Introduction

Weld neck flanges are mainly used for high pressure, high temperature or low temperature conditions to make them stronger. Slip-on flanges are connected to pipes by welding, with both ends of the pipes welded and then connected with bolts.

What is the difference between a slip-on flange and a weld neck flange?

What is a Slip-On Flange?

Slip-on flanges have flat faces and are more commonly used in lower pressure pipelines. This flange is usually connected to the pipe with one or two welds (one inside the flange and one outside the flange). And the inner diameter of the sliding flange is larger than the inner diameter of the steel pipe.

Advantages of Slip-On Flanges

1. Lower cost: less manufacturing complexity and lower production cost than other types
2. Less skills required for welding: compatible with different types of pipes and fittings, versatile
3. Less precision required for pipe cutting
4. No welding preparation required for pipe end welding: this saves time and effort during installation, especially when many flanges are involved

Disadvantages of Slip-On Flanges

Usually requires two welds instead of one.

Reduced mechanical strength

Not suitable for cyclic use.

Some nondestructive testing of welds cannot be performed.

Not available in ASME 1500 grades 2.5 inches and above.

Not available in all sizes in ASME 2500 grades.

Not generally used above ASME 600 grades.

What is a Weld Neck Flange?

The butt welding flange is a flange with high mechanical strength, which can transfer pressure to the pipeline and reduce the pressure at the bottom of the flange. And the butt welding flange has three connection surfaces: flat surface, convex surface, and RTJ. This flange usually has two design forms, one is conventionally used in pipelines, and the other long diameter butt welding flange is mostly used in factories and process equipment.

Advantages of Weld Neck Flange

1. The weld neck design of the weld neck flange makes it stronger and more suitable for use in high pressure and high temperature environments.
2. Good sealing performance
3. It can be smoothly connected to the pipeline to reduce pressure concentration.
4. Corrosion resistant

Disadvantages of Weld Neck Flange

1. High cost: Due to the complex manufacturing process and the increase in materials used, its price is slightly higher than other flanges.
2. High welding requirements: When installing butt-welded flanges, more professional welding masters are required to perform welding.
3. After welding is completed, non-destructive testing (NDT) technology is required to perform welding inspection to ensure that the welding is tight.

Slip-On vs. Weld Neck: How Do They Compare?

The welding point of the butt-weld flange has specific holes, which can make it more secure when welded to the pipe or pipe fitting. It is more conducive to use under high temperature and high pressure. Although the price of the slip-on flange is slightly lower than that of the butt-weld flange, it needs to be welded on both the inside and outside of the flange. And welding inspection is required, which is more troublesome.

How to decide between a slip-on flange and a weld neck flange?

The following aspects need to be considered when choosing flanges:

1. Is the use environment high pressure or low pressure?
2. The use standard and pipeline connection requirements?
3. Requirements for leakage risk and durability

Conclusion

The above are the differences between butt welding flanges and slip-on flanges, each with its own advantages and disadvantages. I hope it will be helpful to you when choosing flanges. If you have other questions, please contact us for professional answers.