Socket Flanges vs Threaded Flanges

　　1. Connection Strength and Sealing Performance

　　In terms of connection strength, socket flanges are fixed by inserting the pipe into the socket and then welding it. The weld can transmit the axial and radial forces of the pipeline, and its tensile strength can reach more than 80% of the base material. In medium and high pressure pipelines (such as Class 300-Class 600), it can stably withstand pressure impacts. Threaded flanges rely on threaded connections. The force-bearing area of the threaded contact surface is small, and over long-term use, the threads are prone to loosening due to vibration and temperature changes. The connection strength is only 60%-70% of that of socket flanges, making them more suitable for pipeline systems with lower pressure requirements.

　　Regarding sealing performance, socket flanges have double sealing protection: firstly, the welded seal between the pipeline and the socket prevents leakage of the medium from the gap between the pipeline and the flange; secondly, the face seal between the flange face and the gasket. The large sealing area and the high reliability of the seal after the bolts are evenly tightened make them suitable for transporting toxic, flammable, and explosive media (such as natural gas and methanol). Threaded flanges rely on the sealing of the threads (sealing adhesive/Teflon tape) and the flange face for sealing. is only about 1/5 that of socket flanges. The risk of seal failure is 30%-50% higher than with socket flanges, making them more suitable for non-toxic, non-hazardous media (such as tap water and compressed air).

　　2. Installation Difficulty and Efficiency: Socket flanges require welding, demanding qualified welding personnel (e.g., AWS D1.1 certification). Welding current and voltage must be carefully controlled to avoid defects such as weld beads and incomplete penetration. Weld slag must also be cleaned after welding. Furthermore, socket flanges require high pipe straightness (deviation ≤1°), otherwise, flange face misalignment will occur, affecting the seal. Threaded flanges require no welding; simply screw the pipe threads onto the flange threads. Ordinary construction personnel can operate them with simple training. They also have lower requirements for pipe straightness and can be installed in slightly curved pipes, making their installation threshold much lower than that of socket flanges.

　　In terms of installation efficiency, taking DN50 and Class 150 specifications as examples, installing a socket flange requires steps such as pipe cutting, beveling, inserting into the socket, welding, cleaning weld slag, aligning bolt holes, and tightening bolts, taking approximately 20-30 minutes in total. 5-10 minutes. The installation efficiency is more than 60% higher than that of socket flanges, making it particularly suitable for projects with tight schedules (such as temporary pipeline repairs and rapid equipment assembly).

　　3. Applicable Working Environment and Cost

　　In terms of applicable working conditions, socket flanges, due to their high connection strength and good sealing performance, can be used in medium and high pressure (Class 150-Class 2500) and medium and high temperature (-40℃ to 450℃) conditions, and are suitable for corrosive media environments (stainless steel/alloy materials). They are commonly used in core pipeline systems in industries such as petrochemicals, power, and natural gas. Threaded flanges, limited by connection strength and sealing performance, are only suitable for low pressure (≤Class 150) and normal temperature (-20℃ to 120℃) conditions, and the medium must be non-toxic and non-corrosive. They are mostly used in municipal water supply, building HVAC, and general industrial auxiliary pipelines.

　　In terms of cost, socket flanges of the same specifications (DN50, Class 150) require welding and processing, use more material (thicker flange), and require matching welding consumables (welding rods, welding wire), so the cost per set is about 1.2-1.3 times that of threaded flanges. However, in terms of long-term usage costs, socket flanges have a service life of 8-12 years (carbon steel) and 15-20 years (stainless steel), and require less maintenance. Threaded flanges, on the other hand, are prone to thread wear and sealant aging, with a service life of only 5-8 years. They require frequent replacement of sealing materials or flanges, and their long-term maintenance costs are about 15% higher than those of socket flanges.