What about pipeline pressure testing?

In principle, all newly built, repaired, and moved pipelines must be pressure tested. Filming is not necessarily required, as long as it is done according to the inspection specifications. Pipes below PN1.0 and not containing highly toxic materials do not need to be filmed. For specific details, you can check the installation and acceptance specifications for on-site equipment and process pipelines. As for whether you are talking about the pressure test of the entire pipe or the pressure test of the repaired pipes, logically speaking, the pipes that have not been touched or inspected should be good and have no problems, so they do not need to be repaired, and there is no need for pressure testing. But in terms of work content, it depends on the work content you have specified. To be honest, all work content involves expenses. If you don't pay this part of the fee and let others do this part of the work, they will definitely not be willing to do it. If there is any work content that exceeds the routine, it must be discussed in advance. For example, you handed over the decoration of your company's office building to the construction team, but your bathtub is broken and you need the construction team to replace it. This part should not be included in the construction agreement (contract), and they have no obligation to do it for you.

1. It is absolutely impossible not to test the pressure, just like the product leaves the factory without being inspected. 2. Even if it is an insignificant pipe, the welds must be randomly inspected for non-destructive testing. Since the construction unit has inspected and repaired this section of pipe, it must be responsible for the pressure test of this section of modified pipe. 3. If there are materials in the equipment, you can add a blind plate at the equipment port to avoid participating in the pressure test, or close the valve on the pipeline. The hydraulic pressure test is not as troublesome and dangerous as the air pressure test. 4. The pressure test is very fast and can be done in one day if arranged well. Will not affect progress. 5. The pressure test can be carried out in sections or as a whole pipeline, but only the modified ones should be checked during inspection. 6. Try to clear the material in the pipeline as much as possible.

Pipelines can be pressure tested on the ground in sections, the welded joints after installation are subject to 100% RT testing, and the sockets are subject to 100% PT testing.； If the blind plate can be tested for pressure after installation, do so after installation. ； As long as the plan is properly arranged, the progress will not be affected and the quality will be guaranteed.

1 Refer to the product acceptance standards 2 Refer to the bid document 3 If there is no explanation, the required fee will be charged in addition

Generally speaking, failure to perform a pressure test is not allowed, but for your maintenance project, you cannot ask the construction unit to perform a pressure test on the entire pipeline system for you. The parts that have been inspected are subject to a pressure test, and the parts that have not been inspected do not need a pressure test. During the pressure test, a blind plate can be used to isolate the dividing line in the middle. If it is considered that some media are inconvenient for water or gas pressure testing, radiation or ultrasonic testing methods can be used instead.

