The selection of valves is an important component of the correct design and maintenance practice of piping and instrumentation systems. If the correct valve is not selected for a specific application, the user unit may face inappropriate or poor performance of the special gas system, longer downtime, and inevitable safety risks.
Valves are usually selected in the initial stage of the design of special gas control systems, and throughout the entire lifecycle of the system, technicians typically use the same type of components already present in the system according to specifications to improve valves and most other components.
Therefore, it is very important to choose the right valve from the beginning, which can help the user unit avoid replacing the valve too early in the future.
How to make the right choice?
The technical and procurement personnel of the user unit can follow the STAMPED method, which considers size, temperature, application, medium, pressure, end or joint, and delivery.
Fully considering each of these operating conditions can guide the selection of the correct valve in the special gas system.
The following text provides a detailed introduction to how STAMPED is applied in the design of special gas systems:
01 S - Dimensions
The size of the valve determines its flow rate, which needs to correspond to the expected or required flow rate of the system. The flow coefficient (Cv) of a valve represents the relationship between the pressure drop at both ends of the valve and the corresponding flow rate.
The valve design factors that affect Cv include the size and geometric shape of the flow path; The size of the valve orifice will affect the fluid flow through it. The larger the orifice, the greater the potential flow rate. The orifice of different types of valves may have significant differences; For example, a ball valve will provide minimal flow resistance, but a needle valve will limit or slow down the flow rate. These should be the considerations in your selection process.
02 T - Temperature
The working temperature of the valve will help control the medium temperature of the system and the ambient working temperature of the surrounding environment. It should be noted whether the temperature of the valve will remain constant or change frequently, which may affect valve selection or the frequency of preventive maintenance required.
Consider temperature fluctuations that may cause expansion and contraction of the sealing material. In addition, metal components may lose strength at high temperatures, thereby reducing pressure ratings, and it is necessary to ensure that the valve has undergone comprehensive testing under extreme conditions.
03 A - Application
Consider what valves need to do in the system, whether to start or stop the flow of the medium? Adjust the flow level? Control the flow? Protect the special gas system from overpressure?
Having a clear understanding of the application of valves in the system will guide you in selecting valve types more accurately. Taking a simple bidirectional ball valve as an example, although some ball valves may provide throttling function, most ball valves should not be used for throttling or regulating flow, but should be used in fully open or fully closed state. If your need is throttling or regulating flow, needle valves or metering valves may be a better choice.
04 M -- Medium
Or adjusting the flow rate, needle valves or metering valves may be a better choice.
When choosing the correct valve with appropriate material composition, careful consideration should also be given to the fluid medium inside the system.
Ensure that the system medium is compatible with the materials that make up the valve body, valve seat, and valve stem, as well as materials with softer gases. If not compatible, it may cause corrosion, embrittlement, or cracking, which can pose safety risks and costly production and safety issues to the user unit.
Like temperature, the position of the valve should also be considered. Is it operating in a climate controlled environment, such as inside a factory building or in a heated instrument enclosure? Or is it for outdoor use, long-term exposure to climate factors such as sunlight, rain, snow, and temperature fluctuations? Valves and their components come in various materials, so it is important to choose the appropriate valve based on the environmental and climatic factors mentioned above, in order to prolong the service life of the valve and enhance its functionality as much as possible.
05 P - Pressure
Another important consideration when selecting valves under pressure.
There are two types of stress:
1. Work pressure: The normal working pressure in the system.
2. Design pressure: the maximum pressure limit of the valve; Do not exceed the design pressure of any special gas system component unless under controlled testing conditions.
The pressure limit of the special gas system is based on its lowest rated component - please remember this when selecting valves. The pressure and temperature of the process medium have a significant impact on the performance of the components. The valve you have chosen needs to withstand pressure and operate within various temperature and pressure ranges as needed. Design, material selection, and validation are all key aspects of valve performance. It should also be remembered that pressure and temperature have a significant mutual influence.
06 E - End Connection
Valves come with various end connections. These may be indispensable pipe fittings, pipe threads, pipe flanges, welded ends, etc. Although not traditionally associated with the structure of the valve, the choice of end connection is crucial for the overall construction of the valve and its ability to maintain a sealed system. Ensure that the termination is suitable for system pressure and temperature, and that the size and material are appropriate. Proper termination can simplify installation and avoid additional leakage points.
07 D - Delivery
Finally, after considering all the above factors and selecting the valve that is suitable for your application, as with any other factor, timely delivery and reliable supply are crucial for maintaining the operation and efficiency of the special gas system. As the final step of the STAMPED method, it is necessary to consider the supplier's strength, whether they can meet the requirements when you need parts, and whether they can work with you to understand your system requirements.
The above is the STAMPDE method compiled by Gesparker for everyone. We believe that through the above steps, the user unit will have a better understanding of how to choose the right valve. If you have any questions, Gesparker also welcomes inquiries from everyone.
Gesparker has been deeply involved in the field of gas applications for thirteen years, and is very familiar with the relevant processes of the gas application industry. We have a strong and stable supply chain and construction technology team, which are our strong backing, giving us the strength and determination to provide the highest quality and most reassuring complete gas application services for various user units.
