Understanding Fluorine Lined Check Valves

Functionality Of PFA Lined Check Valves

Usually valves are kept in an open position when unused. To close them, an external force has to be provided which then blocks fluid flow. But for check valves, it’s the opposite. These valves are normally closed. And then a force is applied which opens the valve. Other check valves can also work on the concept of differential pressure. A higher inlet pressure mixed with lower outlet pressure allows fluid flow.

PFA lined check valves work exactly the same way. The only difference is a layer of PTFE/fluorine which is added to the valves. In turn, this gives the valve added corrosion resistance. And so PTFE lined swing check valves are also termed chemical process valves.

PFA Lined Check Valves Backflow Prevention

PFA lined check valves are designed to allow unidirectional fluid flow. This allows for backflow prevention. But how? Most check valves open due to higher pressures at the inlet as compared to pressures at the outlet. During backflow, this balance is shifted. And as a result, pressure at the outlet exceeds pressure at the inlet. This forces the check valves to automatically close any time this happens.

Types Of Fluorine Lined Valve

Spring Loaded Corrosion Resistant Check Valves

Spring check valves/Piston check valves follow the same functionality as mentioned above. Spring valves are closed using a disc which opens/closes with the help of a spring. Once pressure at the inlet increases, it generates a force on the disc that’s blocking flow. This pushes the disc, in turn pushing the spring which opens the valve and allows flow. Once pressure lowers, the spring moves to the starting position and blocks flow.

PTFE Lined Swing Check Valves

PTFE Lined Swing Check Valves are closed with a flapping disc. Increased pressure at the inlet ‘swings’ the flapper open, allowing fluid flow. Once pressure decreases at the inlet, the flapper moves back to its original spot and blocks fluid flow.

Ball Check Valve

With ball check valves, the only difference is that the disc which closes the valve is now replaced with a ball. Ball check valves can either include a ball which is left freely or attached to a spring. Again, as pressure rises at the inlet, it forces the ball out of position and allows fluid flow. Lowering inlet pressure allows the ball to move back and close the opening, blocking fluid flow.

Fluorine Lined Valves Advantages

Fluorine Lined Valves have the following added benefits to check valves:

• Added resistance to corrosion: Layers of PFA/PTFE are more impervious to chemicals. This is done by preventing chemical solutions from coming in contact with the valves’ structural body.
• Allows for extra durability: Fluorine lined check valves have greater pressure limits as the layer of PFA/PTFE disperses pressure.

PFA Lined Check Valves Applications

PFA lined check valves are found in these applications:

• Chemical Solution Pipes
• Oil/Gas Factories
• Waste Water Plants
• Purification Systems

FAQs

What Are Corrosion Resistant Check Valves?

Corrosion resistant check valves are PFA lined check valves found in high purity fluid systems. These check valves are lined with a layer of PFA/PTFE which increases resistance to chemical solutions.

How Do Fluorine Lined Check Valves Prevent Backflow In Corrosive Fluid Systems?

Fluorine lined check valves prevent backflow by automatically closing when pressures change. Fluid flows through PFA lined check valves when inlet pressure is greater than outlet pressure. If this is reversed, the check valves will automatically close.

Resources:

Backflow Preventer vs. Check Valve: What’s the Difference? (qrfs.com)

Check Valve – Working Principle | Tameson.com

What is a fluorine-lined valve? How to extend the service life of it? (tanghaivalve.com)