Pressure test of process pipeline

What is pressure test of process pipeline?

Pressure testing of process pipeline is an important process in the construction of the project, which is to check whether the pipeline installation is in line with the process, whether there are unsafe hidden dangers, the quality of pipeline construction and other issues.

20211102095328 89066 - Pressure test of process pipeline

The specific steps of pressure testing of process piping are as follows:

Division of test pressure package

The test pressure of the pipeline system is divided into several test pressure packages according to the general flow chart of the pipeline and instrumentation. In accordance with the principle of covering all pipelines, and in line with the design requirements and the specific installation situation on site, they are divided according to different process media, pipeline materials and pipeline grades. Design requirements specify the design and test pressure of the pipeline, but also specify the pipeline test pressure with the medium, the general pipeline test pressure medium is mostly clean water, and a small number of pipelines to do gas tightness test, generally according to the test pressure requirements of the same test pressure level and the same medium of the pipeline together into a test pressure package, in the test pressure package should try to express the matters to be expressed clearly. Such as: valve closure, add pressure gauge, metal hose reinforcement, temporary short pipe, blind plate installed position, etc.

The principle of test pressure block division

Public works part of the corridor pipeline as the main line, according to the different media, different test pressure is divided into several large test pressure block, each large block in the branch to each unit can be subdivided into a number of small test pressure block, according to the different construction progress can also be divided into a test pressure package into several test pressure small blocks to test pressure, but the boundaries should be clear, to prevent dead ends and omissions.
The division of the test pressure package generally starts from the import and export of equipment, such as the import and export of the pump line when the import and export of pipeline pressure difference within 0.5MPa can be connected together for test pressure, if the difference is large, separate test pressure (generally below 100 diameter pressure difference in less than double can be together test pressure, if the diameter of more than 100, pressure more than 0.5MPa kg must be separated test pressure, so as not to (If the diameter exceeds 100 and the pressure exceeds 0.5MPa kg, the test pressure must be separated to avoid damage to the pipeline and other parts connected to the pipeline, causing accidents. In consideration of the test pressure at the same time to consider the specific circumstances of the site, but the main design pressure as a reference, if the actual situation on site and the test pressure flow chart does not match should be changed according to the specific circumstances, so that the test pressure process as far as possible to match the actual site. In the total process should also pay attention to the pipeline pressure level demarcation point, the test pressure of metal hoses, according to the pressure level at the demarcation point to consider whether the test pressure can be together.    

Symbol identification in the test pressure flow chart

According to the design requirements and site conditions to draw a good test pressure flow process should be indicated in the diagram of the corresponding logo in the diagram. For example: the location of the temporary blind and the choice of temporary blind thickness, the thickness of the temporary blind should be different according to the test pressure and pipe diameter, respectively, the use of different thickness blind, if there is no blind thickness requirements in the existing materials selected can be used to strengthen the blind method (blind reinforcement using the central welding in the blind I-beam or crossbar plate, etc.). The water inlet point is located at the low point or put clear valve. The addition of pressure gauge: a test pressure system can not be less than two pressure gauge requirements (a choice in the high point of the test pressure system a choice in the low point of the test pressure system). Pressure gauge should be calibrated and qualified and within the validity period and must have a seal, accuracy of not less than 1.5 levels, the range of the test pressure 1.5 ~ 2 times. The valve closure should be clear (if not clear to cause repeated test pressure of the pipeline and pipeline leakage test) test pressure flow chart will be clearly expressed in the pipeline emptying point.    

Preparation before the test pressure    

Preparation of pipeline before test pressure

According to the markings in the test pressure flow, add the blind plate, pressure gauge and other temporary parts to the pipeline at the locations indicated in the diagram. When adding the blind plate, add the gasket of the corresponding pressure level on both sides of the blind plate and polish both sides of the blind plate smoothly to prevent the blind plate from leaking and scratching the flange sealing surface; use the temporary short pipe instead of the sight glass for the test pressure, the metal hose in the pipe can be brought into the test pressure if the test pressure is within its range, and if it is greater than its test pressure, use the reinforced or temporary short pipe instead for the test pressure.    

