melting point of ducts

geojngl

with ductwork firewall penetrations. Andy, check w/ your local building dept on what code they have adopted. UMC and IMC are good references. The melting point of the duct isn't what is taken into consideration however, it's flamespread.

Andy_26

what is the melting point of galv. ducts

I'm a bldg inspector, and in certain situations ducts are allowed to pass through fire seperations (firewalls) IF they have a melting point above 760C (+/-1400F). I have always assumed that that would mean galvanized steel ductwork that is common around here,and it must be dependent on the gauge also. I can't find any info on the web concerning melting point of ducts. You've enlightened me before...anyone have the answer?

thanks
Andy

scrook_2

~ 1500°C

Mild steel will melt about 1500°C [~2700°F] (and weaken at substantially lower temperature), but the zinc galvanize coating on it will melt around 420°C [~790°F]. Gauge won't change the melting point, but will affect the strength of the duct, so heavier gauge would be preferred.

Edward A. (Ed) Carey_3

Reference N.F.P.A. 921

Andy,

The information you need is in N.F.P.A. 921,


Guide to Fire & Explosion Investigation.

921-2004, Pg37, Table 6.8.1.1


Steel (stainless) 1427C - 2600F


Steel (carbon) 1516C - 2760F

Ed Carey

Edward A. (Ed) Carey_3

PS to previous posts

Thank you for coming here and asking.

Sorry you got beat up a bit for your efforts.

You question was a good question.

I have always been of the opinion that the only stupid questions, are the ones that don’t get asked.

But then again, that just me.

If something else comes up, please come back. Be happy to help if we can.



Regards,

Ed Carey

Mitch_4

Andy

At least you are asking..bettter than most inspectors and I commend you.

next time just ask the question, don't mention you are an inspector, and the people here will be nicer.

GUYS!! I cant count the number of times you complain of inspector ignorance.Many inspectors are not interested in learning, but it is intersting that when someone does, he / she gets flak.


I think that some people need to decide if they want ingnorant inspectors or educated ones...because inspectors are here to stay..

ease up lads...

Dave Yates (GrandPAH)_8

ducts and firestop

Andy,

Welcome to The Wall! It's nice to see an inspector asking questions. We're required to install spring-loaded fire dampers in metal ducts, but we're not allowed to install fire-caulking around the perimeter where the ducts penetrate fire-walls. I was told, by the inspector, that the fire caulk could expand, deflect the ductwork and compromise the fire dampers. So, he had us leave a gap that, in my mind, compromises the fire-wall's integrity. Seems silly to require fire dampers if there's going to be an opening around the ductwork where fire, smoke and heat have a free passage.

Unknown

More kudos...

for trying to learn, or should I say caring enough to try to learn. My motto is I may not know everything but I DO know how to find out what I need to know. The Wall provides just such another avenue to explore when a question needs to be answered. And an excellent one at that.

Brad White_184

Dittos

Andy is to be commended for asking, no question about it.

Our guides for fire dampers in ductwork is UL Standard 555 (which qualifies the fire dampers and their installation) and NFPA-90A which governs where they are installed; get a copy, there is a handy diagram of all conditions of fire dampers in duct systems. Our office standard is based on that standard. In short, a one-hour wall penetration that is continuously ducted with galvanized duct of 24 gauge or greater would not need a fire damper. A transfer duct would. Any partition rated at 1.5 hours or greater gets the appropriate fire damper.

Where we have to penetrate such a partition but cannot install a fire damper (such as a laboratory hood exhaust, grease duct or material handling) the use of welded 16 gauge iron is prescribed. This gauge mirrors the sleeve and frame gauge on most fire dampers so that defines it's value in short. Ruskin for one company, has a comprehensive web site with good information to study.

Good Luck and seriously, I am glad you stopped by.

To Dave Yate's question on not sealing around the damper- Huh? I agree, that defeats the purpose. Per UL, the fire damper is part of the wall not the duct. The ductwork is to fall free in event of collapse, leaving the fire damper intact. Break-away connections are made for this purpose. One town inspector in MA forces EVERY damper to be tripped and re-set, to demonstrate any binding and to show that the access doors are suitable for re-linking. But to not seal? Sorry, but smoke will get me before the fire would...

Plumdog_2

Which set of Codes is adopted in your locale?

I think ductwork must be of proper guage material for it's dimension, and penetrations of firewalls must be thru an approved fire damper, spring loaded and held open by a fusible link, the frame should be 16 guage welded, and painted red. It is important that a fire (smoke) not spread thru the ductwork from one part of a structure to another.

Weezbo

your road game requires a great deal of reading

knowing where to find accurate information seemed so much easier when every one had quick access to specialized libraries ...now with computers you can seek an anwer via the internet, as you are finding out ...it has its own stumbling blocks..never feel you have to Know it all there are rules regs codes standards that were dreamed up as you slept last night that you could not possibly divine through any other means than by asking. good thing that you looked here as there are some very competent professionals.

you have my apology for venting on you the last time you were unlucky enough to catch me wondering as to what kind of inspection process bought about such dangerous installations to private and public properties ..that clearly jeopardise human lives. its one of the plateaus i find myself unable to descend from...i think being an individual basically means my idealism refuses to succumb to the majority that would allow reckless endangerment as a norm by turning a blind eye.

Andy_26

Thanks Guys!

Thanks to everyone for your valuable insight.
I checked the thread on Friday before I left work and saw that somebody (was it Weezbo?) was really pissed that an inspector would need clarification on something.
The range of things that I am supposed to be an "expert"
on is truly staggering. Everything from soils, concrete, wood framing, structural steel welding,cladding, insul/vapour barrier, plumbing, hvac, roofing, fire sprinklering... the list is huge. I figure unless I was born with this info, the only way to learn is to ask smart people smart questions, even if it reveals the fact that I don't know everything. so I'm not offended by your response.
The worst thing I can do as an inspector is try to bluff my way through... so when in doubt I ask a question no matter how stupid it might seem. In the long run this is how I have built a great relationship with the builders and trades that I work with on a daily basis.
Now back to my original question. I work in Ontario and use the Ontario Building Code. The section on penetration of fire separations outlines a few cases where ducts can penetrate fire seps, and fire dampers are not required if the ducts are continuous and have a melting point above 760 C. Like I said in my O.P., I assumed that referred to galv metal ducts and in light of all your responses, I see I was correct.
Regarding the situation where the inspector would not allow fire caulking at the damper, I feel that area should definately be caulked with a non expanding type fire caulk. Perhaps the inspector is only aware of the intumescent caulk, which does expand when heated by fire.

Sorry for the long post, and thanks again for your help.

Andy