LPG Dual-Coil Solenoid Valve for Gas Dispensers

LPG Dual-Coil Double-Action Solenoid Diaphragm Valve — how it works

This dual-coil double-action solenoid valve is the standard shut-off valve on most modern LPG dispensers worldwide. The unique design combines two solenoid coils in a single diaphragm body made of brass, delivering a three-phase fill cycle for high LPG dosing accuracy.

Operating principle (3 phases)

1. Full flow: both 220V coils energized — valve fully open, LPG flows to the nozzle at nominal 5-50 L/min.
2. Slow-down: 1-2 litres before end of preset dose, the dispenser controller de-energizes the first coil — valve switches to slow-flow mode (~10-20% of nominal). This eliminates water hammer and gives the metering system time to count the final dose precisely.
3. Shut-off: at exact preset volume, the controller de-energizes the second coil — the diaphragm fully closes the flow path. Accuracy ±1-2 ml even on 50-100 L doses.

Why diaphragm type is the most reliable

Unlike poppet valves with sliding stems or motorized ball valves, the diaphragm solenoid valve has no sliding seals or dry packings. The closing element is a flexible Viton (FKM) diaphragm that deforms under the coil's electromagnetic field. Design benefits:

• 1-2 million cycle service life without leakage (poppet types: 200-500k)
• Self-cleaning seat from LPG flow — debris does not accumulate
• Stable down to -20°C — diaphragm does not freeze unlike ball valves
• Low power draw — coils hold valve open with minimal force
• Normally-closed (NC) — power loss automatically closes the LPG line

Applications

• LPG dispensers and filling stations — primary electromagnetic shut-off in fuel line
• Retrofit replacement during Gerkon, Tatsuno BMP-405, FAS SX7130, MQF-15/25, TDW-20, Bonomi or Adast dispenser repair/modernization
• Emergency shut-down systems at LPG depots and storage facilities
• LPG dosing skids for tanker loading and bottle filling
• Process equipment with propane-butane metering

Dispenser compatibility

The universal threaded DN20 (G3/4") connection with standard mounting flange fits:

• Gerkon LPG dispensers — drop-in replacement (our own equipment)
• Tatsuno BMP-series (BMP-405, BMP-505) — drop-in replacement
• FAS SX7130, MQF-15/25, TDW-20 — drop-in equivalent
• Bonomi LPG — drop-in replacement
• Adast LPG — via adapter gasket
• Bennett LPG, Petrotec, Galileo — custom order with adapter

Advantages over other valve types

• More accurate than single-stage — two-stage shut-off cuts overflow from ±50 ml to ±1-2 ml
• More reliable than poppet — diaphragm vs stem-and-packing
• Faster than pneumatic — instant actuation, no compressor required
• Cheaper than motorized ball valves — no gearbox or motor
• Field-serviceable — diaphragm or coil replacement with hand tools

Two-coil-in-one-body technical implementation

Both coils 220 VAC 50 Hz are mounted on a shared magnetic core above the diaphragm. The dispenser controller switches them via two independent discrete lines (typically 220V through relays). Total consumption: ~24 W (2×12 W). Ex-rated cable glands enable safe wiring in the dispenser hazardous zone.

Delivery scope

• Assembled dual-coil double-action solenoid diaphragm valve
• Ex-rated cable glands for two power lines
• Manufacturer's passport
• Installation and maintenance manual