What Are Fluoropolymer Lined Butterfly Valves?

Working Of Butterfly Valves

The butterfly valve design is simple. It is made of the following components:

• Outer Valve Structure: Responsible for connecting with pipes. Types include flanged/double lug and wafer connections.
• Disc: Shaped like a butterfly. Main component that controls fluid flow. Acts as a gate. Usually has a hole drilled through it which connects to the stem.
• Seat: Internal elastomer lining which keeps the disc in place. Also works to prevent leaks.
• Stem: Shaft which connects actuation systems to the disc. Helps with opening/closing of the valve.

Butterfly valves handle fluid control by a revolving disc. When opened, the butterfly disc rotates so that the hole/bore is in line with the fluid. And this allows it to flow. When the valve is closed, the bore faces away from the fluid blocking flow.

The Fluoropolymer Coating Process

Butterfly valves are apt for many industrial operations. However, specific pipes like those in chemical factories use PFA or PTFE lined butterfly valves. The components of the valve are similar. The only differentiable point is that these valves come with an extra internal layer. 

Valves are lined with PFA/PTFE by making dovetail grooves on the inner side of the valve. Molten PFA is then poured onto these grooves and allowed to cool down. This solidifies it, creating a layer between the fluid and metal. In turn, this gives valves greater corrosion and temperature resistance.

PFA Lined Butterfly Valves VS PTFE Lined Butterfly Valves

PFA Lining	PTFE Lining
More flexible but lower flex life	Less flexible but greater flex life
More expensive than PTFE	Cheaper than PFA
More susceptible to absorbing water leading to damage	Better hydrophobic properties
Melting point of 260°C	Melting point of 327°C
Generates more friction than PTFE	Lower coefficient of friction

Benefits Of Fluoropolymer Lined Butterfly Valves

Fluoropolymer lined chemical resistant valves have these benefits:

• Greater corrosion protection
• Can withstand higher temperatures than non lined valves
• Chemically inert
• Greater tensile strength
• More resistant to abrasion

Lined Valve Applications

Fluoropolymer lined butterfly valves are used to these operations:

• High Purity Fluid Handling
• Waste Water Treatment Pipes
• Chemical Handling Pipes
• Oil/Gas Handling In Factories

FAQs

How Are Butterfly Valves Lined With Fluoropolymers?

Butterfly valves are lined with fluoropolymers by creating dovetail grooves on the inner valve body. Molten PFA/PTFE is then poured on these grooves and allowed to cool. Once cooled, it solidifies creating a layer covering the inner valve body. This provides greater corrosion resistance and temperature withstanding properties.

Why Are PFA Lined Butterfly Valves Used In High Purity Fluid Handling?

PFA Lined butterfly valves are used in high purity fluid handling because of the internal fluoropolymer lining. This lining prevents contamination by creating a layer between the inner valve body and fluids.

How Do Fluoropolymer Lined Butterfly Valves Improve Performance In Corrosive Environments?

Fluoropolymer lined butterfly valves improve performance in corrosive environments by providing extra durability. This is done through the internal fluoropolymer layer which is chemically inert. This layer also prevents the valve body from coming in contact with corrosive fluids.

Resources:

PTFE Vs. PFA: A Detailed Comparison Guide | DCW (ptfedf.com)

Guide on How a Butterfly Valve Works | Dombor

What is a butterfly valve and where it is used in water supply? – Hawle