Output Flowrate for three nozzles operating in a hydrant system

[analystuc]

We are in the process of installing a fire hydrant system. Our client wants to know the output flowrate for three hose nozzles operating at the same time. Whats the best approach for this? Any tip is appreciated

 

[cdafd]

check the flow rate of the hydant???
flow test

three hose lines connected directly to the fire hydrant??

or three connected off a fire truck that is connected to the fire hydrant??

 

[analystuc]

@cdafd
thanks for your reply. I meant three hoses connected to three different hydrants operating at the same time. Our pump gives out 1050 l/min at 100m head. Please do reply.

 

[cdafd]

OH no your are using that "M" word, sorry over my pay grade


sorry to ask again is the pump part of a fire truck,

or is it pressurizing the underground main with fire hydrants??


and are the hoses just attached to the fire hydrant outlet???

 

[LCREP]

1050 l/min = 277 gpm. Did the client say how much they want you to flow at the 3 hydrants at the same time?

What is the output of the pump at 150% of its rated capacity? In the USA a pump rated at 277 gpm would also have to produce a minimum of 415 gpm ? What is the water source, tank, public supply? How far are the hydrants apart, size of the underground main? You need to provide a LOT more information.

BUT if all you have to do it flow water from 3 hydrants at the same time? Find the smallest nozzle that will fit on hydrant outlet and flow water. Open the hydrant enough to get water and move onto the next hydrant until you have water flowing. A few turns of each hydrant will produce water.



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

 

[MGXFP]

Too much data missing to give an answer. You can find a theoretical value by running some test calculations if you have flow test data (unless this is fed by pump + tank only).

Also type and size of hoses is a big deal, especially how they pertain to friction losses.

 

[786392]

Dear,
It very much depends on Hose(s) in question,their diameters and

their simultaneous usage maximum demand

since these items are not clear in your post(s);

one may consider(1050L/min as becoming the governing factor along-with attributed hose streams and pipeline losses .

Hope this indirectly shows a way forward my dear 'analystuc'

Best Regards
Qalander(Chem)

 

[DavidCR]

Due the lack of information... just a guess to see if I can help.

I reckon that the client would want to know if the system is capable of providing enough water fot three atack hoses.

So the aproach in that case would be to define what is the minimun requirement of pressure and flow for a hose. For example, the pressure would be from 65-100psi, and the flow from 95-250gpm for each hose. You could get that from brigade, fire service people or local regulations. (In my case, Costa Rica, fire service recommends that 1-1/2 hose for occupants use have at least 65psi and 95-100gpm, and the 2-1/2 hose requirements depends a lot on the specific case (in general 250gpm with 85-175 psi, see also NFPA 14).

But as others have said it depends a lot on the hoses, also on the hose nozzles, distances, etc. and who is going to use the hydrants.

So you have to make hydraulic calculations to see if the system is capable of providing three selected worst case hose locations, and after the system is installed, to check it with actual flow and residual pressure measurements.

It seems that your 277gpm pump, that could be consider to be capable of delivering up to 140-150% (387-415gpm) @ 142psi, would not feed three 2-1/2 hoses, but maybe three 100gpm 1 1/2 hoses, but as I mentioned it depends a lot on your local conditions and requirements.

 

[analystuc]

Thanks all.
the design comprises of a 6" ring main, with subsequent 4" pipes feeding the hydrants.
Hoses are directly connected to the hydrants for fighting fire.A total of ten 4" hydrants are used on the pipe network.

Hose sizes are 2-1/2". How can we appropriately size the fire pump? No use of fire truck is envisaged.
Pls find attached a little sketch of the pipe layout. The double line indicates the 6" ring main, while the single lines indicate the 4" pipes feeding the hydrants. the thicker single line along the conveyor indicates a 5" pipe feeding two single hydrants and a double hydrant.
Letter H signifies 'hydrant'

 

[LCREP]

A few comments/questions:

1. What is the occupancy you are trying to protect?
2. The pump is very small if this was in the USA the pump size would be in the 1000-2500 gpm range, depending on what you are trying to protect and the required fire flow.
3. Any buildings have automatic fire sprinklers, if so what is the required flow?
4. NFPA 24 requires pipe to fire hydrants to be minimum of 6"
5. The ring main may have to be 8 or 10" again depending on required flow and occupancy.
6. What is the water supply for the pump? Tank, pond, city water, if tank how many gallons does it contain?


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

 

[786392]

Basically the questions raised by LCREP are right on dot.

Even then if this is a private fire service the pump rate (Max. flow-rate capacity)should have coverage flexibility for the largest credible scenario envisaged
inclusive of

Fire Extinguishing needs,

cooling needs and

safeguarding needs of the nearby structures exposed to radiant fire effects.

Your definition of query lacks too many points in this regard,you will appreciate.

Best Regards
Qalander(Chem)

 

[analystuc]

@LCrep
Fire sprinklers are not included in the design. Our proposed tank size is 54000 litres [14245 gallons], as a source for the pump. The system is designed for a cement bagging factory.
Thanks for the info so far.

 

[DavidCR]

You may also check NFPA 1 appendix H, for aprox. flow demand requirement for buildings as a comparison.

If the hydrants include the 4 1/2NH pumper connection, 6" pipe is recommended or required by fire service people, as LCREP mentioned.

From the drawings and thinking that a factory with paper or plastic bags will be involved..., I think there are lots of background about this design to explain why a 277gpm pump is involved in an industrial fire system.

The size of the factory and risks involved are not clear, is paper/plastic bag storage involved?, is there need for cooling exposed buildings with hoses?, what about sprinklers?, who will combat the fire (is the hydrant system for the private, or public fire brigade) and what do they say?, why 6" and 4" pipes for a 277gpm pump?, too many info needed to tell.