Wafer Check Valve: Features & Uses

• 2024-08-17

Wafer check valves are also known as non-return valves, reflux valves, back pressure valves and one-way valves. These types of valves are automatically opened and closed by the force generated by the flow of the medium itself in the pipeline, belonging to a category of automatic valves.

Technical Parameters

Nominal Pressure or Pressure Class: PN1.0-16.0MPa, ANSI CLASS 150-900, JIS10-20K

Nominal Diameter or Caliber: DN15～900, NPS 1/4 ～36

Connection Mode: Flange, Butt Weld, Thread, Socket Weld, etc.

Applicable Temperature: -196℃～540℃

Valve Body Material: WCB, ZG1Cr18Ni9Ti, ZG1Cr18Ni12Mo2Ti, CF8(304), CF3(304L), CF8M(316), CF3M(316L), Ti.

Different materials can be selected for application in pipelines conveying various media such as water, steam, oil products, nitric acid, acetic acid, oxidizing media, urea, etc.

Operating Characteristics

The operating characteristics of check valves include large load variation and low opening-closing frequency. Once put into the closed or open state, they can maintain the service cycle for a long time without requiring the movement of components. However, once the "switching" requirement arises, they must be operated flexibly, which is more demanding than the common mechanical movements.

In most practical applications, check valves are typically designed for rapid closing. At the moment when the check valve closes, the medium flows in the reverse direction. As the valve disc closes, the reverse flow velocity of the medium rapidly decreases to zero while the pressure rises sharply, resulting in a "water hammer" phenomenon that may cause damage to the pipeline system.

For high-pressure pipeline systems with multiple parallel pumps, the water hammer problem of check valves is more prominent. Water hammer is a pressure wave in the transient flow of pressure pipelines, which is a hydraulic shock phenomenon caused by the change of fluid flow velocity in pressure pipelines. Its physical cause is the combined effect of the incompressibility of fluid, the inertia of fluid movement and the elasticity of pipelines. To prevent the hidden danger of water hammer in pipelines, people have adopted new structures and materials in the design of check valves over the years, achieving gratifying progress in minimizing the impact force of water hammer while ensuring the service performance of check valves.

Applications

Check valves are used in pipeline systems, and their main functions are to prevent medium backflow, prevent reverse rotation of pumps and their driving motors, and avoid medium discharge from containers. Check valves can also be applied to the pipelines that supply supplementary medium for auxiliary systems where the pressure may rise above the pressure of the main system. Depending on the materials, check valves can be used in pipelines conveying various media. Installed on the pipeline, check valves become one of the fluid components of the complete pipeline, and the opening and closing process of their valve discs is affected by the transient flow state of the system where they are located; conversely, the closing characteristics of the valve discs also have a reactive effect on the fluid flow state.