How It Works


The valve is opened by rotating the hex drive (or supplied handle) approximately 180 degrees clockwise. When sufficiently rotated, the valve will automatically latch and stay open. Sending the appropriate actuation signal (see actuation options) will pull the latching spindle and allow rapid gate closure by internal spring force. The valves are designed to operate in any orientation , however a downward shutting gate orientation is preferable.

In the smaller valves, all of the seals including the gate seals are fluorocarbon. In the larger valves, the gate seals are PTFE while all other seals are fluorocarbon. All valve materials are corrosion resistant including aluminum, stainless steel, brass and bronze.
The AIR STOP valve must be in the open position to start the engine on which it is installed. If the engine has multiple air intake lines, with multiple AIR STOP valves installed, all of the valves must be open prior to starting or operating the engine. If multiple valves are installed on one engine, ENVACON recommends the use of gate position indictor switches to ensure all valves are either open or closed in unison.

AIR STOP valve gate position indicator options:

All shut-off valves have either an indictor pin or opening handle attached to the hex drive. When the indictor pin or opening handle points toward the valve bore the valve is in the Closed position. When the indictor pin or opening handle points toward the top of the valve (opposite the bore) the valve is in the Open position.

For applications that require more than one shut-off valve per engine, ENVACON recommends the use of gate position indicator switches. Tied into the engine start and/or control system, the switches are used to ensure all of the valves are open before starting, and all valves are open during engine operation.


As a safety device, the AIR STOP valve must be maintained in good working condition at all times. Weekly testing of the valve and actuation system is recommended, as is confirmation of functionality prior to entering a potentially hazardous work site. It is recommended that the test be performed with the engine running at idle, so as to confirm complete engine shutdown after the valve(s) is/are actuated. If the engine has multiple shut-off valves with gate position indicator switches; with the engine stopped, each valve should be closed while the other(s) is/are left open to confirm individual functionality of the gate position indicator system. In addition, all personnel working within the vicinity of the engine must be familiar with the operation of the AIR STOP valve actuation system, and with the potential 'inhaled combustible gas' engine over-speed scenarios that require its use.

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