Size range and status in 20801
Thread Content
In GB20801-2020, in Table A1 – Table of Allowable Stresses for Materials, why was the third column renamed “Dimension Range/mm and Condition”? In the older version, it was the fourth column titled “Thickness/mm”. The tables related to GB50316 provide two columns: service condition and thickness/mm. A colleague, when calculating the hydrostatic test, mistook this dimension range for the pipe diameter range, which resulted in a significantly higher test pressure.
GB 20801-2020 Standard for Strength Calculation of Pressure Pipeline Components is a Chinese standard used to guide the design and calculation of pressure pipeline components. In this standard, “size range and condition” refers to the size range of the material (such as thickness, outer diameter, etc.), as well as the condition of the material within that size range (such as whether it has been heat-treated, normalized, annealed, etc.). The new version of the standard has changed this name in order to more clearly indicate that, in addition to size information, the processing condition of the material is also an important factor in calculating the allowable stress of the material. In the standards of older versions, “thickness/mm” might have only emphasized one dimensional characteristic of the material, without clearly indicating the impact of the material’s condition on stress calculations. In the new version of the GB20801-2020 standard, it has been changed to “size range/mm and condition” in order to more accurately describe the strength performance of materials of different sizes and conditions in practical applications, as different processing conditions can result in significant variations in material strength. In standards such as GB50316, \"service condition\" and \"thickness/mm\" may be listed separately in order to provide a more detailed description of the specific properties of the material. Your colleague may have misinterpreted “size range” as the diameter range because they are not familiar with the terminology in the standards, or failed to notice the definitions in the context while reading. Unfortunately, such a misunderstanding can lead to calculation errors, such as the use of an inappropriate test pressure in hydrostatic testing. Therefore, when using these standards, it is very important to ensure that the exact meaning of each parameter is understood. In practical work, thorough communication and training on these terms are effective ways to prevent such errors from occurring. If in doubt, it is best to consult an experienced engineer or refer to the detailed explanations in the standards. .