Pipe Flow Calculation

[PurewaterGuy]

I have a TOTAL of 200' of 1" pipe, the pipe runs along the floor at the baseboards on three walls, and doubles back mirroring itself. The outgoing pipe has 13 1" elbows.

The return pipe has 15 1" elbows.

The distribution pump feeding the loop is rated for 5 GPM.

The loop returns to a PRV on a 150 Gallon storage tank.

The sustained pressure on the pumps will be 60 PSI.

What is my actual flow rate?

Is this enough info?

Thanks

 

[cvg]

what type of pump? what does the pump curve look like?
what type of pipe? new or old pipe?
what is the pressure drop from one end to the other?
are they 22, 45 or 90 degree elbows?
are there any other fittings such as tees on the line?
pumping water? at what temperature? is it clean water?

 

[PurewaterGuy]

Grundfros pump

+GF+ Poly, New pipe

Zero pressure drop with no equipment running

90 degree elbows, one 4' rise between two elbows

6 Tees with 1" Ball Valve attached (I have them closed)

From each Tee to the BV there is less than three inches negating a dead leg

Pumping RO water

77 degrees F

Does this help?

 

[katmar]

If the 200' of pipe includes the return piping you will have something like 3 to 5 psi presure drop at 5 USgpm flow. The actual flow will depend on the actual pressure drop, which seems to me to be the difference between your pump pressure and the set pressure on the PRV.

Katmar Software
Engineering & Risk Analysis Software

http://katmarsoftware.com

 

[bimr]

Your velocity is so low that the pressure drop in the piping is minimal and may be ignored.

The flow rate will be whatever rate that you set on the PRV.

Note that your flow rate is too low for a 1" ultrapure water ditribution loop system. You should have a flow rate that allows a loop flow velocity of 3-5 ft./sec to minimize potential water quality problems.

 

[PurewaterGuy]

More info.

I called the Webber rep for Webtrol. The pump is Webtrol model # H5B6S16-3PH

The rep says 5 GPM but can be set as high as 10 GPM

I took the readings today with all the equipment running. The pressure at the pump was fluctuating between 50-60 PSI

The return to the tank was fluctuating between 30-40 PSI

The pump is connected from a 150 Gallon Storage Tank by way of 1" pipe.

Thanks

From this info and the info posted previously, are we able to calculate the GPM?

I need to add a 20" 0.03 Ultrafilter to this loop.

Will this present a flow problem?

 

[katmar]

That pressure drop seems high. There are many different sizes of 1" pipe available so the calculations would be more accurate if you could give the actual pipe inside diameter.

Katmar Software
Engineering & Risk Analysis Software

http://katmarsoftware.com

 

[bimr]

Pull out the Webtrol pump curve. Where the pump curve intersects 50-60 PSI is the operating point. Go straight down from the operating point and read the pump operating flow on the lower axis of the pump curve.

 

[PurewaterGuy]

I pulled up the pump curve chart.

At the 60 PSI intersect it states 3 GPM

At the 50 PSI intersect it states 6 GPM

So am I correct in assuming that when the pump PSI is fluctuating between 50-60 PSI that the flow rate varies in between 3 and 6 GPM?

Is the pressure drop at the return to the storage tank attributed to the amount of fluid being pulled to the operating equipment?

Thanks

Thanks

 

[bimr]

Yes, the pump operating point will always be on the pump curve.

One would thing that the pressure drop at the return would be the sum of the PRV pressure drop plus the pressure drop attributed to the amount of fluid distributed to the equipment.

 

[PurewaterGuy]

If I add the 0.03 Ultrafilter into the loop, I imagine there will be some pressure drop as the fluid passes through it,

Should I expect the pump PSI to rise? even slightly?

Should I be able to adjust the return to the tank accordingly and create more back pressure toward the Ultrafilter?
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Do you think this would be a good thing to do?

1)Shut down the loop and all equipment
2)Add Ultrafilter
3)Turn on the pump adjust so complete loop pressure is 60PSI
4)Turn on equipment and set PRV accordingly

 

[bimr]

You should get the vendor information for the ultrafilter. There should be a manufacturer's data sheet that lists the headloss across the filter at a certain flow capacity.

You have 50-60 psi available. At that pressure, the ultrafilter manufacturer should be able to tell you how much will pass through the membrane.

If the headloss across the ultrafilter is too high, you may not get any flow across the ultrafilter.

It looks like the typical ultrafilter needs 20-30 psi pressure to operate. What will happen is that your pump operating point will slide to the left on the pump curve to compensate for the additional pressure loss through the filter (assuming that you are trying to keep the same flow).

As the pump operating point moves left, your pumped flow decreases while at the same time the pressure is increasing.