Here's some more info for ya....! (insanely long post...)
I'm a field operator for an oil and gas company up here in Alberta. I wanted an air shutoff because my job involves blowing wells to atmosphere to unload them, as well as occasionally bleeding down pipelines, and routine fuel gas venting through pumps etc. Most companies kinda turn a blind eye to diesel-powered operator's trucks... . but some have a policy that anything diesel-powered must have a positive air shutoff-and some even mandate automatic trip ability. Hear that Talisman and Union Pacific Resources make you prove that they work before they let you on lease-if it doesn't you go home until it does. As far as I know Talisman makes tank trucks test every month when they arrive at the battery with a load-if it don't shut down they shut you down-and you leave with your load still on
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Before I became an operator I drove a tank truck for 6 years-so I became fairly familiar with the setup. The old Star I drove had a Roda Deaco valve that was supposedly automatically actuated from a signal from the tachograph-pretty sure it didn't work. It used a Murphy tattletale relay to show that it had tripped and a dash-mounted toggle to manually trip. When you tripped it the Murphy closed which opened an air solenoid plumbed straight to the tank. The valve itself was latched open with a spring and pawl-the air tripped the pawl out allowing the valve to close. Dad drove a newer Star-the trip mechanism was still the same but the auto-speed sense was a bell-housing mounted trigger that sent pulses to an electronic control box. When you exceeded the preselected limit it opened the air solenoid-quite a bit more failsafe than the older truck. The 2000 KW I had just before I quit was even simpler-it took a speed signal right from the Cat ECM-but it still had a separate Amot control box to actually trip the shutdown.
The setup that I have on my truck came from Roda Deaco as well. They are an Alberta company headquartered in Edmonton that do nothing else but build PAS assemblies. They build valves from 2" to I forget how big! They do have a website as well at
www.rodadeaco.com . They make a kit specifically to fit the Dodge/Cummins trucks as well as most other light trucks. It requires you to cut somewhere around 3" (just a little more than that I think) out of the intercooler pipe that runs between the intercooler and the intake manifold. The valve then mounts with silicone-type straight rad hose in between the 2 pieces. It's tight but everything fits with a little room to spare. They will sell you a manually actuated valve if you want-I believe it uses a PTO-style control cable to pull the pawl out of place and then spring pressure closes the valve-but it could be that the cable actually does. I didn't research this style very much as I wanted something automatically controllable. The automatic one uses a solenoid to pull the valve closed. It has a manual toggle in the cab so the operator can throw it if necessary, and a speed-sensing adjustable RPM switch. The slick part is how it senses engine speed. Instead of a flywheel magnet-type thing, it ties a wire to the alternator ahead of the rectifier bridge. By doing this they measure the frequency of the alternator's AC output-which increases with increasing RPM. And the way our alternators are designed you don't even have to dismantle them-just pull them off the truck so you can pull that tin cover off the back.
To set the RPM switch you disconnect its output (so it won't trip the shutdown) and hold down a button on the box's face which makes the module trip its output at 2/3 of programmed speed. Then it's just a matter of throttling to 2/3 of where you want to shut down, adjusting a trim pot until the red LED lights up (indicating shutdown threshold) and letting the button go and running up to governed speed to make sure you're not shutting down there. I tweaked mine to just a whisker over governed so I don't knock the engine down if I have to race a PSD
It does require regular testing though to make sure that the wiring is all intact, as well as a quick check of the alternator sensing wire to make sure all is well. But so far I'm happy with it. It was around $1100 CDN I believe-which is way cheaper than an engine-or skin grafts for that matter. Know of a few guys in the tank truck industry here who got burned badly when an engine ran away and exploded thereby igniting the atmosphere which caused the runaway in the first place. Most of them were running to the truck to try and shut it down-so they ran right into the fireball
I see when I look back at the order sheet for the KW I drove that Kenworth spec'd the PAS from Amot. So maybe they supply a valve small enough to fit our trucks as well. I still lean towards the Roda Deaco stuff though because it comes in a prepackaged kit and their stuff is good. And their customer service is great too-they have an install shop there but they have absolutely no qualms about telling you exactly how to put it in... . in the last e-mail I received from them (when I asked them for some more specific details about the alternator wire tie-in) "If you have any further questions, please contact us. Any problems-let us know. No problems-let others know. Conrad Bodnar, Operations Manager, Roda Deaco Valve Ltd. " So I spread the word near and far that they're the guys to see... .
Sorry for the length of this post-I tried to fit in everything I actually could remember. Probably 10 minutes from now I'll think of something really important
. If you think of something else specific you want to know I'll be glad to answer.
Jason
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