Flanges are quite common in daily management processes. However, most people may not know where slip - on welding can be used and where butt - weld flanges must be selected.
Slip - on flanges and butt - weld flanges are two of the most widely used flange connection forms in industrial pipelines. Their core difference lies in the way they connect to the pipeline, which directly determines their mechanical properties, applicable working conditions, and installation requirements.
Simply put, slip - on flanges have a simple structure and low cost, making them suitable for ordinary working conditions with normal temperature and low pressure. Butt - weld flanges, on the other hand, have superior mechanical properties and are suitable for critical positions with high temperature, high pressure, and harsh working conditions.
The following is a comparison and explanation from several aspects.
| item | Slip - on flange | Butt - weld flange |
| Connection method | The flange is sleeved on the end of the pipe and welded on both the inner and outer sides (or only the outer side) of the fillet weld. | The flange and the pipe are joined by a butt weld, and the weld has the same strength as the pipe itself. |
| Structural characteristics | The flange has a short neck or no neck at all, and its overall thickness is relatively thin. | It has a long conical neck, and the wall thickness gradually transitions to that of the pipe. |
| Stress distribution | There is obvious stress concentration at the weld, and the strength is relatively low. | The neck has a smooth transition, resulting in a uniform stress distribution. This gives it strong anti - fatigue and impact - resistant capabilities. |
| cost | It uses less material, is simple to process, and has a relatively low price. |
It uses a large amount of materials, has a complex processing procedure, and thus has a relatively high price (usually 30% - 50% higher than slip - on flanges of the same specifications). |
| item | Slip - on flange | Butt - weld flange |
| pressure grade | It is usually adopted with PN ≤ 4.0MPa (class150 - class300). | It is usually PN2.5-PN42.0MPa(class150-class2500) |
| temperature range | It is applicable to the temperature range of approximately -20℃ to 300℃ (restricted by the high - temperature creep of the fillet weld). | It is applicable to the temperature range from - 196℃ to 800℃ (suitable for both high - temperature and cryogenic working conditions). |
| Medium operating conditions | Conventional non - severe working conditions such as water, oil, gas, etc. | Highly toxic, flammable and explosive substances, high - temperature and high - pressure conditions, and alternating loads (such as compressor pipelines) |
| common standard | HG/T 20592,GB/T 9116,ASME B16.5 |
HG/T 20592,GB/T9115,ASME B16.5 |
