When I first started as a screw pump supplier, I quickly learned that our clients don’t just want a piece of equipment—they want confidence that it will perform when it matters most. A screw pump’s performance can make or break operations in industries ranging from wastewater treatment to oil and gas, and too many teams rely on guesswork instead of data to evaluate what’s working. Over the years, I’ve walked alongside plant managers, maintenance leads, and process engineers through every step of measuring a screw pump’s performance, and I want to share what I’ve learned with anyone looking to get this right. Screw Pump
First, let’s start with the basics: why measuring a screw pump’s performance isn’t just a factory checkup. For many operations, screw pumps handle sensitive fluids—thick slurries, viscous oils, even abrasive industrial wastewater. If a pump underperforms, it can lead to downtime, increased energy bills, and costly maintenance. Over time, even small drops in performance add up: a 5% efficiency loss across a large processing plant, for example, can waste thousands of dollars in electricity every month. That’s why our team at the supply works tirelessly to help clients measure performance accurately, not just to sell a replacement part, but to keep their operations running smoothly.
The first step in measuring performance is to get clear on what metrics matter most. You can’t improve what you don’t track, so let’s break down the core metrics every screw pump operator should monitor. The big three are flow rate, discharge pressure, and efficiency—but there’s more to it than just reading numbers off a gauge. Flow rate, for example, isn’t just “how much fluid is moving”; it’s the actual volume delivered per unit time under real operating conditions. A pump might hit its rated flow in a factory test, but once it’s installed in a plant with temperature fluctuations or variable fluid viscosity, that number can drop significantly. That’s why when we work with clients, we recommend measuring flow rate in their actual process environment, not just in a controlled test lab.
Discharge pressure is another critical metric, and it’s closely tied to flow rate. Screw pumps are positive displacement pumps, meaning they move a fixed volume of fluid per revolution of the screws. Unlike centrifugal pumps, which drop in pressure as flow increases, screw pumps maintain a steady pressure as flow adjusts. That’s one of their biggest advantages, but it also means that mismatched pressure requirements are a common cause of poor performance. For example, if a client’s system requires 150 psi but the pump is set to deliver 100 psi, it’s not working as hard as it could be—and wasting energy. Conversely, if the discharge pressure is too high, it can cause unnecessary wear on the pump’s components, shortening its lifespan.
Efficiency is where things get a little more complex, and it’s the metric that separates a well-performing pump from an underperforming one. Pump efficiency is the ratio of the hydraulic power (the power used to move the fluid) to the input power (the power the pump’s motor uses). To calculate this, you need two sets of data: flow rate, discharge pressure, and fluid properties to find hydraulic power, and electrical readings from the motor (volts, amps, power factor) to find input power. When we do performance tests for our clients, we take these readings over a range of operating conditions, not just a single point, because efficiency can shift as flow or pressure changes. For example, a screw pump might be 85% efficient at its design point, but drop to 70% when handling a thicker fluid—something that’s easy to miss if you only test at one setting.
Now, how do you actually measure these metrics in practice? Let’s walk through a step-by-step process that our team uses with every client we partner with. First, you need to prepare the pump and the system for testing. Shut down operations safely, lock out/tag out the power supply (always follow safety protocols!), and make sure the pump is clean and free of clogs or debris that could skew readings. If the pump has been running for a long time, it’s a good idea to run it for 15 to 30 minutes at normal operating conditions before testing to get stable readings—this helps warm up the fluid and the pump’s components, so you’re not testing a cold start that doesn’t reflect real performance.
Next, measure flow rate accurately. There are a few ways to do this, depending on your application. For low-viscosity fluids, a magnetic flow meter installed in the discharge line is a reliable tool—it measures the velocity of conductive fluids with high accuracy, which is perfect for wastewater or water-based slurries. For thicker, more viscous fluids (like crude oil or food-grade syrups), a positive displacement meter might be a better fit, as it’s designed to handle higher viscosities without losing accuracy. If you don’t have a permanent flow meter installed, a temporary ultrasonic clamp-on meter can work for a one-time test, though it’s less precise than a permanent installation. When taking flow rate readings, make sure to take multiple readings over 5 to 10 minutes and average them—this accounts for small fluctuations in your process that can throw off a single measurement.
Then, measure discharge and suction pressure. You’ll need calibrated pressure gauges installed at both the suction inlet and discharge outlet of the pump, positioned as close to the pump as possible to avoid pressure losses from piping. For best results, use digital gauges that can log data over time, instead of analog gauges, because they give more consistent readings and make it easy to spot trends. Suction pressure is especially important because screw pumps can suffer from cavitation if the suction pressure is too low—cavitation occurs when low pressure causes fluid to vaporize, creating bubbles that collapse and damage the pump’s rotors. If you notice that suction pressure is dropping during testing, that’s a red flag that your pump is at risk of premature wear.
