I need some help guys.

We are moving a pump in work and i need to work out the performance difference, the only thing changing is the inlet head or pressure

1.
Basically the term "head" when applied to fluid flow. what does it mean? for example what head would a 10m tank of water provide and how do you calculate it?

2.
What is the effect on the pump performance of changing the head of water at the inlet of a pump..

3.
My boss thinks that you can use the affinity laws for pumping to work all this out but i thought the affinity laws were to work out pump perfomance if you were changing the speed or rotor diameter. As these will not be changing i don't think affinity is any use?

Please help i'm in a bit of a pickle here
Cheers guys

[Edited on 25/9/05 by liam.mccaffrey]

have just had word, with our mechanical bod, and he said provided that the flow of fluid to the pump is not restricted, the pump performance should not change, but if the outlet of the pump has to pump higher(i.e to a greater head, its flow rate will be reduced).
HTH

Ray

my thought was that if the speed of the pump could not change then the output flow would not increase. If the new inlet was at higher pressure would the pump require less power to run or be more efficicant or somthing?

i am having trouble with the term "head" could someone explain it?

really appreciate your help

[Edited on 25/9/05 by liam.mccaffrey]

1. Head is simply the height of water either on a suction side that the pump needs to work or on the discharge side of the pump how far the pump can actually push the water till it deadheads/stalls.

10 M of head in freshwater is equalt to 1 bar or 14.7 psi.

2. You don't say what kind of pump you are moving? But in simplest terms if your pump is centrifugal and is capable of raising the pressure by 2 Bar or 20 m of head. By raising the inlet pressure by 10 M of head the pump performance should not change just the discharge pressure will rise by the increase of head so if the pump is capable of raising the pressure 2 bar/20m head and your feeding it with 1 bar / 10 m of head the outlet pressure will rise accordingly to 3 bar or 30 m of head. Thats all assuming you are not changing anything else especially on the discharge side.

A lot depends what you are pumping and its temperature --- when pumping hot or volatile fluids a higher inlet head helps prevent cavitation.

sorry, pumping cold water

right so if i can find out the inlet/ outlet pressures/heads before we moved the pump and then work out what the new locations inlet head/pressure i can find the new outlet head/pressure.

also will the volume of water transferred change?

In theory yes, and you should be about right. But in reality if you are changing the configuration of the pipework then you are going to have a new set of restrictions and different frictions in the pipe which all add up to make a difference, but if your pump is going to be doing basically the same job then the pipework ain't going to be that different.

volume of water pumpeed should not change, unless in your original installation you did not have sufficient head to adequatley feed the pump. Some pumps need a minimum head to work properly, others suck happily from a negative head.

It's all affected by pipe size as well. I used to work out sizes for a friend who was flushing pipes and needed to know the velocity of water needed to move a given size particle. If you are only changing the head you shouldn't really make any difference as jonr says.

also if the feed tank is above the pump inlet does that affect the head?

is head the same as pressure. ie can you convert between the 2

I'm sorry to ask loads of questions but i need to understand this really bad. If I can help anyone with anyhting please ask.
My speciality is scanning(its part of my job)
On a completely unrelated topic i have all issues of PPC

The head is the total height above the pump inlet, so all the pipework and all the water in the tank, . So if you had a 2 m tall tank full to the brim. and an 8 m tower on which the tank was mounted and the total height difference between the pump inlet and the top of the water is 10 m then your head is 10m of water,

Yes you can convert them. 10 M of water is 1 Bar.

"Inches Water gauge " or "/wg is commonly used to measure small pressures, usually a differential pressure across a filter or something.

its slowly falling into place