Why are engine shut-off (shut-down) valves
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
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
Do not hesitate to contact ENVACON to discuss the actuation
requirements or preferences for a specific engine application.