Guide to Choosing the Right Valve

In a process piping system, valves are devices that stop, divert, or control the flow of a fluid (gases, liquids, or slurries) by opening, closing, or partially obstructing a passageway. Valves function in a number of different ways. They are used to start and stop a fluid flow, control the direction of the flow, and vary its amount, depending on the nature of the mechanical barrier used in the valve (a plate, a ball, or a diaphragm).

Valves are also used to regulate a system or process, and relieve overpressure situations in a process line.

Valves are used extensively in process industries such as pharmaceutical manufacturing and food & beverage processing and choosing the correct type of valve for a particular application is important. The simplest valves are operated manually, activated via a handle, lever, pedal, or wheel. More sophisticated valves or valve systems, though, are activated automatically, responding to changes in pressure, temperature, or flow in the process piping.

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In determining the correct type of valve to use for your application, there are a number of considerations to take into account.

• The process media. the nature of the fluid which is flowing through the process piping (e.g., milk, yogurt, etc.). Considerations can include whether the materials are corrosive or abrasive, their viscosity, the desired flow rate, particle size (if a slurry), and so on.
• The process system’s temperature and pressure.
• The valve’s application and function. For example, does the valve just need to start and stop the fluid flow, or will it be used to regulate or throttle?
• How much leakage, if any, can be tolerated? And, how precise does the valve need to be?
• Maintenance. How often the valve needs to be cleaned or serviced.
• The material from which the valve is constructed. Sanitary processing industries such as the food, beverage, and dairy industries may require that valves be made of high purity metals such as 316L stainless steel, and meet hygienic standards imposed by industry standards organizations such as 3-A. (3-A is an independent, not-for-profit corporation dedicated to advancing hygienic equipment design used in the food & beverage industries). For example, for clean-in-place (CIP) and clean-out-of-place (COP) applications, the valves controlling the fluid flow in the process pipelines used in sanitary industries may need to be 3-A certified.
• Safety standards. The pharmaceutical and chemical processing industries in particular may require that valves comply with the safety standards associated with the materials from which they’re made. Considerations here can include constructing valves of non-reactive materials, the operating pressure and temperature of the piping system, and the leakage of potentially hazardous materials.