Alignment Checking

Dear All,

I just want to know if it is needed to perform the alignment checking if the pipe connected to the pump suction has a "rubber bellow"? Based on my initial result, the displacement of the flange connected to the pump nozzle at load case WNC+H is reaching 168 mm. It exceeded the allowable displacement set by API RP 686 of 1.5 mm.

Thank you and hope for your reply.

Regards,

marchie

Sounds to me that you have a spring near the pump that is excessively pushing the pipe up in the empty condition which is a poor design or something else is wrong. Sustained displacements of 6.6" (168 mm) is completely wrong.

Expansion Joints are not intended to permit the fit-up of improper piping design.

While we don't know the size of your pump/pipe, I'd also hazard an assumption that such a displacement even in the operating case, could result in deleterious effects on the pump operation.

Have you considered Rubber expansion joint as flexible for alignment check?

In my opinion, generally locks/transportation bars are removed after correct piping installation-assembly, just before commissioning, so expansion joint will be non-flexible during the alignment check. Of course, the suction piping shall be properly supported and spring supports if any shall be correctly sized.

Marchie,
This is common problem if there is expansion joint on pump/equipment nozzle. Expansion joints are flexible and can show large displacement in alignment check. As rightly pointed out by Sigma, expansion joints will be provided with transportation bars which needs to be removed before commissioning.