Selection Specifications for Primary Valves of Instruments

When selecting primary pressure-taking valves (also known as main valves), secondary valves, and vent valves for instruments, the following standards and specifications need to be considered: 1. **Operating pressure** – The maximum operating pressure of the valve should be higher than the highest pressure that the system may experience. 2. **Working Medium** - Select an appropriate material based on the medium flowing through the valve (such as gas, liquid, corrosive, or viscous media), such as stainless steel, carbon steel, copper, or plastic. 3. **Temperature range** - Select a valve that can withstand the temperature range of the medium inside the system. 4. **Connection method** - Choose valves with threaded connection, welded connection, or flanged connection depending on the way the pipes are connected. 5. **Flow requirements** - Ensure that the flow rate of the valve selected meets the system’s requirements; it should neither be too low nor too high. 6. **Operation Method** – Select valves with manual, electric, or pneumatic operation methods depending on the requirements for on-site or remote control. 7. **International and domestic standards** – Relevant valve design standards such as API (American Petroleum Institute), ANSI (American National Standards Institute), and GB (Chinese national standards) can be referred to for selection. 8. **Safety and environmental requirements** – If there are specific safety or environmental requirements, valves that meet the corresponding standards should also be selected (such as SIL safety levels, leakage ratings, etc.). It should be noted that since different industrial processes and equipment have varying specific requirements for valves, the above factors need to be carefully analyzed and evaluated in light of the particular application scenario. In the actual selection process, it may be necessary to consult valve manufacturers or professionals in related fields for more specific guidance. Additionally, sometimes it is also necessary to select the appropriate model based on other equipment and instruments present on site. In specific industries such as petrochemicals and biopharmaceuticals, there may also be industry-specific standards and regulations that need to be followed. .

The standards do not specify in detail; generally, a shut-off valve is used, along with the functions it should have. The others need to be selected based on the actual conditions of the project.