Maintenance Guide for High-Pressure Metal-Seated Ball Valves

The operation and maintenance of high-pressure metal-seated ball valves are essential to ensuring their safe and stable performance under harsh conditions. Following proper operational steps and maintenance procedures not only extends the valve's lifespan but also helps prevent safety hazards caused by malfunctions. Below are key points for metal-seated ball valve operation and maintenance, along with detailed steps for disassembly, cleaning, reassembly, and testing.

Operational Guidelines

Operating high-pressure metal-seated ball valves safely and reliably is critical. The following guidelines help operators use the valve correctly, prolong its lifespan, and reduce safety risks.

1. Internal Pressure Warning

Even when the ball valve is closed, pressurized fluid may still be trapped inside the valve body. Before performing any maintenance, ensure the pipeline pressure is relieved and the valve is fully opened to guarantee safe operation.

2. Power and Air Supply Cutoff

Before maintenance, disconnect power or air supply, particularly for valves with automated pneumatic or electric actuators. The actuator should be separated from the valve to prevent accidental signals from triggering it and causing danger.

3. Equipment Inspection

Before disassembling the valve, ensure the pressure in the upstream and downstream pipelines is fully released. Disassembly should only begin once it's confirmed that no residual pressure remains, to avoid accidents caused by sudden pressure release.

Disassembly and Maintenance Steps

When disassembling and maintaining high-pressure metal-seated ball valves, take care to protect the sealing surfaces and avoid damaging parts. Follow these steps to ensure safe disassembly and precise maintenance.

1. Sealing Protection

During disassembly or reassembly, protect the sealing surfaces, especially non-metal parts like O-rings. Use special tools to remove O-rings to prevent damage from sharp objects.

2. Flange Bolt Tightening

When disassembling or reassembling, tighten the flange bolts symmetrically, step by step, and evenly. This ensures the flange's sealing and stability.

Cleaning and Maintenance

Proper cleaning and maintenance are crucial for maintaining valve performance. Use appropriate cleaning agents and methods to ensure all components are clean and free of contaminants, keeping the valve in top working condition.

1. Choosing the Right Cleaning Agent

The cleaning agent must be compatible with the valve's rubber, plastic, metal parts, and the working medium. For example, gasoline can be used to clean metal parts when the working medium is gas, while pure water or alcohol is recommended for non-metal parts.

2. Cleaning Method

Parts that have been disassembled can be cleaned by soaking. For components that remain assembled, use a clean, soft cloth soaked in the cleaning agent to gently wipe them, ensuring no fibers are left on the surfaces. Thoroughly remove grease, dirt, adhesives, and dust from all surfaces.

3. Non-metal Parts

After cleaning, remove non-metal parts promptly to avoid long-term soaking, which can cause aging or degradation of materials. Reassemble the parts only after the cleaning agent has completely evaporated, but avoid leaving them out too long to prevent rust or contamination.

4. Cleaning New Parts

Before assembly, ensure that any new parts are thoroughly cleaned to remove any impurities or contaminants that could affect the valve's performance.

Lubrication and Reassembly

Proper lubrication and careful reassembly are essential to ensure smooth valve operation and reliable sealing. Ensure that no contaminants or impurities enter the valve body during this process.

1. Choosing and Applying Lubricant

The lubricant must be compatible with the valve's metal, rubber, and plastic components, as well as the working medium. Apply a thin layer of grease to the sealing grooves, valve stem sealing surfaces, and friction surfaces for smooth operation and reliable sealing.

2. Reassembly Guidelines

During reassembly, avoid contamination by metal debris, fibers, grease (except the specified lubricant), dust, or other impurities. Handle components carefully to ensure no foreign particles enter the valve or adhere to its surfaces, maintaining effective sealing and preventing leaks.

Detailed Disassembly and Reassembly Steps

Disassembly and reassembly must follow a specific sequence to ensure that all parts remain intact. Adhering to these steps ensures safe operation and proper valve functionality.

1. Disassembly Steps

First, place the valve in a half-open position and flush the valve body to remove any hazardous substances. Then, close the valve and remove the bolts and nuts connecting the flanges on both sides, completely removing the valve. Sequentially disassemble the actuator, connecting brackets, anti-loosening washers, stem nuts, spring clips, wear plates, and stem packing. Finally, remove the cover bolts and nuts, separate the cover from the valve body, and remove the valve ball, seats, and O-rings. Take care not to scratch the valve stem surface or the sealing areas of the valve body during disassembly.

2. Reassembly Steps

Clean and inspect all disassembled parts. It's recommended to replace sealing components such as valve seats and cover gaskets using a spare parts kit. Reassemble the valve in reverse order of disassembly, ensuring that the bolts are tightened according to the specified torque and in a cross-locking pattern to ensure secure assembly. After reassembly, test the valve's opening and closing functions using appropriate signals to verify proper operation.

Performance Testing and Safety Checks

After reassembly, conduct necessary performance and safety tests to ensure the valve's sealing and operational reliability under actual working conditions.

1. Pressure and Performance Testing

After reassembly, but before reinstalling in the pipeline, perform pressure sealing tests and operational performance tests per relevant standards to ensure the valve meets all required specifications. Focus on checking the valve's sealing performance and its reliability in opening and closing under actual working conditions.

2. Safety Inspection

Once the valve is reinstalled, perform a full system safety inspection to ensure the valve and related equipment can operate stably under high-pressure conditions, preventing leaks or malfunctions due to improper sealing or installation.

Conclusion

High-pressure metal-seated ball valves play a crucial role in high-pressure applications. Proper operation, regular maintenance, and standardized disassembly and assembly procedures ensure the valve's safety and long-term performance. By following maintenance protocols and operational guidelines, equipment lifespan can be extended, and potential safety hazards can be effectively prevented.