Self-inspection before test pressure

According to the test pressure package in the test pressure before the self-inspection, the self-inspection before the test pressure has the test pressure process and the inspection of the pipeline formulation.    
Before the test pressure, whether the flaw detection and heat treatment work is completed, all the pipeline information in the system will be verified, and the test pressure will be carried out only after the verification is confirmed to be correct.    
The test pressure process check refers to whether the test pressure pipeline is consistent with the process, if the test pressure process does not match the first check whether the test pressure process is divided into errors (errors include errors in the table knowledge, leakage, heavy lines, the existence of dead ends and other possible errors) in the process is correct under the premise of checking whether the master worker will add the wrong location in the table knowledge and some objective factors (design changes). The straight stop test pressure process is in line with the site.    
The inspection of the pipeline formulation is carried out by the pipeline inspector, mainly checking:

  • (1) The installation of the temporary pipe, whether the pressure gauge is installed in place, whether the blind bolt is put full blind on both sides of the gasket and the grinding of the blind flange, etc. Flow meter, sight glass, regulating valve is suitable, blind plate should be hung to mark.
  • (2) The inspection of the main piping system, whether the installation of the main piping is parallel (the installation of the process piping should meet the basic requirements of horizontal and vertical straightness, especially the flange connection and the valve connection on the piping), whether there is any error in the installation of the valve, whether the branch pipe frame, drop frame, pipe card and guard plate installation is complete and reasonable, whether the bolts are oiled, whether the pipe fittings are damaged and the welding quality of the weld seams.
  • (3) All the welded seams of the pipelines that have not passed the test pressure should not be coated with anticorrosive paint as well as insulation and cold pipes should not be wrapped around the welded seams, and if this is found to be the case, the packaging at the welded seams should be removed promptly to reveal the welded seams.
  • (4) Whether the brackets, hangers and special pipe brackets used on the pipeline are properly installed and whether there is any misuse of the phenomenon.    

Confirmation of joint inspection before test pressure

When the test pressure package has the test pressure conditions after passing the self-inspection, notify the general contractor’s representative and the supervisor’s representative in advance for the joint inspection of the three parties (advance notice is convenient for the general contractor and the supervisor to be familiar with the process), the inspection matters during the joint inspection of the three parties are basically the same as the self-inspection matters, and the non-conforming matters inspected should be issued in a timely manner to rectify the notice of rectification of the final work until the test pressure conditions are met, if the three parties do have the test pressure conditions after passing the test pressure, they can The test pressure can be carried out after the three parties have passed the test pressure inspection.

Pipeline test pressure

Information of pipeline pressure test

After the pipeline inspection is qualified, the corresponding information should be prepared and the pipeline test pressure record (SH3503-J407) should be filled in.   

Inspection of test pressure

When the system pressure reaches the test pressure (first slowly rise to the test pressure after stabilizing the pressure and then drop to the design pressure to stop the pressure for inspection) stop the pressure for system pressure maintenance, inspectors start to check the flange connection, welding seam, blind plate addition, valve and flange and equipment connection for leakage, the connection of bolts, the pressure gauge and the pressure gauge. Bolt connections, pressure gauge values have not changed, if the leak detected should be promptly unloading pressure treatment (first the test pressure medium in the pipeline from the valve discharge, until the pipeline no pressure), and so unloading pressure treatment properly before the second test pressure check. If there is no leakage in the pipeline inspection but the pressure gauge value changes, it means that there is air in the pipeline should be emptied in time to make up the pressure, when there is no change in the pressure gauge value, no abnormalities in the pipeline (no sound in the pipeline, no leakage in the welding seam, no deformation in the pipeline, etc.), no leakage is found in the inspection, pressure is maintained for 10 minutes and then unloaded, and the design pressure is slowly reduced, and the pressure is stopped for 30 minutes after inspection, after the three parties confirm that the inspection is passed, it is regarded as Test pressure qualified. The chlorine ion content of the test water for stainless steel pipes shall not exceed 30 PPM, and the water in the pipeline will be completely emptied after the test pressure is completed.

System recovery

After stopping the pressure check qualified, should be drained, shall not be discharged at will, the recovery of the system, the pipeline pressure is slowly reduced after the water in the pipeline will be discharged clean and the blind removed in a timely manner, for blind removal records, check valve backfit or core should be installed in a timely manner to restore the original state, temporary replacement bolts should be removed and the original connection bolts back and put tight, due to the test pressure closed valve should be restored to the original operating state.

Pipeline pressure test is an important work in the construction of the project, through the pipeline pressure test, to determine the quality of pipeline welding, but also to ensure the effective pipeline installation process.

China Pressure Pipeline Manufacturer – Yaang Pipe Industry Co., Limited (

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