Design Characteristics And Applications Of Fluoropolymer-lined Gate Valves

A lined gate valve provides reliable shutoff for extreme corrosive media such as strong acids, alkalis, and oxidizers through a full fluoropolymer lining that isolates the metal body from chemical attack. The gate moves vertically between two sealing surfaces, creating a straight-through flow path with minimal pressure drop when fully open. PTFE handles continuous service up to 180°C. PFA extends to 200°C for more demanding oxidizer service. Selection requires matching the lining material and actuation method to the specific media characteristics and process requirements.

How to select a lined gate valve for corrosive media

1. Identify media composition, concentration, and temperature range.

2. Choose lining material: PTFE for standard acids and caustics ≤180°C, PFA for strong oxidizers and higher temperatures ≤200°C.

3. Verify pressure rating: PN10–PN25 or Class 150–300.

4. Select actuation: manual handwheel for local operation, pneumatic/electric for remote automation.

Common Selection Pitfalls – Why and How to Avoid

• ❌ Unlined valves in aggressive media: Metal corrosion causes leakage. → Specify PTFE/PFA-lined construction for all wetted parts.

• ❌ Overlooking temperature limits: PTFE softens above 180°C. → Specify PFA for services exceeding 180°C.

• ❌ Ignoring vacuum conditions: Standard liners collapse under vacuum. → Specify locked-in liner design with dovetail grooves.

• ❌ Undersizing actuators: Gate valves require high thrust. → Verify actuator torque/force matches operating conditions.

Lining Material Selection – PTFE vs PFA

A ptfe lined gate valve is the standard workhorse for most corrosive services up to 180°C. PTFE resists virtually all chemicals except molten alkali metals and elemental fluorine. A teflon lined gate valve (PTFE) with minimum 3–5 mm liner thickness provides reliable protection for hydrochloric acid, sulfuric acid (≤98%), and caustic soda.

PFA offers the same chemical resistance with lower permeation and higher temperature tolerance to 200°C. PFA is specified for strong oxidizers, hot concentrated acids, and high-purity applications where PTFE would permeate or soften.

Wedge Gate Design – How the Seal Works

The gate has two sealing surfaces forming a wedge. The stem moves the gate vertically. The wedge geometry forces sealing surfaces against the seats, creating a mechanical seal.

Gate types:

• Rigid gate: one-piece for general service

• Elastic gate: compensates for thermal expansion and machining variations

The liner extends to the flange face, preventing metal exposure at gasket joints.

Actuation – Manual vs Automated Operation

Manual (Handwheel):

• Standard for local operation

• Self-locking design maintains position

• Suitable for infrequent operation

Pneumatic Actuator:

• Remote on-off and emergency shutdown

• Spring-return fail-safe options available

• Suitable for automated process control

Electric Actuator:

• Modulating service with position feedback

• Remote operation without instrument air

• Suitable for precise flow control

For automated service, specify ISO 5211 mounting pad. Gate valves are multi-turn devices—slower than quarter-turn valves but offer superior flow characteristics when fully open.

Industry Applications

Chemical Processing: Strong acids, chlor-alkali, fine chemicals. PTFE lining, handwheel or pneumatic actuation.

Pharmaceutical: High-purity API synthesis. PFA lining, electropolished finish.

Petrochemical: Sour water, amine systems. PTFE lining.

Water Treatment: Chemical dosing, chlorine injection. PTFE lining, manual or electric actuation.

Design Summary

For standard acids and caustics ≤180°C: ptfe lined gate valve with compression molded liner, rigid gate, handwheel or pneumatic actuation.

For strong oxidizers and high temperatures >180°C: PFA-lined gate valve with locked-in liner, elastic gate for thermal compensation. Service up to 200°C.

For automated control: Specify pneumatic or electric actuation with ISO 5211 mounting. Verify actuator torque against valve operating torque at maximum temperature.

FVF Pneumatic 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