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If you work with liquid or gas pipelines, then you need valves to help manage and regulate the flow of materials in these pipelines. One of the key valves you need to know about is the check valve, but what exactly are these valves, and how do they work? Take a look at our handy guide.

How does a check valve work?

A check valve is sometimes referred to as a non-return valve or a one-way valve.

Basically, a check valve permits fluids such as liquids and gases to flow one way through the pipework. A mechanism within the valve remains open while fluids are traveling in the desired direction, and is designed to offer only a bare minimum of resistance and impedance.

However, when the liquid or gas begins to flow in the other direction, the valve will close, and movement will not be permitted. Consider a turnstile at a sports event. You show your ticket, and pass through the turnstile, just like the sports fan in front of you in the line did, and just like the one behind you will. Provided that all of you are moving in the same direction, you will be able to move with no problem. However, if you start coming back the other way, the turnstile will lock and block your way.

This is — functionally, if not structurally — how a check valve operates. Let’s take a closer look at the actual structure below.

What is a check valve for?

There are many instances when a reverse flow of a liquid or gas can be highly dangerous. For example, fluids backing up in chambers and lines can cause chemical reactions that damage equipment or even put personnel at risk. This is why it is so crucial for plant managers to understand how check valves work, as these pieces of equipment can be instrumental in maintaining a safe site.

However, such instances of danger and equipment damage are rare. In most cases, check valves are simply used to make the process of piping liquids and gases from one location to another more cost-effective and efficient. If these liquids and gases are allowed to back up, the process could begin to break down, potentially costing your plant or facility rather a lot of money.

Check valves may even be used in the transfer of relatively harmless substances, such as water. These valves are often deployed in water testing and storage facilities, to boost the efficiency of water piping systems.

The valves may also be deployed to prevent odors or gas leaks that may result from materials backing up in the pipes.

What is the structure of a check valve?

There are different types of check valves available, but for this article we are going to be discussing the structure of one of the most common types of valve. The check valve is mounted on the inside of the liquid or gas pipeline. Within this valve is a clapper, which is mounted on a hinge. The hinge operates in a similar way to most of the doors we may find at home, i.e. it will only open in one direction.

If a pump is turned on, and the material is pushed in the right direction, the valve will open and permit the material to pass through. However, when the pump is stopped, or if pressure is applied at the other end of the system, forcing liquid or gas back through the pipe, the clapper will close and the flow will be halted.

For safety purposes, for the integrity of your equipment and for the efficiency of your processes, a check valve is a very handy piece indeed.