I got asked a question the other day about fire suppression systems being able to start automatically. All that I've seen over the years had to be started manually by pulling a pin and mashing down on a button. I don't know that I would care to be sitting on a machine that could fog up my eye glasses and clog my breathing pipes because some long toothed varmint decided that a particular type of insulation was delicious. Can anyone light a fire on this topic?
If the detection cable is triggered, usually there will be a buzzer in the cab and a short delay before the system activates to allow the system to be cancelled if it's a false alarm.
Saw one system that used lots of plastic (special material, I say plastic because we all know what that is, heh) tubing anywhere a fire was likely to start and wherever that tube was melted by excess heat, that's where the fire suppressant sprayed out. Rather new and novel approach, I liked it.
Ditto that, and additionally there are systems with another type of detector that will detect flames and only trigger as a result of a positive detection, again giving the operator (I think) 15 seconds warning before the system triggers. The idea being that he can stop the machine, lower the equipment, and shut off the engine before the system triggers. There's no point in having a fire for real and if the engine is still running pumping hot oil out everywhere to restart the inferno once the fire suppression system has discharged.....
Yair . . . We had a lot of belly guard fires and apart from the possible oil problem, in out situation, getting that engine shut down to stop the fan was the biggest factor in controlling the fire and reignition. Our systems were crude but effective consisting of milk churns full of water in the early days and tanks built into the canopies on later tractors. I have been involved in several power station fires and same thing applies . . . get them off line and shut down ASAP to stop that airflow across the fire which as Nige points out is often the result of (say) a burst hose spraying onto a manifold or turbo. Cheers.
I've been involved in a couple of cases where a fire suppression system discharged as designed and initially was successful in extinguishing a fire which then re-ignited because the engine hadn't been shut off and a burst oil line was still pumping oil on to something that was still very hot. In both cases we were of the opinion that it was oil spraying on to a hot turbo/exhaust that caused the re-ignition. You only get one shot with these systems. Once they're discharged that's it. Where I was working last we were investigating the possibility of connecting the fire system to the remote engine shutdown and looking for ways to interrogate the machine to make sure that it was stopped, transmission in neutral, & park brake on so that the fire suppression system could actually safely shut off the engine before discharging under that specific set of circumstances without taking control of the machine away from the operator. I'm not sure how far they got with that. There are systems around now that have 2 separate suppressant agents. The first one is powder to put out the fire, the second is a liquid agent which is not only designed to keep the fire out but also to cool hot components and assist in preventing re-ignition. The powder fires first, and just as it is coming to the end of its cycle the liquid agent starts spraying.
Yair . . . It's a bad feeling to be out of water and still have lots of smoke. The closest I ever came to losing a tractor was when we ended up with a dry tank because a milk churn had rubbed through . . .ended up clattering an Allis 21 flat out in reverse for near half a mile and took her for a swim in an earth tank. Ended up in about five feet of water let her soak a few minutes and then drove out with no damage other than a couple of scorched transmission hoses. The boys reckoned she was leaving an impressive smoke trail out the radiator . . . took two days to fix the fences I'd driven through. Cheers.
So is a detection cable electrical in nature? Does it have to be hooked up straight to the battery? Is it supposed to be armed all the time or only when the engine is running or when the master switch is turned on?
Our fire suppression system is an extinguisher , 5 gallon bucket of water on the deck with lid split for quick removal ( in case the extinguisher fails ) , and a hand shovel . Also Like to shield hydro hoses with plastic corrugated field tile to prevent oil from spraying on a hot turbo & manifold . http://www.heavytruckforums.com/showthread.php?51-Fwd-Trucks&p=2356&viewfull=1#post2356 The plastic tile also helps keep the operator from getting a bath on the Wabco . HeavyEquipmentForums Notice the bucket on front of the Allis 175 tractor . Fire suppression . HeavyEquipmentForums
Yes, it's special electrical cable running in a loop from the system control panel. When it gets above a certain temperature it shorts internally and activates the system. The system can optionally be on all the time or only when machine is running or whatever you think is necessary when the system is installed.
So it has to be hooked up to the battery to work? What happens if a fire starts with the master switch off?
If you think that that's a danger, there are systems available with a built in back up battery.
Our fire suppression systems were wired direct to the battery, bypassing the master switch. It was the only installation on the machine that was permitted to be wired that way, everything else was wired from accessory circuits that were isolated using the master switch just like the rest of the standard machine electrical systems.
Sometimes customers complain about losing radio memory settings when the master switch is turned off. In that case I offer to link together the two isolator switch terminals with a low amperage fuse. That allows power to retain the memory but if a short circuit bad enough to start a fire occurs or if someone tries to start the machine then the fuse blows. The downside is that the batteries can still be discharged if left for a long period I suppose you could connect a fire suppression system the same way.
Have been working on a wheel loader with an onboard fire system. Looks like a twin 30lb ansul type with two remote stations, one in the cab and one on the tail. I don't think we need it as we are out in the wild and not inside a building but it does a great job of obstructing rearward visibility. Is there any market for this stuff used or just scrap it.
If you're asking the question "should I scrap it or should I try to sell it?", the answer is scrap it. If the question is "should I keep it or should I remove it?", the answer is look at you insurance policy first.
That's how all of our systems are set up. It's standard here, so I'm not sure why it would have been an issue to find ways to do it down there. Unless there is a malfunction in the system, part of the discharge sequence is to shut down the engine before the suppressant is released.
Brian, my comment was in respecto of mobile equipment, not shovels. The shovels used the 2-circuit (dry/wet) agents and did have an engine shutoff built in to the fire suppression system. On the mobile equipment the systems were originally installed without consideration of hooking the engine shutdown into the fire system, simply training the operators to get the machine and engine stopped in the time between the system going into alarm and the powder discharge. The major problem with shutting down the engine on any mobile piece of machinery while it's still moving is that it can take control of the machine away from the operator and cause a far larger problem than any fire.
I'll scrap it out and see if my local gas supplier will give me some trade on on the 4 ansul cartridges, I'd be happy with just a 5lb extinguisher after removing 150 pounds of grease oil and dirt from the machine guts.
http://www.firetrace.com/applications/industrial-fire-suppression/cnc-machines/ Originally on race cars, now on automatic machine tools (screw machines run un-attended) Looks like standard PEX tubing, hooked up direct to CO2 bottle, pressure (pressure drop) switch shuts off mains electricity as well.
Thanks Digger Doug, that is exactly the system I was thinking of! http://www.firetrace.com/applications/off-road-vehicles/heavy-off-road-equipment/
And yes....you can use it to keep your beer cold....