Generic selectors
Exact matches only
Search in title
Search in content
Post Type Selectors

# System Optimization VS Component Optimization

Does it really make sense to increase the efficiency of your pump and motor without addressing the downstream components? What is the value (payback) of a premium efficiency motor VS a standard efficient motor? Is it really worth replacing a 70 percent efficient pump with a 75% efficient unit?   Some people would think this is a no brainer.

There are a number of factors that should be taken into account before replacing a motor or pump. Let’s put this approach in perspective. Would you purchase the most fuel efficient car on the market (to reduce your energy cost) then drive it with the parking brake on? I hardly think so. In simplistic terms, that is component efficiency, gaining efficiency in one area while wasting the energy generated in another.  I have prepared a simple spread sheet that provides in detail the benefits of system efficiency VS component efficiency.

Figure 1

Figure 1 provides four separate scenarios for a given pumping system. The system portrayed is a typical application where the discharge is being throttled over a range of operation. The system in this example operates 24/7, 365 day a year and at this particular load point 50% of the time or 4350 hours per year.

Columns One and Two indicate the various components factored into the system efficiency calculation. Column A is the base condition where the system operates 50% of the time. You will note the component efficiencies for the VFD and gearbox at 100% since they were not utilized. Under the based condition the system the total power required is approximately 362hp, almost 73hp is being lost (wasted) across a throttling valve. In addition, the pump is operating back on the curve at 65% efficiency. Under these conditions the total system efficiency is 49%.

Column B provides total the new operating conditions with the addition of a variable frequency drive. The head required has been reduced to 150’ since the loss across the valve has been eliminated by reducing the speed of the pump to meet required system demand. Motor efficiency remains the same a 2% loss has been added due to heat generated across the drive. Observe the dramatic improvement in the overall system efficiency (81%) and the total operating cost reduction from \$82,148 to \$37,150 = cost savings of \$44,999 per year. Not to mention the improved reliability and subsequent reduction in maintenance cost and increased productivity.

Column C addresses the impact on the system by improving the efficiency of the pump. Nothing else in the system was changed. Note the minimal improvement of the overall system efficiency (53%) by increasing the pump efficiency 5%. The 50’ head loss across the valve remain therefore the total power required is 336hp. Not much of a saving based on the cost of a new pump, installation cost and potential piping changes. Factor in the ongoing reliability issues (pump is still operating back on the curve the \$5,868 dollars would be very difficult to justify.

Column D identifies potential savings when motor efficiency is improved by 2%. Again nothing has changed in the system with the exception of an additional 5 feet of friction loss across the valve as a result of the reduced slip in the premium efficiency motor (head increases to the square of the speed). In this case, the system efficiency remains the same at 49%. Note the power required for the additional friction has increased to 77.9hp. The total power required was reduced to 361.2hp (a reduction of .4hp) with a total savings of \$103 dollars per year.

Now add the increased maintenance cost due to the pump operating away from BEP (you’re driving the energy efficient car with the parking brake on) and the component efficiency approach looks even less attractive.

I think it goes without saying, but I’ll say it anyway, think system!

# Improve Bill of Materials In 7 Steps

What is a Bill of Materials? A Bill of Materials (BOM) is a complete and accurate list of parts for each…

# Uncover Best Practices and Assess Your Plant’s Performance: Examples of Preventive Maintenance

When visiting plants in different corners of the world, IDCON is often asked: “What are the current best practices for…

# Planning Is Everything — How To Plan For Breakdown Maintenance

Breakdown maintenance is an approach to maintenance strategy in which repairs are performed on equipment only after it has completely…

## Related Whitepapers

### Protecting VFD-Driven Motors In Steelmaking

VFDs Improve Process Control and Reduce Energy Costs According to the American Iron and Steel Institute, energy costs account for 20% of the cost of…

### Concrete steps for an energy efficient future with the top industrial efficiency option

Should energy efficiency policy consist of minimum efficiency performance levels that all suppliers need to reach? Or should the industry in addition strive for the…

### The future is energy-efficient, the future is data-driven

By 2050, global energy usage is projected to increase by almost 50% compared to 2020. This includes an increase in energy consumption in the industrial…

### Protecting VFD-Driven Motors In Oil Drilling and Pipelines Applications

The Need for Exceptional Reliability Used for everything from gasoline for vehicles, to power for lights and appliances, to key ingredients in plastics and other…