Selection And Working Principle Of Fluoropolymer-lined Check Valves

A lined check valve prevents backflow of corrosive media through automatic operation, using flow pressure to open and backpressure to close. The fluoropolymer lining isolates the metal body from chemical attack. PTFE handles -29°C to 180°C. PFA serves up to 200°C. This design protects pumps, prevents contamination, and reduces maintenance frequency.

How to select a lined check valve for corrosive service

1. Choose design type: ball check (viscous/particulate) or lift check (clean fluids).

2. Select lining material: PTFE (≤180°C) or PFA (≤200°C).

3. Verify spring encapsulation: FEP/PFA-coated for corrosion resistance.

4. Confirm installation orientation: vertical (ball) or any angle (lift).

Common Application Pitfalls – Why and How to Avoid

•  Using unlined valves in corrosive media: Metal corrosion causes leakage and contamination. → Specify PTFE/PFA-lined construction for all wetted parts.

•  Ignoring spring encapsulation: Unprotected springs corrode and fail. → Specify FEP/PFA-encapsulated stainless steel springs.

•  Wrong installation orientation: Ball check requires vertical upward flow. → Verify orientation requirements before installation.

•  Selecting PTFE above 180°C: PTFE softens and deforms. → Specify PFA for temperatures above 180°C.

How the Lined Check Valve Works – Automatic Protection

Forward flow pressure lifts the disc or ball off the seat, opening the flow path. When forward flow stops or reverses, backpressure and gravity (or spring force) close the valve.

Protection mechanisms:

• Forward flow: disc/ball lifts, allowing flow

• Backflow: disc/ball seats, blocking reverse flow

• Spring-assisted closure: ensures positive seal at zero flow

• Self-cleaning: ball rotation prevents particle adhesion

A ptfe lined check valve with solid PTFE ball suits vertical lines with upward flow. A pfa lined check valve with spring closure can be installed at various angles.

Liner Design – The Corrosion Barrier

PTFE, PFA, or FEP liners cover all wetted surfaces, including flange faces.

Design features:

• Solid one-piece liner: minimum wall thickness 2.38 mm (3/32") to prevent pinholes.

• Dovetail grooves: mechanically lock liner to body, preventing vacuum collapse.

• Full coverage: all wetted surfaces fluoropolymer-lined, eliminating metal contact.

A teflon lined check valve provides corrosion resistance for hydrochloric acid, sulfuric acid (≤98%), and caustic soda. PFA lined valves extend service to 200°C for hot acids and oxidizers.

Industry standards: ASME B16.34, API 598, HG/T 3704.

Spring Encapsulation – The Reliability

Unprotected springs corrode in aggressive media. Full FEP/PFA encapsulation isolates the spring from the media.

Encapsulation benefits:

• FEP-encapsulated stainless steel spring: prevents corrosion

• Maintains closing force over thousands of cycles

• Eliminates spring replacement maintenance

• Available in 316 SS, Alloy C-276, or Inconel

Typical encapsulated spring designs withstand >10,000 cycles without performance degradation.

Ball Check vs Lift Check – Selection Decision Matrix

Ball check valves in solids-laden services show 3-5 times longer service life than lift check designs.

Industry Applications

Chemical Processing: Acids, alkalis, chlor-alkali. PTFE/PFA lining, FEP-encapsulated spring.

Pharmaceutical: High-purity media. PFA lining for low extractables. Electropolished finish.

Semiconductor: Wet chemical distribution (HF, H₂SO₄). PFA with locked-in liner. Spark testing at 10 kV.

Water treatment: Chemical dosing lines. PTFE lining. Stainless steel spring encapsulation.

Guide

For standard acids ≤120°C: ptfe lined check valve, carbon steel body, FEP-encapsulated spring.

For hot acids >120°C: pfa lined check valve, 316L body, PFA-encapsulated spring.

For viscous/particulate-laden media: ptfe lined ball check valve with self-cleaning ball design.

For vacuum service: locked-in liner design with dovetail grooves prevents liner collapse.

Spring-encapsulated designs are certified for >10,000 cycles in corrosive services. A ptfe lined check valve with solid PTFE ball is the standard choice for vertical lines with upward flow. A pfa lined check valve with spring closure offers flexibility for installations at various angles. A teflon lined check valve provides corrosion resistance for hydrochloric acid, sulfuric acid (≤98%), and caustic soda. A ptfe lined ball check valve is recommended for viscous and particulate-laden media.

FVF FEP Lined Lift Through-Way Check Valve

• FVF lined check valve only allow one way flow direction and prevent the back-flow of liquids in pipeline. Generally check valve is automatically working.Under the pressure function of one direction flow, the disc open, while when the liquid back flows, the valve will cut flow.When it is used as vertical installation, it will not set the spring. Using the disc weight and backflow pressure to achieve the check effect.
• FVF lined check valve is mainly used in chemical industries,such as sulfuric acid, alkali etc.

Product Parameter

Materials of Main Parts

Technical Specification