Pressure test or flaw detection must be carried out. The following is the "Code for Construction and Acceptance of Industrial Metal Pipe Engineering" GB 50235. I hope it can help you. 7.5 Pressure test 7.5.1 After the pipeline is installed and the heat treatment and non-destructive inspection pass, a pressure test should be carried out. The pressure test should comply with the following requirements: 7.5.1.1 The pressure test should use liquid as the test medium. When the design pressure of the pipeline is less than or equal to 0.6MPa, gas can also be used as the test medium, but effective safety measures should be taken. It is strictly prohibited to use gas for pressure testing of brittle materials. 7.5.1.2 When site conditions do not allow the use of liquids or gases for pressure testing, with the consent of the construction unit, the following methods may be used instead:: (1) All welds (including welds on attachment parts) shall be inspected by liquid penetrant method or magnetic particle method. (2) Butt welds are inspected by 100% radiography, 7.5.1.3 When performing a pressure test, a restricted area should be defined and irrelevant personnel are not allowed to enter. 7.5.1.4 After the pressure test is completed, no repairs are allowed on the pipeline. 7.5.1.5 The construction unit should participate in the pressure test. After passing the pressure test, the "Pipeline System Pressure Test Record" should be filled in with the construction unit in the format specified in Article A.0.8 of Appendix A of this specification. 7.5.2 The following conditions should be met before pressure test: 7.5.2.1 Except for painting and insulation, all pipeline installation projects within the test scope have been completed according to the design drawings, and the installation quality complies with relevant regulations. 7.5.2.2 Welds and other areas to be inspected have not yet been painted and insulated. 7.5.2.3 Temporary restraints have been installed on the expansion joints on the pipeline. 7.5.2.4 The pressure gauge used for testing has been calibrated, and during the period of weekly inspection, its accuracy shall not be less than level 1.5. The full scale value of the gauge shall be 1.5 to 2 times the maximum pressure being measured. There shall be no less than two pressure gauges. 7.5.2.5 Liquids or gases that meet the pressure test requirements are ready. 5.2.6 According to the requirements of the test, the pipeline has been reinforced. 7.5.2.7 For pipelines transporting highly toxic fluids and pipelines with design pressures greater than or equal to 10MPa, before the pressure test, the following information has been reviewed by the construction unit: (1) Quality certificate of pipeline components. (2) Inspection or test records of pipeline components. (3) Pipe processing records. (4) Welding inspection and heat treatment records. (5) Design modification and material substitution documents. 7.5.2.8 The pipeline to be tested and irrelevant systems have been separated by blind plates or other measures. 7.5.2.9 The safety valves, blasting panels and instrument components on the pipeline to be tested have been removed or isolated. 7.5.2.10 The test plan has been approved and a technical briefing has been conducted. 7.5.3 Hydraulic test shall comply with the following regulations: 7.5.3.1 Clean water should be used for hydraulic tests. When testing austenitic stainless steel pipes or pipes connected to austenitic stainless steel pipes or equipment, the chloride ion content in the water shall not exceed 25×10?6 (25ppm). When a flammable liquid medium is used for testing, its flash point shall not be lower than 50°C. 7.5.3.2 Before the test, the air should be exhausted when filling the liquid. 7.5.3.3 During the test, the ambient temperature should not be lower than 5°C. When the ambient temperature is lower than 5°C, antifreeze measures should be taken. 7.5.3.4 During the test, the test temperature should be measured, and it is strictly forbidden for the material test temperature to be close to the brittle transition temperature. 7.5.3.5 The test pressure of above-ground steel pipelines and non-ferrous metal pipelines that bear internal pressure should be 1.5 times the design pressure, and the test pressure of buried steel pipelines should be 1.5 times the design pressure, and should not be less than 0.4MPa. 7.5.3.6 When the pipeline and equipment are tested as a system and the test pressure of the pipeline is equal to or less than the test pressure of the equipment, the test shall be carried out according to the test pressure of the pipeline. ； When the pipeline test pressure is greater than the test pressure of the equipment, and the test pressure of the equipment is not less than 1.15 times the design pressure of the pipeline, the test can be carried out according to the test pressure of the equipment with the consent of the construction unit. 7.5.3.7 When the design temperature of the pipeline is higher than the test temperature, the test force should be calculated as follows:: Ps＝1.5P1/2 (7.5.3) where Ps——test pressure (gauge pressure) (Mpa) ； P——Design pressure (gauge pressure) (MPa) ； 1——Allowable stress of pipe at test temperature (MPa) ； 2——The allowable stress of the pipe at the design temperature (MPa). When 1/2 is greater than 6.5, take 6.5. When Ps produces stress exceeding the yield strength at the test temperature, the test pressure Ps should be reduced to the maximum pressure that does not exceed the yield strength. 