Non-Return Valves: Reliable Backflow Prevention for Industrial Pipelines

Material, Designs and Selection of the Right Check Valve

The choice of the right check valve for your pipeline depends on medium, pressure, temperature, and installation position. High-quality valves are available in materials such as brass, stainless steel, steel (1.0460), ductile iron (GGG40) or plastic (PP, PVC-U). For aggressive media, stainless steel check valves are the first choice. The seals are selected according to the medium, common ones are EPDM, NBR, FKM/Viton, PTFE, or metal.

The range includes nominal diameters from DN8, DN10, DN15 up to DN500 and even DN600. Various flange standards (DIN, ANSI) or threaded connections are available. For complex requirements, our expert team will be happy to help you select the optimal valve from our extensive stock program.

How a Non-Return Valve Works

In the forward-flow direction, system pressure lifts the disc or flap off its seat — flow passes freely. As soon as flow decelerates to zero or backpressure exceeds forward pressure, the disc returns to closed under gravity or spring force. No actuator, no control signal, no energy input required.

Without spring return: closure by gravity only — suitable for vertical upward flow or low-velocity horizontal lines where water hammer risk is low. With spring return: faster, position-independent closure in any orientation, significantly reducing pressure surges at pump shutdown. Spring-return types require a slightly higher cracking pressure to open.

What a non-return valve protects against

• Backflow — prevents reverse flow through pumps and compressors, protecting equipment from reverse rotation and mechanical damage.
• Water hammer — fast-closing designs, especially dual plate valves with integral spring, close before reverse velocity develops, eliminating destructive pressure transients.
• Cross-contamination — stops dirty or processed media from entering clean supply lines or separate process circuits.
• Pump siphoning — keeps the suction line primed after pump shutdown, preventing dry-start damage on the next cycle.

Design Types: Which Non-Return Valve Suits Your System?

Wafer Check Valve (single-flap)

Installed directly between two existing flanges — no integral flanges, minimal face-to-face length. Standard choice for medium and large bore industrial pipelines. Body in stainless steel 1.4408 or galvanised steel 1.0619; DN 32 to DN 600, PN 6–40 and ANSI Class 150/300. Versions with spring return close faster in horizontal installations and reduce water hammer — standard at pump discharge outlets and wherever gravity-only closure is unreliable.

Dual Plate Check Valve

Two symmetrical half-discs on a central shaft — each plate travels only half the swing angle of a full disc, so closure is significantly faster. Lower pressure drop than an equivalent single-flap valve. Suited to large bore sizes (DN 100–600), high flow rates and frequent pump start/stop cycles. Body: ductile iron GGG40 or stainless steel CF8M; flange connection DIN/ANSI.

Threaded Check Valve

Female thread to ISO 228/1 for direct connection without flanges. The most compact and economical option for small bore sizes DN 10 to DN 50. Body: brass or stainless steel 1.4408, seats in PTFE or metal. For building services, HVAC, laboratory lines and general industrial installations.

Body Material and Seat Selection

Body materials

• Stainless steel 1.4408 (AISI 316) — First choice for corrosive media, food and pharmaceutical processing, seawater and outdoor installations. Hygienic, durable and low-maintenance.
• Ductile iron GGG40 — Robust and economical body for medium and large bore sizes in water, gas and general industrial service.
• Galvanised steel 1.0619 — For standard industrial applications at elevated pressures with additional corrosion protection from the zinc coating.
• Brass — For small bore sizes in building services, HVAC and drinking water. Economical and easy to install.
• PVC-U / PP-H — Chemical resistance, light weight and electrical isolation for chemical and process industry applications.

Seat materials

• NBR — Mineral oils, fuels, neutral aqueous media and wastewater. To approx. 80 °C. Not for hot water or steam.
• EPDM — Water, hot water, steam, dilute aqueous solutions. Standard for drinking water and water treatment, to approx. 120 °C. Not oil-compatible.
• FKM / Viton — Aggressive chemicals, solvents, fuels, elevated temperatures to approx. 180 °C. For chemical dosing and oil & gas.
• PTFE — Near-universal chemical resistance, −10 °C to +200 °C, FDA-compliant. Requires spring return for reliable sealing.
• Metal — High-temperature service, steam, abrasive media, wherever elastomer seats are not permissible. Maximum durability.

Application Areas

Water and wastewater treatment

Wafer and dual plate check valves in GGG40 or stainless steel with EPDM seats for drinking water mains, pump stations, waterworks and sewage treatment plants. Fast-closing dual plate types protect high-capacity pump sets from water hammer.

Chemical and petrochemical industry

Stainless steel wafer check valves (1.4408) with PTFE or FKM seats for aggressive acids, alkalis, solvents and chloride-bearing process media. Spring-return versions for fast closure during frequent pump cycling.

HVAC and building services

Threaded brass check valves for heating circuits, chilled water and condensate at small bore sizes. Wafer check valves with EPDM for larger HVAC plant and district heating systems.

Food and pharmaceutical industry

Stainless steel 1.4408 with FDA-compliant EPDM or PTFE seats. Smooth internal surfaces for CIP/SIP cleanability. Electropolished versions available on request.

Oil, gas and power generation

Wafer and flanged check valves in stainless steel or carbon steel at PN 25/40 and ANSI Class 150/300 for pipeline systems, compressor protection and power plant service. Metal seats for high-temperature and high-pressure applications.

Marine and offshore

Duplex stainless steel and 1.4408 for seawater circuits, bilge pump systems and cooling lines. High resistance to chloride corrosion and stress corrosion cracking.

Fergo: Non-Return Valve Specialist Since 2004

Fergo stocks over 493 non-return valves in all standard designs, materials and sizes, with next-day delivery for most stock items within Germany. All products are supplied with full technical documentation — data sheets, 3D models and declarations of conformity available immediately as downloads.

For special requirements — PFA-lined check valves for highly aggressive media, Gestra steam trap check valves, flanged check valves in special alloys or 3.1 material test certificates per EN 10204 — our technical sales team is available directly.