check valve: Two half-discs with spring, compact wafer body (fits between flanges), faster closing (less water hammer), lighter weight, higher pressure drop than swing type. Use swing check for large steady-flow pipelines. Use dual plate for space-constrained installations, pulsating flow, or where water hammer is a concern.

What is water hammer and how do check valves prevent it?

Water hammer is a pressure surge caused by sudden stoppage or reversal of flow in a pipeline. It creates shock waves that can damage pipes, fittings, and equipment. Check valves prevent water hammer by: (1) Stopping reverse flow before it builds momentum. (2) Non-slam check valves use springs to close the disc before flow reversal occurs. (3) Tilting disc check valves close faster than swing check valves, reducing slam. For critical applications, use spring-loaded dual plate or tilting disc check valves instead of standard swing check valves.

What is API 594 check valve?

API 594 is the standard for wafer, wafer-lug, and double-flanged check valves. It covers dual plate (butterfly type) and single plate (tilting disc) check valves for petroleum and natural gas industries. API 594 specifies design, materials, dimensions, testing, and marking. Sizes covered: 2 inch to 48 inch. Pressure classes: 150 to 2500. API 594 check valves are compact, lightweight, and fit between standard ASME B16.5 flanges.

What materials are check valves made of?

Common check valve body materials: Carbon Steel (ASTM A216 WCB) for general service, Stainless Steel SS316 (A351 CF8M) for corrosive media, SS304 (A351 CF8) for food and chemical, Alloy Steel WC6/WC9 for high temperature, Duplex 2205 (F51) for chloride environments, Super Duplex 2507 (F53) for seawater, Cast Iron for low-pressure water, and Bronze for marine. Disc materials: same as body or Stellite overlay for erosion resistance. Seat materials: integral (metal-to-metal), Stellite overlay, or soft seat (PTFE, EPDM).

How to select the right check valve?

Check valve selection criteria: (1) Flow direction – horizontal or vertical (swing check for horizontal only, piston check for both). (2) Flow type – steady flow = swing check, pulsating flow = dual plate or non-slam. (3) Water hammer risk – high risk = spring-loaded dual plate or tilting disc. (4) Space – limited space = wafer dual plate. (5) Pressure drop – critical = swing check (lowest drop). (6) Size – small (1/2 to 2 inch) = lift check, medium to large = swing or dual plate. (7) Media – clean fluid = any type, dirty/slurry = swing check with full bore. Contact Supreme Valves at +91 97732 78770.

What is the difference between check valve and NRV?

Check valve and NRV (Non-Return Valve) are the same thing – different names for the same type of valve. NRV is the term commonly used in India and some Asian countries. Check valve is the international/American term. Both refer to a one-way valve that prevents backflow. Other names include: reflux valve, retention valve, and foot valve (when installed at pump suction with strainer).

Non-Return Valves

Check Valves (NRV) – Swing, Dual Plate & Piston

Name: Check Valve (Non-Return Valve / NRV)
Brand: Supreme Valves
SKU: SV-CHECKVALVE
Price: 300 INR
Availability: InStock
Rating: 4.8 (127 reviews)

Industrial check valves (non-return valves / NRV) from Supreme Valves India. Swing check, dual plate, piston lift, tilting disc, and wafer types. API 6D, API 594, BS 1868 certified. Carbon steel, stainless steel, duplex. Sizes 1/2" to 48". Class 150 to 2500. Prevents backflow and protects pumps.

Key Applications

Pump ProtectionPipeline SystemsWater Systems

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Quick Summary – What is a Check Valve?

Check valve (also called NRV = Non-Return Valve) = one-way valve that allows flow in one direction and automatically prevents reverse flow (backflow). No external actuation needed – fluid pressure opens it, gravity/back-pressure closes it. Protects pumps, prevents contamination, stops water hammer. Types: swing check (BS 1868), dual plate wafer (API 594), piston lift, tilting disc, non-slam. Materials: WCB, SS316, SS304, duplex, alloy steel. Standards: API 6D, API 594, BS 1868. Sizes: 1/2" to 48". Pressure: Class 150 to 2500.

