Prescreening to Pick Out Problem Pumps

Pump system optimization boosts reliability, energy efficiency, and the ability to meet process requirements. But which systems need optimization? This is not always apparent, especially in plants that have tens, hundreds, or even thousands of pumps.

Category: Blogs, PSM Newsletter September 23, 2021

Pump system optimization boosts reliability, energy efficiency, and the ability to meet process requirements. But which systems need optimization? This is not always apparent, especially in plants that have tens, hundreds, or even thousands of pumps.

That’s where prescreening comes in. It helps engineers and technicians prioritize which systems will benefit most (in terms of ROI) from money spent on optimization.

Here are some tips on how to go about it:

Target the biggest pumps first. To increase the likelihood of large ROIs, start with your largest pumps and those with the heaviest duty cycles. These are the pumps using the most energy.

Get the facts. Once you have some target pumps, get their boilerplate data. This might include pump system description, horsepower, annual operating hours, control methods, and instrumentation. Then look at their behavior. Start with observed system conditions, such as cavitation noise, reduced flow, foundation cracks, and the like. Also look at their energy usage to see if it is noticeably higher than expected.

Dig into history. Go back and check the pumps’ history. Have they suffered unplanned failures or caused lost production? Were they pressed into service to do a job they were not originally designed to do? Has their piping changed since it was installed? A pump’s maintenance record may show hidden costs and may also hint at some root causes of the problem.

Prioritize. Once you have tabulated the data you need, you can start prioritizing systems. Put the ones with the highest maintenance and energy costs on top. Then flag the ones with known issues, such as cavitation, changes in usage without modifying the pump, throttle control, and frequent cycling.

Pick the low-hanging fruit. It would be great if every system could be assessed and optimized. Unfortunately, there are not always enough resources to get the job done. Also, experience shows that energy cost savings alone do not always have a large enough ROI to justify assessments and optimization investments. Instead, focus on issues unearthed during the prescreening that have a larger financial impact—unplanned failures resulting in system downtime, lost production, potential safety or environmental problems, and high ongoing maintenance costs.

The Hydraulic Institute provides a free, Excel-based template to walk you through prescreening. Image 1 shows a completed prescreening example form, simplified to include only annual maintenance and electrical cost estimates. The ranking provides a quick read on the systems that will likely benefit the most from allocating additional resources to assessment and optimization.

Of course, this is never as clear cut as a simple arithmetic ranking. One could, for example, argue that Boosters 3 should be evaluated before Boosters 1 because the maintenance cost is higher. Someone with different priorities might counter by noting that Boosters 1 should be reviewed first because its electrical cost is higher and it is a variable load system without variable speed control. If both sets cannot be assessed, then some additional screening data may be required to clarify the path forward.

Begin a more in-depth assessment. Three levels of assessment may be appropriate depending on the situation.

Level 1. A Level 1 assessment is a qualitative review or paper audit. It is intended for smaller pumps and those with shorter duty cycles that are generally not worth a major investment of time or resources. It makes sense to investigate any major discrepancies between equipment design and operational performance.

Level 2. In systems with little or no pumping variability, use a Level 2 quantitative review based on limited in-field measurements. Most often, the assessment team can use the plant information system or portable measuring devices to gather the data needed to provide a snapshot of conditions at the time of measurement.

Level 3. In systems with greater variability and a high potential for savings, engineers may want to conduct a more intense Level 3 assessment. This measures data over a timespan long enough to characterize the system’s various operating conditions. The resulting data can be used to develop a long-term system load profile. If the pump or pump system has known maintenance issues, the team may choose to do more extensive monitoring and data analysis, as well as a detailed component failure analysis or hydraulic system modeling to help identify what is contributing to those failures. For example, if unexpected bearing failures are an issue, a proper assessment would include a detailed analysis of the bearing temperatures at various system operating conditions, and an inspection of the failed bearings.

Use the free prescreening tool. The Hydraulic Institute provides a free, Excel-based template that organizes the information needed to prescreen pumps. This includes spaces to enter such basic information as operating hours and pump horsepower and to calculate energy usage. It helps guide users through the prescreening process and presents the resulting information in logical order. You can find it—and other free tools—at https://pumps.org/FreeTools.

Pump prescreening is a building block of pump system optimization. This is covered in Hydraulic Institute’s Pump System Optimization training and also its Pump System Assessment Professional training. You can learn more at https://www.pumps.org/Training.aspx.