Pump Rating

What does your class notes say? You did take notes didn't you?

Unfortunately the cost of buying new pumps and moving the system will cost far more than what little energy you may save for the effort which will put the return on investment for up front costs way beyond realistic time frames for the financial savings to balance it out.

You are on a fool's errand. Don't do it.

Your unrealistic quest to squeeze the last penny of profit out of your plant is not realistic.

If you insist of doing this, call a pump supplier, who will be happy to take your money.

Otherwise, don't waste our time.

You should check actual power consumed by motor at your desired head. If motor used is of good quality than power consumption at low head should be lower. and will go up with increase in head.power consumed should be about min power consumption of pump(Zero head power) +MgH.

M- Flow rate Kg/Sec.

g- 9.81

H- Head In meters.

I don't think you need to change anything.

Add - you should use by pass valve to control flow of pump. This will keep pump power consumption almost constant at a given head.Don't control flow by by restrictive method.

You have too little information for anyone to make an intelligent informed comment on....

Schematic would help, flow rate, systems pressure would be good.

Anyone giving any information with what little information you supplied, are no doubt,.... uninformed.

As far as a savings, I just updated one of our plants, cooling water system and the ineffenciencies of the current pumps was costing us 6 figures (that's hundreds of thou$and$ of dollars) a year just from the electricity to run the pumps, not including the ineffenciencies of the system itself.

Efficient design and Pump spec'd application itself will pay for the upgrades in a very short time, less that 2 years.

So more information is needed, then and only then can anyone make an informed suggestion.

Yes your correct with that........ But there are pump out there....of which I am very surprise about that require low suction head.....he's no asking for none, just low suction head

I just install German pumps called 'Ruhrpumpen' where most pumps require a minimum of 15-20 ft of suction head, wth outputs of 3000 GPM @ 77 psi..... These Ruhrpempens can have outputs of 4500 GPM @ 78 PSI with a suction head of, get this........ Only 6 feet of suction head.

South Africans are known not to be able to read. "Now i want to place the all pumps at 6 meter level"

I Already Mentioned it is a primary circuit, it means water is circulated to the machine and this water is cooled by the secondary circuit ( Cooling tower circuit ).

Now the Primary circuit pumps is on ground floor and the machinery is at 6 mt level. If I shift the Pumps to that level , i will get power saving hugely and my payback period for that is would be around 2 years., more ever natural resource can be saved.

Nithin

You still haven given the height of the cooling towers as opposed to the level of the process or the how the pumps are fed.

• do you have an accumulation tank,
• size of the tank, physical size Dia. and Height
• Flow rate, (need this to ensure that there is no air entrained in the supply side.)

we could go on with this and milk the information out,...... but we have our own responsibilities also....

Forget about replacing the pumps due to their costs. Use the old pumps. They will work just as good as new ones and you will only have the relocation expenses. Pumps of the type you are speaking of cost a lot of money. Replace the old pumps with new when they wear out. This will be a bargain basement cost compared to penthouse prices for new.

First determine what size of new pumps would work best. Relocate the old ones and make any piping changes for the new pumps if possible. Replace the old ones when they fail and are not cost beneficial to repair.

Good Luck, Old Salt

Why were multistage pumps chosen in the first place?

How high is the water source for the pumps?

Look at these.
What is a Variable Frequency Drive? - VFDs.com

Well, the first stage is to hire a Process Engineer, ideally one who can do some basic calculations and to a preliminary selection on the pumps and pipework alterations required and work-up an investment scheme.

However, as others have said above, the justification for the investment will probably not yield an economic return-on-capital-employed, and it would be better to leave things as they are.

If you have excess pressure at the machines you could skim the impellers to reduce the head and power consumption , but leave the pumps , motor , RPM and placement the same.

If he could give some information as requested.... But frankly.... Who knows what one really has to work with....

Process engineering is not a true or false question/answer. Usually there are compromises...... Scratch usually...... And replace with always.

Hendrik-

Bypass valves allowing the material to partially recycle around the pump from outlet to inlet would probably be better and accomplish the same effect. That way the pumps could be reused without any reduction in original capacities such as skimming the impellers would.

Good Luck, Old Salt

Losing surplus pressure by control valve in an over-designed pump unit is generally better than a return flow bypass. A bypass will generally result in moving to the right of the pump curve and consume or waste more energy.

Hendrik-

If I'm not correct please explain why. With a pump running with a discharge pressure control valve, the motor has to work harder because it is dead heading against a closed line. Therefor the motor current will increase as the control valve is closed to reduce the discharge flow.

With a pump running with a bypass valve, the motor continues to run at the same speed with a reduced load to control the decrease in desired delivery pressure. Since the excess pressure is being relieved back to the inlet the motor continues to run at the same speed but with a reduced load.

For a reduction in load pressure the control valve motor load increases. For a reduction in load pressure the bypass motor load stays the same or decreases.

This is even more apparent in liquids with higher viscosities

Your opinion please.

Good Luck, Old Salt

These are centrifugal pumps. When the outlet is restricted, the flow decreases more than the pressure increases, for a net decrease in power consumed.

Tornado-

Thanks for jarring the old cranium back into working position! I must have had a temporary brain flatulence attack. Had the Grund fos pump confused with another brand.

Despite what someone recently stated about me recently, I do eat humble pie if put on the plate for me. Again, thanks for your efforts on my behalf.

Good Luck, Old Salt

Typical centrifugal pump curve - D = Duty point on too big pumpA = what the pump see with a control valve B = what the pump see with a return bypass 7.5 HP to almost 10HP

Hendrik-

Thank you for posting the performance curves. I also am familiar with centrifugal pumps but was apparently suffering from a self induced pump name confusion. As said previously I am human and sometimes suffer from flatulence of the cranium. I was also thinking in terms of a very viscous dispersion which is impossible to pump in a centrifugal without some sort of bypass. With a pressure control valve it might crack part of the system.

To err is human, to forgive is divine: especially with cranial flatulence.

Good Luck, Old Salt

I also suffer from that. VFD was not available when I was doing pumps , I now never consider VFD as a solution to loose pressure .

Try to wok out the TDh required if u place the pump at that location. once you have got that, try to map the value on the pump caracteristic curves given by pump supplier. if the head that you have calculated lies within the operating range of pump without the pump going under shut off, guess then the pump may be able to operate. once done contact the pump supplier gettin his recommendations. Else try to locate an orifice near the final discharge point, there by modifying the curve.