Article 21: Pumps Reliability and Energy Efficiency Improvement Program

A recent Energy Blackout Crisis was a shock to many of us. It reminded us how depended we are on the energy supply and the importance of the equipment reliability and efficiency. Pumps are major consumers of energy, and by making them operate more efficient we can save a very substantial amount of money and reduce operating energy bill by a lot.

Even though we take pump efficiency for granted, most pumps actually operate inefficiently. A very significant impact on the pump energy consumption is where it operates on its Head-Capacity curve, with regard to Best Efficiency Point flow (BEP). Consider a typical example below:

A plant operation changes. A pump, sized for a certain flow many years ago, may no longer be required to deliver that flow. A pump sized and installed to operate at the peak capacity of 3000 gpm, for example, may by now be required to provide only 1500 gpm to a changed demand.

When a pump capacity is throttled, or by-passed, the energy to move the “un-needed flow” is wasted. If, for example, the initial efficiency at the BEP was 80% at 3000 gpm, then at 1500 gpm the efficiency may be only 40%. Even if a pump operating point has not changed significantly, the wear of the internal components (mainly impellers, rings and bushings) would still reduce the efficiency (75% in the example above).

Have you ever wondered how much energy does a typical 100 HP pump consumes in a year? Well, the answer may surprise you. 100 hp (75 KW) delivered to a fluid 24 hours per day, 365 days per year, at \$0.07 per kilowatt-hour is:

75 x 24 x 360 x 0.07 = \$45,360 per year

If, as in the example above, a pump is operating to the left of the BEP at HALF the original efficiency, then only half the energy is consumed for useful purpose, and another half is wasted.

Which means that \$22,680 is wasted – and that is for just one pump only!

Studies show that more then 50% of the plant pump population no longer operates at the original design efficiency, for various reasons, - sometimes knowingly, and sometimes not.

Everything has a solution. But the question is – at what cost? Clearly, replacing a big inefficient pump with a smaller one sized for proper flow is one way. But a complete pump cost a lot of money, and - that is only part of the problem. Changing piping is another story. Removing of the casing from piping, cost of modifications and all associated logistics can run-up manifold more then a pump itself. And, in some cases, it is almost impossible to even think of changing the piping.

A better solution is to modify the internal hydraulics, by fitting the existing casing with a new impeller, specifically designed for the new required flow. That is a much more economical, expedient, and practical way. Also, if application allows, the impeller can be made from the engineered composites, with 80% weight reduction in comparison to metal. Simsite composites have excellent resistance to most chemicals, good to 300-400 deg. F, and with strength approaching metal. Salt water applications, brine, brackish, raw water or sewage intake, circulation, waste and storm water, condensate, etc. – are just some of the examples. Another benefit of such dramatic weight reduction is lower shaft deflections, and therefore longer life of seals, bearings, and couplings.

We offer such pumps reliability and energy efficiency evaluation and upgrade service. We will not try to push-sell anything. What we will do is perform a thorough engineering analysis of your plant pumps. We will work with you. You will then have a clear picture of which pump operates fine, and which ones can be improved, and how. You will see a total financial impact of your pumps on your maintenance and operating budget, and evaluate the difference yourself.

Give us a call.

Also, you can do a quick preliminary Energy Factor Evaluation of your pump by using our Evaluator Program at www.PumpingMachinery.com – and click on Pump Efficiency Evaluator Form. Also, for more information and technical details, see Pump Technical Papers section at the same www.PumpingMachinery.com (papers 16 through 20).

We would like to hear from you and to answer any questions. And – guaranteed – your pumps dependency on energy will ease up a lot.

Lev Nelik

Pump Magazine