Check Valves which are also known as One-way Valves, a device that is designed to allow fluid flow movement only in one direction. The main purpose that the check valve serves is to prevent any backflow within the installed system.

Backflow can cause several system damage due to a variety of reasons, especially if the water is contaminated. Since check valves are generally inexpensive, efficient and a simple solution, their use is popular in different applications.

Check valves come in various materials, sizes and designs to ensure that there is an available check valve for every application. But before you decide on installing check valves make sure to learn all its basics.

Keep reading till the end to find out all things essential about check valves.

Check Valve Work Mechanism

Cracking Pressure

In order to open a check valve and passage of media through it, there is a requirement for a minimum upstream pressure (pressure differential between inlet and outlet). This minimum upstream pressure is known as the check valve's ‘cracking pressure.’ 

The specific cracking pressure alters depending on the valve size and design, hence, it is needed to ensure that the system’s pressure can create the cracking pressure of the chosen check valve(s).

Closing

If the upstream pressure goes below the cracking pressure or there is back pressure (flow attempting to move from the outlet to the inlet), then the check valve closes. Generally, a check valve has a ball, gate, diaphragm, or disc pressed against a seal to shut the check valve.

Gravity or spring also guides the closing process. As the inlet pressure falls below the cracking pressure or there is backpressure, the valve closes by spring, gravity and/or by the backpressure use.

Installation Orientation

It is important to learn about the correct installation orientation as a check valve operates to allow flow in one direction only. Generally, an arrow on the valve’s housing represents the flow direction. 

However, if there is absence of an arrow, make sure to assess the valve carefully to ensure it is installed in the intended flow direction. But in case of wrong installation, the media will not be passing through the system, and as a result the build-up pressure can cause damage.

Normal open and closed check valves

A normally open check valve enables free flow of the medium but shuts off in case of backflow. Whereas, the normal closing of the check valve prevents the media flow through it until the cracking pressure accumulates, at which point the valve opens.

Common Check Valves Used for Wastewater Application

Check valves are popularly used in wastewater application and there are commonly two distinct types of check valves installed for it. They are -

Swing Check Valves

This type of check valve is typically mounted using a disc that is present in the valve’s shaft or hinge. The disc swings off the seat to enable the fluid flow forward and when the fluid flow ceases, the disc swings back onto the seat for blocking reverse flow.

The reverse flow along with the weight of the disc has an impact upon the closing characteristic of the valve.

Ball Check Valves

Ball check valve is another type of check valve that is used for wastewater application. It operates by means of a ball that moves up and down internally. The seat is tailored to fit the ball and its chamber is conically shaped to assist the ball into the seat to shut and seal the reverse flow.

To make the right choice of check valve, make sure to get in touch with the experts.