Fully Welded Ball Valves: Installation & Disassembly

In industrial pipeline systems, fully welded ball valves are widely used due to their excellent sealing performance and durability. However, correct installation, maintenance, and effective resolution of common issues are essential for ensuring long-term stable operation. This article will detail the installation steps, maintenance points, and solutions to common problems to help you better manage and utilize the fully welded ball valve.

Installation Precautions for Fully Welded Ball Valves

When installing a fully welded ball valve, it is crucial to follow the correct steps and precautions to ensure the valve's performance and longevity. Below are the key points to pay attention to when installing a fully welded ball valve.

1. Pre-Installation Checks

Before installing a fully welded ball valve, a series of checks must be conducted to ensure the valve's quality and performance meet the requirements. First, carefully verify the valve's specifications to ensure they align with the pipeline system's design requirements. Check for any damage, particularly to the valve stem, as it is susceptible to misalignment during transportation. Rotate the valve stem manually a few times to check for smooth operation. If any misalignment or sticking is found, the valve must be repaired or replaced immediately. Additionally, clean any debris inside the valve, which may have accumulated during transport or production. Failure to clean this debris could severely affect the valve's sealing performance and service life.

2. Valve Hoisting

When hoisting a fully welded ball valve, great care must be taken to avoid damaging any components. Never tie the hoisting rope to the handwheel or valve stem, as these parts are relatively fragile and prone to damage during lifting. The correct method is to tie the hoisting rope to the valve's flange, ensuring safe and stable lifting. During the hoisting process, try to maintain the valve's balance to prevent undue stress caused by tilting.

3. Pipeline Cleaning

The pipeline connected to the valve must be kept clean, as this is crucial for ensuring the valve's normal operation. Before installing the valve, use compressed air to blow through the pipeline to remove iron oxide debris, sediment, welding slag, and other contaminants. These debris can wear down the valve’s sealing surfaces or even cause clogging, leading to valve failure. This is especially critical for small-diameter valves, as large particles are more likely to cause blockages. Thorough pipeline cleaning before installation is an essential step.

4. Valve Connection

When installing threaded balance valves, it is important to use sealing fillers. Lead-based oil or PTFE tape can be used, but the filler must be wound onto the pipeline and kept out of the valve interior. If the filler enters the valve, it may accumulate and disrupt the medium's circulation. For flange fully welded ball valves, bolts should be tightened symmetrically and evenly. The valve flange needs to be parallel with the pipeline flange and maintain proper spacing to avoid excessive pressure on the valve, which could cause cracks. Special attention should be paid to valves made from brittle materials or low-strength materials, as these are more prone to damage.

5. Welding Considerations

For integrated fully welded ball valves, extra caution is required during installation. First, spot weld the valve, fully open the valve seat, and then perform the final welding. This ensures the valve does not suffer damage due to thermal stress during welding. During welding, strict control of welding parameters is necessary to avoid excessive heat that could adversely affect the valve.

6. Post-Installation Checks

After installation, when pressure testing the system or pipeline, the valve must be fully opened to prevent damage from incomplete opening. The valve markings should match the usage requirements, and the flow direction markings on the valve body should align with the pipeline flow direction. If the connecting flange sealing surfaces are metal, fluoroplastic sealing gaskets must be added to ensure a proper seal. During installation, aim for a horizontal installation with the valve stem facing up to avoid tilting. Additionally, large installation stresses from pipes or supports should be avoided. When hoisting the valve, do not use the handwheel. If the pipeline has sufficient strength to bear the valve's weight and operational torque, no support is needed; however, for fluorine-lined valves, support is recommended to ensure valve stability.

Disassembly and Maintenance of Fully Welded Ball Valves

Disassembling and maintaining a fully welded ball valve is essential for ensuring its long-term stable operation. Correct disassembly methods prevent unnecessary damage, while regular maintenance helps extend the valve's service life and maintain its performance.

1. Preparation Before Disassembly

Before disassembling the fully welded ball valve, ensure the valve is in a semi-open state to prevent contaminants inside the valve body from damaging the sealing materials. Thoroughly clean the valve body to ensure no residual impurities remain. Close the ball valve and remove the bolts and nuts from both ends of the flange, then remove the valve from the pipeline.

2. Disassembly Steps

Disassemble the various components sequentially, including drive devices, actuators, connecting brackets, gaskets, nuts, and stem packing. Next, remove the connecting bolts and nuts, separate the valve cover from the valve body, and remove the gasket inside the valve cover. Once the ball valve is in a closed state, it is easy to remove the valve body and seat. Then, remove the stem, O-ring, and packing under the stem. Throughout the disassembly process, be gentle to avoid unnecessary damage to the stem or valve body seal components.

