Friction loss calculations for Hosemonster testing scenario

[ContractorDave]

Please feel free to correct this process wherever an error in methodology or assumption is made.

Electric VIL Fire pump data plate: Net 500 gpm @ 90 psi, 150% = 79 psi, max = 100 psi. Assume suction side is always 50 psi. The fire pump is in a mechanical space with a test header that requires 100' of 2 1/2" hose. We are using a 2 1/2" Hosemonster with a 1 3/4" orifice (we have the tables but the coefficient is .975).

Start fire pump by dropping pressure at the control sensing line. Pump is operating in churn at 150 psi. Take rpms and controller v/a readings etc., typical of all stages.

Now here is where the Hosemonster procedure becomes problematic when plotting curves. If we throttle the test header valve so that the discharge reads 140 psi expecting to get our 500 gpm, we're not actually going to see that at the pitot correct? Would we not have to account for the friction loss of the hose at 500 gpm and add that number to the psi we are attempting to throttle the discharge psi to in order to see an actual 500 gpm?

 

[SprinklerDesigner2]

NJ1,

You made this comment earlier-
Doesn't matter, no hose or 5,000' of hose the readings will be the same. The gauges are located at the pump not at the playpipe.

The readings are taken at the end of the hoses not at the pump.

We're talking about the same thing.

The reading is taken at the fire pump discharge flange and that will not change as long as the same amount of gpm is flowing through a hose.

The reading at the end of the pipe is simply pitot pressure we use to establish a discharge rate. The 32 psi pitot simply establishes 500 gpm flowing through a 1 3/4" underwriters nozzle.

Assume 32 psi pitot on a single playpipe and the discharge pressure at the pump discharge flange reads 122 psi.

As cumbersome as it would be you could replace the playpipe with a super accurate turbine meter giving flow rates in gpm. Throttle the valve so 500 gpm is flowing through the turbine meter and you are going to read 122 psi on the discharge flange.

As the hose gets longer, as it goes around more corners, the valve at the test header will have to be opened to compensate for the additional head loss in order to keep the 32 psi reading on the pitot. Eventually, as the hose gets longer and more kinky, there will be a point where the hose valve is fully opened and you are still unable to obtain a 32 psi pitot reading. At this point you need to start adding more hoses and perhaps change to 1 1/4" playpipe tips.

 

[ContractorDave]

FPP1 :"The inspectors have great intentions and they put their best effort towards the tasks, but they are simply not properly trained."

There is NOT a wealth of resources for inspections and fire pump testing. Especially where I am. Before posting this here I even went to Hydroflow (Hose Monster) and got little in the way of useful information. (I am glad I did post here though .. as I usually am). I have gone to CASA seminars and read everything I could to become as knowledgeable as possible... Again though, I've learned more here really than any where else.

Some suggestions would be nice. I would greatly welcome the opportunity for hands on training under the tutelage of a Sensei. A more likely scenario would be some sort of distance learning training or dvd's though.

Thoughts?

Dave

 

[cdafd]

http://www.chubb.com/businesses/service/chubb5974.html

http://www.chubb.com/businesses/service/chubb5954.html

agree the additional hose has affect on outcome

 

[SprinklerDesigner2]

cdafd,

Only insofar as the ability to discharge 500 gpm through a playpipe.

If the pump has the ability to discharge 500 gpm through a 1 3/4" playpipe it doesn't matter if the hose is 25' long or 500' long.

 

[ContractorDave]

Hmmm

Thx cd

Perhaps I'll be in the New Jersey area in October(ish)

This has been yet another very good thread as I have come away a more knowledgeable gent than I was before.

Dave

 

[LCREP]

Dave if u need more info on the Chubb fire pump seminar let me know.

****************************************
Fire Sprinklers Save Firefighters’ Lives Too!

 

[ContractorDave]

Thx LCREP

I'm tentatively looking at perhaps getting in 4 fire protection related modules sometime in the October schedule, but the fire pump seminar interests me the most.

Dave

 

[LCREP]

Dave,

If u are a AFSA member u get 20% discount.

http://www.chubb.com/businesses/service/chubb5970.html

The fire pump seminar is very hands-on and includes annual pump testing on both an electric and diesel pumps. How to evaluate the annual fire pump test results are reviewed and explained in detail. More details are here

http://www.chubb.com/businesses/service/chubb5941.pdf

Hope to see you in October.


****************************************
Fire Sprinklers Save Firefighters’ Lives Too!

 

[Cidona]

Patterson pump provide a good 2 day class (free!). Nice part of the world too. Near the smokie mountains. Good for the work and play balance.