Pump Head & Thrust Forces

[JoelTXCive]

I have a question regarding thrust forces. Please be kind..I'm just the lowly structural guy who's overworked and under-appreciated by all the mechanical engineers.

I need to design the anchor bolts and supporting steel framework for an Axial flow pump. I want to make sure I'm accounting for any thrust forces if they exist.

The pump has the motor at the top; and the actual pump at the bottom.

In our current design; we need to lift the water about 16ft. Our pump will introduce 16ft of head to the system, then the water will be lifted.

Am I correct in saying that all the thrust forces will gone after the lift? The system will basically be returning to gravity flow?

See below cut sheet we received from the pump salesperson. My mounting bolts will be located at Point 'A'.

Thank you in advance!

 

[1503-44]

It's not free fall until the water hits the air.
Theoretically thrust forces reappear at every change of momentum. Momentum is a vector quantity, so they are at every change of direction in flow. The extra 90° bend isn't going to help. Now add internal pipe pressure forces P x A[sub]pipe[/sub] shear load to the anchor bolts. 10K gpm = lots of flowing mass there. Fortunately pressure is not so high, but a 20" has a lot of area.

Weight of pump, pipe, water column in the suction pipe and the motor, plus the weight of discharge pipe and contents, all be supported vertically.

There also is the potential short-circuit torque load from the motor.

 

[JoelTXCive]

Thank you 1503.

I'm partway there now. My 10,000gpm on a 20" pipe results in a velocity of 10.21 feet per sec.

Do I have enough info to determine how much pressure would be left after the lift though? I'm thinking that nets out to zero; or near zero.

Using one of the online helpers, with my velocity (10.21 fps) and IF I'm down to 5psi; then I'm only dealing with a 2.85 kip thrust force on a 90-degree turn. I might be able to work with that.

 

[1503-44]

Looks about right. 50 Hp will only lift to the 17 TDH, with the LWL where it is, that's 4ft over the discharge centerline. I only get a couple of psi pressure.