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Old 07-07-2017, 10:43 AM
Nate Steinbrink Nate Steinbrink is offline
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Fire Sprinkler head temperature?

We are building a hot glass studio in Denver and are required to put in a fire sprinkler system. The installer wants to put in 155 degree heads and we want him to put in 286 degree heads.

Does anyone have supporting evidence that would help make our case for higher temp heads. We have had experience in another studio, that when the fan was not working correctly the temp rise caused a fire sprinkler alarm to trigger.

Any evidence appreciated.

Nate
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  #2  
Old 07-07-2017, 11:51 AM
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Pete VanderLaan Pete VanderLaan is offline
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Well, as you say, the ventilation failed. The fire wasn't all that far behind when the sprinkler went off. 286 heads are going to pop off when things are seriously out of hand. It's just a fusible link . How far above the tooling will the heads be? Pretty typically restaurant hoods take more heat than glass shops. You might take a look at what they want to do with them .
It is the case that 135F or so will begin the pyrolizing process but it takes about 20 years to gas off. I used to think that 165F was OK for radiant wood contact and I stopped believing that years ago after documenting a number of pyrolitic fires when support beams lit up that had six inches of concrete above supporting the heating unit in warehouse fires.
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Old 07-07-2017, 03:03 PM
Art Freas Art Freas is offline
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I might see if the local Fire Department can point you to an NFPA resource on this.
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Old 07-07-2017, 09:15 PM
Tom Fuhrman Tom Fuhrman is offline
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I had one of the low temp heads go off in my old studio. I got it switched over to the hotter head as otherwise I would have never been able to use my GH. Sprinkler heads were only about 6-7 feet above the height of GH and I had an 8' x 8' door open behind the GH with a fan blowing out the door. When it gets to be 100 degrees outside it's almost impossible to keep the temps inside below 135 even with good ventilation.
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Old 07-08-2017, 08:16 AM
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Pete VanderLaan Pete VanderLaan is offline
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If you indeed are popping off 155 heads you don't say if they were in the hood, or above it and whether the hood itself is insulated which I have for years. It keeps a studio pretty cool.
I think the trouble in this scenario is that if a sprinkler was above a gloryhole with no shielding then, if it popped off, it would likely eventually put the flame out and leave raw gas. I don't see many gloryholes with UV sensors. Further, if indeed it did cause that link to break, then it would be hot enough that you would not want any flammables anywhere near that site. 160F is more than enough to cause gassing off of flammables and they do burn.

I do tend to think that if the ventilation system coupled to insulation is good enough that this would not be an issue but really good ventilation is not commonly found in hot shops. I don't know why.
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Old 07-09-2017, 02:12 AM
Nate Steinbrink Nate Steinbrink is offline
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Good info! Very interesting to hear that the heads could weaken in 20 years. Our set up will have the sprinkler heads above the vent hood that is not insulated? Definitely will dive into the nfpa codes again to see if I can find anything for there. Worried about the a 155 degree head on a 100 degree day. Our heads will be about 5' above the glory holes. Insulating hood maybe needed and hopefully can find enough info to convince inspector to up the temp on the heads.
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Old 07-09-2017, 07:02 AM
Victor Chiarizia Victor Chiarizia is offline
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pyrolic fires........pete your giving me a flashback. it took somewhere around 10 years for mine to happen. v
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Old 07-09-2017, 07:44 AM
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you're hearing what you want to hear. I didn't say the heads weaken at all. I said the combustible materials will be tinder dry gassing off and can combust easily after 20 years. I said you should insulate your hood.

Victor was one of the fires I looked at.
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Old 07-09-2017, 08:40 AM
Steve Stadelman Steve Stadelman is offline
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Quote:
Originally Posted by Nate Steinbrink View Post
Good info! Very interesting to hear that the heads could weaken in 20 years. Our set up will have the sprinkler heads above the vent hood that is not insulated? Definitely will dive into the nfpa codes again to see if I can find anything for there. Worried about the a 155 degree head on a 100 degree day. Our heads will be about 5' above the glory holes. Insulating hood maybe needed and hopefully can find enough info to convince inspector to up the temp on the heads.
Code really doesn't mean anything, it's a jumping off point for the inspector. You need to be very good at explaining you unique situation and equipment.
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Old 07-09-2017, 08:55 AM
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Steve is correct. At the beginning of the Standard code books is a phrase that says "Or acceptable to the Authority having Jurisdiction" (AHJ) which is saying "that makes sense".
It's really hard to get the AHJ to abandon the code given the liability but it happens. I used to occasionally do it.

