Fisher Fisher - Why do steam pipes often have to be bent a section?

We often see such a scene on the steam pipeline, the pipe section that can obviously "go straight" suddenly bends a section, I believe that many people who have seen it will have such doubts like me, this is not "painting a snake to add foot", in fact, the design of the pipeline operation has its own principle, let me take you to understand the role of the steam pipe bend.

Fisher Fisher - Why do steam pipes often have to be bent a section?

The steam pipeline is divided into two working states, one has a high temperature, one is approximate to the ambient temperature, in the alternating transformation of cold and heat, it will produce displacement and force due to the principle of thermal expansion and contraction, the longer the pipeline, the greater the displacement and the force, in order to prevent damage to the pipeline, measures need to be taken to avoid, so there is this bend, also known as the "expansion joint", which is used to absorb the axial expansion displacement of the pipe, and also has the requirement of avoiding concrete beams and columns, killing two birds with one stone.

China has relevant regulations for expansion joints, such as Article 4.8.17 of the "Design Code for Heating, Ventilation and Air Conditioning"; Heating pipes must calculate their thermal expansion. When the natural compensation of the pipe section cannot meet the requirements, a compensator should be arranged. Others, such as the design code of the electric power chemical industry, have this requirement, and some even require the use of software for calculation, such as the power plant design institute generally uses GLIF, and the chemical design institute generally uses Caesar and so on.

The amount of compensation should be calculated before installation, and the installation process requires cold drawing, especially for the main steam outlet, and the bracket is also very important.

So how long is the expansion of the pipe? According to the test calculation, 1 meter long distance, the temperature rises by 100 degrees, and the expansion is about 1.2mm. Pipelines in some industries, such as power plants, can reach more than 500-600 degrees Celsius. At this time, 1 meter is to expand by 7-8mm. Metal is a pullable but non-pressable material, imagine that the temperature difference between the rails at the ambient temperature is 50 degrees, and the early rails still have the situation of protruding, and later the use of segmented rails to solve this problem. The pipeline is often hundreds of meters or even dozens of kilometers, and the next change in the cold and hot state will produce great stress, and the stress exceeds the limit of the pipeline, and the pipeline will naturally be unbearable, which may have serious consequences.

When the natural compensation cannot meet the requirements of the pipeline, we usually use a compensator to compensate, which can absorb the cold and hot deformation of the pipeline in the axial, transverse and angular directions, and reduce the impact of equipment vibration on the pipeline. The U-shaped section on the steam pipe acts similarly to this.

Fisher Fisher - Why do steam pipes often have to be bent a section?

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