Static Suction Lift (Pipe "up and over")

[lh-chem-eng]

In this example, the static suction head for the pump at point D is -2m right? not -4m right?

I believe so on the basis that pumps don't suck, it is atmospheric pressure which pushes fluid into the pump, through the pipe (A to D), once the pump creates a low pressure at point D (high to low pressure allows the fluid to flow through the pipe). In that case the -2m lift makes sense, however if I try and think of it where the pump "sucks", then I can't get my head past the fact there is a 4m lift, rather than just 2....

The -2m lift is correct right? Once at point C, the fluid is flowing by gravity and a syphon is occurring? Where does the syphon start at point C, or mid id way past in the pipe between point A and B?

 

[goutam_freelance]

Static suction lift is -2m is correct. But the arrangement of suction pipe is problematic. Priming will be a problem. Also air may accumulate at high point and impair pump functioning.

Engineers, think what we have done to the environment !

https://www.linkedin.com/in/goutam-das-59743b30/

 

[1503-44]

It is -2m when the suction pipe is full. When priming it is effectively -4m -pipe and fitting friction losses -pipe inlet loss in the basin- vapor pressure of the fluid.

 

[TiCl4]

Additionally to 1503’s correct statement, priming may be impossible with that arrangement. If the liquid flow through that inverted loop seal during priming is not high enough to carry the air along with it, the air will remain in the loop, meaning a full prime will not be achieved. There is a reason suction priming piping is generally recommended to slope slightly upwards to the pump.

 

[lh-chem-eng]

Thank you for all of the responses. Good to know I was on the right track, and just as importantly that I need to be very careful to consider priming, and even that it may be very problematic. Much appreciated. Luke