Fire Dampers installation detail 3

[mechanical3010]

The question is about the minimum acceptable gauge thickness for sleeves used to house the fire damper which is then secured to the fire rated wall using angles bolted to the sleeve on all four sides.
For UL Listed Type B Fire Dampers, the minimum gauge thickness of the sleeve must be the same as the gauge of the duct to which it is attached. The gauge thickness of the duct is governed of course by SMACNA standards. The duct gauge for small sized ducts (14 inches) the gauge thickness for low pressure ducts (1/2 inch W.G. Static pressure) is gauge 26. Is it permissible to use the same gauge thickness of 26 for fire damper sleeves or is there a minimum gauge thickness for sleeve of type B fire dampers also, as gauge 18 is the absolute minimum for type C fire dampers? Likewise if the duct gauge is 22 can the sleeve be gauge 22 also or there is a minimum gauge.

 

[AnotherEllis]

You are getting into a gray area here between designer/installer required expertise. The installer of the damper has to know which gauge steel to use. If you are pressed for guidance, defer to the installation details provided by the manufacturer for their particular UL listed product.

A similar question I have been asked on a sheet metal duct job was "what gauge thickness do we use for this pressure class 2 duct?" This was in a meeting with the owner and architect on site, and an instant answer was expected of me (yay).

I replied that the answer depended on the size of the ductwork, the type of seam and seal used, whether there was cross breaking or beading... then I looked at the mechanic and asked if he had ever done this before, and if he knew of SMACNA.

It was an aggressive way to have a discussion, and a bit risky with the owner there as you don't want to get into a pissing match with an audience, but the point was made and it all worked out. The contractor acknowledged that there were several ways to build the duct and meet spec, and that he would take care of it.

http://www.ellisconsultingengineers.com

 

[mechanical3010]

The fire damper has been purchased from the manufacturer and the question now is about the gauge of sleeve in which it will be housed for fixing this assembly in the wall using an angle frame on both sides of the wall. The Contractor is insisting to fabricate the sleeve from the same gauge as the duct to which the fire damper is to connect. The duct gauges is 22 to which the fire damper will be connected using an S-slip on all four sides for it to be a break away type connector. Since the minimum gauge of sleeve acceptable for type C Fire dampers is 18, I feel there must be a minimum for type B fire dampers also and so gauge 22 for the sleeve is not sufficient and the sleeve might not have the same fire rating of the wall as the fire damper namely 1-1/2 hours, and would yield in the event of fire, therefore I feel it should be at least gauge 18.

 

[ChrisConley]

AnotherEllis - sounds like you've been having the month I've been having. Lately it seems contractors (and owners) expect construction drawings to work like Ikea furniture assembly instructions.

I had a similar discussion with a contractor (Owner present) when the asked about sealing class. My response was similar, but when I mentioned SMACNA the contractor complained that the manuals were to expensive! The were working on a multi-million dollar project, and the SMACNA manuals were to expensive...

 

[mechanical3010]

But the SMACNA manual that I have does not answer my question either.
Can you?

 

[AnotherEllis]

What damper model and manufacturer was specified/submitted?

http://www.ellisconsultingengineers.com

 

[mechanical3010]

Ruskin is the manufacturer of the UL listed fire damper and there are no issues with the damper itself as it clearly has the 1.5 hour fire rating. The question revolves around the gauge of the sleeve in which it is housed. The contractor argues that for type B fire dampers, the gauge of the sleeve is the same as the guage of the duct to which it connects using the S-Slip. Well the gauge of the ducting is 22 and I feel this would be somewhat flimsy in a fire situation and would need to be a heavier gauge to withstand fire for 1-1/2 hours. However, I need more than my intuition to require the contractor to use gauge 18 or heavier for the duct that is gauge 22.
Thanks in advance for any tips or reference to the code that would support my contention.

 

[AnotherEllis]

OK, so I assume you are using a dynamic type FD, a Ruskin D1BD2 or something like the same. Here is what Ruskin says:

http://www.ruskin.com/catalog/default.aspx?id=12216

"3. Damper Sleeve
Sleeve thickness must be equal to or thicker than the duct connected to it. Sleeve gage requirements are listed in the SMACNA Fire, Smoke and Radiation Damper Installation Guide for HVAC Systems and in NFPA90A. If a breakaway style duct/sleeve connection is not used, the sleeve shall be a minimum of 16 gage (1.6) for dampers up to 36" (914) wide by 24" (610) high and 14 gage (1.9) for dampers exceeding 36" (914) wide by 24" (610) high. Damper sleeve shall not extend more than 6" (152) beyond the fire wall or partition unless damper is equipped with a factory installed access door. Sleeve may extend up to 16" (406) beyond the fire all or partition on sides equipped with a factory installed
access door. Sleeve shall terminate at both sides of wall within dimensions shown."