3. Maintenance Points

The valve seat of a fully welded ball valve consists of PTFE seals and disc-shaped springs, which provide excellent sealing performance within the specified pressure and temperature range. For maintenance, it is generally recommended to keep the valve in the open position, although in some cases, closing the valve for maintenance is acceptable. For other ball valves, maintenance is not always determined by the open position. For example, forged steel extended-end ball valves require inspection of the pressure regulator valve diameter and sealing seat alignment. If there is interference in the open position, the limiters should be adjusted inward to ensure the diameter is straight before finalizing the adjustment. When adjusting the limiters, the positions of both open and closed states should be considered together. If the open position is aligned but the valve cannot close fully, the valve may fail to seal properly. Similarly, when adjusting the closed position, the corresponding open position should also be adjusted. After greasing the valve’s angular travel, seal the grease port to prevent contaminants from entering or grease oxidation. Apply anti-rust grease to the cover to prevent rusting and ensure the valve operates properly during the next use.

Pressure Testing for Fully Welded Ball Valves

Before installation, fully welded ball valves must undergo strict pressure testing to ensure their sealing and strength meet design requirements. Below are the steps and methods for conducting pressure tests.

1. Strength Test

Before installing the fully welded ball valve, a strict strength test must be conducted to ensure the valve’s strength and sealing performance meet the requirements. For larger diameter welded ball valves, standard valve pressure testing equipment may not be adequate for the required pressure. In such cases, high-pressure caps should be welded onto the valve's sleeve, and after opening the valve to a 45-degree position, clean water that meets the pressure testing requirements should be injected as the medium. Gradually increase the pressure to 1.5 times the nominal pressure of the valve, hold the pressure for 15 minutes, and check for any leaks. If no leaks occur, the valve body strength is qualified.

2. Sealing Test

A sealing test is typically conducted using nitrogen as the medium. Close the ball valve, inject nitrogen into the valve body from the sleeve, and raise the pressure to 1.1 times the valve's nominal pressure. The cavity’s vent valve is connected to a soft hose leading to a water container for detection, with the insertion depth set at 1 cm. If no bubbles are produced within 5 minutes, the valve's sealing performance is considered qualified.

Hoisting and Welding Considerations

During the installation process of a fully welded ball valve, hoisting and welding are critical steps, and any misstep can damage the valve and impact its performance and service life. Therefore, strict adherence to operating standards is essential to ensure the correctness and safety of hoisting and welding operations.

1. Hoisting the Fully Welded Ball Valve

Given that fully welded ball valves are typically quite heavy, often weighing several tons, it is crucial to use the correct hoisting methods. To protect the valve stem, avoid attaching the hoisting chain to the handwheel, gearbox, or actuator. The proper method is to attach the hoisting chain to the valve's flange, ensuring safe and stable lifting. Additionally, maintain the valve’s balance during hoisting to prevent unnecessary stress from tilting.

2. Welding the Fully Welded Ball Valve

The connection between a buried fully welded ball valve and the main pipeline is typically made using butt welding. The butt welding seam must undergo non-destructive testing, such as radiographic inspection. One-time welding may result in defects, so when ordering valves, the manufacturer should be asked to add a long sleeve pipe to both ends of the valve. The sleeve pipe length should be reasonable based on the valve’s diameter. If the weld is defective, the long sleeve pipe allows the defective weld to be cut and re-welded without affecting the valve's functionality. When welding the valve to the pipeline, the valve should be in the fully open position to prevent the ball valve from being damaged by welding splatter. Additionally, ensure that the internal sealing components of the valve do not exceed 140°C. Cooling measures should be implemented if necessary to control the welding temperature.

Conclusion

As an important piece of industrial equipment, fully welded ball valves must adhere to strict guidelines and requirements during installation, maintenance, and operation. Through the detailed introduction provided in this article, we understand that pre-installation checks, hoisting, pipeline cleaning, valve connection, welding, and post-installation inspections are all critical steps. Furthermore, during disassembly and maintenance, it is vital to protect the valve's components to avoid unnecessary damage. The article also provides effective solutions to common issues such as clogging, welding, and temperature problems. Finally, by conducting rigorous pressure tests and following correct hoisting and welding methods, the performance and safety of fully welded ball valves can be ensured, guaranteeing their long-term stable operation in industrial pipeline systems and providing reliable protection for industrial production.