May I ask about the issues with branch pipe welding?

This can be done for pipes containing water, air, nitrogen, etc. However, it is not advisable to do this for toxic and flammable pressure pipes, as the pipe diameter is too small and the weld lengths are short, making it difficult to ensure welding quality; it is better to use socket-welded reducer tees or reinforce them with pipe supports.

It is not recommended to do this! The main problem is that the weld strength is too poor! It cannot withstand pipeline vibration even in the absence of pressure and medium requirements.

In current designs, reinforced pipe fittings are generally used

Hehe, there are many factors to consider: medium type, pressure rating, and so on. Take a look at the pipeline rating table

It is better not to weld directly; use one of the following two methods: 1. Use an eccentric tee for connection (more labor-intensive), 2. Use a reinforced nozzle for connection (less labor-intensive)

Generally, when the diameter of the branch pipe is less than 1/2 of the diameter of the main pipe, open welding can be used; if it is larger, a tee is required

For a pipe diameter of 40, open welding is not recommended; it is better to use an elbow with different diameters

This post was last edited by nepisces on 2009-9-3 15:20. Training material for national pressure pipeline design approvers 6.8.18: Common branch structures fall into three categories: integral fitting type, reinforced joint type, and welded branch type. The integral fitting-type branching structure is a type of piping branching that uses integral fittings such as tees and crosses. This type has good pressure resistance and a reliable branching structure, but it is more expensive. The reinforced pipe joint type is a method of branching pipes using special fittings such as reinforced nozzles and reinforced pipe joints. This type is commonly used in situations beyond the scope of three-way or four-way branches, but it is often limited by the size of the branches. Under normal circumstances, reinforced nozzles (sometimes called half-fittings) are commonly used for branches of DN40 and below, and are connected by socket welding or threading ； Strengthened pipe fittings (sometimes called branch fittings) are commonly used for branches ranging from DN50 to DN200, and are connected by butt welding. SH 3059-2001 General Rules for Material Selection in Petrochemical Pipeline Design 6.3 Pipeline Branches 6.3.1 For branch pipe connections where the branch pipe is welded directly to the main pipe, a stress reinforcement check shall be carried out unless one of the following conditions applies; corresponding reinforcement measures shall then be taken based on the results of such check: 1 The branch pipe is connected to the main pipe through a reinforced joint; 2 The connection between the branch pipe and the main pipe is designed, manufactured as a single pressure-bearing element, and has passed inspection. 6.3.2 Branch connections welded directly to the main pipe shall meet the following requirements: 1 They should not be used in areas subject to mechanical vibration, pressure fluctuations, and rapid temperature changes, nor in pipes for which the design temperature exceeds 425°C ； 2 When the branch connection is subjected to stresses caused by thermal deformation of the branch, external loads, and support displacement, it is necessary to analyze the effect of these additional loads on the branch connection and take appropriate reinforcement measures. 6.3.3 For pipe branches with a design pressure equal to or greater than 2.0 MPa, a design temperature exceeding 250°C, and a ratio of the nominal diameter of the branch pipe to that of the main pipe greater than 0.8, or those subjected to mechanical vibration, pressure pulsations, and rapid temperature changes, tees, 45° elbows, and crosses shall be used for connection ； For pipes with a nominal diameter of 40 mm or less, socket welded (or threaded) forged tees should be used ； For pipes with a nominal diameter of 50 mm or greater, butt-welded tees should be used.

There are also tees with a nominal diameter of 80*80*40; it’s better to use these. If the pressure is not high, welding at the openings is also an option

If a tee is used, a butt-welded tee or butt-welded elbow should be chosen. I just checked the manual