Avoiding Spring at Pumps

[Dj364]

Hello every one,
Is designing piping layout at pump discharge nozzle ( downstream) as 180 deg elbow( 2x90 deg) could avoid putting spring hanger? ( because of adding flexibility?).
I haven t gone thru calculations.
Just want to know from your experience.
I will appreciate any comments.
Dj.

 

[BigInch]

Probably not more flexible, unless there is length and preferably some offset between the 90º ells, and a much worse configuration for pump piping. Try turning the pump around and get rid of the 180.

http://virtualpipeline.spaces.msn.com

 

[NozzleTwister]

Dj364,

Are you talking about a Top Discharge and turning the discharge piping 90 deg. and going out beside the pump and turning down, then running you pipe along side the pump foundation with the valves in this section, then turning back up again and routing your piping where it needs to go? If you do this, the horizontal section with the valve should be at the same elevation as the pump support point to cancel thermal growth.

This is a great way to provide flexibility and support the piping load without springs and putting minimal loads on the pump nozzle. I have done this numerous times.

This layout used to be more popular in the past than it is today. Some previous clients have insisted on this configuration to avoid spring supports. The down side is that it has pockets, is not free draining back into the pump, takes up valuable space you may not have and might block maintenance access to the equipment.

To prevent the pocket you could turn out and stay flat but this may not eliminate a spring on a hot system.


NozzleTwister
Houston, Texas

 

[RossABQ]

Hard to believe this would work to completely eliminate spring supports with piping say > 4" diameter, CS piping, etc. The offsets described (to the side of the pump pad) are not that great to provide much flexibility in large sizes.

 

[Dj364]

Hello,
sorry for the delay,
Nozzle twister, you said that you have done this many times , and it worked? could you state one of your previous experience ( size, design conditions)? it will help me a lot.
The layout is top discharge, going up then going down using 2x90 elbow, then elbow(90)straight line and going up (elbow 90) again. check valve is in straight run, isolation valve upper run and close enough to be operated.
In this design
1-I don't see any problem for maintenance access.
2- How does pocket affect since it s pressurized line?
May be a discharge cavitation may occur,and the pressure causes the majority of the fluid to circulate inside the pump instead of being allowed to flow out the discharge.
Please correct me if I am wrong,
your comments will be very much appreciated.
Thanks.
Dj.

 

[NozzleTwister]

Dj364,

Experience: Refineries, 500-600 deg. F., 6" or 8" NPS piping is about the limits that I've used this type of configuration.

You scare me with the '2x90 elbow' term, I think you're talking about back to back elbows making a 180 turn, I don't do that.

Normally you'd come out of the pump with a reducer (swaging up) and an elbow. You can have a pup piece between the reducer and elbow. Then you may not have room to go directly to the side, so your horizontal pipe can angle towards the suction end and then 90 down. The turn down and 90 back with the optimum elevation being the same as the pump mount elevation. For an API pump this would be at the centerline of the shaft, for an ANSI pump it would be lower. The idea is to support and restrain your pump piping so the thermal expansion difference is negligible between the support/restraints and the pump nozzle. You can adjust the elevation of the first elbow on the discharge as required for all the fittings to fit with pipe between, valve placement etc.

The problem with the pocket is that that section of pipe is not free draining back into the pump and requires an extra drain valve. For Process piping, that's an extra drain into a process sewer.

The purpose of this type of configuration is to eliminate the requirement for spring supports to support the pipe loads and the extra elbows and pipe length give much more flexibility than just coming straight up out of the discharge nozzle with reducer, block valve and check valve and then turning straight over to the spare pump's piping.


NozzleTwister
Houston, Texas

 

[Dj364]

Hello NozzleTwister,
Thanks for your valuable explanation,
I've rarely seen this type configuration what you described above. At the present most of pumps discharge lines are like going up after reducer check+block valve..etc..
Even the piping designer, whenever he has design the discharge High Temp, he puts a spring hanger on the first elbow then going into the rack.

Isn't it worth to put drain (drain valve)and connect it to whatever is the system ( sewer ), rather than having a
spring hanger with its maintenance.
Regards.
Dj.