Will steam pipeline pressure testing cause pipeline expansion?
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As shown in the picture, there is a steam pipe. It has just been pressurized and the steam is not flowing. It is found that one section has expanded by about 5cm and the expansion joint has shrunk. The other end has not changed. What is the cause and how to solve it? The diameter of the pipe is 325 and the medium flows from left to right.
If the fixed frame is displaced, protective measures should be taken for the fixed frame during the hydrostatic test of the unconstrained bellows compensator.
How to solve this situation? Why is there no displacement in the other section?
First, the fixed frame should meet the requirements of the calculated horizontal thrust value. Secondly, protective measures should be taken for the fixed frame during the hydraulic test (such as installing longitudinal tie rods, etc.).
The purpose of the steam pipeline pressure test is to test the pressure resistance of the pipeline. The test is usually conducted at about 1.5 times the design pressure. During the test, if the pipeline expands, it may be due to the following reasons:: 1. Pipe material and structural issues: Pipes may have defects, bends, or weak joints that cause expansion due to stress concentrations that cannot be tolerated under test pressures. 2. Temperature changes: Steam pipelines are usually cooled before pressure testing, and the temperature gradually increases after pressure testing. Due to the characteristics of thermal expansion and contraction, pipes will expand during the heating process. For pipe expansion problems, the following solutions can be considered: 1. Check the pipe material and structure to confirm whether there are defects, bends, etc., and repair or replace them. 2. Increase the pipeline support points, reduce the free movement space of the pipeline, and limit its expansion range. 3. Set up an expansion joint compensation device at the expansion joint position of the pipeline so that the pipeline can have a certain amount of expansion and contraction space when it expands. 4. Consider installing a temperature compensator on the pipe to automatically adjust the length as the pipe temperature changes. It needs to be analyzed and solved according to the specific situation. It is recommended to find a professional engineer for inspection and consultation to determine the specific reasons and solutions. .
I checked pages 2 and 9 of the specification "Pipeline Stress Analysis and Engineering Application". After the pipeline is installed, the temperature of the pipe changes around 50 degrees Celsius when exposed to direct sunlight. According to the calculation formula on page 5 of the specification "Pipeline Stress Analysis and Engineering Application": The amount of expansion = 12.5X50X80 is approximately equal to 6cm, within the normal range
check: Design the maximum deformation of the expansion joint, and pre-stretch the amount during installation
It may be due to the weather. Please refer to the specifications mentioned on the 6th floor to check.
This post was last edited by Zhong Shanlang on 2023-6-24 18:23 In this case, it should be that the fixed bracket on the left side near the elbow has been pushed and displaced by the internal pressure thrust of the bellows. The bellows should usually be stretched. It is difficult to understand now that it is compressed by 5cm. Unless it is a negative pressure (vacuum) pressure test. Or the expansion joint is an external pressure axial expansion joint.
The expansion joint at the right end is fine, indicating that the fixed bracket at the right end near the elbow is strong enough.
Is there a 5 cm displacement? Generally, the displacement of hydraulic test pipelines is mostly due to the movement of the fixed bracket under the thrust of internal pressure.