NIBCO Silent Check Valve Overview: F-910-B-LF and F-960-B-LF

The NIBCO F-910-B-LF and F-960-B-LF are flanged, spring-actuated check valves built for one-directional flow control in commercial and industrial piping systems. Both are lead-free certified, globe-style, and available in sizes from 2½" through 36".

When customers search for a NIBCO check valve, the most common information they seek is valve specifications, pressure ratings, and the correct model/type for quick replacements to keep plants running safely. This guide is built with these factors in mind to answer those questions clearly.

We have put together this overview to help engineers, contractors, and facility managers confidently replace and source the NIBCO F-910-B-LF (also referenced as NIBCO F910, NIBCO F910B, or NIBCO F-910) and the F-960-B-LF - without project delays.

What Is a Silent Spring Check Valve?

A spring-silent check valve is an automatically operated valve that permits fluid to flow in only one direction. When the flow stops or reverses, the spring-loaded disc closes as forward velocity decays, preventing significant reverse flow from developing inside the piping system.

The distinction from a conventional swing check valve is the manner of closure. A swing check relies on gravity and a swinging disc, which closes only after some reverse flow has already occurred - producing the familiar slamming effect and accompanying pressure spike known as water hammer.

The NIBCO F-910/F-960 series uses a spring-loaded, center-guided disc. When forward flow is present, line pressure lifts the disc against spring tension. The moment flow drops, the spring reseats the disc quietly and immediately - before reverse momentum can build.

Because of the spring-assisted closure, the F-910 and F-960 are often referred to as non-slam check valves or silent check valves.

Spring vs. Swing Check Valve
Video credit: RFS Hydraulics

This design eliminates water hammer, protects the system components, and delivers silent performance across a wide range of pressures and pipe sizes.

This rapid closure minimizes:

Water hammer
Pressure surges
Reverse-flow slam
Pipe vibration
Backflow through the system

For this reason, silent spring check valves such as the NIBCO F-910-B-LF and F-960-B-LF are commonly installed in pump discharge lines, HVAC systems, water distribution systems, and industrial piping applications where quiet operation and system protection are important.

The Two Models: NIBCO F-910-B-LF and F-960-B-LF

The NIBCO F-910/F-960 series is offered in two pressure classes, both with flanged end connections and a bronze seat (designated by the "-B" in the model number).

NIBCO F-910-B-LF - Class 125

The NIBCO F-910-B-LF is a Class 125 flanged silent check valve rated for 200 PSI non-shock cold working pressure in sizes 2½" through 12", and 150 PSI CWP in sizes 14" through 36".

Additionally, an external Valve can be mated directly to the downstream side in those same sizes without spacers or adapters - a design convenience that simplifies installation in mechanical rooms and pump stations. (arrangement under factory consultation).

NIBCO F-960-B-LF - Class 250

The NIBCO F-960-B-LF is rated for 400 PSI non-shock cold working pressure in sizes 2½" through 12", and 300 PSI CWP in sizes 14" through 36". When system pressures exceed what the Class 125 valve covers, or when the project specification explicitly calls for a Class 250 valve, the F-960-B-LF is the correct selection.

Both models share the same spring-actuated globe-style body, renewable seat and disc, and lead-free certification. The differences come down to pressure class, flange dimensions, and weight - the F-960 carries a heavier body wall to accommodate higher working pressures.