7.5.3.8 The test pressure of buried cast iron pipelines withstanding internal pressure should be twice the design pressure when the design pressure is less than or equal to 0.5MPa. ； When the design pressure is greater than 0.5MFa, 0.5MPa should be added to the design pressure. 7.5.3.9 For pipelines with large position differences, the static pressure of the test medium should be included in the test pressure. The test pressure of liquid pipelines shall be based on the pressure at the highest point, but the pressure at the lowest point shall not exceed the bearing capacity of the pipeline components. 7.5.3.10 For pipelines that bear external pressure, the test pressure should be 1.5 times the difference between the design internal and external pressures, and should not be less than 0.2MPa. 7.5.3.11 The test pressure of the inner pipe of the jacketed pipe shall be determined according to the higher of the internal or external design pressure. The test pressure of the outer pipe of the jacketed pipe shall be in accordance with the 7.5.3.5 The provisions of the paragraph shall be carried out. 7.5.3.12 The hydraulic test should slowly increase the pressure. After reaching the test pressure, stabilize the pressure for 10 minutes, then reduce the test pressure to the design pressure, and stop the pressure for 30 minutes. The test is qualified if the pressure does not drop and there is no leakage. 7.5.3.13 After the test, the blind plate and expansion joint limiting facilities should be removed in time to drain away the accumulated fluid. The formation of negative pressure should be prevented when draining liquid, and it should not be discharged anywhere. 7.5.3.14 When leakage is discovered during the test, no pressure treatment is allowed. After the defects have been eliminated, the test should be repeated. 7.5.4 The air pressure test should comply with the following regulations: 7.5.4.1 The test pressure of steel pipes and non-ferrous metal pipes withstanding internal pressure should be 1.15 times the design pressure, and the test pressure of vacuum pipelines should be 0.2MPa. When the design pressure of the pipeline is greater than 0.6MPa, there must be provisions in the design document or the consent of the construction unit before gas can be used for pressure testing. 7.5.4.2 It is strictly forbidden to make the test temperature close to the brittle transition temperature of the metal. 7.5.4.3 Before the test, a pre-test must be conducted with air, and the test pressure should be 0.2MPa. 7.5.4.4 During the test, the pressure should be gradually and slowly increased. When the pressure rises to 50% of the test pressure, if no abnormality or leakage is found, continue to increase the pressure step by step by 10% of the test pressure, and stabilize the pressure for 3 minutes at each level until the test pressure. Stabilize the pressure for 10 minutes, then reduce the pressure to the design pressure. The pressure stop time should be determined according to the needs of leak detection work. The foaming agent is deemed to be qualified if there is no leakage. 7.5.5 Pipelines transporting highly toxic fluids, toxic fluids, and flammable fluids must undergo leakage tests. The leakage test shall be carried out in accordance with the following provisions: 7.5.5.1 The leakage test should be carried out after the pressure test is passed. The test medium should be air. 7.5.5.2 The leakage test pressure should be the design pressure. 7.5.5.3 The leakage test can be carried out in conjunction with the commissioning work. 7.5.5.4 The leakage test should focus on inspecting valve stuffing boxes, flange or threaded connections, vent valves, exhaust valves, drain valves, etc. The foaming agent is deemed to be qualified if there is no leakage. 7.5.5.5 Pipes that have passed the air pressure test and have not been disassembled after the test do not need to undergo the leakage test. 7.5.6 After the vacuum system passes the pressure test, it should also undergo a 24-hour vacuum degree test in accordance with the design documents. The pressure increase rate should not be greater than 5%. 7.5.7 When the design document stipulates that the leakage test shall be carried out with halogen, helium, ammonia or other methods, it shall be carried out in accordance with the corresponding technical regulations.

This must be done in close cooperation with the production personnel. According to the characteristics of the medium, the test pressure may not necessarily be strictly followed. Low-pressure inflation can be used to extend the inspection time. However, the test scope, inspection location, and partition method must be agreed by the workshop and closely cooperated. The handling of leaks, test marks, exhaust and recovery must also be considered at the same time.

Newly built and overhauled chemical material pipelines must be purged and pressure tested. This is a rule that cannot be changed. If not done, the consequences will be very serious, not to mention leakage, which may damage downstream equipment, especially the pump. It may result in long-term product quality failure.