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POSITIVE AIR SHUTDOWN

Bruce Smith August 17, 2012

NO PAS, NO ENTRY! 

A positive air shutdown system on your diesel pickups is a must-have upgrade for many mining, forestry, refueling and petroleum contract work

 

By Bruce W. Smith

It’s a small device that can be held in the palm of your hand, yet it’s  the most important safety item on diesel pickups working in or around petroleum production facilities.

If your truck does’t have one, you’re not getting onsite.

The device is called a positive air shutdown system, or PAS.

If you are a contractor who has spent much time around the mining and petroleum-production trades, PAS devices are old hat. 

But bring up the subject to the typical construction or landscaping contractor who is trying to expand their business and you’re more than likely to get a blank stare. 

BD Diesel’s PAS kit comes with the controller, special boots and the automatic/manual shutdown unit.

Yet having a PAS on a heavy-duty pickup is one of those upgrades that provides a safety benefit like no other aftermarket product out there.

It also opens the doors to getting a contract where such a device is a mandatory component on diesel pickups working where gas vapors pose a safety hazard.

Installing a PAS also makes diesel pickups compliant with regulations mandated by many contracts including septic tank removal, forestry projects and oil/gas well service.

 The operation of a PAS is very simple: A diesel engine only needs air and fuel to run. Cut off one and the engine quits. 

 Where an emergency shutdown system like PAS comes into play is when that fuel source comes from outside the truck in the form of hydrocarbon vapor; you can turn off the truck’s ignition or kill the diesel supply, but the engine will keep running and revving until it blows up using that volatile outside fuel source.

(Think spraying a can of starting fluid into the air intake but with an unrestricted supply.)

So to prevent a runaway diesel engine there has to be a mechanical component that closes off the air supply, ensuring that outside fuel source through the air intake stops. Hence, the PAS.

There are a number of different PAS systems available. One of the best designs for diesel pickups is the one offered by BD Diesel Performance.

The $1,135 (US) kit is compact, smartly designed and easy to install. 

All the parts are aluminum and stainless, so corrosion will never be a factor, and the electrical connections are waterproof. 

We mounted the on/off toggle switch just below and to the left of the steering wheel so it’s within easy reach/sight of the driver, yet not likely to get bumped accidentally. Note the BD Variable Vane Brake Control dial just above.

 BD’s PAS, an in-line butterfly valve activated by a heavy-duty solenoid, is placed in the charge-air-cooler air intake line (CAC). The rpm sensor is wired into the main engine harness to pick up the crankshaft position. 

The system’s computer, housed in a small control box, will trip the solenoid and close the valve automatically when the engine hits a predetermined rpm (our Duramax is set to 4,600rpm ) – or manually when the driver flips the dash-mounted switch to the “off” position. 

Shutdown is almost instantaneous. To restart the engine requires opening the hood and physically resetting the trip mechanism on the PAS. 

We installed a BD PAS kit on the Duramax in our 2008 GMC Sierra 3500HD, Big Red, so whomever wins it next April will be all set to use the truck for whatever work comes its way.

PAS Contacts:

BD Diesel Performance; 800-887-5030; dieselperformance.com

Truck Supply & Outfitters; 205-553-4203; trucksupplyandoutfitters.com

 How-to steps: 

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    The DTI Guardian Shutdown System is unlike any other engine shutdown system in the market today. With traditional

    shutdown systems operators have no way of determining why their engine has stopped and once it has stopped, the

    valve is very difficult to be reset.

    The system is designed so that the valve will not close unless users want their engines to shutdown, whether it is by

    dash control, preset RPM shutdown or by key fob. In our more advanced models, the DTI system records the status of the

    valve at the time of a shutdown and the butterfly design of the valve prevents the loading of unburnt fuel into the engine

    when activated.

    Equipped with the Valve Control Unit (VCU) controller lets the user know the status of the

    valve through the LED light display and constantly monitors the status of the Valve for any faults.

    This enables a failure-free performance and makes it the only shutdown valve of its kind on the market.

    Shutdown system’s are essential due to the nature of how diesel engines operate, that is, by the combustion of

    controlled fuel fed into the engine to control its speed. In the presence of airborne hydrocarbons, such as those caused

    by a fuel spill, a running diesel engine will rapidly enter into a “runaway state” by ingesting hydrocarbon vapor.

    If not stopped immediately, an engine in a “runaway state” can become a dangerous source for the ignition of a fire or

    explosion. This can result in the loss of lives, destruction of equipment and facilities plus extensive environmental

    damage.

    With the DTI Guardian Shutdown Systems, companies will protect their operators, equipment and themselves by

    avoiding unnecessary costs due to litigation, property loss and environmental liability.

    The DTI Guardian System monitors the engine’s exact RPM at all times. If the engine reaches above the programmed

    RPM the valve will shut off the air supply to the engine, this is the safest, most practical and most effective way of

    shutting down a diesel engine in a “runaway state”.

    Diesel Tech Industries

    (780) 455-9876

    info@dtiguardian.com

    http://www.dtiguardian.com

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