Regarding pipeline pressure testing

The typical test pressure for pipes is 1.5 times the design pressure. During normal operation, the operating pressure is the design pressure; over a long period of time, of course, a longer testing time is required for pressure tests! :lol

The test pressure is used for conducting strength tests on the pipeline, while the design pressure is used for conducting integrity and leakage tests on the pipeline (pressure retention test).

Under a certain pressure, the longer the holding time, the easier it is to detect leaks in areas such as flange surfaces, threaded connections, and fillet welds. The main purpose is to conduct a tightness test to ensure normal operation after the system is put into use.

Only by maintaining it for a long time can the pressure drop caused by minor leaks be amplified, and there is also time to locate these leaks.

The test pressure is for strength testing, while the design pressure is for tightness testing. The operating pressure is lower than the design pressure. Maintaining high pressure for 10 minutes is to test the strength of the pipeline and identify any defects, while the test pressure is used to check for leaks. Maintaining the pressure for 30 minutes allows for a thorough inspection and detection of any leakage points

This is a simulation of the accident scene; from the occurrence of the accident to its resolution, the pressure will be 1.5 times higher, and this condition should not last more than 10 minutes, while the pressure reaching the design level will not persist for more than half an hour.

Correction for the second floor: the design pressure is equal to or greater than the peak pressure during operation. It is generally greater, so it cannot be the operating pressure

This is a strength test; it requires long-term testing to obtain relatively useful results

The purpose of holding pressure is to check for leaks at the flange connection.

The test pressure is for the overload strength test, and the duration is short

Consequences of incorrect pressure testing: This is a recent incident in Shanghai that was caused by gas pressure testing. The experimental pressure is 15.6 MPa. If it is a gas transmission pipeline, it is acceptable to use gas for pressure testing; however, it is not appropriate to use liquid for pressure testing on a 900-mm pipeline mounted on a pipe rack. The key is whether the construction party gives its approval, and whether safe and appropriate isolation measures and distances are determined through calculations. Judging from the pipe diameter, it should be a gas transmission pipeline. An explosion occurred suddenly during the airtightness testing of the LNG pipeline at the west gate of Xiaoyangshan in Shanghai LNG Company. The diameter of the pipeline under test was 36 inches, and the general contractor for the construction was a consortium composed of Ishikawajima-Harima Heavy Industries from Japan, Zhongding from Taiwan, and Wuhuan Technology. The accident resulted in one death; the victim was a staff member of 14th Construction Group. More than ten others were taken to Nanhui Central Hospital for treatment. According to the provisions on pressure testing in GB50235-97, the test medium for pressure testing should be liquid; when the design pressure of the pipeline is less than or equal to 0.6 MPa, gas can also be used as the test medium, provided that effective safety measures are taken. When the design pressure of the pipeline is greater than 0.6 MPa, a pressure test using gas is permitted only if specified in the design documents or with the approval of the project owner. Currently, the scale of our devices is increasing, and there are no limits on the diameter of the pipes. Due to constraints related to on-site pressure testing, it is becoming more common to use air pressure instead of water pressure for these tests. I hope this incident will draw everyone’s attention to the issue of pressure testing

The information provided by Gray Rabbit is accurate. I saw the photos; the scene was extremely terrifying. Using gas at such high test pressures is extremely dangerous.

The following conditions must be met prior to the pressure test: 1. The pipeline installation work within the scope of the test, except for painting for insulation, has been fully completed in accordance with the design drawings, and the installation quality meets relevant regulations. 2 The welds and other areas to be inspected have not yet been painted or insulated. 3 The pressure gauges used for testing have been calibrated and are within their periodic inspection period; their accuracy must be at least 1.5 grade. The full scale value of the gauges should be 1.5 to 2 times the maximum pressure to be measured, and there must be no fewer than two such gauges

This is because an excessively high test pressure constitutes overpressure use for pressure vessels, and of course, maintaining such conditions for too long is not good. Since the inspection cannot be completed in just a short time, it is lowered to conduct a pressure retention test to check for any deformation issues.

A certain engineering project has a desalinated water system with a capacity of 800 t/h. The individual unit tests have been largely completed, and joint commissioning is imminent. Is there anyone who possesses a comprehensive commissioning plan for this system or similar desalinated water systems that could be used as a reference? Alternatively, even a list of commissioning plans would be helpful. I kneel in gratitude!

Strength testing is a destructive test that determines whether the pipeline or equipment has sufficient strength; it mainly focuses on detecting any deformation, which is why the testing time must be short to prevent plastic deformation of the material； The design pressure is the pressure that can ensure operational safety after taking safety factors into account; it does not cause damage to the equipment or pipes. It can be set at a high level to facilitate inspections for leaks along the pipeline. For long-distance pipelines, the integrity of the system is assessed based on whether there are any leaks, and many projects do not impose a limit of half an hour, opting instead for a period of 24 hours.