There are significant differences between flat welding flanges and butt welding flanges in multiple aspects, and the following are the main differences between the two:
1. Weld seam form and inspection
Flat welding flange: Its weld seam form is a fillet weld, that is, the weld seam formed between the pipe and the flange is a two corner circumferential weld. This type of weld seam cannot usually be detected by X-rays, so there may be certain limitations in quality control.
Butt welding flange: Its welding seam form is a circumferential weld, which requires double-sided welding of the inside and outside of the pipe. This design enables strict control of weld quality through X-ray or other testing methods, ensuring the stability and safety of the connection.
2. Material and Manufacturing
Flat welding flanges: mostly made of ordinary steel plates (such as carbon steel plates, etc.), with relatively low cost. Its flange plate is relatively thin and does not have a neck design.
Butt welded flanges are mostly made of forged steel, with higher density and better mechanical properties, but the corresponding cost is also higher. It is usually equipped with a protruding long neck design, which not only enhances the rigidity and strength of the flange, but also allows the neck to match the outer diameter of the pipeline.
3. Nominal pressure and pressure bearing capacity
Flat welding flange: The nominal pressure range is usually 0.6~4.0MPa, suitable for medium and low pressure pipeline systems. Due to only one side being welded, its load-bearing capacity is relatively low.
Welding flange: The nominal pressure range is usually 1-25MPa, suitable for high-pressure pipeline systems. Through the design of double-sided welding, its load-bearing capacity has been significantly improved.
4. Connection method and sealing performance
Flat welding flange: Generally, it is a joint between the connecting pipe and the flange corner, and cannot be directly connected to the butt welded pipe fittings. The weld seam is located on the outside of the flange, and the sealing performance is relatively weak. There may be a risk of leakage in flat welded flanges under high-pressure environments or frequent temperature changes.
Butt welding flange: It is the connection between a flange and a connecting pipe, which can not only be connected to pipelines, but also directly connected to various types of butt welded pipe fittings (such as tees, elbows, etc.). The weld design is located on both the inner and outer sides of the flange, significantly enhancing its sealing performance and enabling it to more effectively withstand high pressure and temperature changes.
5. Application scope
Flat welding flange: mainly used for low-pressure, small-diameter pipeline systems, with a wide range of applications, covering multiple fields such as construction, water supply and drainage, HVAC, etc.
Welding flange: suitable for high-pressure, large-diameter pipeline systems, commonly used in industries such as petrochemicals, power, nuclear energy, etc. that require strict pipeline connection requirements.
6. Installation and maintenance
Flat welding flange: The installation process is relatively simple, but attention should be paid to the quality challenges that single-sided welding may bring, and more attention may need to be paid to the quality of the weld during maintenance.
Butt welding flange: Installation is relatively complex, but due to double-sided welding, the quality of the weld seam is more guaranteed, so maintenance requirements are relatively less.
In summary, there are significant differences between flat welding flanges and butt welding flanges in terms of weld seam form, material, nominal pressure, connection method, application scope, and installation and maintenance. The choice of flange depends on factors such as specific engineering requirements, pressure rating of the pipeline system, medium characteristics, and cost budget.
