Maintenance of Pneumatic Ball Valve in Coal Chemical Application

In the modern coal chemical industry, the application of gasification technology is becoming increasingly widespread, and pneumatic ball valves, as key equipment, play a crucial role. Pneumatic ball valves must not only maintain efficient operation under complex working conditions but also meet multiple requirements, including wear resistance, corrosion resistance, erosion resistance, anti-scaling and anti-coking, rapid opening and closing, frequent actuation, while ensuring good sealing performance to guarantee high efficiency, low energy consumption, and safe and reliable operation of the entire plant. However, in practical applications, pneumatic ball valves often face various challenges, such as valve jamming, erosion and wear, and seal failure. These issues not only affect production efficiency but may also pose safety risks. Therefore, thoroughly understanding the application characteristics, common failures, and solutions of pneumatic ball valves in the coal chemical gasification field is of great significance for improving equipment operational efficiency and safety.

In the gasification units of coal chemical plants, pneumatic ball valves play an extremely important role. They must handle complex media such as solid particles, ash, and sulfur, and meet a series of stringent requirements including wear resistance, corrosion resistance, erosion resistance, anti-scaling and anti-coking, rapid opening and closing, frequent actuation, while maintaining good sealing performance to ensure high efficiency, low energy consumption, and safe and reliable operation of the entire plant.

During coal chemical gasification, the medium often contains a large amount of solid particles, ash, and sulfur. These special media impose extremely high requirements on the valve's wear and corrosion resistance. For example, solid particles create strong erosion on the sealing surface as the medium passes through the valve, while sulfur can cause corrosion. Therefore, pneumatic ball valves need excellent wear and corrosion resistance to withstand these media's damaging effects.

The rapid opening and closing and frequent actuation characteristics of pneumatic ball valves allow them to meet the demand for high-efficiency operation in coal chemical plants. During the gasification process, valves need to be frequently operated to control the flow rate and direction of the medium. The fast response capability of pneumatic ball valves can effectively reduce operation time and improve production efficiency.

Good sealing performance is critical for pneumatic ball valves in coal chemical gasification. The valve's sealing directly affects the safe operation of the plant. Once internal or external leakage occurs, it can lead to material loss and may also trigger safety incidents. Therefore, pneumatic ball valves must have reliable sealing structures to ensure safe and stable operation.

Although pneumatic ball valves play a key role in coal chemical gasification, in actual operation they face many challenges and issues. The following section delves into common failures of pneumatic ball valves during use and their causes to better understand and prevent these problems.

After some time in service, pneumatic ball valves may experience jamming or fail to fully open or close. These issues are usually caused by severe erosion of the sealing surfaces of the ball and seat, resulting in sealing surface damage. In more severe cases, internal components of the ball and valve cavity may be damaged, leading to internal leakage. Increased clearance between the valve stem and packing gland can also cause external leakage.

Valve erosion and wear problems mainly originate from the characteristics of the medium. As the medium passes through the valve, the flow velocity increases and the pressure difference across the valve grows, causing strong erosion and wear. This is especially severe for ball valves with frequent operation. In addition, fine spherical particles formed by local melting of high-temperature media further increase erosion on the valve and sealing surface.

If dust or powder enters the valve seat spring cavity, it can cause spring failure or flipping. This situation affects normal valve operation and may even lead to leakage. Therefore, protection and maintenance of the valve seat spring are crucial.

If the grinding precision of the ball valve and seat is insufficient, it can result in poor concentricity and surface roughness, leading to internal leakage. These problems not only affect sealing performance but also shorten valve service life.

To cope with the complex conditions and challenges faced by pneumatic ball valves in coal chemical gasification, it is essential to carry out improvements and optimization. By continuously optimizing material selection, structural design, and manufacturing processes, the performance of pneumatic ball valves can be significantly enhanced, extending their service life while ensuring reliable operation in harsh environments.

To improve wear and corrosion resistance, the ball is usually made of forged stainless steel and coated with chromium carbide. This treatment significantly enhances hardness and wear resistance. Depending on different working conditions, ceramic-metal composite balls or surface coatings of tungsten carbide or zirconium carbide can also be applied.

For hard-sealed ball valves, the seat adopts a scraping-type design, enabling self-cleaning during opening and closing. This effectively prevents particle deposition and adhesion, ensuring smooth valve operation and avoiding jamming. At the same time, the auxiliary seat, valve body, and main and auxiliary seats use special structural designs with metal rings, increasing packing stiffness and toughness, preventing debris from entering the spring cavity, and ensuring long-term effective spring operation.

The upper and lower surfaces of the valve stem use bearing positioning, providing both rotation and guidance, ensuring coaxial alignment between the stem and ball. The upper part of the packing uses a disc spring to maintain preloading for sealing. Designed as a live-load type, it provides good sealing performance and can extend the life of sealing materials.

To ensure the long-term stable operation of pneumatic ball valves in coal chemical gasification, effective maintenance and servicing are indispensable. Through regular inspections, timely repairs, and reasonable operational procedures, failure rates can be significantly reduced, valve service life extended, and the safety and reliability of the entire system ensured.

Regularly inspect key components such as the sealing surface, valve seat, and valve stem, and promptly replace damaged parts. Especially when the seat is fractured or damaged, replace it immediately to prevent leakage. If scratches or wear appear on the valve core surface, causing incomplete closure, the entire valve body may need replacement.

Applying a smooth PTFE coating or evenly spreading anti-acid and anti-alkali coatings on the valve core surface can significantly enhance corrosion resistance, ensuring stable operation. PTFE coating also has good sealing properties, improving overall valve sealing performance.

For materials with low crystallization points, particularly during autumn, winter, and early spring, inadequate insulation or heating can lead to crystallization inside the valve, causing jamming. Steam purging can melt the crystals, while severe crystallization requires disassembling the valve to remove internal deposits. External jackets and proper insulation or heating may be added to maintain the valve core at a temperature suitable for medium flow.

Fibrous or magnetic impurities in the medium can accumulate around the valve core, causing malfunction or jamming. Manual cleaning after disassembly is necessary. Installing appropriate filters upstream of the valve and regular cleaning can reduce impurity-related jamming.

The connection between the pneumatic ball valve and pipeline is rigid; long-term vibration may loosen the gland, causing leakage. Simply retighten the gland, avoiding excessive torque that may affect stem rotation. If the packing under the gland is compressed, add packing material promptly. Long-term open-close vibration may also loosen intermediate support bolts, causing incomplete valve movement and connection failure. Reinforce the support during maintenance. Severe wear of the splined sleeve connecting the cylinder and valve body can also result in incomplete opening and closing, requiring replacement with the correct model.

During operation, pneumatic ball valves may malfunction due to abnormal working conditions, abnormal temperature/pressure ratios, or excessive corrosion. Faults are generally diagnosed using the elimination method: first inspect the air circuit, then wiring, actuator and accessories, and finally the valve body. Once the fault location is identified, appropriate corrective measures should be applied.

Pneumatic ball valves play an indispensable role in coal chemical gasification. Through proper material selection, optimized structural design, and strict maintenance measures, their service life and operational efficiency can be effectively improved. Regular inspections, timely replacement of damaged parts, anti-crystallization and impurity removal measures, and proper installation and cleaning methods are key to ensuring safe and reliable operation. Only with these measures can coal chemical plants achieve high efficiency, low energy consumption, and safe and reliable operation under complex working conditions.