Two pumps connection

[Paciallas]

Hi to ALL.

I would like to ask what do you think about connection of two pump, where suction line of pump 1 is rooted directly from discharge of pump 2 (process medium flow through air cooler and then part of it is rooted to pump 1)? What disturbances could occur in such configuration? Process medium is diesel oil, about 40 t/h (pump 2) and 15 t/h (pump 1), discharge pressure of pump 2 is about 4 barg. In attachment I place a simple sketch, without any valves and PIA devices.

The designer claims, that such solution will not work properly and may cause big problems with the new one pump. I have no experience with this. Have you ever saw refinery where pumps work in such configuration?
I have never met such arrangement but also I have never met any standards saying the pumps should not be used this way.

 

[LittleInch]

Pacialias

It's "routed", not "rooted".....

This is a standard arrangement, but you need to look at the whole system and the impact of adding pump P1

E.g. will it lower the pressure at the tie-in point or will the flow to the "others" be controlled to avoid this? As the pump starts the inlet pressure might fall until it equalizes with the other system.

Where is your flow control ( if any)

The pump P1 needs to be designed with a max inlet pressure of 4 bar, but that's not really a very big pressure. Clearly the output pressure / head of pump P1 will be max 4 bar plus the differential head of the pump.

There may be other reasons we don't know about as to why your designer would think this, but on what you've given us so far, I can't see any major issues. Ask him or her what the issue is then get back to us.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Paciallas]

LittleInch, thank you for response.

In my opinion, the flow controller should be in the discharge pipe of the new one pump and I will suggest this to the designer. It should be enough to avoid any problems with the whole system. "The rest" of diesel oil is directed to the surge drum so I think this solution is properly.

As I konw the main reason the designer do not want do this arrangement is he has never seen such solution (frankly speaking I have not seen it too). Could you give any examples where such solution was implemented? It would be very helpful with my discussion with designer.

The second thing to consideration is if such arrangement will not cause any problems with work of the new one pump, e.g. if P2 pump will emergency shut off.

 

[mk3223]

It's a good start as shown on your sketch for the design of a system. And, then, you can consider different design options to improve the design, or add the control and PIA for the possible operation issues, such as flow control, overpressure issue, shutdown protection, etc., to make the system work.

 

[Paciallas]

Thanks. Of course there should be considered additional PIA and shutdown protection, etc... I have attached only a simple idea, i left the rest to the designer.

If I show him that such arrangement is used somewhere, it should be the strong argument to convince the designer. So please, can anyone give me such information?

Best Regards

 

[LittleInch]

Paciallas,

Quite frankly I would get a different designer.

The system shown is very common and if he or she hasn't seen it before then they won't be able to design it very well with all the requisite alarms and trips, control system etc. All you're doing is taking a supply into a pump from a pressurised supply. What is unusual about that?

If you're the client / owner then it's your choice who to use.

It's not our place to provide you with examples.

LI

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Paciallas]

Thank you for response.

Best Regards