Pacbrake Blog

Understanding The Air Intake Shut Off Valve

July 12, 2014

Also known as ASOV, AISV, ESD or emergency shutdown valves, air intake shutoff valves are systems that allows for emergency over speed shutdown and protection for diesel engines. They are by far the most efficient systems are used to prevent engines getting into runway situations today. The valve fully cuts off uncontrolled fuel source from external sources to the engine and air that is required to keep the engine running. Other common brands in this country include Chalwyn, AMOT, Roda Deaco and Rigsaver. Depending on the set budget as well as personal preferences, there are many other types or models in the market for your selection.


Diesel engine runway

Speed in diesel engines is managed by controlling fuel amounts into the engine through the normal inboard speed governor and fuel system. There are cases where flammable materials get drawn into the air intake system of the engine resulting to ungovernable fuel supply into it. This results into a condition that is generally known as an engine runaway, with results ranging from catastrophic explosions to complete engine damages.

How do prevent a runaway?

If you turn off an engine with a runaway issue, then you are only turning off the standard source of fuel to it. If the inflammable material is still in the engine, then ungoverned additional fuel supply still goes on. The problematic engine fuel issue can’t be stopped the normal way. It can only be stopped by the use of a valve system that completely shuts off the air intake. The system fully shuts down the runaway diesel engine. How so, you may ask. The system totally blocks air coming into the engine system, and the source of fuel keeping the engine running.

Actuation of air intake shutoff valve system in diesel engines

1. Automatic self contained air intake shutoff valve system

This is a self contained automatic over speed shut down system. The flow actuated air intake shutoff valve requires no external mechanical or electrical input devices. With this system, the valve closes automatically when the speed goes beyond a pre-set point and opens as soon as your engine is stopped. This simply means that the engine once again is ready to be restarted. The system comes with several integral air filters and a number of manual override mechanisms.

2. Manual actuation of air intake shutoff valve system

There are five basic kinds of manually actuated air intake shutoff valve over speed protection systems available in the market today. These systems include the following:

• Manual electric over speed shutdown system that actuates an air intake shutoff valve with an electric toggle switch.

• Manual electric to pneumatic shutdown system that utilizes a manual toggle switch to actuate a 3-way pneumatic solenoid that pressurizes the shutoff valve to close.

• Manual pneumatic shutdown system that utilizes a manual pneumatic toggle valve to force the valve to close.

• Cable or local operated shutdown system that makes use of a T-handled pull cable to manually close the air intake.