Understanding Control Valve Sizing

Appropriate control valve sizing is critical to proper operation. If your valve is sized incorrectly, it can lead to poor control and performance.

Common Control Valve Sizing Mistake: Oversizing

The most common mistake we see customers make in control valve sizing is selecting a valve that is too large. An oversized control valve will not only cost you more, but it will be very sensitive and can quickly lead to production headaches.

Small changes in an oversized control valve position can cause large changes in flow. This will make it extremely difficult for the valve to adjust to your desired flow. This can result in “chattering,” where the valve opens and then shuts quickly, causing unnecessary wear on the trim. Any stickiness caused by friction will be amplified by the overly sensitive oversized valve. This will reduce the precision with which you can control flow and may lead to valve positioning errors like stiction and dead band.

How to Size a Control Valve

You want to size a control valve so it will be no more than 80% open at the maximum required flow rate and no less than less than 20% open at the minimum required flow rate.  The idea is to use as much of the valve’s control range as possible while maintaining a reasonable safety factor to allow for surges.

The Kimray Control Valve Sizing Tool on kimray.com enables you to size a control valve based on your conditions. In addition, the tool can identify the specific Kimray products that will work for your application based on your conditions and parameters. The tool features tabs for gas sizing, liquid sizing, glycol pump sizing, and steam sizing, as well as some advanced features.

When utilizing this tool, you will be asked for the conditions of your production fluid or gas. You will need to type in the specific gravity, flow rate, pressures, and temperature of your production media.

Converting Units to Size a Control Valve

Sometimes you will have these numbers in their appropriate units. Other times, however, you will need to perform some conversations to get them into the correct unit.

For example, you may know your flow rate in pounds per hour, but for the sizing tool you need a volume flow rate, such as gallons per minute.

In order to make these conversions easier, we have created calculators preloaded with the appropriate formulas for converting these numbers. You can convert by entering your pounds per hour and the specific gravity, and the conversion tool will give you the flow rate in gallons per minute.

Click the buttons below to grab your free calculators:

Breck Swigart serves as a Product Manager at Kimray, and is responsible for Kimray’s line of pneumatic valves, pneumatic pilots, regulators and temperature controllers. He collaborates with Kimray’s engineering, manufacturing, and quality teams to optimize the performance of our products and make a difference for our customers.