Why are engine shut-off (shut-down) valves used?

The main reason for installing an engine shut-off valve is to ensure that there is a means of stopping the engine in the event of an over-speed due to an inhaled combustible gas or fumes from the surrounding atmosphere (examples: natural gas or propane leak, fumes venting from a tank that has or had hydrocarbons in it, or fumes from spill on the ground etc). In the event of such an over-speed, shutting off the engine electronics and / or the ignition system will not stop the engine because it can continue to run, and over-speed, due to compression ignition of the combustible gas in the engine cylinders. Without an engine shut-off, an uncontrolled engine can result in a catastrophic failure and / or the ignition of the surrounding combustible gas or fumes. Eliminating the engine air supply and / or the combustible gas supply are the most practical means of stopping such an over-speeding engine, and an installed air intake shut-off valve is the fastest and most cost effective device for doing so.

Where is the best location to mount the shut-off valve on the engine?

In a general sense, the best place to install a shut-off valve is as close to the air intake manifold (as close to the engine cylinders) as possible. This minimizes the chance of air leaks, or alternate air entry routes into the airline between the valve and the cylinders. However, the actual shut-off installation location is typically dependant on the physical space available in the air line and on engine accessories mounted nearby. In such a case the the shut-off valve may have to be mounted further upstream in the engine air-line, however except for customer specified installations, the install location is usually defined by ENVACON when a specific installation kit is designed.

Do not hesitate to contact ENVACON to discuss the valve installation location for a specific engine application.

What type of valve is used?

The ENVACON AIR STOP valve was specifically designed for engine air intake shut-off applications. The guillotine design of the AIR STOP valve offers an unrestricted through bore and the gate and its seals are out of the air flow and protected when the valve is open. There is no reduction in engine air line efficiency, air flow turbulence is avoided, and the narrow in-line profile of the valve enables maximum adaptability to the engine piping. Once closed, the gate can not be re-opened by engine backfire and any reverse flow would be blocked by the momentary reseat of the gate to the upstream seal.

How are shut-off valves mounted into the engine air intake line?

The ENVACON AIR STOP shut-off valve can be supplied with a wide range of outlet connection types that accommodate most, if not all engine requirements. These include but are not limited too; hose mount, flanged, O-ring, and V-band (see examples). In addition, combinations of these connection types or miss matched sizes can also be accommodated, and ENVACON has a broad range of pre-designed installation kits to suit many common engine makes and models.

How is the shut-off valve actuated?

ENVACON AIR STOP shut-off valves can accommodate a range of actuation methods including; manual via ‘throttle type’ pull cable, manual electric, manual pneumatic, manual electric over pneumatic, automatic electric, automatic pneumatic, and automatic electric over pneumatic. In addition, application and / or customer specific manual or automatic hydraulic, loss of pressure to trip, and low-pressure actuation systems have been supplied. It should be noted that any manual actuated system requires that the engine operator(s) be in close proximity to the manual control at all times, and that they must recognize an over-speed situation and react to it immediately by actuating the manual control. For the highest level of safety, ENVACON recommends a fully automatic system be used.

Do not hesitate to contact ENVACON to discuss the actuation requirements or preferences for a specific engine application.


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