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What are the differences between butt-welded pipe fittings and socket-welded pipe fittings?
2025-01-18
1. Connection Methods:
1) Butt welding connects two parts after spot welding. This method requires a higher level of welding skill, as it necessitates 100% radiographic testing under strict conditions. Butt welding is commonly used in the chemical, petroleum, power, natural gas, and steel industries.
2) Socket welding involves welding a pipe into a valve body, resulting in a shape similar to a threaded connection. Generally, socket welding is used for carbon steel and stainless steel pipes of 2 inches or less. Stainless steel pipes under 2 inches are also used in butt welding, such as flange-to-flange connections; titanium pipes, duplex steel, nickel-based alloys, etc., are mainly used in butt welding.
2. Differences
1) Socket welding forms a fillet weld, while butt welding forms a butt weld. Analysis of weld strength and stress state shows that butt joints are superior to socket joints. Therefore, butt welding should be used in high-pressure applications and harsh service conditions.
2) Socket welding is typically used for smaller diameters, DN40 or less, due to its cost-effectiveness. Butt welding is generally used for DN40 and above. Socket welding is mainly used for welding small-diameter valves and pipes, fittings, and pipes. Small-diameter pipes usually have thinner walls, making them prone to misalignment and burn-through, thus making welding more difficult. Socket welding is more suitable in these cases. Additionally, the socket in socket welding provides reinforcement, allowing its use under high pressure. However, socket welding also has drawbacks. One is the poor stress state after welding, leading to potential welding defects and gaps within the piping system. Therefore, it is unsuitable for piping systems carrying gap-corrosion sensitive media or those with high cleanliness requirements. Furthermore, for ultra-high-pressure pipes, even small-diameter pipes have thicker walls, and butt welding can be used to avoid the limitations of socket welding.
3) The former requires one large and one small diameter for insertion welding. The latter can have the same or different diameters. 2. Different weld bevel forms. 3. Different welding processes. 4. Different weld strength.
4) Most lower pressure ratings use smaller socket welds, while higher pressure ratings typically use butt welds. Butt welds undergo 100% non-destructive testing to ensure leak tightness.
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