How to Precisely Monitor a Metering Pump’s Turndown

Accuracy is vital when you have a chemical dosing application for chemical manufacturing, water treatment, or oil and gas. Turndown ratio is the key measurement you will use to determine precision metering. The acceptable turndown ratio should have a tolerance of no more than ±1.0%. After that, there is not much wiggle room.

What is Metering Pump Turndown?

Turndown is a performance measurement of a metering pump’s output capabilities. For example, a metering pump with a ratio of 500:1 should pump between 500 GPH and 1 GPH within the same accuracy rating. In other words, the pump is providing precision metering results (ideally within the desired ±1.0% tolerance) whether it is operating at its maximum capacity or its minimum flow rate.

Accuracy Despite Changing Conditions

One other factor to consider with metering is that operating conditions can and will change. Most chemical dosing applications require a metering pump that allows you to alter flow rates without losing any accuracy. A good example is a multi-state chemical dosing process which requires different volumes of chemicals released at precise points in the process. Exceptional turndown accuracy means your pump can handle these changing conditions while maintaining its precision performance.

Turndown ratings must be repeatable and sustainable with steady-state accuracy, even in multi-state metering applications.

How to Assess Turndown Accuracy

First, you must understand your metering application(s). Municipal water treatment requirements may be different than chemical processing or oil and gas refinement. In this instance, you have to determine the required turndown ratio and acceptable accuracy tolerance. If the turndown ratio exceeds 100:1, you will have a more significant challenge on your hands–your pump system must provide accurate dosing, whether it’s running at 100 GPH or 1 GPH. The higher your ratio, the more challenging it is to achieve precision results under variable conditions.

To achieve better turndown accuracy, you must carefully monitor your pump system at different output levels. What is your accuracy tolerance when running at full capacity? What is the tolerance when running at the lowest speed? It may take some time and effort to dial in the equipment thoroughly, but it is worth it.

Is it Time for a New Metering Pump?

You can use these same tests to monitor and evaluate existing metering pump system equipment to determine if a replacement or redesign is in order. Older metering pumps may simply not give you enough accuracy across all output levels. No amount of adjustments and reconfigurations will change that fact. To meet your exacting turndown specifications, consider a new metering pump system.

Milton Roy Chemical Metering Pumps

Milton Roy is one of the world’s leading manufacturers of metering pumps and monitoring systems. Their line of chemical pumps, like the PRIMEROYAL and MAXROY Series, are built for precision output performance and exceptional corrosion resistance–even in the most demanding chemical dosing applications.

DXP Cortech is a longtime product partner of Milton Roy. We recommend their top-quality chemical pumps and precision metering equipment to many of our clients in the wastewater treatment, oil and gas, and chemical processing industries. Their pumps are dependable and accurate, time and time again. Contact us today to learn more about their pump systems and for help in selecting and installing the ideal chemical metering pump for your specific application.