5 replies to this topic

[linda_pro]

Dear all,
my client has problem in their operation.
they pump oil from CPP platform to FSO at pressure from 1 (LL) to 4 (HH) barg.
in case of minimum flowrate, pressure of fluid is 1 barg which make the PZLL activated and shutdown their system.
To avoid this, they want to increase the pressure of discharge pump by installation of a Restriction Orifice on this line.
The main pipe size is 12 inch and orifice size is 3.5 inch. Their idea is based on the change of pipe area, it will increase the pressure at upstream of RO and based on back pressure, the pressure of fluid at all points will be increase which will be higher than 1 barg and then their system will not be shut.

Honestly, I just know RO used to control minimum flow, and reduce pressure.....
I've never done any thing similar like this.

any one has experience about this or if you have another idea can increase the pressure, please advise me

many many thanks..

[Zauberberg]

If you spend a couple of minutes in preparing a clear sketch of the system, that would make things so much easier for everyone. This way, I am not 100% sure if we can understand what are you speaking about. There is no information about the pump (reciprocating, centrifugal?) itself, nor about the pressure sensing signal, and why pressure goes low in case of "minimum" flowrate (what do you consider by the "minimum"?).

As you can see, a lot of basic information is missing. I doubt you can get any serious response on your query unless you come up with the minimum set of data required to make comments.

[linda_pro]

Thanks for your comment Zauberberg,
see attached P&ID.
as i understand, client usually pumps oil from CPP to FSO at max operating flow of 50000bopd. Dischange pump pressure in this case is about 3 barg
However,at currently, oil is pumped to FSO at minimum flowrate of 15000bopd which produces discharge pressure is 1 barg equal ESD pressure of pump of 1 barg.

When discharge pressure of pump is 1 barg, the ESD will be activated and trip the pump, and then oil can not be pumped to FSO.

However, client sill wants to operate at this condition and then they want to find out a solution to increase pressure of discharge pump. the installation of RO is their way to increase pressure to over 1 barg which is out of shutdown signal.

I've never seen this solution before then my question is this solution can be use and if it is efficiency for a 12inch pipe size.
secondly, if I should consider the cavitation at downstream of RO which may occur and damage the pipe, instrument.....

Hopefully my writing is clear enough

thanks in advance for your help

(Heyzza..writing in English is not really easy )

Attached Files

•  P&ID.pdf   158.2KB   68 downloads

[Art Montemayor]

We still don't have the very basic and essential requested information: what type of pump(s) is being used?

I suspect that it is one - or more - centrifugal pump(s) that are feeding the FSO. If so, how is the centrifugal pump(s) protected against minimum flow? I doubt a centrifugal pump would have a 3:1 turndown ratio on capacity for continuous service on this type of application.

What is being proposed is nullifying the existance of the pig receiver. The pig receiver is there for a purpose - to pig the 12" line. By installing an RO in the flowline upstream of the pig receiver, there can be no pig passage through the line. Is this true and OK?

I recommend the transfer centrifugal pumps be controlled for flow at the pump discharge - not downstream. Surely these transfer pumps have capacity control (discharge throttling) and minimum flow protection (other than a plain shutdown). If that is not acceptable, then throttle or install an RO in the flowline DOWNSTREAM of the pig receiver.

[linda_pro]

I don't have any informaton about pump yet. they just give me that drawing and explain to me what happened with their system and what their solution is.
They aware the pig receiver and then they will install RO on a by-pass line.
And the by-pass line is used when pump runs at minimum flow. (I guess this will be fine)

I will discuss with Client about the transfer pump be controlled for flow as your recommendation.

Thanks for your help, Art.

Rgds,

[Art Montemayor]

My comments and my recommendations may be well off-base, and wrong because of the lack of detailed basic data - but it seems (from what you describe) that what is being proposed is practically and economically the wrong solution.

A 12" by-pass will require a minimum of two 12" block valves and a barred Tee - plus all the associated piping and the RO. And I'm not even accounting for the downtime.

A 10" control valve on the same line will probably cost the same and maintain the pump discharge pressure constant - regardless of the capacity - for approximatly the same cost. And you can still pig the line if you put the CV close to the pump(s).

Good Luck.