In the realm of fluid control systems, the selection and specification of valves stand as pivotal tasks, dictating the efficiency, safety, and reliability of operations. Valves serve as gatekeepers, managing the flow of diverse fluids, from liquids and gases to slurries and vapors, amidst varying conditions and environments. To embark on the journey of valve selection and specification, a comprehensive understanding of fundamental principles is indispensable. From the intricate nature of the transported fluid to the precise functionality requirements and considerations of size, pressure loss, material compatibility, and temperature-pressure parameters, each facet intricately weaves into the fabric of optimal valve selection. Let's delve into these key principles, unraveling the essence of informed decision-making in the realm of valve engineering.
Valve selection & specification valve selection principle
1, The nature of the transport fluid
The valve is used to control the fluid, and the nature of the fluid has a variety of, such as liquid, gas, steam, slurry, suspension, viscous liquid, etc., some fluids also have solid particles, dust, chemicals and so on. Therefore, when choosing a valve, we must first understand the nature of the fluid, such as whether the fluid contains solid suspended matter? Is it possible for a liquid to vaporize as it flows? Where does it vaporize? Does the gas phase liquefy when it flows? How corrosive is the fluid? When considering the corrosiveness of a fluid, it should be noted that the corrosiveness of a mixture of several substances is often different from that of a single composition.
2, the valve function
The function of the valve should also be considered when selecting the valve. Is this valve used to shut off or to regulate flow? If it is only cut off, it is also necessary to consider whether there is a fast opening and closing requirement; Does the valve have to be closed so tightly that no leakage is allowed? Each valve has its characteristics and application occasions, to choose the appropriate valve according to the functional requirements.
3. Size of valve
The size of the valve is determined according to the flow rate of the fluid and the allowable pressure loss. Generally, it should be consistent with the size of the process pipe.
4. Pressure loss
A considerable part of the pressure loss in the pipeline is caused by the valve. Some valve structures have large resistance, while some have small resistance; But all kinds of valves have their own inherent functional characteristics. The same type of valve some resistance, some resistance is small; Proper consideration should be given when selecting.
5, the valve material
When the pressure, temperature rating and fluid characteristics of the valve are determined, the appropriate material should be selected. Different parts of the valve, such as its body, gland, disc, seat, etc., may be made of several different materials to achieve an economical and durable effect. Cast iron valve body allows 200℃; The steel valve body can be used at 425℃; More than 425℃ should consider the use of alloy steel materials;
High temperature resistant Cr-Ni stainless steel is usually used for more than 550 ° C. For the transport of chemically corrosive medium of the valve, according to the nature of the medium made of stainless steel, Monel alloy, plastic and other materials, can also use anti-corrosion material lining and so on. Appropriate and economical materials should be selected.
6. Temperature and pressure
The material and pressure level of the valve should be determined according to the working temperature and pressure of the valve.
