Materials And Compatibility Of Fluoropolymer-lined Gate Valves

A lined gate valve provides reliable on-off isolation for highly corrosive media in chemical, petrochemical, and pharmaceutical plants. The fluoropolymer lining covers all wetted surfaces, protecting the metal body from chemical attack. PTFE handles -29°C to 180°C. PFA serves up to 200°C. FEP covers -29°C to 150°C.

How to select a lined gate valve for corrosive media?

1. Identify the media composition, concentration, and operating temperature.

2. Match the lining material: PTFE for standard acids ≤120°C, PFA for hot acids >120°C or oxidizers, FEP for steam.

3. Verify pressure class and select actuation type (manual, pneumatic, or electric).

Operating Rule – No Throttling

Gate valves are designed for on-off service only. Partial opening causes vibration, chatter, and seat erosion.

Proper operation:

• Fully open for flow

• Fully closed for shutoff

• Never use for flow regulation

Wedge Gate Design

The gate has two sealing surfaces forming a wedge. As the handwheel rotates, the stem lifts or lowers the gate. The wedge geometry forces sealing surfaces against seats for positive mechanical seal.

Gate types:

• Rigid gate: one-piece for general service

• Elastic gate: compensates for angle deviations

A ptfe lined gate valve uses this wedge design for bubble-tight shutoff. Lined gate valves conform to API 600 and ASME B16.10 dimensions.

Lining Material Selection

PTFE (Standard Duty)

• -29°C to 180°C, PN 16-40 (Class 150-300)

• Hydrochloric acid, sulfuric acid (≤98%), nitric acid, caustic soda

PFA (High-Temperature / Oxidizer Duty)

• Up to 200°C, lower permeation

• Hot concentrated acids, oleum, bromine, high-purity chemicals

FEP (Steam & Hot Water)

• Up to 150°C, cost-effective for utility services

Full-Bore Design

When fully open, the gate retracts completely, creating a straight-line port with virtually no pressure drop. The flat-bottom seat prevents debris accumulation that could prevent tight closure.

Bidirectional Sealing

The gate mechanism is symmetrical, allowing effective shutoff from either direction.

Safety features:

• Primary seal: wedge gate-to-seat interference

• Secondary seal: PTFE stem packing prevents atmospheric leakage

• Upper sealing device: protects stuffing box when fully open

Industry Applications

Chemical Processing – Sulfuric, hydrochloric, nitric, hydrofluoric acid, aqua regia. Full-bore handles viscous media.

Petrochemical – Hot acids, oleum, hydrocarbons. PFA for high-temperature oxidizers.

Pharmaceutical – High-purity services. Smooth surface prevents contamination.

Metal Processing – Pickling lines. Elastic gate compensates for thermal expansion.

Actuation Options

Actuator types:

• Manual handwheel: self-locking

• Worm gear: reduced torque for larger sizes

• Pneumatic: remote on-off and emergency shutdown

• Electric: automated on-off with position feedback

Gate valves are multi-turn devices. Slower than quarter-turn valves but offer superior flow characteristics when fully open.

Selection Checklist

1. Define media composition, concentration, and temperature.

2. Select lining material:

   • Standard acid/caustic ≤120°C → PTFE.

   • Sulfuric acid >98% or hot acid >120°C → PFA.

   • Saturated steam ≤150°C → FEP.

3. Verify pressure class (PN 10/16/40, Class 150/300).

4. Confirm full-bore design.

5. Specify gate type (rigid or elastic).

6. Select actuation type.

7. Verify face-to-face dimensions (API 600 / ASME B16.10).

Chemical Resistance Quick Reference

Sulfuric acid

• ≤98%, ≤120°C → PTFE

• ≤98%, 120–200°C → PFA

• Oleum → PFA only

Chloride and caustic

• HCl, any %, ≤100°C → PTFE

• Wet chlorine → PFA

• NaOH ≤50%, ≤120°C → PTFE

Utilities and solvents

• Saturated steam → FEP (≤150°C)

• Organic solvents → PTFE (≤180°C)

Standard acids and caustics ≤120°C: A ptfe lined gate valve with full-bore design provides reliable shutoff.

Hot acids, oxidizers, or high-purity: PFA lining is required. Lower permeation justifies the premium.

Steam and utility services: FEP offers a cost-effective option where temperature is ≤150°C.

After selecting the lining, verify gate type matches service conditions. For high-temperature applications, specify elastic gate. Confirm actuation torque meets operating torque at maximum temperature. For emergency shutdown, consider pneumatic or electric actuation with fail-safe positioning.

For pressure-temperature curves and flange drawings, request the full specification sheet. Verify torque against operating requirements and confirm dimensions match piping layout before installation. Never operate the valve partially open — fully open or fully closed only.

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FVF PTFE FEP PFA Lined Flanged Gate Valve With Electric Actuator

• 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