What is a Lift Check Valve?

A Lift Check Valve, also known as a non-return valve, one-way valve, backflow valve, or pressure retaining valve, is classified as an automatic valve and belongs to one of the two major types of check valves (the other being swing check valves). This valve opens its disc via the pressure of forward medium flow and closes automatically by means of reverse medium pressure and the disc's own weight when flow reverses. Its primary function is to prevent backflow of media in industrial pipelines and protect pumps and driving equipment. The valve disc slides vertically along the centerline of the valve body, and its fluid passage structure is similar to that of a globe valve but with higher flow resistance. Both the valve body and disc can be designed with all-metal construction or rubber composite structure.

Classification of Lift Check Valves

Lift Check Valves are categorized into two types based on installation requirements:

• Straight-through type: Suitable for horizontal pipelines (horizontal disc design requires vertical installation)

• Vertical type: Suitable for vertical pipelines (vertical disc design requires horizontal installation)

Key Specifications

• Sealing Surface: Adopts stainless steel overlay welding technology for enhanced durability and leak tightness

• Valve Body Materials: Available in cast steel, stainless steel, and other corrosion-resistant alloys

• Applicable Media: Water, oil products, steam, and various industrial fluids

• Typical Applications: Petroleum, chemical, power generation, and fire protection systems

• Nominal Pressure Range: 1.6-32.0MPa (PN16 to PN320)

• Connection Types: Welded, flanged, and threaded connections

• Operating Temperature Range: -196℃ to 550℃ (suitable for cryogenic to high-temperature working conditions)

Working Principle of Lift Check Valves

The disc of a Lift Check Valve is seated on the sealing surface of the valve seat inside the valve body. Similar to a globe valve in structure (except for the freely movable disc), the valve operates as follows:

1. Opening Mechanism: Forward fluid pressure lifts the disc off the valve seat, allowing media to flow through unobstructed.

2. Closing Mechanism: When media flow reverses, the combination of reverse pressure and the disc's own weight forces the disc to seat back on the valve seat, effectively blocking backflow.

3. Disc Design Options:

1. All-metal disc for high-temperature, high-pressure, or abrasive media applications

2. Rubber-faced or rubber-ring inlaid disc for improved sealing performance with non-abrasive media

Note: The fluid passage of a Lift Check Valve is relatively narrow (similar to globe valves), resulting in a higher pressure drop compared to swing check valves. However, swing check valves offer minimal flow restriction in comparison.

Installation and Maintenance Guidelines for Lift Check Valves

To ensure optimal performance and longevity, follow these professional installation and maintenance practices:

1. Storage Requirements:

1. Plug both ends of the valve passage to prevent contamination.

2. Store in a dry, well-ventilated indoor environment.

3. Regularly inspect for corrosion if stored for extended periods.

2. Pre-Installation Preparation:

1. Thoroughly clean the valve to remove debris, dust, or contaminants.

2. Inspect for any damage incurred during transportation and repair or replace defective parts.

3. Installation Verification:

1. Carefully verify that the valve's markings and nameplate specifications (pressure, temperature, size) match the application requirements.

4. Orientation Requirements:

1. Vertical disc Lift Check Valves must be installed on horizontal pipelines.

2. Horizontal disc Lift Check Valves must be installed on vertical pipelines.

5. Support and Loading:

1. Do not allow the valve to bear the weight of the pipeline system.

2. Provide independent support for large-size Lift Check Valves to avoid stress from pipeline expansion or vibration.

6. Flow Direction Compliance:

1. Ensure the medium's normal flow direction aligns with the arrow marked on the valve body. Incorrect orientation will block normal flow.

2. Foot valves (a type of Lift Check Valve) must be installed at the bottom of the pump suction pipeline.

7. Special Installation Notes:

1. Straight-through Lift Check Valves are designed for horizontal pipeline installation.

2. Vertical Lift Check Valves and foot valves are typically installed on vertical pipelines with media flowing from bottom to top.

8. Water Hammer Prevention:

1. Valve closure may generate water hammer pressure in the pipeline, which can damage valves, pipelines, or equipment—especially in large-diameter or high-pressure systems.

2. Select appropriate valve sizes and consider installing water hammer arresters for critical applications.