Check Valves (NRV) — Types, Selection, and Standards

Technical guide · Supreme Valves India · Updated 2026-09-19

A non-return valve (NRV), or check valve, allows flow in one direction and closes against reverse flow. Wrong type selection causes slam, water hammer, chatter, or chronic leakage. This guide compares disc, wafer, barstock wafer, swing, and dual-plate checks used on industrial water, process, and steam-associated lines, with links to Supreme Valves product pages and RFQ guidance.

Product index

• I.C. Disc Check Valve (DCV)
• I.C. Wafer Check Valve
• Wafer Check Valve — Barstock
• Swing Check Valve — Flange End
• Dual Plate Check Valve
• WCB Swing Check Valve
• NRV overview

Selection criteria

Start from reverse-flow consequence, not from catalogue familiarity:

• Media and cleanliness — Dirty services favour swing checks with larger clearances; tight disc seats can stick on solids.
• Flow regime — Continuous flow versus intermittent pump start/stop changes slam risk.
• Minimum flow to hold open — Some wafer and dual-plate designs chatter if velocity is too low.
• Orientation — Horizontal versus vertical upflow; not all types are suitable in every orientation.
• Face-to-face and weight — Wafer and dual-plate save length between flanges; swing checks need more lay length.
• Pressure class and material — Match piping class; carbon-steel steam/water often uses WCB — see ASTM A216 WCB guide and the pressure class selector.
• Isolation still required — Pair NRVs with gate, globe, or ball isolation for maintenance.

Type comparison

Swing check (flanged)

A hinged disc swings open with forward flow and closes under reverse flow or its own weight. Full-port swing checks have low pressure drop when open and are widely used on pump discharge and larger water lines. Closing can be relatively slow, which may allow reverse velocity to build — slam is a design consideration on long columns. Product pages: flange-end swing check, WCB swing check.

Dual-plate (double-door) wafer check

Two spring-assisted plates fold open and close quickly, reducing slam versus heavy single swing discs on many services. The body is wafer-style, clamped between flanges, saving weight and length. Springs must be specified for the media and temperature. See dual plate check valve.

Disc check / DCV

Compact disc checks (including I.C. disc check designs) suit smaller lines and installation where short face-to-face is required. Confirm cracking pressure and flow coefficient against the pump curve. Product: I.C. disc check valve.

Wafer and barstock wafer

Wafer checks fit between flanges with minimal length. Barstock wafer constructions are machined from bar for smaller sizes and higher integrity of the body blank. Products: I.C. wafer check, barstock wafer check.

Standards and testing

Common references include API 594 (wafer and dual-plate check valves), API 6D (pipeline check valves where specified), ASME B16.34 for pressure–temperature ratings, ASME B16.10 / manufacturer face-to-face tables, and API 598 for shell and seat testing. Project specs may require EN 10204 3.1 MTCs and third-party witness. For boiler steam circuits under Indian Boiler Regulations, flag IBR documentation early — IBR valves, IBR checklist, and the documentation article IBR approved valves.

Failure modes

• Slam / water hammer — Disc closes on high reverse velocity; can damage seats, piping, and pumps.
• Chatter — Flow too low to hold the disc stable; seats and springs wear rapidly.
• Stuck open — Debris or corrosion prevents seating; reverse flow continues.
• Stuck closed — Scale or wrong orientation; pump deadheads or starves the process.
• Spring failure (dual plate) — Wrong spring material for temperature or corrosive media.
• Seat leakage — Erosion on wet steam or flashing condensate; improve drainage and consider a moisture separator upstream on wet steam systems.

Layout notes

Install checks the manufacturer’s recommended number of diameters from pump discharges and elbows. Avoid vertical downflow unless the design is rated for it. Provide isolation valves and a drain so the check can be maintained. Do not use a check as a block valve for blinding.

Engineering aids: calculators, pressure class selector.

RFQ checklist

• NRV type preferred (swing / dual plate / disc / wafer) or “recommend”
• NPS/DN, class, quantity, ends (wafer / flanged / BW)
• Body and trim materials; spring material if dual plate
• Media, design P and T, flow rate / velocity if known
• Orientation (horizontal / vertical up)
• Pump discharge or compressor discharge application flag
• Test standard, MTC, TPI
• Companion isolation valve types if quoting a set

FAQ