Water Tanker 1

[Multiserv]

I got 57kw motor to run a 5" by 4" pump and the flow rate required is 3000l/min. i am not sure what kind of pipe material i am going to used to reduce the pressure loss in the pipe and the pipe diameter i am using is 4" then tee out to 3" pipes.
The purpose for this water tanker is for fire fighting and wetting the road, so it consists of 2 nozzles and a spray pipe. Is it ok to keep the whole pipe network in 4" pipe, even after it has split to 2 pipes before reaching the nozzles.

Any comments will be helpful to me.

Thank you

 

[Artisi]

as you probably only talking about a couple of feet pipe for the whole installation, 4" pipe should be fine.

Phitsanulok
Thailand

 

[Multiserv]

If the pressure in the main 4" pipe is 80psi. what pressure will be in the tee(Split) out pipe of 3" or 4" pipe?

 

[Artisi]

The pressure in the 4" pipe will only be 80psi if the nozzles and / or spray pipe impose this restriction. However, if the system operating head is 80psi, for an installation like this the pressure will be the same throughout the system.

Phitsanulok
Thailand

 

[Multiserv]

you mean if the 2 nozzles were turn on at the same time the
system pressure head will still stay the same through out the system?

 

[Artisi]

To answer this question you need to undertake a hydraulic study of the system.

There is insufficient information to give you any detail.

At the moment the only information we have is a flow 3000l/m
and a pressure of 80psi -- how are these 2 figures related to each other?

What are the nozzle diameters or flow rate at the presure you want to operate them at?

What is the flow rate for the spray bar?

What are the pipe lengths?

Also need a pump performance curve to make any sense of your enquiry.

Phitsanulok
Thailand

 

[Multiserv]

In the pump performance curve with the flow rate of 3000l/min, the pump will generate a pressure head of 56 meter. If the pressure head in meter needs to convert into PSI it has to convert to feet 1st then multiply 0.4333.This will give us 80PSI.

The total length for the pipe system is 13 meter including the 2 tee out pipes.
I am not really concern about the spray pipe because it got sufficient pressure to wet the road and the motor rev can be turned down to reduce the pressure so the water tanker will not have to refill every 10 minutes and during fire fighting situation the spray pipe will be shut off.

The nozzles diameter are 1.2"at the end of the tip, according to the table supplied by Nelson(nozzle company)the projectile
Water can reaches an estimated distance of 50 meter with 50psi at each nozzle. The flow rate for each nozzle will be 1500l/min.
My concerns is, if the tee out pipe kept in 4", will each nozzle still has the minimum pressure of 50psi.if using the rule of thumb, after the tee out the pressure will divided into half so if the pressure in the main pipe is 80psi and it is divided into half, it means each nozzle only left 40psi.This will not be sufficient to meet the minimum pressure for the nozzles.
If you have the formulas to determine the pressure or the pipe size after the tee out , it will be a big help for me .
Thank you

 

[Artisi]

The pressure is still 80psi at each leg of the "T". If both nozzles are operating the flow at each leg of the "T" will be halved at a pressure of 80psi.
However if you want to get very academic, there will be a slight pressure drop at every bend, elbow and T but not even worth considering for your application.

Phitsanulok
Thailand

 

[Multiserv]

Thank for your replied, i have already calculated all the loss es due to the fitting and the length,although the result was not large but the total loss still 7psi in 4" pipe. Anyway my last question is the tee(split) pipe should keep at 3" or 4" after the 4" main pipe?

 

[Artisi]

why don't you just stay in 4" less losses.

Phitsanulok
Thailand

 

[Multiserv]

i wish to stay in 4" but my boss want me to prove to him if the split pipe keep in 4", will it pressure still be sufficient for both of the nozzles, when they are turn on together.

just want to let you know the water tanker fire figthing capability is very critical in steel plant due to high fire hazard from the molten steel.In case the molten steel spill
on the vehicle or plant, the water tankers need to dump a huge amount of water on the molten steel to quench it.
So every advise from you is very valuable for me to be sucessfully design a capable fire figthing water tanker to save lifes.

 

[Artisi]

The 2 nozzles will govern the flow and pressure, if the nozzles require 50 psi to give a flow of 1500l/m at you have something nearer to 80psi at the upstream side of the nozzles, the flow rate will be greater. This means that the pumps could overload.

You need to undertake a full study of the"system" ie, pipe length, bends, nozzles etc to establish if the flow rate / pressure is within the capabilities of the pump.

However, as this appears to be a very critical life saving / fire fighting system, I strongly suggest that you get some professional advise in the design of this system.

Phitsanulok
Thailand