Forward flow testing DCVA 1

[ContractorDave]

I have a sprinkler / standpipe system designed in 1989 with a fire pump and a 6" Hersey backflow preventer. There is no hydraulic data. How might you go about the forward flow testing of the device in this instance?

It's a high-rise office building with a retail mall area and underground parkade. Fire pump is rated at 500usgpm @ 100psi. Would the parkade require an ordinary gp 1 or gp 2 classification?

Thx
Dave

 

[stookeyfpe]

Techo,

What device? The fire pump or the BFP? I would perform a pump test and standpipe flow test and begin the analysis with that data.

I'm assuming an underground "parkade" is a parking garage. If that is what you are speaking of, Ordinary Hazard Group II is the minimum discharge density and design area prescribed in NFPA 13.

Am I correct that "parkade" is one Canadian word for a parking structure?

 

[TravisMack]

If the DCVA is on the supply side of the BFP, then doing a pump test will also be accomplishing the forward flow testing of the DCVA. If it is on the discharge side of the pump, you can use the standpipe system to do the forward flow test of the DCVA.

If parkade just means automobile parking, then according to NFPA 13, 2007:
A.5.3.1 Ordinary hazard occupancies (Group 1) include occupancies having uses and conditions similar to the following:
Automobile parking and showrooms

I hope this information helps.

Travis Mack
MFP Design, LLC

http://www.mfpdesign.com

 

[ContractorDave]

Hi Stookey

Forward flow testing the backflow. (And yes 'parkade' refers to a sheltered (generally speaking) area to park one's vehicle. This one is under the mall.)

I found a flow curve for the backflow. The darn internet can be pretty handy! I'll have to start with the DCVA and flow test it through one of the 2 1/2 standpipe valves bypassing the fire pump.

As noted though, I have no hydraulic calc information. Do I have to assume pipe scheduling for my water supply requirements?

Thx
Dave

 

[TravisMack]

I wouldn't assume pipe scheduling if the pipe sizing does not match a pipe schedule sizing.

Assuming the standpipes are the most demanding, can you find a standard that would govern the installation to determine what an approximation of the standpipe demand would be - something like 65 psi or 100 psi at the top most outlet flowing 250-500 gpm, etc...

Travis Mack
MFP Design, LLC

http://www.mfpdesign.com

 

[ContractorDave]

Hi Travis

If I can't determine for sure that it's calc'd, wouldn't it be safer to default to a scheduled design water supply? There appears to be something like that in 2010 NFPA 13, 11.2.2.

Or would you take the design density for OH2 and add 100gpm for the hose allowance?

The DCVA is before the fire pump by the way which is why I was thinking one would have to verify it first. If I flowed the FP and found unsatisfactory results there, the DCVA might still be the cause.

Regards
Dave

 

[TravisMack]

Dave:

You could use the pump test header to do the forward flow testing for your DCVA. Then, if that tests out properly, then continue with the test to verify the pump is working properly. All done through the test header.

If you have a system with 5 heads 1¼" pipe before it gets to a cross main (not uncommon with a big fire pump) then it is going to be more demanding than any scheduled system. If it is critical, I would try to trace down the system and run a quick estimate calc on it. Being in a parking structure, everything should be exposed. You can sketch an rough layout of the system pretty quick, then through it in a program and viola' you have a calc sticker available.

Good luck on it! Sounds like an "interesting" project.

Travis Mack
MFP Design, LLC

http://www.mfpdesign.com

 

[stookeyfpe]

Everything that Travis said and:

The standpipe needs to be flowed. The pump is driving the pressure demand. I know your trying to establish the system capabilities. However, the standpipe was installed because of the building height and needs to be functional for the firefighters.

You need to look at all of the functions of the fire protection system, not just the discharge density and design area of the sprinkler system.

 

[ContractorDave]

Hi Stookey

The reason I posted though was if there is a backflow preventer on a system, forward flow testing of the device is supposed to be done at system demand. So I was trying to see how this was typically done if the calc's aren't available. This is what I was assuming: Take OH2 + 100gpm for hose and you need to flow about 550gpm through the device. This would be the same figure you would be looking to achieve at the hydraulically most remote valve on the stand-pipe also, correct? (Though of course you will lose some through friction loss, so we should see better than 550 at the dcva.) Have I got this figured more or less correctly?

Thx
Dave

 

[TravisMack]

The standpipe system is likely the driving factor. You would need 500 gpm at the most remote standpipe and 250 at each additional to a total demand of 1000 - 1250 depending if fully sprinklered or not. You could use that as an estimate for the flow for the DCVA forward testing. More often than not, the standpipe system will be more demanding than the LH or OH sprinkler system.

Travis Mack
MFP Design, LLC

http://www.mfpdesign.com

 

[ContractorDave]

There you go. Earned another star. Thx Travis