Selecting an industrial gas butterfly valve for a gas train (fuel gas skid, burner system, etc.) is mainly about safety, sealing, and control performance. Here’s a practical engineering guide you can follow.

1) Define process conditions (first step)

Always start from your gas system data:

Key parameters

• Gas type: natural gas, LPG, biogas, hydrogen mix

• Pressure (PN/Class) and temperature range

• Flow rate / velocity

• Function:

  • Isolation (ON/OFF)

  • Modulating (flow control)

👉 Valve selection must match pressure, temperature, and medium characteristics to avoid failure or leakage

2) Choose the correct valve type (structure)

Butterfly valves for gas trains are typically:

(A) Concentric (centerline)

• Simple, low cost

• Suitable for low-pressure gas lines

• Usually soft-seated
  ✔ Use for: air, low-pressure natural gas

(B) Double eccentric (high-performance)

• Better sealing, less wear
  ✔ Use for: medium-pressure gas trains

(C) Triple eccentric (metal-seated)

• High temperature & tight shut-off
  ✔ Use for:

• High-temp combustion air/gas

• Critical safety shut-off

👉 Eccentric designs improve sealing and durability in demanding gas systems

3) Select sealing type (very critical for gas)

Gas systems require tight shut-off (leakage control):

Soft-seated (EPDM / NBR / PTFE)

• Near zero leakage

• Limited temperature
  ✔ Common in standard gas trains

Metal-seated

• Higher temperature resistance

• Slight leakage allowed
  ✔ Use for:

• High temp (>200–300°C)

• Dirty or aggressive gas

👉 For natural gas, tight sealing and bidirectional sealing are recommended to prevent leakage risk

4) Material selection (safety & corrosion)

Choose materials based on gas composition:

Body & disc

• Carbon steel → standard gas

• Stainless steel (e.g. 316) → corrosive gas (H₂S, biogas)

Seat material

• PTFE → chemical resistance

• NBR → fuel gas

• Metal → high temp

👉 Gas with H₂S requires corrosion-resistant materials like stainless steel

5) Size & flow (DN selection)

Valve size depends on flow rate and velocity:

• Typical gas velocity:

  • Low pressure: 2–10 m/s

  • Medium pressure: 10–20 m/s

Engineering tips:

• Oversized valve → poor control

• Undersized valve → high pressure drop

👉 Butterfly valves already create higher pressure drop than gate valves, so sizing is important

6) Pressure loss & control performance

• Butterfly valves = compact but higher pressure drop

• For gas trains:

  • Use larger DN if pressure loss is critical

  • Avoid using as precision control valve unless designed for modulation

7) Actuation method (automation)

Gas trains are usually automated:

Common options

• Pneumatic actuator → fast, safe (preferred)

• Electric actuator → precise control

• Manual → only for isolation / maintenance

👉 Butterfly valves are easy to automate and operate quickly (quarter-turn)

8) Safety & standards (VERY important)

For gas applications, ensure compliance:

• EN 161 → automatic shut-off valves (Europe)

• DVGW → gas approval (Germany)

• ATEX → explosive atmosphere

• API / ISO standards (oil & gas)

👉 Gas valves must meet strict sealing and safety certifications

9) Installation considerations

• Prefer flanged connection (gas tightness)

• Stem orientation:

  • Avoid downward stem (leak risk)

• Ensure:

  • Enough space for actuator

  • Easy maintenance access

10) Typical selection example (gas train)

For a standard industrial burner gas train:

• Type: Double eccentric butterfly valve

• Size: Based on flow (e.g., DN100–DN300)

• Pressure: PN16 / PN25

• Seal: Soft seat (NBR/PTFE)

• Body: Carbon steel

• Actuator: Pneumatic

• Certification: EN 161 + ATEX

✔ Quick selection checklist

Use this before finalizing:

•  Gas composition (H₂S? corrosive?)

•  Pressure & temperature

•  Required leakage class

•  ON/OFF or modulating

•  DN & flow velocity

•  Pressure drop acceptable

•  Actuator type

•  Certification (EN, ATEX, DVGW)

• Phone: 86 185 6630 3837
  WhatsApp: 86 185 66303837
  Email: ekelairn@gmail.com
  Web.: http://ekgas.com