Why Should We Look at the Operating Performance of Industrial water Pumps

It is critical to look at the operating performance of Industrial water pumps.

Why we need to pay attention to that

Pumps are at the core of most industrial processes, and the second most widely used machine in the world. Though the performance of process pumps has improved with enhancements to design, materials, and the emerging use of digital technology to monitor performance, the basic structure of pumps has changed little in the past years. Because they are so widely used, pumps are often overlooked as a potential source of improved productivity or a cause of excess costs if not operated properly.

1. Operating efficiency

It is important to look at the operating performance of pumps as the operating efficiency of these pumps affects the energy consumption of water or wastewater facilities a lot. Energy consumption in water and wastewater treatment facilities can get a significant portion of a local governments’ operating budget. In wastewater plants, pumping system electrical usage is 20-30% of total energy consumption and 46% in municipal water pumping systems. Energy costs are an estimated 75% of pump life cycle costs. That means improving pump efficiency has been proven to reduce operating costs. I have to say that improving pump efficiency is worth it!

Improperly sized pumps are the major culprit when it comes to pump inefficiency. But for many reasons, process pumps are sometimes oversized for the needs of the process. One reason is that process parameters are often not fully defined because pumps are being specified. And since“no one was ever fired for having too much horsepower,” engineers tend to on the side of overestimating pump needs without completely thinking. It’s possible for a pump that is perfectly suited to its first installation to become oversized or undersized when the demands of the process change.

2. Life cycle cost

The components of a life cycle cost analysis typically include initial costs, installation and commissioning costs, energy costs, operation costs, maintenance and repair costs, down time costs, environmental costs, and decommissioning and disposal Industrial water pumps costs. If we pay attention to the operating performance of industrial water pumps, we can evaluate efficiency options and quantify cost savings. According to the EPA, pumps and other equipment operating continuously throughout the year make these facilities one of the largest energy consumers (about 4% of the energy used in the U.S.). Some studies have shown that 30% to 50% of the energy consumed by pump systems could be saved through equipment or control system changes.

For a majority of facilities, the lifetime energy and maintenance costs will dominate the life cycle costs. It is therefore important to accurately determine the current cost of energy, the expected annual energy price escalation for the estimated life, along with the expected maintenance labor and material costs.

Obvious reasons cause a pump run off of its performance curve

If the plant is having process issues, to some extent, they must be caused by centrifugal pump. And most pump problems can be attributed to system pipe and system friction changes. A pump might run off of its curve for any of the following reasons:

1. Cavitation

Pump cavitation is the formation and subsequent collapse or implosion of vapor bubbles in a pump. It occurs when gas bubbles are formed in the pump due to drop in absolute pressure of the liquid below vapor pressure. Cavitation is the implosion of vapor bubbles when the suction pressure has fallen below the vapor pressure at the pump suction. The fluid vaporization and implosion energy disrupts pump performance and the motor's energy is wasted. Cavitation actually decreases the pump head, which will alter pump performance. The factory performance curve actually documents this drop in head for the net positive suction head required (NPSHr) curves. The NPSHr, sometimes called NPSH3, is recorded as the suction head that produces a 3 percent drop in pump head. Significant cavitation may drop the pump performance much more where it does not appear to be running on the curve since it is starved at the suction.

2. Pump Speed Differences



Many people believe that we might reach the limit of pump system performance once variable frequency drives (VFDs) and premium efficient motors have been installed. No! If a variable frequency drive (VFD) is used, then determining the actual running speed and pump performance must be matched to the correct curve. Different motor slips may cause small differences but typically only in the 15 to 20 RPM range. If the connecting power transmission element (coupling, belt, clutch, etc.) from the driver (motor) to the pump has any slip, then decreased pump performance relative to the curve will result.

3. Plugged Pump

Pump impeller and casing wear can significantly affect pump performance when compared to the original conditions that produced the factory pump curve. But pump plugging will immediately cause a decrease in performance which can throw the pump off of curve. Pumps may plug in many areas, such as pump suction, casing passages, or between impeller vanes. Some pump curves will list the max solids that the pump can handle or pass without plugging. Enclosed impeller cannot handle much solid material. So some specially designed impellers and pumps (recessed impeller or chopper pump) are selected for handling process fluids and may have plugging type material.

3. Pump Wear

The size, type and concentration of abrasive materials which being pumped can affect the wear rate. Impeller wear on the front edge, like suction side of impeller vanes, will directly affect the capacity of the pump because impeller in the pump gets thinner than before. The truth is that the wear is not always obvious because the target impeller thickness may not be known or difficult to verify. It may go unnoticed until one day when the pump will no longer effectively support the process. Pump materials and optimizing the operating point can reduce abrasive wear on a pump. See Table 1.

As a vital part of your application’s thermal system, taking care of pump performance helps identify opportunities for improving efficiency and reducing costs, especially operating costs.