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Breather valves: Everything you need to know

Posted on January 27th, 2023

3B Controls are UK Manufacturers of breather valves and other bulk storage tank equipment, our valves help keep people safe in countries worldwide in industries including Biogas, petrochemical, chemical, and oil and gas storage

If you have a question about breather valves that isn’t answered below, or you’d like more information about our products, please feel free to contact a team member. Call: 01928 567 069. 

What is a breather valve? 

A breather valve is a safety product usually found on storage tanks, Silos and Digester Tanks. 

Also known as pressure/vacuum relief valves (PVRV), pressure/vacuum relief vents, or storage tank breathers, breather valves get their name because they allow the Storage tank to ‘breath’ in and out when the tank is filling or emptying, or when temperature fluctuates in the atmosphere. 

Why do we need to use breather valves?

A breather valve’s most important function is safety. Many gases, liquids, and chemicals must be stored at the right pressure. 

Failing to store them in a pressure-controlled tank can have grave consequences. 

Generally speaking, if the pressure inside a tank gets too high, there’s a chance the tank can rupture or explode. This can lead to a loss of containment, property damage, and loss of life. 

Conversely, if the pressure inside a tank gets too low, it can create a vacuum. This can cause the container to implode with similar consequences. 

A number of things can cause overpressure and vacuum conditions, including filling up or emptying tanks, changes in heat transfer, fires, and exothermic or endothermic reactions caused by mixing substances.

Breather valves open when the pressure inside the tank rises to the designated safe set point, allowing air to flow in or out to relieve the excess pressure or vacuum. 

Aside from safety, breather valves can also:

    •       Prevent wastage by evaporation and vapour loss

    •       Protect the tank contents from external liquids and contaminants

    •       Make it easier to store, transport, and discharge certain substances

How do breather valves work?

A breather valve usually has two separate valves – the out-breather and the in-breather. 

When the pressure inside the tank reaches the pre-determined valve set point, the out-breathing valve will open to allow vapour release. 

This will usually happen when the tank is being filled or if there is a rapid temperature change. 

When the pressure inside the tank falls to the pre-determined vacuum set point, the in-breather valve will open to allow air into the tank and prevent the vacuum from exceeding the design limitations. 

This usually happens when a tank is emptying. 

The opening pressure of the valve is determined by a weight or spring-loaded mechanism. 

This is calibrated to a specific pressure or vacuum, so when the internal pressure or vacuum exceeds the force applied by the weight or the spring mechanism, the valve will open.  When the pressure inside the tank is below the set point of the valve, the valves are sealed tightly

Breather valve considerations

There are several factors to consider when you’re specifying a breather valve for your application. 

Paying close attention to these considerations will help you protect your tank and its contents. 

    •       Breather valve size

Breather valves come in a variety of sizes. You must choose one that’s appropriate for the size of your tank, the liquid or gas it holds, and the kind of flow you expect to see in and out of the tank.

    •       Breather valve location

Breather valves are generally installed on the top of storage tanks. This helps protect the contents of the tank and prevent vapour leaks. Breather valves must be positioned so engineers can carry out inspections and maintenance operations with ease. 

    •       Breather valve inspection and maintenance

Breather valves need to be inspected and maintained regularly. At 3B controls, we recommend valves are inspected at least once per year for things like damaged diaphragms, corrosion, and potential blockages. Our team of trained service engineers can support and service all our supply equipment. 

For more information about relief valves or 3B Controls’ range of valves and valve services, speak to a team member today. Call: 01928 567 069.

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