So if you call for breakaway sleeves, "equal to or greater than duct thickness" when using a sleeve gives you discretion. What did your drawings call for? If they were not clear you could be setting your owner up for a change order as the contractor could have reasonably assumed a minimum thickness to meet the install requirements.

If there are no breakaway sleeves then minimum gauge is 16 and could go higher.

And I would like to reiterate a couple of points: this is a question the contractor should be able to answer for themselves. It is listed in SMACNA. Unless the EOR made a more stringent requirement (and set it out clearly in the plans or specs), then the contractor would be correct to use the smaller gauge and should expect a change order to go up to the higher gauge.

Of course, if in your engineering judgment you feel that the higher gauge is necessary for your particular and unique situation, then by all means force the issue and make the thicker sleeves go in.

Good luck.

http://www.ellisconsultingengineers.com

 

[cry22]

Fire dampers installation are governed by UL 555, see page 8 for sleeve thickness requirements.

 

[mechanical3010]

Figure 6.2 of this UL555 allows the duct connection with flat drive slip. This is enigmatic, because the connection of duct to sleeve does not remain breakway if jointed by drive slips on two verticle sides.
The breakaway connection is to enable the duct to detach from the sleeve without pulling down the damper assembly with it. Once the duct is fixed to the sleeve with drive slips, it does not appear to be break away anymore?

 

[Drazen]

This is not code of my jurisdiction, but NFPA generally explains the principles behind concepts to enable differing key issues from arbitrary issues.

Sleeve thickness is not related to fire rating as sheet metal has no fire rating, it's zero.

It is only smoke extract ducts that have recommendation for thicker gauges to maintain structural integrity at higher temperatures, but not to resist fire.

 

[cry22]

Drazen,
UL override all codes. NFPA is not a code unless specifically referenced in the code book.
If you violate any UL listing of any equipment, the contractor will not install it (a knowledgebale contractor of course).

 

[AnotherEllis]

UL 555 is a testing standard. Dampers are built and tested to withstand the hardships and environments as dictated in the standard. They are then issued a label. The major model building codes recognize the value of this standard, and require dampers to comply with the requirements.

It's important to know the difference between codes and standards. It's not really a standard over riding a code. It is a relationship between the two.

Most important to me is the manufacturer's UL listed installation instructions. These are the documents detailing how the product complied with the standard, as required by the code.

Here in Florida I have been getting a lot of comments lately as I generally in the past had not included fire damper install details on the plans. The AHJs want them shown. My standard answer to the building officials is that different manufacturer's have different install requirements, and I do call for cut sheets/submittals to be provided, reviewed, and appended to the plans of proposed dampers.

Some of them accept this. Some insist on a generic detail (which our code requires to be on the drawings, in my opinion mistakenly). For these individuals I include a generic install detail that has notes indicating that in the case of any disparity between the engineer's detail and the manufacturer's UL install details, the UL approved detail prevails. And I also call for shops/submittals.

http://www.ellisconsultingengineers.com

 

[Drazen]

Of course, I agree that manufacturer's instructions for rated product have priority, but knowing principles behind allways help, as even when intention exists that everything be precisely defined, some vague points often remain.

Ellis, if you give them manufacturer's installation detail, you can even be in danger - in 99% of cases manufacturers include clause in their docs that they retain right to change product without prior warning.

So, by the time construction takes place, they could already have modified and newly-listed product, similar to what you desiggned, but with some differences. They will guarantee equivalent function, but if contractor installs according to detail you gave in your official design, you can be left as the only responsible for trouble.

 

[cry22]

Ellis,
It seems to me that UL is more than just a testing tandard, it is also an installation standard.
Standards suchs ASTM, NIST, UL are referenced as the highest authority in equipment performance.

Same as calling for ASTM B31.1 for example, any other product would not be compliant, and yet, ASTM is not a code.

In esence, the Testing and isntallation standards involving performance and life safety are above all.

