Tips for selecting the appropriate valves for industrial fluid systems.

Valves play a critical role in the proper functioning of industrial, piping, and instrumentation systems, and it is essential to choose and maintain them correctly. Inadequate valve selection may result in issues ranging from avoidable safety hazards to poor performance and increased downtime.

Valves are typically one of the first components selected during the system design stage. As they wear out, maintenance technicians usually replace them with the same model specified initially to maintain consistency and ensure proper functioning. Therefore, it is evident that selecting the right valve during the initial system setup is crucial.

Thankfully, the STAMPED method - Size, Temperature, Application, Media, Pressure, Ends, and Delivery - can assist designers and technicians in choosing the appropriate valve every time.

S: Size

Before choosing the size of a valve, operators need to determine the required flow rate for the intended system. Once the necessary flow rate is established, the valve with the appropriate flow capacity should be selected. It is helpful for suppliers to provide a flow coefficient (Cv) on their products, as it indicates the relationship between pressure drop across the valve and resulting flow rate.

Cv is measured in U.S. gallons per minute of water and represents the flow rate with a 1 psi pressure drop at a temperature of 60°F. When compressible fluids like gases are flowing through pipes, the calculation becomes more complex but still helpful in selecting the right valve size for specific applications.

T: Temperature

The temperature is an important consideration when selecting a valve as it affects both the substance controlled by the valve and the temperature of the environment where it will be used. The consistency of the temperature should be taken into account when choosing a valve and can impact the frequency of maintenance and replacement. Temperature changes can cause damage to the seals, leading to wear and tear, and potential failures and leaks. The metal construction of a valve may also become weaker at higher temperatures, which can affect the pressure ratings of certain valves. It's advisable to check with suppliers for specific test results that show the valves have been tested at varying temperatures to ensure they function correctly.

A: Application

To select the appropriate valve for a particular application, it is essential to consider the specific role it will play within the system. Operators need to determine if the valve needs to start or stop flow, regulate flow levels, control the direction of the flow, or prevent overpressurization. Answering these questions will aid in selecting the correct valve for the intended purpose. For instance, a two-way ball valve may not be suitable for throttling fluid flow as it is designed for complete opening or closing. In such cases, a needle or metering valve would be more appropriate for regulating or throttling flow.

M: Media

Valve operators must carefully consider how the fluid running through their systems will interact with the valves and choose appropriate materials accordingly. It is crucial to select materials that are compatible with each other and with the valve bodies, seats, and stem tips, among other components. Failure to do so could result in corrosion, embrittlement, or cracking, leading to operator risk and significant downtime.

P: Pressure

The pressure that a valve will experience in a specific application is another important consideration for designers and operators. The term "pressure" can have two different meanings, depending on how it is used: working pressure and design pressure. Working pressure refers to the normal operating pressure in the system, while design pressure is the maximum pressure limit provided by the valve manufacturer that should never be exceeded, except under controlled testing conditions.

E: End connections

The type of end connection used for valves can greatly affect their ability to prevent leaks. Different options, such as tube fittings, pipe threads, flanges, or welded ends, may be available and it is important to select the right one based on factors such as system pressure, temperature, and size. Choosing valves with appropriate end connections will not only make installation easier but also reduce the risk of additional leak points.

D: Delivery

After taking into account all the aforementioned factors, the delivery of the required number of valves by the supplier within the given timeframe is the final aspect to consider. It is equally important to find a supplier that can deliver the valves on time and consistently to ensure a reliable valve supply. Adhering to the STAMPED method provides a solid framework for operators to choose the appropriate valves for designing safe and efficient fluid systems.

As a summary, selecting the right valves for your fluid systems is crucial for safe and efficient operation. Using the STAMPED method can help guide you through the selection process, considering key factors such as size, temperature, media, pressure, end connections, and delivery.

Therefore, if you are involved in the design, operation, or maintenance of fluid systems, it is important to take the time to carefully consider these factors that are detailed here in this article.