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PIPE HEADER 1

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Gearero

Gearero

Mechanical
Jul 7, 2021
9
thread378-341586
Hi Everyone,

I have 3 pipes with the same ID of 1200mm, and I need to design a header pipe for these three pipes.
Can anyone show me how to compute or design the needed header?

Your inputs will be highly appreciated.

Thanks!
 
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You may get a lot of complicated opinions on this, but mine is rather simple, as long as you don't have a complex case of many diameters, many flow rates and a spaghetti arrangement.

To have a more or less balanced flow in each branch, make your header diameter 1.33 x largest branch diameter.
.
 
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That is more like 3 branch lines departing from one supply pipe.. all the same diameter. The ratios of pipe flow area of each one to the total area of all branches will tend to set the flow into each branch, so they will want to be equal. Whether they will be equal or not depends on the downstream pressures of each branch.

If the flow to each branch is roughly equal, the velocity in the "header" will tend to reduce by 1/3 after passing the first branch and another 1/3 after the 2nd branch, but it will require that all downstream pressures near the header also remain roughly equal. The reduction of velocity at each branch, reduces friction in each succeeding section of the header, but that will not be significant, because the length of each segment is only a few meters.

As with all pipe flow analysis, you must know upstream and downstream pressures of each branch to determine the actual flow going into each one. If downstream pressures of the branches are different from one another, then flows could distribute unequally, otherwise flow area ratios will have the greatest effect.


 
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You need to look at flow and flow distribution.

Your header can generally be any size from 1200 upwards.

If you do the equivalent area method then you end up at 2 m diam.

So anywhere from 1200 to 2000 is my range.

Equal tees are a bit odd so you usually want to go to at least one pipe size above the branch but it's all about flow distribution and flow control.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
 
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I think you misunderstood that the water flows from header and it will branch outflow to 3 pipes..

This is the set-up Sir,

I have 3 water pumps with 3 discharge pipes of 1200mm inside diameter each going to 1 header (no pipe size yet), can I use the area method to calculate the header?

I really appreciate your inputs.. Thank you very much!
 
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I am actually calculating the size of the pipe header that will receive water from 3 discharge pipes with ID=1200mm each..
 
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Yes, the area method is as good as any other if you don't have any complex flow issues.

Can be a little bit conservative.

Also you don't seem to know which way this is flowing?

" water flows from header and it will branch outflow to 3 pipes"
then two lines later
"3 discharge pipes of 1200mm inside diameter each going to 1 header "

Which is it?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
 
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3 discharge pipes of 1200mm inside diameter each going to 1 header Sir..

Thanks..
 
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Is this the formula of area method?

D = sqr rt (4(A)/3.14)

where A is the Sum of the areas of 3 pipes
 
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Do all three pumps run at the same time? What I am really asking is "does the header have to cope with the flow from 1, 2 or 3 pumps"?

You cannot really design something like this without knowing the pressures and flow rates. It is common to use higher than normal flow velocities immediately after a pump discharge so you may want to design for a lower velocity in the header. This would make the header diameter larger than a simple area ratio would predict. On the other hand, the pressure drop in turbulent flow varies with the fifth power of the diameter so you might not need the header to have the same area (= same velocity) as the combined pump discharge pipes.

The header seems to be part of a main delivery line. If that delivery line is long then the calculation of its diameter would be more important than the sizing of the header and it might be possible to simply continue the size of the delivery line into the header.

Katmar Software - AioFlo Pipe Hydraulics

"An undefined problem has an infinite number of solutions"
 
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For header size just increase the header to a diameter of at least 1.33 x the diameter of the largest branch. That is usually enough to give a good distribution of flow to all branches.

Given same nearby downstream pressure for all branches, branch flows will be closely distributed in a ratio of each branch area of flow to the total of all branch areas.

If header inflow Q is 200gpm, Branch1 area is A1 = 25in2, branch2 area A2 is 50in2 and branch3 is A3=10in2

Branch1 flow Q1 will be approximately equal to
Q x A1 /(Sum of all branch areas)
Or
Q1 = Q x A1 / (A1+A2+A3)
= 200gpm x 25 / (25+50+10)

Q2 = Q x A2 / (A1+A2+A3)
Q3 = Q x A3 / (A1+A2+A3

 
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The pumps will be used at the pumping station, it can run one pump at a time or 2 pumps or 3 pumps all at the same time, depends on the level of floodwater.

The header will only act as a discharge pipe of the 3 pipes, regardless of velocity and pressure.. the only purpose of the header is to discharge the water all from 3 pipes.

Pump data per pipe:
Q=2cms

Pipe size : 1200mmID
 
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Thank you so much for your inputs!

Keep safe! :)
 
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Because you're doing it to go backwards, then you can simply do Diam header = SQRT(D1^2+D2^2+D3^2) as the PI term cancels out

So it is SQRT(3 x 1.44 x 10^6) = 2078. so say 2000 or the next smallest nominal size in whatever pipe you have available.

Possibly a bit big when you're only flowing one pump, but the other way of looking at this is what size pipe / pipeline is this header connecting to? It shouldn't be any bigger than that.



Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
 
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I agree with LittleInch ..... 2000 mm is nice and safe if three pumps are to operate at the same time,

But, you cannot do your job and confirm this because you do not have enough information .... like the damn massflow rate in each branch !!!

If you are laying out piping, you must know something about the pumps. What is the pump design point ?... Are all three pumps going to operate at the same time ?

Why don't you use massflow rates and calculate the velocity in each pipe ? .... This will size the header !!!

A design massflow rate of 9 - 12 ft/second is typical for pump discharges ...


MJCronin
Sr. Process Engineer
 
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Hi LittleInch and MJCronin, I appreciate your inputs..

For info, the header is connected to a surge tank which have another pipe to discharge the water.

The flow rate of each pump is the same which is 2 cubic meter per second.

Yes, I don't have enough knowledge on this because Im new at my job.. and I really appreciate you guys educating me. this means a lot.

Thanks!
 
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My suggestion will be,the first step, design the discharge pipeline.. The max. flow ( in this case if three pumps operates ) will be for a short time..The flow rate 0.9 m/ sec to 1.5 m /sec could be reasonable for the steady state flow. In your case, try to optimize the dia. of discharge pipe. IMO, you may adopt 2.0 m /sec for the max. flow rate.
 
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Another important issue that must be addressed is the pressure reinforcement necessary at each branch to header junction.

What is your piping wall thickness for your 1200mm pipe ? .... Has the wall thickness been calculated for your desired material ???

Every piping code has rules about evaluation of pressure reinforcement at fabricated branches and this piping forum has had many discussions about this. I believe that you must Perform a calculation as per ASME B31.3 304.3. If you don't satisfy the area replacement in 304.3.3, you will need a pad.

Evaluation of the pressure reinforcement pad (RF pad)at this stage of your project is important because it affects your layout of the pumps and thereby the locations of your branch intersections. You do not want welded RF pads (on the header pipe) to be "too close" or overlap by placement of the pumps "too close"

The gap between circumferential welds on your header pipe and your RF pad edge weld must be carefully considered also


Since you seem new to piping layout and design, you may not have considered this...

More info here:



This may help also:


The afternoon medication is wearing for this old Geezer .... Time for more painkiller

Keep us posted on your learning experience !!!


MJCronin
Sr. Process Engineer
 
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