Rubber-Flex Duckbill Check Valves - RF-DBF Flanged | Cla-Val

Rubber-Flex Duckbill Check Valve Cla-Val RF-DBF

The RF-DBF is an elastomeric duckbill-type check valve with flanged connection, designed for backflow prevention in applications where metallic moving parts, shafts, or seats are undesirable. The flange is integrated into the valve body and reinforced with a metal backing ring for direct installation onto pipe flanges, tanks, or outfall walls.

Typical Applications

• stormwater outfalls, sewage and pump stations
• wastewater treatment plants and sludge lines
• protection against tidal or river backflow
• tanks, headwalls, and marine discharges
• systems with solids, sludge, or suspended matter

Operation is based on differential pressure. Forward pressure opens the valve lips, while backpressure compresses them to restrict reverse flow. No electrical, pneumatic, or hydraulic actuator is required.

Connection, Dimensions, Standards

RF-DBF is available in sizes 1"–72". Standard flange drilling is ANSI 125/150#, with options for ANSI 250/300, DIN, JIS, BS, or AS patterns. 316SS retaining rings are standard for the flanged version.

Elastomer Selection

Material selection is based on media, temperature, and chemical compatibility:

• EPDM: sewage, dilute acids
• Buna-N / Nitrile: oils, greases, hydrocarbons
• Neoprene: general use, ozone, greases, moderate chemicals
• Natural Rubber: abrasion, elasticity, organic acids
• Viton / CSM / Butyl: special chemical or thermal requirements

Elastomer combinations cover temperatures up to 82–121 °C, depending on material. NSF/ANSI 61 certification is available on request for suitable configurations.

Installation and Maintenance

For horizontal installations, the duckbill should be oriented vertically unless space constraints apply. Flange bolts must be tightened in a cross pattern with torque appropriate to size, typically 20–800 ft·lbs. Periodic inspection should focus on cuts, wear, and debris trapped at the lips.

FAQ

When is RF-DBF selected over a flap check valve?
Used where passive backflow prevention is required in contaminated water or sludge, without hinges, seats, or mechanical parts prone to blockage.

Is there a low headloss version?
Yes, the RF-DBI-LH series is available for in-line applications with reduced headloss.