Performance And Advantages Of Ptfe/pfa/fep Lined Double-disc Wafer Check Valve

Backflow damages pumps, contaminates product, and creates hazards. The lined check valve stops reverse flow and resists corrosion. Select PTFE (180°C), PFA (260°C), or FEP (205°C). Install vertically with flow arrow upward. Verify liner integrity with spark testing. Provide 5D upstream and 3D downstream straight pipe runs.

The Hidden Danger of Backflow

Backflow occurs when downstream pressure exceeds upstream pressure – during pump trips, valve closures, or batch transitions. Without protection, reverse flow drives corrosive media back into equipment, dilutes upstream streams, spins pump impellers backward (damaging bearings), and creates water hammer that stresses pipe joints. Standard metal check valves suffer pitting, galling, and seat leakage in aggressive services. The lined check valve isolates all wetted surfaces with fluoropolymer liners to eliminate these failures.

Fluoropolymer Lining as the Protective Barrier

A lined check valve incorporates a fluoroplastic layer that shields the metal body and internals from corrosive fluids. PTFE, PFA, and FEP resist acids, caustics, solvents, and halogens across a wide pH range. The smooth internal surface reduces permeation and prevents product build‑up that could obstruct disc movement.

Liner performance comparison:

For most acid and caustic services at moderate temperatures, a ptfe lined check valve offers the widest chemical resistance and low friction.

When process temperatures regularly exceed 200°C or permeation of aggressive media is a concern, a pfa lined check valve provides higher thermal stability and reduced permeation.

For less demanding duties with cost constraints, an FEP lined version balances performance and price. The lined check valve – regardless of liner type – offers the dual‑plate wafer design that minimises pressure drop and installation space.

Dual-Plate Design Advantages

• Two spring‑loaded semicircular plates – open with forward flow, close instantly on flow reversal

• Short face‑to‑face dimensions (wafer style) – fit between standard flanges

• Low cracking pressure – plates respond to minimal forward flow

• Non‑slam closing action – springs close plates before reverse flow develops

• Replaceable seat inserts – allow maintenance without removing the valve body

Installation and Connection Standards

Mount with flow arrow pointing vertically upward – plates close by gravity and spring force. For horizontal lines, the disc shaft must be vertical. Provide straight pipe runs upstream (5 diameters) and downstream (3 diameters) to stabilise flow. Use gaskets compatible with the liner material. Torque flange bolts evenly – over‑tightening compresses the liner.

Installation checklist:

• ⬆️ Flow arrow vertical (preferred); for horizontal lines, disc shaft vertical

• 🔧 Provide 5D upstream / 3D downstream straight runs; use PTFE or graphite gaskets

• 📐 Torque bolts in star pattern to spec; spark test liner after installation

Performance verification steps:

1. After installation, run a low‑pressure test to confirm full plate opening at design flow

2. Listen for clicking during reverse‑flow conditions – rapid closure indicates proper spring function

3. During turnarounds, inspect liner and seat surfaces with a spark tester to detect pinholes

4. Replace the valve if liner shows cracking, delamination, or permeation blisters

Fire Safety and Special Services

Fluoropolymer liners are not fireproof. In an external fire, the liner softens and loses sealing. For flammable media, specify a valve with a fusible link that closes an upstream isolation valve when ambient temperature exceeds a safe threshold. This passive system isolates the fuel before liner failure, without external power.

Common Installation Errors to Avoid

• Mounting with flow arrow horizontal/downward – prevents gravity closure

• Using standard gaskets without raised faces – gasket edges can intrude and obstruct disc movement

• Installing adjacent to elbows without straight runs – turbulence causes plate flutter

Frequently Asked Questions

• Q: Why choose a lined check valve over a metal one?
  A: Metal valves suffer pitting and seat wear in corrosive services. The fluoropolymer liner protects all wetted surfaces, while the dual‑plate design provides fast, non‑slam closure.

• Q: How to detect liner failure before leakage occurs?
  A: Use a spark tester during shutdowns. Any pinhole produces a visible arc. Positive results mean immediate replacement – field relining is not possible.

• Q: What is the typical pressure rating?
  A: PN 10–PN 40 (150–300 lb) for wafer flanged connections. The metal body provides pressure containment; the liner does not bear pressure.

FVF PTFE PFA FEP Lined Dual Plate Wafer Check Valve

• The dual plate check valve is an all purpose non return valve that is much stronger, lighter in weight and smaller in size compared to a conventional swing check valve or lift check valve. The double plate check valve employs two spring-loaded plates hinged on a central hinge pin.
• In addition to the valve body and valve disc, the return spring is also fully lined with corrosion-resistant fluorine materials. The reasonably designed spring enables the valve disc to generate sufficient sealing specific pressure in the low-pressure area.And it ensures the reliability of the valve sealing in the low pressure area.
• FVF lined check valve is mainly used in chemical industries,such as sulfuric acid, alkali etc.

Product Parameter

Materials of Main Parts

Technical Specification