First, what are the principles and characteristics of slip-on welding flanges?
A slip-on welding flange is a flange that connects to a container or pipeline using a fillet weld. It is an arbitrary type of flange. During design, it is checked as either an integral or loose flange, depending on the degree of integrity of the connection between the flange ring and the straight section. Flange rings come in two types: with and without a neck. Compared to necked welding flanges, slip-on welding flanges have a simpler structure and use less material, but their rigidity and sealing performance are not as good. Slip-on welding flanges are widely used in the connection of medium and low-pressure vessels and pipelines.
Characteristics of Slip-on Welding Flanges: Slip-on welding flanges not only save space and reduce weight, but more importantly, they ensure that there is no leakage at the joint, providing excellent sealing performance. The compact flange size is reduced because the diameter of the sealing element is reduced, which reduces the cross-section of the sealing surface. Secondly, the flange gasket has been replaced by a sealing ring to ensure the matching of the sealing surfaces. This means that only a small pressure is needed to tighten the sealing surface. As the required pressure decreases, the size and number of bolts can be reduced accordingly, resulting in a new product that is small in size and lightweight (70%–80% lighter than traditional flanges). Therefore, the slip-on flange is a relatively high-quality flange product, reducing weight and space, and playing an important role in industrial applications.
The sealing principle of a slip-on flange: The two sealing surfaces of the bolts press against the flange gasket to form a seal, but this also leads to seal failure. To maintain the seal, a huge bolt force must be maintained, requiring larger bolts. Larger bolts require larger nuts, meaning larger diameter bolts are needed to tighten the nuts. However, the larger the bolt diameter, the more likely the flange will bend, which can be solved by increasing the flange wall thickness. The entire assembly will require a very large size and weight, which becomes a particular problem in offshore environments, where weight is always a major concern. Moreover, fundamentally, the slip-on flange is an ineffective seal, requiring 50% of the bolt load to press against the gasket, leaving only 50% for maintaining pressure.
Second, the difference between socket welding flanges and plain welding flanges.
Socket welding flanges are suitable for small-diameter, high-pressure, and high-temperature pipeline connections.
Plain welding flanges have a boss, similar to butt welding flanges, with a groove cut into the boss, into which the pipe is inserted and welded.
Socket welding flanges do not have a boss; a groove is directly cut into the flange body, similar to a blind flange with a hole and then a groove. Plain welding flanges have slightly better weldability than socket welding flanges.
Post time: Dec-02-2025