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Revised hydraulic calcs.

C

cheyer

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Nov 3, 2009
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Sunny California..well mostly..
In a T.I. setting, at what point would you require revised calcs. for head relocations?

I would think the main concern would be the addition of fittings and pipe, would you agree?
 
Re: Revised hydraulic calcs.

Not sure what is meant by TI setting!

I require calcs when they reach more then a 12 new heads being added. I believe the code allows up to 20. It also depends on what type of alteration or expansion is being done.
 
Re: Revised hydraulic calcs.

We typically require them for situations of (> 5 heads) and require hydrostatic for (> 20 heads). We will also require new calcs where the hazard classification is changing. Some are of the school of thought to require them for any change or renovation and I can agree with their methodology for doing so. We will also require them if the renovation is going to be on the remote area designed and verified previously for the building system since these changes could affect the system design regardless of safety factor previously verified. Followed by all verification inspections.
 
Re: Revised hydraulic calcs.

FM William Burns said:
We will also require them if the renovation is going to be on the remote area designed and verified previously for the building system since these changes could affect the system design regardless of safety factor previously verified. Followed by all verification inspections.
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That's pretty much what I require.

It would all depend on what it submitted. If they're adding a lot to branch lines I would require calcs. Look at the existing piping, existing calculations (are they just making it, or is there pressure to spare? What are the current static and residuals? Get an update form the water authority and see what the lowest recorded reading is-- is it lower than previous?) proposed changes and take it case-by-case.

Tim
 
Re: Revised hydraulic calcs.

Thanks for the replies.......

The bulk of what I am seeing is just relocating of existing heads a few feet for a new ceiling layout...not necessarily adding heads.

And these jobs are typically in high-rise's and office building suites.

I would then think the sprinkler contractor would have to do some digging to locate the most remote area, etc.

Would you say that all the above recommendations apply to larger buildings when the scope of work is one or two suites?

I would like to get our plan checker to start requiring revised calc's if they are indeed warranted.

Thanks again. :D
 
Re: Revised hydraulic calcs.

In addition to the other responses, we ask for revised calcs when they feed 2 heads in the same room from one drop if the system was not calced that way originally.
 
Re: Revised hydraulic calcs.

It depends on a few things:

1. Are these changes in the sprinkler system in the most remote design area, those 9-12 heads they calculate for the 1500 part of .10/1500? If not a few feet of pipe and few heads should not matter. Remember the closer you get the riser the better the flow and more pressure you will have.

2. What is the safety cushion in the original calculations? Was it 2 psi or 80 psi? If 2 psi do you really thing the job went in exactly as the plans indicated, do you think they did not have to add an extra elbows or a few tees, or a few feet of pipe?

3. If it is a high rise building were the calculations done for the 30th floor and the renovations are on the 1st floor? Sometimes I will get one set of calculations saying this is worse case. If on the 1st floor we will have a lot more psi available then the 30th floor.

4. IF the occupancy is the same i.e. light hazard to light hazard, less of a concern. If it is light hazard to ordinary hazard, now you have a whole bunch of issues, head spacing, higher density etc etc.

5. If you have a pressure reducer valve (PRV) on the floor control valve what is it set at and do they need to change that too?

Oh what fun....

Hope this helps.
 
Re: Revised hydraulic calcs.

And these jobs are typically in high-rise's and office building suites.
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In addition to InsEng's excellent advice, I would also check how good the adjusted supply was for a fire pump (if applicable) since the additions of extra piping could cut it close if the adjusted pressures in the remote area were just at 10 to 15 psi cushion. If even close, I would require new calcs for high rises but don't have to deal with them anymore in Mayberry :D
 
Re: Revised hydraulic calcs.

FM WB,

With reference of the hydrostatic test over 20 heads, do you still require that even if the modified work can not be isolated?

24.2.1.6 specifically talks about relocated heads and not requiring a test over system working pressure.
 
Re: Revised hydraulic calcs.

C,

Nope just system working pressure if it can't be isolated :!: Defended that same question in a Linkedin thread in the NFPA group that went on for about 50 postings ;)
 
Re: Revised hydraulic calcs.

Hydraulic calculations are specifically required by NFPA 13 (2007) if the revamping provisions of Section 8.15.19.5 are utilized, even for a single head addition or relocation.
 
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