Four Steps to Pump System Optimization

When it comes to energy use, pumps are low-hanging fruit. They account for 25 percent of all energy consumed by industrial electric motors, and the figure is much higher for pumping intensive applications like municipal water, wastewater, and process plants. 

While pumps can be highly efficient—up to 90 percent for individual units—many facilities do not come close to their generally attainable efficiency. In fact, a Finnish study of 1,690 pumps at 20 process plants found the average pump was operating at less than 40 percent efficiency—and one out of 10 pumps was under than 10 percent.

So, when it comes time to replace pumps or when competitive pressures require slashing costs, optimizing pumping systems might be one way to go.

Here are four steps you can take to optimize your pumping system.

Reduce system head. Reducing system head and the energy needed to achieve it is the first place to begin. System head is the sum of (1) the pressure difference and elevation the pump needs to lift a fluid (static head), (2) the resistance generated by the fluid moving through pipes (friction head), and (3) the resistance from any partially closed valve (control head). 

Of the three, control head offers the best target for energy reduction. Most systems use valves because their pumps have been over-specified and require throttling to maintain the proper flow. For most systems with excessive control head and ongoing maintenance issues, buying a smaller pump that better matches the flow requirements or switching to a variable speed pump lets users reduce system control head and save on electricity and maintenance costs.

Lower flow rate or operating time. Some pumps run all the time, whether the process needs all that flow or not. When systems divert flow, operators are paying for power they are not using productively. There are two ways to attack this problem. One is to switch to variable-speed pumps that can increase or decrease flow as needed. The second is to use a bank of mixed pumps, some larger and some smaller, and stage them to turn on and off to meet demand. Both approaches reduce bypass flow, which saves energy.

Modify or replace equipment and controls. If the energy savings from lower head and lower flow rates/operating times look attractive, owners should consider replacing equipment and control systems. If a system uses a lot of valves for throttling, replace them with smaller pumps that will not require throttling and that are less costly to run. For a system with multiple pumps and fluctuating demand, an overhaul might include smaller or variable pumps and control logic that automatically turns pumps on and off as needed.  

Improve installation, maintenance, and operational practices. It is surprising how many maintenance problems begin with installation. A cracked foundation or improper aligned pump may cause vibration and wear. Improperly configured suction piping may lead to premature wear due to cavitation or hydraulic loading. Always discuss installation support when buying a pump. For critical applications, it may make sense to pay third-party experts for pump commissioning to ensure a new pump runs as designed over its full service life.

There are many ways to handle ongoing maintenance. For small, inexpensive pumps that do not serve a critical need, it may pay to run them to failure. For most pumps, conventional preventative maintenance makes sense. Predictive maintenance—gathering data and using it to determine when operators need to intervene—is a powerful tool to keep pumps in spec. This does not need to be complicated or expensive. Simply measuring things like pump pressures, energy consumption, and vibration on a monthly or quarterly basis would enable operators to catch changes in efficiency and plan remediation before issues arise that could lead to failure. 

These four steps are just the tip of the iceberg. Follow the links to learn more about Hydraulic Institute’s books and training classes on pump system optimization.

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