Differences Between Swing Check Valves And Lift Check Valves: Selection Guide

A check valve is an automatic valve that opens through the forward flow of the medium and closes when the flow stops or reverses. Its primary functions are to prevent reverse flow, protect pumps from reverse rotation, and prevent cross-contamination or crossflow between different piping systems.

Swing check valves and lift check valves are two common designs used in industrial piping. Although they perform the same basic function, they differ significantly in disc movement, flow resistance, installation requirements, closing behavior, and suitable applications.

Correct check valve selection requires more than comparing nominal diameter and pressure class. Engineers must also consider medium properties, normal and minimum flow rates, allowable pressure loss, pipe orientation, operating frequency, and the potential for water hammer.

1. Operating Principles

1.1 Swing Check Valve

A swing check valve uses a disc connected to the valve body through a hinge or pin. When the medium flows in the correct direction, the fluid force pushes the disc away from the seat. When flow decreases or reverses, the disc swings back toward the seat under gravity and reverse-flow pressure.

Because the fully opened disc moves largely away from the main flow path, the internal passage is relatively unobstructed.

1.2 Lift Check Valve

In a lift check valve, the disc moves vertically or axially along a guiding structure. When the upstream pressure produces sufficient force, the disc rises from the seat and allows the medium to pass. When forward flow stops, gravity, spring force, or reverse pressure returns the disc to the closed position.

The internal passage of a conventional lift check valve resembles that of a globe valve. The medium normally changes direction and passes through a relatively restricted seat opening.

Installation requirements can vary among manufacturers and valve designs. Spring-assisted, axial-flow, and other special check valves may have fewer installation restrictions than conventional gravity-operated valves. The installation manual for the selected product should always be consulted.

2. Differences in Flow Resistance

When a swing check valve is fully open, its disc is positioned mostly outside the principal flow path. The medium passes through the body with a relatively small change in direction. Swing check valves therefore usually have a lower pressure loss and are often suitable for large-flow systems where pumping energy is an important consideration.

In a conventional lift check valve, the medium passes through the valve seat and changes direction inside the valve body. This creates additional local resistance, making its pressure loss generally higher than that of a comparable swing check valve.

The local pressure loss can be estimated using the following equation:

Δp = ζρv⊃2;/2

Where:

• Δp is the pressure loss;

• ζ is the local resistance coefficient;

• ρ is the fluid density;

• v is the fluid velocity.

This equation shows that pressure loss increases approximately with the square of velocity. Even a relatively small increase in flow velocity can therefore produce a significant increase in valve pressure drop.

For final selection, engineers should use the manufacturer’s flow coefficient, resistance coefficient, or pressure-drop curve. Valve body geometry, disc opening, internal diameter, and seat design can all affect flow performance. The actual pressure loss cannot be determined solely from the terms “swing type” or “lift type.”

3. Characteristics and Applications of Swing Check Valves

Swing check valves have a relatively open flow passage and are commonly used in large-diameter circulating-water systems, water supply and drainage pipelines, petroleum transportation, fire-protection systems, cooling-water systems, and general industrial services.

Because their opening resistance is normally low, they are particularly suitable for systems with:

• Relatively large and stable flow rates

• Low allowable pressure loss

• Medium or large pipe diameters

• Continuous operation

• Clean liquids or gases

• Moderate flow changes

However, the disc of a swing check valve has a relatively long travel distance. If a pump stops suddenly or the pipeline flow reverses rapidly, the fluid may develop a significant reverse velocity before the disc reaches the seat. The disc may then strike the seat at high speed, producing noise, mechanical impact, and pressure surges.

In high-head pump discharge lines, long-distance water pipelines, or systems with frequent flow changes, the transient behavior should be evaluated carefully. Depending on the risk, the system may require a swing check valve equipped with:

• A damping device

• An external lever and weight

• A hydraulic control mechanism

• A spring-assisted closing mechanism

• A controlled or non-slam closing design

Swing check valves should also not remain at very low flow rates for extended periods. If the fluid force is insufficient to hold the disc in a stable open position, the disc may repeatedly move or flutter. This can cause hinge-pin wear, vibration, noise, and sealing-surface damage.

4. Characteristics and Applications of Lift Check Valves

The disc of a lift check valve moves along a defined guide. The closing travel is relatively short and concentrated, and the seating surfaces can normally be manufactured with high precision. Lift check valves are therefore suitable for clean media and applications where reliable sealing is important.

They are commonly used in:

• Steam pipelines

• Boiler feedwater systems

• Oil and fuel lines

• High-pressure process piping

• Chemical process systems with clean fluids

• Small- and medium-diameter industrial pipelines

Because the internal flow changes direction and passes through a restricted seat area, a lift check valve generally produces a higher pressure loss. In systems with a low available differential pressure, large flow demand, or strict energy-efficiency requirements, the valve’s flow capacity must be checked carefully.

A conventional lift check valve is normally installed in a horizontal pipe with the cover facing upward so that the disc can move vertically and return to the seat under gravity. If the valve is inclined, improperly installed, or affected by deposits inside the guide, its movement may become restricted.

Media containing suspended solids or scale can enter the guide clearance and cause the disc to stick. Lift check valves are therefore normally more suitable for clean or adequately filtered fluids.

For vertical pipelines, a conventional lift check valve should not be assumed to be suitable. A straight-through, axial-flow, piston, or spring-assisted check valve specifically approved for vertical installation should be selected.

