Tank to pump drain/hose size

[neiowa]

I'm looking for a formula to estimate expected flow thru a given size tank drain thru hose to suction/intake side of pump.

Existing tank drain is not as large as I would spec if ordering. But is what, it is, and would rather not cut it out a replace if we can get sufficient flow to keep up with the portable pump. In this application pump will be used to pump the water off tanker into a portapond (volume not pressure applicaton). Pump is a CET 18hp Honda - rated at 600gpm/0psi has a 4" suction intake.

[neiowa]

Anyone???

[npfd801]

Will this thing help you? There's so many variables, I'll look through some of our sprinkler stuff and see if I can find something relating to this. Obviously you'll only be pulling the water out of the tank at what atmospheric pressure can give you, which should simplify things.

Flow capacity of steel pipe

I'll keep digging.

[neiowa]

Thanks but I don't think that is the applicable situation as the centrifugal pump is pulling a partial vac/suction. Not just gravity drain. I think. The tank drain I'm working on has nominal 2" camlock fitting.

The link shows 4" has 260gpm for gravity/atmosp drain. We have a portable pump rated at 350gpm (285 ft hd). When I have hooked this pump up to a 60ft of 4" suction line to a water storage tank I can get 500gpm output from the pump (which corresponds to the pump curve). So I don't think the 2" = 45gpm max is correct.

[neiowa]

I found some info at gouldspumps.com

The Suction pipe should never be smaller than the suction connection of the pump, and in most cases should be at least one size larger. Does not directly address the possible flow from the tank drain but says can have vortex and air pocket problems otherwise.

[Thrilbilly61]

I am told that the 3in. standard valve with a 3.5 to 4in. pipe will flow around 650 gpm on your standard fire pumper. Waterous offers a 3.5in. valve which when paired with the 4in. piping will flow over 700 gpm.

[CaptOldTimer]

?? Why don't you check with NFPA on what is the standard for this operation!

[neiowa]

NFPA sets engineering standards, not the laws of physics or hyraulics.

[kfactor]

neiowa,

That's a pretty straightforward fluid mechanics calculation. Need some info though. Assuming the pump is at 0' elevation, what is the elevation of the bottom of the tank and top of the tank? Bottom of the tank elevation will be min flow, top will be max. Also need approx I.D. of tank to suction piping/hose and material of construction along with suction pipe/tubing length. If there are any valve, etc. in the suction line, need to identify those as well.

A centrifugal pump creates no "suction" or "vacuum." The calculation with regard to flow rate available from the tank is primarily dependent on two factors - the energy comes from gravity and the losses that are associated with the exit from the tank, the piping/hose, and any other fittings/valves, etc.

Also, with regard to flow available from the pump it will always pump somewhere along its curve. Where it ends up is dependent on both the characteristics of the water supply and suction/discharge piping,hose, nozzles, etc.

If you provide the information mentioned above, I'll run a couple calcs and post it. If you want to try it yourself, it is the extended or modified Bernoulli equation. You'll find it on the web with a simple search.