Chinese Chemical Industry Emphasizes Valve Selection for Safety

I. Selection of chemical valves

1.1 Working environment and medium characteristics

In the selection process, the first thing to consider is the working environment and medium characteristics of the valve. Different chemical media have different requirements for the material and structure of the valve.

- Medium corrosiveness: For corrosive media, corrosion-resistant materials such as stainless steel, Hastelloy, etc. should be selected.

- Working temperature and pressure: According to the working temperature and pressure of the medium, select the appropriate valve type and material to ensure that it can still work normally under extreme conditions.

1.2 Valve type

There are many types of chemical valves, including gate valves, stop valves, ball valves, butterfly valves, etc. Each type of valve has its unique application occasions and performance characteristics.

- Gate valve: suitable for fully open or fully closed working conditions, not suitable for regulating flow.

- Stop valve: suitable for occasions where flow needs to be adjusted, but its resistance is large.

- Ball valve: suitable for occasions with frequent switching, with good sealing performance and low resistance.

- Butterfly valve: suitable for large-diameter pipelines, compact structure and easy operation.

1.3 Sealing performance

The sealing performance of chemical valves directly affects the safety and stability of the system. In the selection process, the appropriate sealing form and material should be selected according to actual needs.

- Soft seal: suitable for low temperature and low pressure occasions, with good sealing performance, but not resistant to high temperature and high pressure.

- Hard seal: suitable for high temperature and high pressure occasions, with good wear resistance and corrosion resistance, but relatively poor sealing performance.

II. Precautions for the use of chemical valves

2.1 Inspection before installation

Before installing the valve, it should be inspected in detail to ensure that it is intact.

- Appearance inspection: Check whether the appearance of the valve is obviously damaged, corroded or deformed.

- Sealing inspection: Check whether the sealing surface of the valve is damaged or has foreign matter, and clean and repair it if necessary.

2.2 Correct installation method

The installation method of the valve has an important impact on its performance and life. The following points should be noted:

- Directionality: Some types of valves (such as stop valves and check valves) have clear installation directions. When installing, ensure that their flow direction is consistent with the flow direction of the medium.
- Support and fixation: The valve should be installed on a solid support to avoid damage caused by pipeline vibration or stress.
- Flange connection: During the flange connection process, the flange surface should be flat and the bolts should be tightened evenly to avoid leakage caused by uneven force.

2.3 Monitoring and maintenance during operation

During the operation of the valve, regular monitoring and maintenance should be carried out to ensure its normal operation.

- Regular inspection: Regularly check the working status of the valve, including pressure, temperature, leakage, etc., and deal with problems in time.
- Lubrication and cleaning: Lubricate and clean the valve regularly to prevent failures caused by impurities or wear.
- Recording and analysis: Keep a good record of the valve operation, analyze its operating status, predict possible problems, and take preventive measures in advance.

III. Common problems and solutions

3.1 Valve leakage

Cause analysis: Valve leakage may be caused by damage to the sealing surface, impurities between the valve disc and the valve seat, or loose springs.

Solution:
- Check the sealing surface: Disassemble the valve, check whether the sealing surface is damaged or corroded, and repair or replace it if necessary.
- Remove impurities: Clean impurities between the valve disc and the valve seat to ensure good contact.
- Adjust the spring: If the spring is loose, adjust the compression of the spring appropriately to restore its elasticity.

3.2 Valve stuck

Cause analysis: Valve stuck may be caused by wear, rust or impurities on the valve stem or valve disc.

Solution:
- Cleaning and lubrication: Disassemble the valve, clean the valve stem and valve disc, and apply an appropriate amount of lubricating oil to reduce friction and wear.
- Replace parts: If the valve stem or valve disc is severely worn or rusted, new parts should be replaced.

The selection and use of chemical valves is a complex and critical process that requires comprehensive consideration of multiple factors. Through reasonable selection and correct use methods, the service life and safety of the valve can be effectively improved to ensure the smooth progress of chemical production. It is hoped that the selection and use guide provided in this article can provide a reference for the majority of users and help everyone better manage and use chemical valves.