Material Selection And Installation Guide For Fluorine-lined Bevel Gear Driven Gate Valves

Selecting a lined gate valve for water treatment requires focusing on three factors: liner material (PTFE for most chemicals), body material (ductile iron for buried service), and actuation (bevel gear for DN150 and above). This combination prevents corrosion from aggressive influents and eliminates leakage paths. For municipal and industrial wastewater applications, this valve type delivers reliable shutoff and extended service life.

The Hidden Threat: Corrosion and Fugitive Emissions

Water treatment facilities handle a wide range of aggressive media. Raw wastewater contains hydrogen sulfide and organic acids. Chemical dosing lines carry ferric chloride, sodium hypochlorite, and lime slurry. These fluids corrode standard metal valves, leading to wall thinning and leakage.

Fugitive emissions from leaking valve stems pose another risk. In potable water systems, any leak introduces contaminants. In chemical feed lines, escaping vapors create safety hazards and compliance issues. A lined gate valve addresses both problems through its design.

Liner Material Selection for Water Treatment

The fluoropolymer liner provides the primary barrier against corrosion. Choose based on the specific service.

 PTFE lined gate valve – Polytetrafluoroethylene resists the broad spectrum of chemicals used in water treatment, including ferric chloride, sodium hypochlorite, sulfuric acid, and caustic soda. A ptfe lined gate valve operates effectively up to 150°C (302°F), covering all ambient applications and most heated process streams.

 Teflon lined gate valve – “Teflon” encompasses PTFE, PFA, and FEP. A teflon lined gate valve must be specified with the exact polymer grade matching the process chemistry. PFA offers lower permeation for sodium hypochlorite service, while PTFE suits general chemical resistance. Verify the grade against compatibility charts.

Mechanical Design Features for Reliability

Construction details ensure leak‑tight operation and extended service life.

• Bevel gear drive – For gate valves DN150 and larger, a bevel gear operator reduces handwheel torque to manageable levels. The gear mechanism provides precise positioning and maintains the gate in any position without drifting.

• Rising stem design – The stem moves upward as the valve opens, providing a visual position indicator. The stem seal (packing or O‑ring stack) prevents fugitive emissions during operation.

• Full encapsulation – All wetted metal surfaces are completely covered with the fluoropolymer liner, eliminating metal‑to‑fluid contact. This prevents galvanic corrosion and ion leaching into treated water.

• Wedge gate – The gate wedge design ensures tight shutoff across the full pressure range. The liner covers the wedge faces, creating a bubble‑tight seal against the body liner.

Selection Criteria Summary

Installation and Operational Guidance

• Orientation – Install with the stem vertical for rising stem designs. This reduces packing wear and ensures smooth gate movement.

• Avoid over‑torquing – Excessive force on the handwheel or gear operator deforms the liner or wedge. Use the travel stop to prevent over‑closure.

• Periodic inspection – Check the stem seal for leakage during routine rounds. Monitor liner condition through pressure tests or visual inspection during outages.

• Lubrication – The bevel gear drive requires periodic lubrication to maintain low torque and prevent gear wear.

Temperature and Pressure Parameters

• PTFE liners – max continuous temperature 150°C (302°F)

• PFA liners – max continuous temperature 180°C (356°F)

• Pressure rating – Class 150 (PN10/PN16) standards

• Shell test pressure – 1.5 × nominal rating

• Seat leakage – zero visible leakage per API 598 or ISO 5208

Final Selection Logic

For water treatment or environmental protection applications requiring isolation:

1. Define the fluid composition (pH, oxidizers, chlorides, temperature).

2. Select PTFE for general chemical resistance; PFA for sodium hypochlorite and halogens.

3. Choose body material based on external environment (buried, indoor, corrosive atmosphere).

4. Specify actuation type based on valve size and frequency of operation.

5. Verify liner thickness (minimum 3mm) and encapsulation completeness.

This structured approach ensures a lined gate valve delivers corrosion‑free, leak‑tight service in demanding water and wastewater applications. The bevel gear drive enables safe operation for large‑diameter valves, reducing operator fatigue while maintaining precise control.

FVF PTFE Lined Bevel Gear Driven 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