Misallignment/deflection acceptance limit for VTP

[sowhatso]

Dear friends ,

for a deep water well with 10" casing , 8" vertical turbine pump is planned to be installed. can you tell me what is the accepted range of deflection for a vertical turbine pump to be installed inside this well ( Degree of deflection / Unit meter ), any input is highly appreciated .

Thanks

 

[BigInch]

Deflection of what in relation to what?

Torsional deflection, vertical deflection?

Degrees would imply you're interested in a torsional rotational deflection on pump starts and stops. You may also have some vertical deflection due to weight of pipe string and pump.

http://virtualpipeline.spaces.msn.com

 

[Artisi]

Is this a line-shaft driven vertical unit?

 

[sowhatso]

The unit is line-shaft driven vertical unit , I need to know the limit of the vertical misalignment ( inch / foot ) for the 6" steel riser column pipes inside the 10" casing.

 

[Artisi]

Are you referring to the allowable bending (straightness) of the riser/shaft because the casing is not straight and deflecting the pump riser/shaft - I çan't give you any figures but bear in mind that due to the down thrust on the impeller when it is operating, the shaft is trying to straighten itself, this of course puts a lot of load onto the lineshaft bearings.
If the casing is straight but off vertical this should not cause any problems provided the column/shaft remains "straight", however, you might need some casing/riser stabilisers to keep the riser central in the casing if the casing is not vertical and there is the risk of the riser being deflected from "straight" by the casing.

What I am trying to say is that a lineshaft driven turbine pump can be installed anywhere from vertical to horizontal provided the riser is maintained straight and isn't allowed to sag or be deflected.

 

[sowhatso]

Dear Artisi ,

I have a misalignment with the casing ,it is about 0.6cm/m with two sections of pipes( 2 X 12 ), the misallignment started from 170m depth to 190m depth with a rate of 0.6cm/m to the right direction, I suppose that during lowing the 6" riser pipes with the pump I will hit the casing with the possibility to cause deflecting to the riser pipes.as you said we will have load onto the lineshaft bearing which will quicken the failure of pump. due to the location and rate of misalignment of casing I think using the stabilisers will not prevent the deflection.

Artisi , I`m concern to know the maximum accepted value of deflection that we can run the pump with it with no direct effect.


Thnaks alot for your help and input

 

[Artisi]

I cannot give you any indication what is aceptable for line shaft deflection but would think there is very little as it must be straight otherwise you will have high wear rates on the line shaft bearings.

As it is a 6" riser in a 10" casing you do have considerable clearance so you need to measure the OD of the riser and the ID of the casing and then either calculate or model (draw) the riser in the casing and see if it will pass the bend in the casing without deflecting the riser.