5. How to Select Between the Two Designs

5.1 Consider Pipe Size and Allowable Pressure Loss

For large-diameter piping, high flow rates, and systems requiring low resistance, a swing check valve is often the preferred choice. Its relatively straight flow path helps reduce pressure loss and pumping energy.

For small- or medium-diameter, high-pressure systems where compact construction, guided disc movement, and sealing performance are important, a lift check valve may be more suitable.

The final decision should be supported by a hydraulic calculation rather than size alone.

5.2 Consider the Medium

Both swing and lift check valves generally perform best with clean or filtered media. Suspended particles, fibers, crystals, or high-viscosity fluids can interfere with disc movement or accumulate on the sealing surfaces.

Lift check valves may be especially sensitive to deposits in the guiding mechanism. Swing check valves have a more open flow passage, but particles can still collect around the hinge or valve seat.

For media containing solids, the selection process should evaluate:

• Particle size and concentration

• Settling behavior

• Fluid viscosity

• Risk of crystallization

• Potential for corrosion or erosion

• Cleaning and maintenance requirements

A ball check valve, specially designed slurry check valve, pinch valve, or another valve type may be more appropriate for certain contaminated or high-solids services.

5.3 Consider Flow Variation

An oversized check valve is not necessarily safer. If the valve is too large for the actual operating flow, the disc may remain only partially open. This can cause unstable movement, vibration, impact, accelerated wear, and excessive noise.

The valve should therefore be sized according to:

• Normal operating flow

• Minimum stable flow

• Maximum design flow

• Fluid density

• Available differential pressure

• Manufacturer’s minimum velocity or flow recommendations

In some systems, selecting a check valve smaller than the pipeline and using appropriate reducers may provide more stable disc operation. Such an arrangement must still be checked for acceptable velocity and pressure loss.

5.4 Consider Installation Direction

Standard swing check valves are generally suitable for horizontal pipelines. Some designs may also be installed in vertical pipelines when the medium flows upward.

Conventional lift check valves normally require horizontal installation with the cover facing upward. This ensures that the disc moves freely and returns correctly under gravity.

For both designs:

• The valve body arrow must match the medium flow direction.

• Sufficient space should be provided for inspection and maintenance.

• The installation must comply with the manufacturer’s instructions.

• Vertical installation suitability must be confirmed for the specific model.

6. Water Hammer and Closing Characteristics

Water hammer occurs when fluid velocity changes rapidly, creating a pressure wave inside the piping system. Although check valves prevent reverse flow, an improperly selected check valve may contribute to a severe pressure surge.

A swing check valve may close relatively slowly because of its long disc travel. If the flow reverses before the disc reaches the seat, the reverse-flow momentum can cause a strong closing impact.

A lift check valve generally has a shorter disc travel, but this does not automatically mean that it will eliminate water hammer. Closing behavior also depends on:

• Fluid velocity

• Pump deceleration

• Pipeline length

• Fluid compressibility

• System elevation

• Disc mass

• Spring force

• Valve orientation

• Downstream pressure

For high-risk systems, transient hydraulic analysis should be performed. Specialized non-slam, axial-flow, nozzle, or controlled-closing check valves may be more appropriate than conventional swing or lift designs.

A check valve should not be treated as a replacement for a complete surge-control system. Long or high-pressure pipelines may also require air valves, surge vessels, pressure-relief devices, variable-speed pump control, or other protective equipment.

7. Material and Pressure-Class Selection

After selecting the structural type, the valve body, disc, seat, stem or pin, gasket, and sealing materials must be compatible with the medium and operating environment.

The pressure class should be selected according to design pressure and temperature rather than normal operating pressure alone. The pressure-temperature rating of the material must also be checked because the allowable pressure usually decreases as temperature increases.

Transient pressure, pump shutoff pressure, thermal expansion, and possible surge pressure should be included in the design assessment.

8. Common Check Valve Selection Mistakes

One common mistake is assuming that a larger nominal diameter always produces lower resistance. An oversized valve may not open fully and can experience severe disc flutter and mechanical wear.

Another mistake is selecting the pressure class only according to steady-state pressure. Pump trips, valve closures, and rapid flow changes may generate transient pressures substantially higher than the normal operating pressure.

Installation position is also frequently overlooked. Elbows, reducers, pump outlets, and other disturbances can create turbulent or uneven velocity profiles that interfere with disc stability. The valve should be installed with adequate straight piping and maintenance clearance according to the manufacturer’s recommendations.

Finally, the check valve should not be expected to solve every water-hammer problem. If the pipeline has a significant surge risk, a complete transient analysis and additional control equipment may be necessary.

Conclusion

Neither swing check valves nor lift check valves are universally superior. Swing check valves generally provide lower flow resistance and are well suited to larger pipe diameters and high-flow systems. Lift check valves offer guided disc movement, compact construction, and reliable sealing for clean media and selected high-pressure applications.

The final selection should consider the medium, flow range, pressure, temperature, installation direction, allowable pressure loss, closing characteristics, and water-hammer risk. Manufacturer data such as flow coefficients, pressure-drop curves, minimum stable flow, pressure-temperature ratings, and installation instructions should also be reviewed.

A scientifically selected check valve not only prevents reverse flow but also helps reduce pressure loss, disc impact, vibration, abnormal noise, leakage, and premature valve failure.

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