What might help if you can do it is to get a thermocouple probe up at the height you propose in someone else's studio and fire the gloryhole off and see what the probe indicates. the temperature to be.
If you do that, it might sway an inspector. It could also convince him to shut everyone down, you never know. Try to keep in mind that 155 degrees is really hot and is an invitation to a fire. Roast beef is best eaten at 130F.

If you insulate your hood, it will give back years of pleasure. Sheet rock the interior, then dead air space, then more rock, then insulation, then metal. Then an air change every two minutes or lessfor the whole shop. Use multiple exhaust fans so it can be varied. It's not hard to do. My shop is never more than 2F above the outdoor temperatures.
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Old 07-09-2017, 10:32 AM
Tom Fuhrman Tom Fuhrman is offline
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Pete, what's the temp 18-24" in front of your glory hole with an 8-10" opening in the front of the GH?
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Old 07-09-2017, 11:21 AM
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I 'll try to measure that Tom. I have portable units that are very accurate. I would imagine it to be quite high at 18 inch. It's the five feet above that interests me. What I may be hearing is that there's a low ceiling issue in play. The water lines and heads have to attach somewhere. I have had 13-16 ft ceilings since 1985 with ventilation up to 30K plus per minute. Now it's much less but the hood has the vents built in and the hood is rather well insulated to the point that we bring the gloryhole out on the shop floor in winter so we don't freeze.
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Old 07-09-2017, 11:32 AM
Scott Mitchell Scott Mitchell is offline
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Quote:
Originally Posted by Pete VanderLaan View Post
If you insulate your hood, it will give back years of pleasure. Sheet rock the interior, then dead air space, then more rock, then insulation, then metal. Then an air change every two minutes or lessfor the whole shop. Use multiple exhaust fans so it can be varied. It's not hard to do. My shop is never more than 2F above the outdoor temperatures.
That's bringing back a memory... I coordinated a tour of the (short-lived) Mazda GTP race shop in Charlotte in '92. The RX-792P used a 4 rotor Wankel that put out a ton of heat in the exhaust (more so than the reciprocating engines). The drivers were given the instruction to shut the engine down and pull over immediately if they heard an exhaust leak, because it could light the car on fire very quickly. In normal race conditions they had difficulty keeping the exhaust system and the muffler cool enough. In the end the fix was to insulate the muffler from the exhaust instead of insulating the muffler from everything else. Seemed counterintuitive at the time.
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Old 07-09-2017, 01:55 PM
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I took a number of temperature readings in the shop. I did not have the gloryhole running but I think I have a reasonable simulation from keeping the furnace door open and using it. I'll try to get gloryhole readings in the next few days.
Above the hood, which is insulated: 78.5F ( one vent on) five feet above furnace
Inside hood vent half on at the top: 100F
Inside hood vent off:114F
Inside hood 30 inch above furnace door 106F
" " " door fiber removed : 121F
Furnace door open 30 inches above inside hood 156F
18 inches in front with door open 114F
Above Flue six inches 1044F
Ventilation half on 30 inches above furnace door inside hood 96.5F
Ventilation on full 30 inches above furnace door inside hood 87F
Ventilation on full inside top of hood five feet 90F

Temp at my bench 82F
Outside temp 80F.

The hottest I could get was the furnace door open 30 inches above it with the ventilation shut down. If one used a 285 head I suspect the whole place would be well involved if there were combustibles in the hood. View leaking gas as combustible. The number one thing that ruins sprinklers is an explosion.
I have complete confidence in the test equipment provided to me by Los Alamos Labs.

Insulation works, I encourage people to use it. Serious ventilation works. I very rarely see it. Over the decades I've taken quite a beating from this trade. I see no point in doing that needlessly.
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Old 07-11-2017, 05:57 PM
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So I got the other numbers today in the hood.

