Vacuum brake release valves (also known as double-branch vacuum brake release valves) are used on the continuous automatic vacuum brake system found on railway rolling stock.

Previously, valves were made from brass and iron castings. Thieves realised that scrap merchants were willing to pay handsomely for these brass castings and theft thus increased by alarming proportions.

Benefits of our Nylon Release Valve

  • it has no commercial scrap value, eliminating theft
  • savings in unit costs of more than 70% compared to original brass valve
  • it reduces maintenance costs
  • It reduces disruption of services
  • improved functioned capabilities
  • directly interchangeable with traditional components


  • Durability
  • Fully serviceable
  • Flexible: left and right handed designs
  • Adaptable: adaptor flanges for various mounting requirements

Functioning of the Release Valve

The valve incorporates a precision ground stainless steel ball and nitrile rubber O-ring which together create a renewable seat. The ball has a precise mass which creates a difference in vacuum across the seat, which in turn prevents the brakes from creeping.

To release the brakes, the vacuum release valve allows the vacuum exhauster to evacuate the spaces above and below the vacuum cylinder piston and, in the case of the C-Class valve, maintains a two kilopascal (2 kpa) pressure difference between the two spaces.

To apply the brakes, the vacuum release valve maintains the vacuum in the space above the vacuum cylinder piston, while simultaneously breaking the vacuum in the space below the vacuum cylinder piston, by allowing air in at atmospheric pressure.

When for instance a wagon is coupled and uncoupled during shunting operations, the release valve allows the brakes to be released manually, by pulling the release valve lever.

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