Flooded Suction 3

[EmmanuelTop]

Good evening from Muscat,


After finding so many references related to the "flooded suction" term in process design literature, this particular subject is still not clear to me. Can somebody shed additional light in resolving this issue, regardless of the type of pump being employed in any service?

What does the term "flooded suction" mean, irrespectible of the pump type?

http://antwrp.gsfc.nasa.gov/apod/astropix.html

 

[dcasto]

I'd say it means having enough NPSH to assue no flashing of the liquid and a proper piping arrangement so that ther are no high point traps.

 

[roker]

hello,

sometimes it is specified as ample for the NPSH AVAILABLE so the required NPSH as specified by the pump supplier is generally lower enough (at least 1 meter difference).

In any case my recommendation is to calculate the NPSHavail and compare it to the required.

regards,
roker

 

[25362]

From Pumpworld:

A Suction Head exists when the liquid is taken from an open to atmosphere tank where the liquid level is above the centerline of the pump suction, commonly known as a Flooded Suction.

 

[MJCronin]

Emmanuel.....

25362 is correct..... whenever the normal operating level of the liquid reserviour is above the pump centerline, it is considered "flooded suction"

The opposite of "flooded suction" is the case where the pump must pull the liquid up into the casing. This occurs whenever the pump is located above the NOL of the reservior. For example, "self-priming" pumps are located above the NOL and are normally NOT used in "flooded suction" service.

_MJC

 

[djack77494]

It's tough to go against the likes of PumpWorld, but I don't like the given definition. If you have (say) a vertical vessel with a liquid draw from the bottom, and you let your liquid level drop low enough that a vortex forms and causes gas to be sucked into the pump suction, then (IMHO) you do NOT have a flooded suction. I do not see how that would fit with PumpWorld's definition, but would love to hear more.
Doug

 

[EmmanuelTop]

In case of vertical pumps this definition of "flooded suction" becomes senseless. I posted this question on ChE forums as well, and got an excellent reply from Art Montemayor - the living legend.

Attached is his reply in form of Excel sheet. Very simple and 100% clear.

http://antwrp.gsfc.nasa.gov/apod/astropix.html

 

[rmw]

As usual Art's answer linked to here has nailed it. Since the thread is now mature and the OP dealt with, I'd like to take it OT and ask is it just me or has it been a while since I've seen Art Montemayor post on this site? I've looked and he has visited the site recently and regularly but I am searching my memory to try to remember when he has posted anywhere herein. Is he just lurking where I don't?

rmw

 

[pumpking]

Important to stress importance of not getting flooded suction and NPSH mixed up - totally different meanings and impacts on system and pump design.

Please dont measure flooded suction height/pressure as NPSHa as it may well lead to pump problems, especially with increased temperatures etc.

Ash Fenn

http://www.cdrpumps.co.uk