From there, calculate input power. If your pump is connected to an electric motor, you’ll need to measure the electrical power input. A power quality analyzer can measure volts, amps, and power factor, which are necessary to calculate real power (the actual power used by the motor). If you don’t have an analyzer, a clamp-on ammeter and voltmeter can give you a rough estimate, but keep in mind that this will be less accurate. For pumps with diesel or gas engines, you’ll need to measure fuel flow rate and engine power output to get input power.
Once you have all these numbers, you can calculate the key performance metrics. Flow rate is your measured volume per minute (or hour, depending on your units), discharge pressure is your measured pressure difference between discharge and suction, and efficiency is (hydraulic power / input power) x 100%, where hydraulic power is (flow rate x pressure difference) / 1714 (a conversion factor for US units; the metric version is (flow rate in m³/s x pressure in Pa) / 1000). We always share these calculations with our clients, and we also compare them to the pump’s design specifications to show where it’s performing as expected and where it’s falling short.
But measuring performance isn’t just about a one-time test—it’s about ongoing monitoring. A screw pump’s performance can change over time due to wear on the rotors, seals, or bearings. For example, even minor wear on the screw rotors can reduce volumetric efficiency (the ratio of actual flow to theoretical flow) by 10% or more, over time. That’s why we recommend setting up a regular monitoring schedule, either with a permanent data logging system installed on the pump or with quarterly performance checks by a qualified technician. Many of our long-term clients install basic sensors on their pumps that send data to a dashboard, so they can track performance trends and catch issues before they lead to downtime.
I’ve seen too many operators wait until their pump breaks down to check its performance, which is always more expensive. Last year, we worked with a food processing plant that had been using the same screw pump for 10 years. They thought it was working fine, but a routine performance check by our team showed that its efficiency had dropped to 65% from a design 82%. The cause? Minor wear on the rotors that had developed gradually. We were able to refurbish the rotors and seals, bringing efficiency back up to 80%, and save the plant from having to buy a new pump—or deal with a sudden breakdown during a busy production run. That’s the value of regular performance measurement: it’s not just about tracking numbers, it’s about extending the life of your equipment and avoiding avoidable costs.
Now, common mistakes to avoid when measuring screw pump performance. One big mistake is testing the pump at conditions that don’t match its actual operating environment. For example, testing a pump designed for thick sludge with water will give you false, inflated flow rate readings that don’t reflect real performance. Another mistake is ignoring suction pressure and cavitation, which I mentioned earlier. Many operators focus only on discharge pressure, but low suction pressure can cause serious damage that reduces performance over time. A third mistake is relying only on analog gauges, which can be inaccurate due to drift or user error. Digital gauges and data logging give consistent, reliable readings that make it easy to track changes over time.
If you’re unsure about how to measure your screw pump’s performance correctly, don’t hesitate to reach out to a qualified supplier or technician. Our team has spent years working with all types of screw pumps, from small industrial units to large-scale ones for oil and gas, and we’re always happy to walk through the process with you. We can help you set up a testing schedule, recommend the right tools for your application, and interpret the results so you can make informed decisions about maintenance, repairs, or replacements.
At the end of the day, measuring a screw pump’s performance is about taking control of your operations. When you understand how your pump is working, you can reduce energy costs, extend equipment life, and avoid costly downtime. If you’re ready to get a performance check for your screw pump, or if you have questions about choosing the right pump for your application, we’re here to help. Get in touch with our team to start a conversation about your screw pump needs.
Diaphragm Pump References:
- Karassik, I. J., Messina, J. P., Cooper, P., & Heald, C. C. (Eds.). (2001). Pump Handbook (4th ed.). McGraw-Hill.
- American National Standards Institute. (2016). ANSI/HI 1.3-2016: Rotodynamic Pumps – Standard for General Requirements for Testing Centrifugal, Mixed-Flow, and Axial Pumps. Hydraulic Institute.
- Ramadhan, A. A., & Mohammed, S. J. (2018). Performance analysis of screw pumps handling viscous fluids. Journal of Petroleum Science and Engineering, 167, 742-748.
- Hydraulic Institute. (2020). Positive Displacement Pump Performance Monitoring Guide. Hydraulic Institute.
- Garcia, F., & Perez, R. (2019). Cavitation in positive displacement pumps: Causes, effects, and monitoring methods. Proceedings of the International Pump Users Symposium, 35, 112-119.
Botou Hengyang Pump & Valve Co., Ltd.
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