Key Specifications

Feature	F-910-B-LF (Class 125)	F-960-B-LF (Class 250)
CWP - Sizes 2½"–12"	200 PSI / 13.8 Bar	400 PSI / 27.6 Bar
CWP - Sizes 14"–36"	150 PSI / 10.3 Bar	300 PSI / 20.7 Bar
Max. Temperature	200°F / 93°C	200°F / 93°C
Actuation	Spring	Spring

Material List

Both models are constructed with the same lead-free material specification:

Body - Cast Iron ASTM 126 Class B
Seat - Bronze ASTM B584 Alloy C87600 (B)
Disc - Class 125, 2½"–10" - Bronze ASTM B584 Alloy C87600 / Class 250, 12”–36” - Alloy ASTM B148 C95500
Spring - Stainless Steel ASTM A313 UNS S31600
Bushing - Aluminum Bronze B505 C95400
Set Screws - Stainless Steel Type 316 ASTM F879

Note on seat options: The "-B" designation indicates a standard bronze seat. NIBCO also offers a "-W" variant (F-910-W-LF / F-960-W-LF) with a Buna-N-bonded bronze seat for applications requiring elastomeric seating.

Available Sizes and Dimensions

Both the F-910-B-LF and F-960-B-LF are available from 2½" through 36". The table below lists the face-to-face dimension (A) and the approximate shipping weight for each size.

Certifications and Compliance

Lead-Free Certified -WQA to NSF/ANSI 61 & 372 (weighted average lead content ≤ 0.25%)
MSS SP-125 - Industry standard for spring-loaded check valves
MIL-V-18436F - Military specification compliance
FM Approved - 2½" thru 10" (ONLY F-910-B-LF)

Typical Application

The NIBCO F-910 and F-960 silent check valve series is commonly specified in:

Pump discharge lines - prevent backflow and water hammer when a pump shuts down
Commercial HVAC systems - hydronic heating and cooling circuits requiring reliable one-way flow control
Fire protection piping - FM Approved in select sizes (F-910-B-LF, 2½"–10" only)
Municipal and waterworks systems - large-diameter applications up to 36" for water distribution
Industrial process piping - anywhere a flanged, cast iron, spring-actuated check valve is required
Mechanical rooms and central plant equipment - boiler rooms, chiller plants, and pump stations

Check Valve - Applications
Image credit: Yinke Valve

Installation Tips

Correct installation is a critical part to ensure the optimum valve performance and system integrity.

Flange and Gasket Requirements

These valves must be used only with a flat-face flange and a full-face gasket.
The seat end of the valve must be mated to a standard flat-faced metal flange.
Rubber flanges are not acceptable.

Pump Discharge Installations

Install a minimum of 5 pipe diameters downstream from the pump discharge or any change in flow direction to minimize turbulence.
Flow straighteners may be required in cases of extreme turbulence.

Orientation

The valve shall be installed in horizontal pipelines or vertical pipelines with upward flow.

Flanged Check Valve Installation
Video credit: CheckAll - Valves

Frequently Asked Questions

What is the difference between the NIBCO F-910-B-LF and the F-960-B-LF?

The primary differences are the pressure class. The NIBCO F-910-B-LF is rated for 200 PSI CWP and uses Class 125 flange dimensions. The F-960-B-LF is rated for 400 PSI CWP in the same size range and uses Class 250 flange dimensions. If your system flanges are Class 125 and the operating pressure is below 200 PSI, the F-910-B-LF is the standard choice. Higher-pressure systems require the F-960-B-LF.

What makes this a "silent" check valve?

The spring-actuated disc closes before reverse flow develops enough momentum to cause a slamming effect. The result is a quiet and surge-free closure that protects pumps and downstream equipment.

Is the NIBCO F-910-B-LF lead-free?

Yes. Both the F-910-B-LF and the F-960-B-LF are certified lead-free by the Water Quality Association (WQA) to NSF/ANSI 61 & 372, with a weighted average lead content of ≤ 0.25%.

Is the F-910-B-LF FM Approved for fire protection?

Yes - in sizes 2½" through 10" only. The F-960-B-LF does not carry FM Approval. Specify the F-910-B-LF for FM-approved fire protection applications within that size range.

What standards do these valves conform to?

Both models conform to MSS SP-125 (spring-loaded silent check valves) and MIL-V-18436F. They are also certified to NSF/ANSI 61 & 372 for lead-free compliance.

NIBCO Parts and Valves Available in Liberty Supply

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