GB 8650-88 provides a method for a fracture test that assesses the ability of steel pipelines to withstand different conditions. This test involves a pipe filled with water, the pressure of which is gradually increased. At each stage, the pipe is blocked off, and then examined afterwards to see if any signs of fracture or leakage are present.
The intent of GB 8650-88 is to evaluate the susceptibility of petroleum and natural gas pipelines to failure due to fractures caused by different loading conditions. The test is performed by subjecting a test piece of pipe (which may be welded), to a tension-torsional, or torsional-shear loading. As the tests are conducted, it is necessary to observe any changes in the condition of the pipe, such as the appearance of cracks and other visible indications that the strength of the pipe has been reduced.
The tests conducted with the GB 8650-88 standard must be conducted in accordance with specific criteria established for the appropriate combination of ambient temperature, pressure and duration of testing. Particular requirements towards the number of test pieces to be tested, their dimensions and the applied forces, are all laid out in the Standard.
The test results are usually expressed in terms of a fracture-strength index, which is determined by dividing the maximum load at which the pipe fails to the minimum load applied in the test. The fracture-strength index can give an indication of the performance of a particular group or type of pipes when subjected to dynamic loading conditions.
In order to ensure accurate results, it is important to perform the tests in accordance with the standard laid out in GB 8650-88, taking into consideration all of the relevant factors, such as pipe size, pipe material and the loading conditions. The results of the tests should be documented and reported to the responsible authorities.
GB 8650-88 has become an accepted and reliable method for assessing the resistance of steel pipelines to fractures caused by dynamic loading conditions. With its accuracy and reliability, it is an invaluable tool for the safe operation of pipelines in the petroleum and natural gas industry.
