Why do flanges and elbows need short pipe joints?

What is flange and elbow pipe joint?

In industrial pipeline connections, common pipe connection methods include flange connections and threaded connections, and pipe elbows are a commonly used pipe fitting in industrial production. When it is necessary to connect an elbow to a pipe, in many cases it is necessary to use a flange to connect the two. Flange connection provides a convenient and reliable connection method and is widely used in liquid, gas transportation, chemical industry, shipbuilding and other fields.

Why do we need to short pipe joints?

When connecting pipe flanges and elbows, we will find that many projects require flange nipple pipe. Short connection refers to installing a straight pipe fitting between the pipe and the elbow. This straight pipe fitting is the so-called short nipple pipe fitting. So what exactly does adding a short nipple pipe do?

The reasons for adding pipe joints when connecting flanges and elbows mainly include avoiding scrapping of flanges and elbows during pipeline maintenance or modification, and reducing stress concentration. ‌

In the pipeline system, flanges and elbows are common connecting parts. Their function is to turn the pipeline or change the flow direction. ‌When flanges and elbows are connected directly, ‌you may encounter some problems. ‌Especially when carrying out pipeline maintenance or renovation, ‌if the flange and elbow are directly welded, ‌once these parts need to be replaced or repaired,‌it will be very difficult,‌and may even lead to the flange and elbow being scrapped at the same time,‌increased reduce cost and maintenance difficulty. ‌In order to avoid this situation, ‌ add a short section of pipe joint(‌steel pipe nipple) ‌to connect the flange and the elbow. ‌When replacement or repair is needed, ‌ only the short pipe joint part is required to be replaced, ‌ without the need to replace the whole Flanges and elbows, thus reducing maintenance costs and improving system maintainability.

Main functions:

1. Provide fastening conditions
When the flange and the elbow are connected, because the curvature of the elbow is different from the plane of the flange, the friction between the two is low, making it difficult to fix, and it is easy to loosen due to pressure and other reasons. By adding a short nipple pipe, the friction and the stability of the connection can be improved, ensuring the fastening conditions at the interface, and effectively avoiding the leakage problem of the pipeline.

2. Eliminate installation errors
If the flange and the elbow are directly connected, due to manufacturing and installation errors, two of the four symmetrical connecting bolts of the flange may not be installed properly, resulting in loose pipe connections, air leakage or air leakage. the occurrence of liquid phenomena. With the addition of steel pipe nipple, its offset filling properties can be used to automatically adjust the relative position of the pipeline, eliminate pipeline concentricity errors, and thereby reduce the risk of liquid or air leakage.

In addition, for low-temperature pipelines and high-temperature pipelines, direct welding of flanges and elbows may cause stress concentration. This is because the elbow itself does not have a straight pipe section, and stress concentration is easy to occur during direct welding. This is May affect pipeline safety and stability. ‌By adding a short section of nipple pipe, ‌ the stress can be effectively dispersed, ‌ reducing the problem of stress concentration, ‌ improving the safety and reliability of the pipeline system.

How to perform the correct steel pipe nipple operation?

1. Choose a suitable short steel pipe nipple
When performing a short-circuiting operation, you must first select a suitable steel nipple pipe. The short nipple pipe must have the same pressure level, specifications and dimensions as the flange and elbow, and must be inspected before use. At the same time, attention should be paid to the length of the short nipple pipe when using it. Generally speaking, the length of the short nipple pipe should be 1.5 to 2 times the outer diameter of the elbow.

2. Correct installation
During the installation process of the steel pipe nipple, attention should be paid to the correct installation sequence. First, tighten the flange and the short-circuit pipe with bolts, and then connect the nipple pipe and the elbow. During the installation process, attention should be paid to the tightening strength of the bolts, not too tight or too loose, and the stress should be uniform to prevent damage to the flange and elbow sealing surfaces and cause leakage problems.

Conclusion:

From the article, we can see that short steel nipple pipes play an important role in pipeline connections. It can not only improve friction and connection stability, but also eliminate installation errors, facilitate future maintenance and repair work, and reduce stress concentration phenomenon, ‌ improve the safety and reliability of the pipeline system. ‌Correct steel nipple pipe operation can effectively avoid liquid or air leakage problems in pipelines, bringing comprehensive protection to the production process.

Read more: Can pipe elbows and flanges be connected directly?