How to select and maintain an instrument valve?
Release date:
2022-10-11
How to select and maintain instrument valves? When selecting instrument valves, some basic factors need to be considered. Important criteria to consider when choosing instrument valves include the basic valve/packing design, pressure fluctuations, pressure and temperature considerations. Other key factors to consider include the flow medium, specifications and standards, actuator design options, flow analysis, and orifice sizing. Before determining the specifications of the instrument valve, it is very important to correctly assess all aspects of the system. Understanding various operating conditions will greatly impact
How to select and maintain instrument valves?
Selection Instrument valve When selecting, some basic factors need to be considered. Instrument valve Some important criteria to consider during selection are as follows. Each factor is important:
Basic valve/packing design, pressure fluctuations, pressure and temperature considerations. Other key factors to consider include the flow medium, specifications and standards, actuator design options, flow analysis, and orifice sizing.
Before determining Instrument valve specifications, it is very important to correctly assess all aspects of the system. Understanding various working conditions greatly influences the choice of instrument valves.
Understanding the design methods of instrument valve packing and the available valve design types plays an important role in specification development. Unlike manual operation, the basic core of the valve consists of control components such as balls or needles, sometimes including automatic actuators for valve operation. The flow through the seat material is controlled, while the packing limits leakage between the seat and the driving element. Overall performance is significantly affected by structural materials, stiffness, stem position, and correct valve selection. Generally, among all valve designs on the market, the following four valve types are suitable for instrument applications involving flow control and analysis.
The main failure parts of instrument valves include the valve body, valve core, and valve seat. Regularly inspect the inner wall of the valve body for corrosion and wear, especially for valves used under harsh process conditions such as corrosive media, high pressure differentials, and cavitation. It is necessary to ensure their pressure resistance, corrosion resistance, and wear resistance. The valve core functions to regulate and shut off fluid and is a movable throttling element. Therefore, it is severely affected by medium erosion, corrosion, and particle impact, and is more prone to damage under high pressure differentials and cavitation. Hence, it is necessary to check whether its parts are damaged, worn, or corroded, and whether repair or replacement is needed. The sealing surface of the valve seat is key to ensuring valve closure. It is subject to severe corrosion and wear. Due to medium penetration, the internal surface of the threads fixing the valve seat is often corroded and loosened. This part should be specially inspected.
There are some key components in different types of instrument valves that are also prone to failure, such as pneumatic and hydraulic actuators. The diaphragm is an important part of diaphragm-type pneumatic actuators. When the air supply system is normal but the actuator does not operate, consider whether the diaphragm is ruptured or improperly installed. When the metal contact surface has sharp edges, burrs, or other defects, the diaphragm can be punctured and will leak. Additionally, if the diaphragm has been used for a long time, material aging will also affect its use. Pneumatic and hydraulic actuators generate driving force through pistons, so piston damage and wear are not allowed. The air (or fluid) pipe is the channel from the input pressure to the actuator and needs to be checked for secure connection and no leakage. Check whether the push rod is bent, deformed, or detached. The push rod should be firmly connected to the valve stem and its position adjusted to ensure sufficient travel and valve closure. Check whether the spring is broken; improper manufacturing, processing, or heat treatment can cause spring breakage, and some springs may also break under excessive load.
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