5 replies to this topic

[arvind]

Hi to all,

before I start I would like to tell you about my self.
I am Arvind working with detail engg contractor as a process engineer in India.

I am working with PTA ( purified terephthalic acid ) project. and facing some problem regarding pump MCF line.

For the two pumps one working and one standby with pressure auto start arrangment I have seen the three arrangment:

1) Either pump is connected with common MCF line (design with considering single pump MCF)
2) Either pump is connected with common MCF line (design with considering combined pump MCF)
3) Each pump with their own MCF line ( i.e individual MCF line to the suction vessel)

I am facing problem for to which case I suppose to go for? And what are the criteria for the same ?

Your reply is highly appreciable

Regards

Arvind :

[katmar]

Hi Arvind,

Before I get to trying to answer your question I have a request. Please avoid abbreviations like "MCF" because they can mean different things to different people, and can be especially troublesome to non-native English speakers.

Assuming MCF stands for something like "Mininmum Circulation Flow" I would suggest that you look at the valving on the pump discharges and how the valves are operated. If there is a likelihood that the MCF line will be isolated from the pump at the very time when it is needed for the pump's protection then you need to move the connection. Based on this logic I would select your option 3.

[JLMONTREAL]

The most important point is to avoid slurry block in the pipe when one pump is standby.

[Cheetha]

Hello Arvind,

All 3 types of pump minimum continuous flow (MCF) protection is used in the industry. However, based on the operation philosophy of licensor and end customer experience, you have to decide.

As you have said 1Working+1standby philosophy, the MCF line is to be designed for MCF of the single pump and not for both pumps. Aghain check with your Licensor about likely hood of both pump operating in parallel.

Also, option 3, each pump having it's own MCF line before the 1st isolation valve is the best possible option.

However, when you are using option 1, ensure that MCF lines are located in such a way that this line doesnot get disconnected when either of the pump is isolated.

Request you to put the P&ID or the scheme in drawing alongwith your query so it becomes clear while explaining.

Regards,

[arvind]

Thanks Cheetha for your valuable response for the subject.

Here I have attached two pdf file for the pump recirculation scheame
In 1st sketch Minimum Circulation Flow ( MCF ) line is tap-off individually from the either pump before isolation valve where as in the 2nd sketch it is tap-off from the combined discharge line to the suction vessel.

And either pump is with ROP ( restricted orifice plate ) kindly suggest for what is the design criteria for the selection of the scheame .


Waiting for your valuable info.


arvind

Attached Files

•  PUMP.pdf   942.01KB   162 downloads

[flash]

Per your drawings it looks like you are always going to circulate some liquid back to the suction vessel. This arrangement will consume excess power and heaps of energy will be wasted for no reason. Instead why do not you consider minimum continuous line under flow control?