Hi
Recently I have been envolved in a pump trouble shooting project as a process engineer. A centrifugal pump is beeing used as a booster pump to transfer condensate from condensate coalescer to export line in an offshore gas platform.

Based on submitted work request, operators complain loss of condensate level control in production separator which is an immediate 3 phase separator downstream of production wells to separate water and condensate from gas. Separated condensate is gravity discharged to above mentioned coalescer. In some cases during operation which production flow is low operators have hard time too keep condensate level in normal range and usually low level alarm is activated by droping condensate level in production separator.

Although in such operating conditions operators close LCV (this LCV is located on pump dischrge to control the level of condensate in production separator by level signal input from level transmitter in condensate side) manually from DCS and fully open recycle valve but condensate level depletion has not been stopped. To prevent Shut Down activation by further condensate level drop, they have opened manual by pass live around reccle control valve to pass more flow through minimum recycle line and this has resolved problem.

As a design check I have done a CV calculation for this recycle valve based on retrieved operating conditions. The result is that recycle control valve can meet pump minimum flow on 75 % opening.

Theoritically every thing OK but there is no consistency between calculation and real operation experience.

They have also experienced regular seal failure which is a second problem about this pump and may be independent from above problem. Abnormal pump discharge fluid temperature has been reported too.

A simplified scheme is attached.

Does any body have similar experience to share about above problem?

Thanks
Majid

Majid,

Engineer likes drawing more than wording.

The way you present the flow sheeting a bit confusing... Readers need to guess...

Can you pls sketch in Excel sheet to provide necessary information, clear definition of unit, clear problem statement, etc so that CheJedies here understand and assist ?

Without proper understanding, any advice will just drive you to no way.

Joe,
Thanks for your comment. I have added a simple sketch to original post.

Majid,
Thanks.

I have some comments in the sketch.

Click to view attachment

I guess Joe and I are on the same wave length.

The attached workbook contains my revised sketch which is a copy of what I have always basically designed and has worked for me. Note that it is greatly simplified and I always ensure a positive pump liquid feed by NOT ELEVATING the suction line and forming a vapor trap. I also always equalize the vapor spaces of two vessels - never the connecting lines.

Note how I control the level of the last vessel. This can be done differently - usually with another control valve, if you don't like 3-way CVs.

I find this scheme to be much simpler and with less controls and capital costs.

I hope this experience helps.

Click to view attachment