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Pumping Liquid Hydrocarbons At Their Bubble Point

bubble point pump npsh

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#1 immy_huss23

immy_huss23

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Posted 14 July 2014 - 04:34 AM

Hi,

I am doing some concept level design work and I am quickly sizing pumps and layouts (like their elevation differances from the source etc) and some of the pumps are for liquids that have either been flashed from a gas stream or reflux streams. The issue with these liquids are that they are either on or near there bubble points, so there is a particular importance to prevent vapour breakout and cavatation.

What are good (and simple) design practices that you can in out in place to make sure you have sufficient NSPH? Such as sufficient drop in elevation rom source to benefit from static head and good piping layout etc etc



#2 PingPong

PingPong

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Posted 14 July 2014 - 06:42 AM

Most pumps in the petroleum and petrochemical industry pump liquids that are at their bubble point, so that is nothing special.

 

As you already know, the elevation difference between lowest liquid level and pump impeller eye shall be enough to assure that the available NPSH (NPSHA) is higher than the required NPSH (NPSHR defined by pump vendor).

The pressure drop of the pump suction line (including vortex breaker, valves, bends and pump suction strainer) shall be low enough to assure that NPSHA > NPSHR.

 

Moreover the pump suction line shall not have any high points, where a gas bubble might accumulate that at a certain point might get pushed into the pump. For gthe same reason a reducer at the pump inlet nozzle shall be excentric with the straight side at the top.

 

For a bubble point liquid NPSHA is a function of elevation difference and suction line pressure drop, so it is just a matter of doing a simple calculation that can even be done by hand. That's all.






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