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Pump nsph 2
- Thread starter jvyw9917
- Start date
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1
- #2
Increase inlet pressure.
Raise source tank, increase inlet diameter, remove all restrictions in inlet line, lower pump elevation, lower temperature of product.
Going the Big Inch!![[worm]](/data/assets/smilies/worm.gif "[worm] [worm]")
Raise source tank, increase inlet diameter, remove all restrictions in inlet line, lower pump elevation, lower temperature of product.
Going the Big Inch!
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1
- #3
It is difficult to give advice when the system and fluid characteristics aren't given. Can you add on this respect ?
The subject of NPSHA has been discussed many times. I suggest you visit the following threads to get ideas:
thread407-6587
thread407-9873
thread407-12387
thread407-34369
thread407-41042
thread407-45276
thread407-51468
thread407-59805
thread407-61239
thread407-61919
thread407-85933
thread407-130418
thread798-63268
If you can only get 1 m of NPSH, its symptomic of problems in the suction piping system that are not being adequately addressed. Tip: Its not a pumping problem.
Going the Big Inch!
Going the Big Inch!
I generally prefer a horizontal pump as well. There are horizontal pumps made with inducers to reduce NPSH(r). We use some on crude tank services. Otherwise, the advice above covers it. Raise the tank, lower the pump, reduce suction line losses or buy a higher Nss pump and pay the price in downturn capability.
I assume you are still in the design stage, Yes ??
As BigInch has pointed out, It is not a pumping problem at this stage but a poor pump selection for the duty, or poor inlet engineering or something we don't understand at this stage - more information from you will help us to help you.
Naresuan University
Phitsanulok
Thailand
As BigInch has pointed out, It is not a pumping problem at this stage but a poor pump selection for the duty, or poor inlet engineering or something we don't understand at this stage - more information from you will help us to help you.
Naresuan University
Phitsanulok
Thailand
No kidding. Drag reduction by the addition of polymers, the discovery of which is attributed to the british chemist B.A. Toms, became popular knowledge by about 1948.
Toms's effect has been reported as being applied, for example, in the Alaskan oil pipeline, in enhanced oil recovery, in firefighting, and in various military uses.
Nowadays, the principle is being studied in medicine to reduce drag in blood vesels by injection of polysaccharides.
One theory -among others- trying to explain the phenomenon says that the length of the polymer molecule is related to the microturbulent eddies in liquids, keeping waves from propagating from the eddies, thereby reducing turbulence.
Those of you involved in hydraulics may be able to add info. for our own education.
You're 2nd guessing.
For drag reduction technologies to apply here it would necessitate that there be drag to reduce and that it can be reduced by the addition of drag reducer compounds.
Going the Big Inch!
For drag reduction technologies to apply here it would necessitate that there be drag to reduce and that it can be reduced by the addition of drag reducer compounds.
Going the Big Inch!
Yes, I'm trying to do some lateral thinking looking for alternative strategies. Aren't we speaking of reducing friction to overcome undesirable NPSH conditions, as with streamlining the flow to the pump, or installing fins as "airfoils", or adding an inducer ? Drag-reducers may even reduce the NPSHR by diminishing the pump internal friction.
NPSH requirements are generally given for clean, cold water with full-size impellers.
Gas-free hydrocarbons and some other fluids show a reduced NPSHR vs water (See graph by the Hydraulic Institute, 14th Ed., 1983). These liquids when warmer result in larger permissible NPSH reductions from the NPSHR for water!
Jvyw9917 hasn't provided details on the fluid and operating conditions, not even the NPSHA and NPSHR values were submitted. Thus, any assumption on our side would have to be momentarily valid.
If this is an existing situation, you can consider digging a hole and lowering the pump 1 m.
"Do not worry about your problems with mathematics, I assure you mine are far greater."
Albert Einstein
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"Do not worry about your problems with mathematics, I assure you mine are far greater."
Albert Einstein
Have you read FAQ731-376 to make the best use of Eng-Tips Forums?
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