Fully Welded Ball Valves: Design and Maintenance
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Fully welded ball valves have become essential equipment in industries such as oil, natural gas, chemical, and power due to their superior sealing performance, unique structural design, and broad adaptability. Under harsh working conditions, their stability and reliability make these ball valves highly favored. This article delves into the characteristics, structural design, maintenance, disassembly, and installation of fully welded ball valves, providing a detailed analysis of their industrial applications and technical points.
Characteristics of Fully Welded Ball Valves
Fully welded ball valves are renowned for their excellent sealing performance and good adaptability to changes in pressure and temperature. The valve seat is composed of a Teflon sealing ring and a disc spring, which can achieve zero leakage under fluctuating pressure and temperature conditions. This design not only extends the service life of the valve but also enhances the safety and reliability of system operation. Additionally, fully welded ball valves possess good corrosion resistance and fatigue resistance, making them suitable for complex working conditions involving high temperatures, high pressures, and corrosive media.
Structural Design
The structural design of fully welded ball valves comes in two forms: cylindrical and spherical structures, catering to different working conditions. The cylindrical structure uses a double welding process, which, although having a larger heat input, is suitable for low-stress situations. In contrast, the spherical structure reduces heat input through a four-point welding method, effectively controlling axial and radial deformation, making it suitable for scenarios with high sealing requirements.
The advancement of modern technology has further optimized the production process of fully welded ball valves. For instance, the left and right valve bodies are formed by hot forging and pressing, with a single welding in the middle, reducing residual stress from traditional welding processes. Meanwhile, the split-body design connects the valve body with the connecting body through bolts, and simulation design optimizes the flange thickness and bolt strength to prevent connection loosening or sealing failure due to pipeline stress.
Maintenance and Care
Routine maintenance of fully welded ball valves is generally performed in the fully open state, but special circumstances may require maintenance in the closed state. After maintenance, lubricating grease should be injected, and the grease injection port should be sealed to prevent the entry of impurities or oxidation of the grease. Adjustments to the switch limiter should consider the coordination of the open and closed positions to avoid valve sealing issues or failure to open fully.
Furthermore, during maintenance, attention must be paid to the accuracy of the right-angle stroke. If the valve has a smooth bore but cannot close completely, the limiter may need readjustment. Adjustments should be gentle to avoid damaging the valve stem surface and other sealing components.
Disassembly Method
Disassembling fully welded ball valves requires extra care to protect the sealing components and other critical parts. The specific steps are as follows.
Preliminary Preparation: Place the valve in a half-open state, clean internal impurities, and prevent damage to the sealing materials.
Remove the Valve: Close the valve, dismantle the flange bolts and other connecting parts, and remove the valve from the pipeline.
Dismantle Components: Sequentially disassemble the driving equipment, actuator, brackets, gaskets, and packing, ensuring gentle movements to avoid damaging the valve body and sealing components.
Valve Body Separation: Remove the connecting bolts and nuts, separate the valve cover from the valve body, and remove internal sealing parts, valve stem, and O-rings.
Throughout the process, special attention must be paid to avoid external forces damaging key components such as the valve body packing gland, ensuring stable performance in subsequent use.
Installation Key Points
When installing fully welded ball valves, it is necessary to strictly follow operational specifications:
Pre-installation Inspection: Verify the valve model and specifications, check for damage, and clean internal impurities. Pay special attention to checking if the valve stem is skewed to prevent damage from collisions during transportation.
Lifting and Securing: When lifting the valve, ropes should be attached to the flanges, not the handwheel or valve stem, to avoid damaging important components.
Pipeline Cleaning: Use compressed air to blow out impurities such as iron oxide shavings and welding slag from the pipeline to prevent particulate matter from wearing the valve sealing surface or blocking small valves.
Installation Process: When connecting with flanges, tighten the bolts symmetrically and evenly to ensure the flanges are parallel and maintain an appropriate gap to prevent excessive pressure on the valve or even cracking. For one-piece fully welded ball valves, spot welding should be done first to secure the valve, ensuring the closure member is fully open before complete welding.
Sealing Packing Treatment: For threaded connection valves, sealing packing should be wound around the pipeline to prevent the packing from entering the valve interior and affecting the medium circulation.
Conclusion
Fully welded ball valves, with their unique design and exceptional performance, provide strong assurance for the safety, stability, and efficiency of industrial systems. Proper maintenance and care can further extend their service life, and strict adherence to operational specifications during installation and disassembly can ensure optimal performance during operation. In the future industrial development, fully welded ball valves will continue to provide indispensable support to various industries with their reliability and versatility.