I had a newer ISC with a DPF run away on me yesterday at work. Came in from an 'oil leak' which was wrong. It should have been check for lose of oil. Anyway once I fired the unit up I notices a white haze coming from the stack which you don't see one these new units with DPF. I reved the engine a couple times and it took off like a rocket. Scary I tell you. The turbo was blown and feeding oil into the intake causing it to run away on the oil. Luckily the truck was equipped with a positive air shut down and stopped the engine. If it didn't have it, it would have blown up for sure. Ecm recorded 3500 rpm before the valve kicked in. This got me thinking about my own diesel truck and the newer unit I plan to buy in the next year. I am thinking a positive air shut down is something I would want to invest in. I know this isnt a common problem, but it sure is a possible one.

Anyone else ever thought about positive air shut downs, aka RodaDeaco valves, or sour gas shut downs?

 

Engineered Diesel makes a nice one . . . .




Gotta fix the pull-cable . . .

 

very interesting.

why do you have it mounted in the compressor intake piping? I guess it still has the same effect choking engine of all fresh air.
However I prefer to mount them as close to the intake inlet as possible.

 

You gotta kill the air going into the turbo not coming out, you're trying to stop boosted air on the intake side instead of nonboosted air. Killing the air going in the turbo stops the air supply and the boost. Must stop supply.

 

What does it cost?

 

They are really expensive. Back when I worked on lots of diesel trucks at a dealer, I had the same worry of a runaway. What I did was ordered a CO2 fire extinguisher to keep on my work bench, just in case. If needed, It can be deployed into the air intake to displace the oxygen and kill the engine. Those extinguishers aren't common anymore, and it wasn't cheap either, but I thought it was a good safety measure. It might be a good idea to keep one in your truck if you are worried about a runaway.

 

okay now what happens if the CAC cracks or a hose connections pops off? the engine could continue sucking sour gas from these locations. the best place is closest to the intake. if the pistons cant draw any air in then no fire will happen. boosted vs non boosted air doesn't enter the equation


the CO2 extinguisher is a pretty good idea.

 

That is certainly true . . . in the oil field setting, etc.

My main concern is with a runaway IP.

As far as where I have mine mounted, I think it's a case of substantial boost pressures could "reconfigure" the valve-plate assembly on activation if used on the high pressure side of things. Those used in the oil field settings that I've seen are of VERY substantial construction. This one isn't quite that obviously.
The voices in my head suggest that on the intake installation, there's just 14.7psia on the atmospheric side plus that vacuum at WOT on the backside of the shut-off plate to contend with.

I'm still intent on supplementing CA shut-off with a spring-loaded 3-way valve on the IP's fuel supply line eventually. (Of course, that won't address a turbo lube seal blowing and fueling the engine now will it? )

 

If a hose comes off then she's not going to run wild on oil being pushed in by the turbo. Put your shut off anywhere you like.

 

Sound reasoning to me BC847. If that valve isn't heavy duty then compressor inlet is probably best place for it. Still it sure beats not having anything at all. The majority of the shut offs I see are and the few I've installed are stand alone electronic units with a slider (guillotine) style valve. Lately with the I have seen a couple butterfly style valves come in due to space confinements on new units. Not even sure what the units cost...I probably don't want to know either LOL

 

I guess my example was a little miss leading. As a turbo failure is just one example of a cause for an engine running away.