How Does a Check Valve Work?

Forward Flow

Fluid pressure pushes the disc (swing, plate, or piston) off the seat, opening the valve. Flow passes through freely.

Flow Stops

When flow velocity drops, gravity or spring force begins to close the disc back toward the seat.

Reverse Flow

If flow tries to reverse, back-pressure pushes the disc firmly against the seat, creating a tight seal. Backflow is blocked.

Automatic

No handle, actuator, or external power needed. The valve operates automatically based on flow direction and pressure.

Check Valve Types Comparison

Type	Pressure Drop	Water Hammer	Installation	Best For
Swing Check	Very Low	Moderate Risk	Horizontal only	Large steady-flow pipelines
Dual Plate (Wafer)	Low	Low Risk	Horizontal or Vertical	Compact spaces, pulsating flow
Piston / Lift	High	Low Risk	Horizontal or Vertical	Small sizes, high-pressure
Tilting Disc	Low	Very Low Risk	Horizontal only	Fast-closing, critical pipelines
Non-Slam	Medium	Eliminated	Any orientation	Pump discharge, water hammer prevention

Technical Specifications

Product Type	Check Valve
Category	Non-Return Valves
Size Range	1/2" to 48" (DN15 to DN1200)
Pressure Class	150# to 2500# (PN10 to PN420)
End Connections	Flanged, Threaded, Socket Weld, Butt Weld
Operation	Manual, Gear Operated, Electric Actuated, Pneumatic Actuated
Standards	ASME B16.34, API 600, API 602, BS 1873, DIN 3352

Material Options

Carbon Steel

ASTM A216 WCB, A105, A350 LF2

Stainless Steel

SS304, SS316, SS316L, SS321, SS347

Alloy Steel

ASTM A217 WC6, WC9, C5, C12

Duplex Steel

F51, F53, F55, Super Duplex

Exotic Alloys

Monel, Hastelloy, Inconel, Titanium

Bronze & Brass

Gunmetal, Aluminum Bronze, Naval Brass

Features & Benefits

High Performance

Designed for reliable operation under demanding conditions with minimal maintenance requirements.

Quality Assurance

Complete material traceability, mill test certificates, and compliance with international standards.

Wide Application Range

Suitable for Pump Protection, Pipeline Systems, Water Systems and many other industrial applications.

Expert Support

Technical assistance for valve selection, sizing, and application engineering from our experienced team.

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Test Type	Pressure	Standard
Hydrostatic Body Test	425 PSI (Class 150)	API 598
Seat Test	300 PSI (Class 150)	API 598
Air Test	80 PSI	API 598

Part Name	Material Specification
Body	ASTM A351 Gr. CF8/CF8M/CF3/CF3M, ASTM A216 WCB, Cast Iron
Ball/Disc	AISI 304/316/304L/316L Stainless Steel
Stem	AISI 304/316/304L/316L, AISI 410
Seat/Seal	PTFE, Reinforced PTFE, Graphite
Gaskets	Spiral Wound Metallic, PTFE, Graphite
Bolting	ASTM A193 Gr. B7/B8, Carbon Steel

Check Valves (NRV) – Swing, Dual Plate & Piston

Key Applications

Quick Summary – What is a Check Valve?

How Does a Check Valve Work?

Forward Flow

Flow Stops

Reverse Flow

Automatic

Check Valve Types Comparison

Technical Specifications

Material Options

Carbon Steel

Stainless Steel

Alloy Steel

Duplex Steel

Exotic Alloys

Bronze & Brass

Features & Benefits

High Performance

Quality Assurance

Wide Application Range

Expert Support

Request a Quote

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Technical Specifications

Design & Exporting

Testing & Inspection

Pressure Rating

Temperature Rating

Test Pressure Requirements

Materials of Construction

Size Range & End Connections

Technical Notes

Standards Compliance