With the gloryhole and the furnace running with the ventilation on full a probe in the hood, five feet above the center opening of the gloryhole door, an 18 inch unit read 114F with the vents pulling 7,000 CFM.

I then shut off the vents and pulled a reading in the same spot of 148F.
I then turned the vents to 3,500CFM and pulled 117F/

I then put the probe 18 inches out from the gloryhole directly in front of it and pulled 129F at the door middle. That would be outside the hood.

It was 86F outside and the base studio temperature was 85F, rising to 92F at the shift end. There is a large hot plate and pipe warmer contributing to the temperature. They are not under the hood.

The hood is 18x10x9 equalling 16,200 cu feet. The vent on full pulls 7,000CFM. On half, it pulls 3,500CFM. So on full it changes the hood air every 2.4 minutes. On half it changes the hood air every 4.6 minutes. I view this as somewhat underpowered on half vent but on full, it does the job. I view the job as taking toxins, not heat out of the building. The old Santa Fe shop changed the air every 20 seconds and we did a lot of cad sel melting. There are those from the first class who might recall that system. If you run that in winter it gets really cold. Not nice.

I view anything better than 2 minute air change as excellent, so mine is a bit under my standard. I have a hole for a third vent and have never used it. I do have a 20 foot ceiling mid building along with 3 multiple sliders and two ten foot garage doors. So it works pretty well, not perfect.

The trick here is isolating the heating units in an enclosed insulated space and concentrating the vents there as Scott notes. Having vents at ceiling level would be really hot since the fans would have to exhaust a 240,000 cu ft area with the same tooling bringing the air change to some god awful number and will make you one hot puppy. . That's a very high number. So if you are planning to build a hot shop think on it. Isolate the tooling. The fans cost about $800 bucks these days for both. By having more than one I can vary the exhaust. The Santa Fe shop had eight in two rooms, one being batch mixing. Most shops I see have a single 24 inch fan and that's about one change every seven minutes or so. You're going to fry. Building the hood with sheet rock, dead air spaces, insulation, and more rock and then metal ran more. I think this hood was about two grand. Every day I work in here is a nice day except when I break stuff.

As to the 135F sprinkler, I think these numbers address that.
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Old 07-12-2017, 06:50 AM
Eben Horton Eben Horton is online now
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I would buy the higher temp heads and instal them myself after all the people who know more than you are gone. That's assuming you have the knowledge, the tools and a ladder.
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Old 07-15-2017, 09:25 PM
Nate Steinbrink Nate Steinbrink is offline
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Thanks for clarification, understand now that heads do not degrade.

The temperature readings around the hood are very helpful, I think we may just see how the 155 degree heads work for us. The sprinkler heads are above the hood, in an area with out much clearance about 10 inches between hood and ceiling, which worries me about heat build up in the small space so we are taking the idea of insulating the hood on the top to hopefully isolate the heat in the hood as much as possible.

Appreciate all of the info!
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Old 07-16-2017, 08:45 AM
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My opinion about the heads is based on having been a paid fire chief. What I would point out although I consider it unlikely is that if you did switch out the head and something happened you would not necessarily have any insurance coverage . It could be viewed as fraud to change it yourself and then file a proof of loss. Insurance inspectors are fairly unmotivated people who don't spend much time on a claim unless the claim is really big. They do love weaseling out of things though.

What matters here is heat build up and fan exhaust. If the exhaust is inadequate I think it entirely possible to be around 150 degrees in there. If you plan to have a long term investment here, I really think it's worth building the hood and vent in such a way that your studio doesn't beat you up every day for the rest of your career.
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Old 07-29-2017, 12:08 AM
Nate Steinbrink Nate Steinbrink is offline
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Thanks!

Pete

Appreciate all of the hard numbers on temps, we are taking your advice on insulating the hood and did size the exhaust fan as high as we could afford for now at around 6,000 CFM, also have windows and garage doors in the space to get a crossflow of air.

It looks like the sprinkler company is willing to change the sprinkler heads above the hood to a higher temp, based on info we have gathered. Will let you know how it goes from here when we get running in a couple months.

Nate
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