How Do Fluoropolymer-lined Pneumatic Gate Valves Achieve Zero Metal Contact

A lined gate valve achieves zero metal contact through full fluoropolymer lining of all wetted surfaces—body interior, gate, and flange faces. The PTFE, PFA, or FEP liner isolates the metal from the fluid. The gate is fully encapsulated with the same material. The liner extends to the flange face, creating a complete seal at the gasket joint. This design eliminates corrosion and product contamination.

How does a lined gate valve achieve zero metal contact

1. The fluoropolymer liner covers all internal surfaces—body cavity, gate, and flange faces.

2. The gate is fully encapsulated with PTFE/PFA, preventing metal exposure at sealing surfaces.

3. The liner extends to the flange face, creating a full seal at the pipe joint.

4. The stem is isolated from the media by the stem seal system and liner.

Common Design Pitfalls

•  Unlined valve in corrosive service → Metal corrosion causes leakage. → Specify PTFE/PFA-lined construction.

•  PTFE above 180°C → PTFE softens and deforms. → Specify PFA above 180°C.

•  Vacuum with standard liners → Liners collapse under vacuum. → Specify locked-in liner with dovetail grooves.

•  Partial gate encapsulation → Exposed metal contacts media. → Specify full encapsulation of all wetted surfaces.

Lining and Gate Encapsulation – The Complete Barrier

A ptfe lined gate valve uses compression-molded PTFE to line the body and encapsulate the gate. The liner covers the body cavity, sealing surfaces, and flange faces. The gate is completely encapsulated with PTFE or PFA, preventing metal contact at the gate-to-seat sealing surfaces.

Liner features:

• Full coverage of all wetted surfaces

• Mechanical locking via dovetail grooves

• Minimum 3 mm liner thickness

Liner Material Selection

A teflon lined gate valve (PTFE) provides broad chemical resistance for acids, caustic, and solvents up to 180°C. A ptfe lined gate valve with PFA extends service to 200°C for chlorine and hot acids.

Gate Design – Encapsulated Wedge

The gate is a wedge-shaped assembly fully encapsulated with PTFE or PFA. The encapsulation covers both sealing surfaces and gate edges. The wedge design provides positive sealing force as the gate descends between the seats.

Gate features:

• Full encapsulation with PTFE/PFA

• Wedge profile for positive sealing

• No metal exposed to media

• Dovetail retention for encapsulation

Stem Sealing – Preventing Leakage

The stem is isolated from media by the liner and stem seal system. PTFE V-ring packing with live-loaded spring maintains constant seal pressure. The packing box is fully lined.

Packing features:

• PTFE V-ring packing: Standard

• Live-loaded spring: Maintains compression

• Multiple packing rings: Secondary sealing

• Lined packing box: Prevents metal exposure

Actuation Options

• Manual handwheel: Local operation

• Pneumatic: Remote on-off with fail-safe options

• Electric: Automated control with position feedback

Applications

Chemical Processing: Strong acids, chlor-alkali. PTFE/PFA lining, full gate encapsulation.

Pharmaceutical: High-purity media. PFA lining, electropolished finish.

Semiconductor: Wet chemicals. PFA with locked-in liner.

Water Treatment: Chemical dosing. PTFE lining.

Design Principles

A lined gate valve achieves zero metal contact through full fluoropolymer lining of all wetted surfaces, complete gate encapsulation, and a lined packing box. PTFE suits standard acids up to 180°C. PFA extends to 200°C for hot acids and chlorine. Full gate encapsulation prevents metal exposure at sealing surfaces. Locked-in liners with dovetail grooves prevent collapse under vacuum. Stem seals with live-loaded packing maintain sealing integrity. Zero metal contact eliminates corrosion and product contamination.

FVF Pneumatic Actuated PFA FEP PTFE Lined Flanged Gate Valve

• FVF gate valve can be divided into rising stem gate valve, which refers to the disc doing lift movement in straight line along with the valve stem, and nonrising stem gate valve which refers to the stem nut located in the disc, when the stem rotates, the disc doing lift movement in straight line.
• The inner cavity of the valve body and bonnet, the gate, the outer surface of the valve stem and other components that directly contact the medium are all lined with FEP (F46) or PCTFE (F3) and other fluorine materials.
• The sealing pair are FEP (F46)/ FEP (F46) or combination of other materials, with small friction coefficient and low opening and closing torque.PTFE (F4) is used as the packing, which feactures good sealing performance and convenient maintenance and replacement.
• FVF lined gate valves are commonly used in chemical, petroleum, pharmaceutical, food, metallurgy, paper, hydropower, environment protection etc.
• They can be equipped with a manual lever or can be actuated with electric or pneumatic actuators. A full range of accessory items are available including limit switches, solenoid valves, positioners and manual override devices.

Product Parameter

Materials of Main Parts

Technical Specification