What is an expansion joint used for?

Release time:

2021-04-12

An expansion joint is a flexible structure installed on vessel shells or pipelines to compensate for additional stresses caused by temperature differences and mechanical vibrations. Below are some professional application guidelines: 1. Cement industry (equipment accessories, process pipelines, waste heat power generation, etc.); 2. Power industry and metallurgical industry.

1. Cement industry (equipment components, process pipelines, waste heat power generation, etc.);

2. Power engineering and metallurgical engineering;

3. Chemical industry professions (toxic, hazardous, anti-corrosion, etc.);

4. Heating pipelines (heating network, boilers, Northeast);

5. Transportation pipelines (for fire protection, oil, gas, water, etc.);

6. Shipbuilding industry.

In addition to the pre-tensioning, pre-compression, or “cold tightening” pre-deformation required by the design specifications, it is strictly prohibited to rely on the deformation of the bellows to compensate for equipment misalignments in the piping system. Doing so could impair the normal functioning of the expansion joint, shorten its service life, and increase the load on the piping system, equipment, and supporting components.

The pipeline has better neutrality. If no other method can guarantee it, after laying the straight pipe, you can cut pipes of equal length and then install expansion joints to ensure proper alignment.

Before installing expansion joint equipment, check the type and standards of the corrugated expansion joint and verify whether the pipe support devices meet the design requirements.

For expansion joints with liners, care should be taken to ensure that the liner’s orientation is consistent with the direction of the medium flow (refer to the flow direction markings on the expansion joint for proper installation). In planar angular expansion joints, the plane of the hinge rollers should align with the plane of displacement.

For expansion joints requiring “cold setting,” the auxiliary components used for pre-deformation should be removed after the expansion joint has undergone its initial deformation.

Immediately after completion of the piping equipment installation, the auxiliary positioning devices and fasteners used for equipment transportation and maintenance on the expansion joints shall be removed. The limiting devices shall then be adjusted to their normal positions according to the planning requirements, so as to ensure adequate compensation of the piping system under environmental conditions.

Bellows metal expansion joints, regardless of their structural design and installation configuration, are used to accommodate relative displacement between two fixed supports along a pipeline. Specifically, only one bellows expansion joint is permitted between any two fixed supports; otherwise, the compensation capacity of the expansion joint will become uncertain. Among these, the primary fixed support must be capable of withstanding the combined forces exerted on it under operating conditions, including the thrust from the pipeline and its internal medium, elastic forces, frictional forces, the weight of the pipeline itself, and other external loads such as wind loads. When the bend radius of a directly buried pipeline is less than 30 times the pipe diameter (D) or when the pipe diameter exceeds 325 mm, a fixed support and a fully balanced bellows expansion joint must be installed. The primary fixed supports on either side need only bear the elastic and frictional forces; they must not be used in conjunction with partially balanced bellows expansion joints. If such mixed use is unavoidable, both primary fixed supports must be designed based on the internal pressure thrust—that is, the blind flange force must be taken into account.

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