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How to sizing the pipe diameter for additional Fire Pump

How to sizing the pipe diameter for additional Fire Pump

How to sizing the pipe diameter for additional Fire Pump

(OP)
Hopefully you guys can help me here. I'm a fresh graduate mechanical engineer. I have a task to do a sizing an additional new fire pump and designing the piping system for it. After doing the pump performance it was decided to add new pump with capacity 2000gpm to the system.
My questions are:
1. how to check weather the chosen pump specification is match what the system needs?
2. how to design the piping size due to the pipe will be connected to the existing fire header (the header pressure is maintained at 10kg/cm2)?
3. Whay is the other things that I need to consider?

thanks for the response...
Hageshii

RE: How to sizing the pipe diameter for additional Fire Pump

It depends what you are actually trying to achieve.  Higher pressure?  More flow?  Better reliability?  When you define the question it is easier to find the answer.

Katmar Software
Engineering & Risk Analysis Software
http://katmarsoftware.com

RE: How to sizing the pipe diameter for additional Fire Pump

(OP)
What we are trying to achieve is to get more flow, that is why we decided to add a new pump with a certain capacity, which is 2000 gpm. My next task is to design the piping system n to define the pump specification, such as head, etc.
Any suggestion where I can start?

Thank you for the response.
Hageshii

RE: How to sizing the pipe diameter for additional Fire Pump

You still haven't even begun to define what you are trying to do. I guess your new pump will be in parallel with existing pumps?  Learn how to combine the pump curves of parallel pumps into a single combined curve.  Plot the system curve for your piping system on this pump curve.  Where the system curve and the combined pump curve intersect is your answer.

Katmar Software
Engineering & Risk Analysis Software
http://katmarsoftware.com

RE: How to sizing the pipe diameter for additional Fire Pump

(OP)
In my opinion, I need to calculate the pipe diameter first, then calculate the head loss, and get the system head, then  I wil get the required head pump. Is that correct?

To get the pipe diameter, I need to know what is the allowable max and min speed of the water inside the pipe for fire fighting purpose. I have trying to find in the internet, they said that the speed should be 5-10ft/s, is that correct..? so from the flow and speed, I will get the pipe diameter.

I still confuse how to calculate the head loss for the pipe that is connecting to several pump, any advise?

thanks for the response, sorry for my stupidity :(
Hageshii

RE: How to sizing the pipe diameter for additional Fire Pump

Yes, you work from the diameter to calculate the head loss.  If the assumed diameter does not give you a system curve that intersects your pump curve at the correct flow and head combination then try a different diameter.

10 ft/s is probably a reasonable velocity for 2000 gpm. I am no firemain expert, but I would think that having sufficient pressure at your hose points and fixed cannons would be more important than the velocity.

If your firemain is fed from a bunch of pumps at one point then the pipe pressure drop calculation is not affected by the number of pumps.  The pipe sees the combined flowrate. (Of course the manifold between the pumps and the main must be properly designed.) But if you have pumps in several places along (or around) the main then you have a much more complex situation and you will need to use software for pipe networks.

Katmar Software
Engineering & Risk Analysis Software
http://katmarsoftware.com

RE: How to sizing the pipe diameter for additional Fire Pump

A bit of the surprise that you have picket your pump and now are going to design your pipe. Normally it's vise versa! the correct design direction would be
- Setting the required flow
- design the piping system to calculated the friction losses and required pressures at the outlet taps (demand nodes)
- selection of the pump having the flow and head

That being said, there are usually regional code and standards to define the system requirements in respect of the fire flow and minimum available pressures at the demand points. i suggest that you look for such standards depending on your location, city, state, country and the industry you're dealing (an oil rig has certain considerations over a fire tap in a city) to go along with the standard.

This is are my thoughts for question 1 and 3. For question 2, you have your pump so you have the flow and head. size your system (pipes and valves) so that you get the required pressure (10kg/cm2) at the demand. you can try Epanet for this.
 

RE: How to sizing the pipe diameter for additional Fire Pump

hageshii,
You wrote:
"My questions are:
1. How to check weather the chosen pump specification will match what the system needs?
2. How to design the piping size due to the pipe will be connected to the existing fire header (the header pressure is maintained at 10kg/cm2)?
3. What are the other things that I need to consider?"

Answers:
1 If someone has already defined the spec for the new pump and the pump is purchased then there is no reason to check.

2 If you already have an existing Firewater distribution header and you have the new pump nozzle then the connecting line will be a minimum one size larger than the pump discharge nozzle but not larger than the existing header.

3 (a) You might consider trying to find out why this was done in such a manner. and (b) you might want to consider looking for a job where the people are more professional.

 

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