Because all these other hopscotch "for-profit" standards, such as ASHRAE, NFPA do not put their money where their mouth is. Try to get a true guide on stair pressurization, smoke control, TB isolation room pressure differential set points or anythimng involving life safety from any of these standards, all you will find is burried gobbledigook that discourages more than one.

UL remains a higher authority in my opinion, compared to NFPA.

 

[AnotherEllis]

Cry22, I agree that the UL is more than a testing standard, and I should have just removed the word "testing" in my post. The UL 555 gives direction to manufacturer's for suggested installation particulars and sets a performance test. There is some discretion in design (as there always must be).

I do not look to other standard providers such as ASHRAE (disclaimer: I am an active member and supporter) to provide "how to" manuals. They provide a standard approach or considerations. For anything as unique as stairwell pressurization for smoke control, the engineer's input and discretion is VITAL.

In fact, there are a couple of engineers down here I know who often are called as expert witnesses and, if you are being sued for not following a design standard, will tear asunder the idea that a standard is anything more than a recommendation for designers.

The engineer's discretion should be wide and deep. This requires well educated and experienced people. It's a key reason we need to maintain a high bar to entry to the field and demand excellence from our members. Otherwise some C++ program could design "satisfactory" HVAC systems.

http://www.ellisconsultingengineers.com

 

[iken]

The fact that the "minimum" gauge for the sleeve is to eqaul the duct gauge does not nessecarily mean the sleeve should not be a heavier gauge.

My understandng is the sleeve is to hold the fire damper in the wall/floor. With that in mind, then the fire rating of the sleeve must be equal or greater than the wall it is connected to (30 mins or 60 mins etc). If not, the sleeve may fail before tha wall, resulting in the fire damper coming away from the wall it was fixed to.

So with that in mind, if you have duct in 18 gauge, but 20 guage offers a suitable fire rating, then yes the sleeve should be the same as the duct (as the minimum). However, if your duct is 20 guage, and 18 gauge offers the correct fire rating then 18 gauge should be used for the sleeve.

Also, on the slip joints, we tend to use nylon bolts and nuts with ductmate flanges (with no cleats of course).

Let me know if I am way off the mark.

 

[mechanical3010]

Iken seems to have hit the nail on the head, because if the duct gauge is 24 (and it duly conforms with SMACNA as per duct size and pressure class) the sleeve of gauge 24 appears flimsy and might just melt away. To wrap up the issue it would be useful to have black and white answers about the following:
Firstly, does SMACNA really state or imply that the gauge of sleeve can be 24 if the duct to which it is connected is guage 24?
Secondly, is there any code (UL etc.) that calls for a heavier gauge?
Thirdly is the question that arises from Iken's comment: Is there is any data of fire rating of different gauges to see how long the different gauges will last in fire?
Fourthly and very importantly: Figure 6.2 of UL555 shows the duct connected to the sleeve with a flat drive slip that would make a NON BREAKAWAY CONNECTION with the duct. This is not like the plain S that will allow the duct to fall without pulling out or distorting or effecting the fire damper. Clarification about this would settle the matter with one more point as follows:
Fifthly: The detail about connection of the sleeve with duct also calls for the use of No. 10 Bolts on all sides of the duct. Once again this appears to contravene with the requirement of the BREAKAWAY CONNECTION.
Many thanks

 

[cry22]

As an engineer, you will ultimately be the one with the seal on the drawing.
We first and foremost design and build to code, whichever is more stringent, not to guidelines.
If you feel SMACNA is the prevailing authority, then do so. Keep in mind that SMACNA is not a code.
This is the trouble with most US guidelines, they always go to the AHJ, no one wants to take responsibility.

They want you to adopt their guideline as a code so they can sell more of their books, but they want to remain a guideline (think ASHRAE 90.1 189.1 62.1 NFPA, SMACNA, AABC, NEBB, etc...) without taking any liability.

UL, ARI, ASTM, NIST, IMC, IBC, etc do stand for what they say and have more authority in my opinion, I'd give them more consideration.

 

[mechanical3010]

Can it be concluded from response of cry22 that a sleeve of 24 gauge is allowed by SMACNA for ducts of 24 gauge to which it connects by means of breakaway connectors?
The meaning and methods of breakaway connectors is also pending. The drive slip (C Cleat that is a sort of clamping type connection that will not let go like the S Slip would) certainly does not look like breakaway or is it? Nor do steel bolts affixing sleeves and ducts appear to be breakaway!