Design Features And Selection Of Fluorine-lined Butterfly Valves

A lined butterfly valve handles corrosive fluids, high-purity media, and viscous or particle-laden slurries through a fluoropolymer liner that isolates the metal body from process media. PTFE handles standard acids up to 180°C. PFA serves up to 200°C with lower permeation. This design makes the valve suitable for flue gas desulfurization slurry lines, where unlined valves fail within 3-6 months.

How to select a lined butterfly valve

1. Choose liner material: PTFE for standard acids ≤180°C, PFA for high temperatures ≤200°C.

2. Verify disc encapsulation: PFA/PTFE coating protects the disc from direct media contact.

3. Confirm pressure rating: DN 50–450 at 10 bar, DN 500–600 at 6 bar.

4. Specify stem sealing: Belleville spring-loaded seals for fugitive emissions compliance.

Common Application Pitfalls – Why and How to Avoid

• 🔹 Specifying unlined valves in slurry service: Unlined valves erode within 3-6 months. → Specify lined butterfly valves with fully encapsulated disc; service life extends to 3-5 years.

• 🔺 Ignoring temperature limits: PTFE softens above 180°C. → Specify PFA for temperatures up to 200°C.

• 🔻 Overlooking pressure drop: Improper sizing causes solids settling. → Select full-bore design to minimize pressure loss.

• 🔸 Using standard stem seals: Leakage risk in toxic/corrosive services. → Specify Belleville spring-loaded stem seals per TA-Luft/VDI 2440.

Lined Butterfly Valve Selection – Decision Matrix

Lined butterfly valves conform to API 609 and MSS SP-67.

Liner and Disc Encapsulation – Corrosion and Abrasion Protection

Design features:

• Minimum 3 mm liner thickness for standard service

• Minimum 4 mm liner thickness for abrasive slurry service

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

• PFA-coated disc: 30% higher abrasion resistance than uncoated discs in slurry services

A ptfe lined butterfly valve with minimum 3 mm liner provides permeation protection for acids. A ptfe butterfly valve with PFA-coated disc offers abrasion resistance for slurry services.

FGD Slurry Service – Why Lined Butterfly Valves Are Required

FGD systems circulate limestone-gypsum slurries that are abrasive and corrosive.

FGD parameters:

• Temperature: 60-80°C

• Solids content: up to 30%

• Full-bore design: prevents solids settling

Service life comparison:

• Unlined valves: 3-6 months

• Lined butterfly valves: 3-5 years

Pfa lined butterfly valves with spherical sealing surfaces reduce friction and torque during operation.

Stem Sealing – Belleville Spring Design

• Primary sealing: preloaded contact between disc and liner hub

• Secondary sealing: oversized shaft diameter

• Belleville springs: maintain constant stem seal pressure, compensating for wear and thermal cycling

• TA-Luft/VDI 2440 approval: fugitive emissions compliance

Actuator Sizing and Torque Considerations

• PTFE/PFA friction increases at elevated temperatures

• Oversize actuator by 25-30% for high-temperature operation

• Installation torque: follow manufacturer specifications to prevent liner deformation

• ISO 5211 mounting pad: enables standard actuator installation

For standard acids ≤180°C: ptfe lined butterfly valve with 3 mm liner, PFA-coated disc, Belleville spring stem seals.

For hot acids >180°C: pfa lined butterfly valve with PFA-coated disc.

For FGD slurry service: full-bore design, 4 mm liner, PFA-coated disc (30% higher abrasion resistance), 60-80°C rating.

Service life: lined butterfly valves achieve 3-5 years vs 3-6 months for unlined valves. Actuator oversize: 25-30% for high-temperature operation.

Standards: API 609, MSS SP-67, EN 12266-1, ISO 5752/EN 558-1, ISO 5211. Teflon lined butterfly valves with PFA-coated disc offer FDA compliance. PFA lined butterfly valves with locked-in liner design suit vacuum service.

FVF  PFA Lined Worm Gear Butterfly Valve With Flange Connection

• FVF lined butterfly valve can realize  bi-directional flow under the maximum working pressure. Since the valve port corresponds to the piping diameter, a high flow capacity is guaranteed.
• It features ease of maintenance, repeatable on-off, long life durability.
• It is commonly used in the power generation, brewing, water and food industries and suitable for both gaseous and liquid service. Typically applied in chemical/petrochemical process, food and beverage, and pulp and paper etc.
• They are available with Wafer style or Lug style 150# ANSI flange connections. 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.