At the Emerson Exchange conference in Austin, Emerson’s Tony Foster and Leah Stanley and Vinson Supply’s Robert Lange presented, Selecting the Right Valve for Your Application to Reduce Cost and Increase Performance. Their abstract:
Selecting the optimum valve for the application can sometimes be a daunting task, even with a “simple” on/off valve, especially when the process operates at high or low temperatures and/or has high levels of particulate. This workshop will cover process variables that should be considered when selecting a valve. Also, the merits and tradeoffs of each valve type will be discussed in order to understand how to best reduce cost and increase performance.
Tony by stating the objective of providing guidance on how to select the right valve for your application. The wrong valve can be costly in terms of safety, downtime, maintenance and more. Here are some important factors:
Gate valves provide is a multi-turn valve. The common type is a wedge gate valve. Advantages are less pressure loss, good bi-direction sealing, less energy to close since perpendicular to the flow. Disadvantages are long opening and closing times, large area to operate and maintain. Operates in fully open and close modes and not in throttling applications.
Globe valves have good sealing performance, used for cross throttling, stroke is shorter than gate valves. These valves have a great pressure drop than gate valves.
Butterfly valves are small, lightweight and have fewer to maintain than other valve types. Disks are always in the flow increasing the pressure drop. The seats wear more since they are always in the flow stream.
Triple Offset Valves are small and lightweight and are suitable for many types of fluids. Ball valves provide tight closure and are smaller and lighter that gate valves. They are not suitable for sustained throttling applications.
Valve selection criteria include: size, temperature/pressure, media, required standards, cycle-speed / number, manual or automated, flow rate & direction, and process characteristics. These criteria must be considered in parallel when selecting a valve.
Robert walked through each of these criteria against the valve types. You can find more on these criteria and valve types in chapter 5, Control Valve Selection in the Fisher Control Valve Handbook. The isolation valves are being reviewed to see how the handbook and Specification Manager tool can be updated to include them.