Voltage test pressure coefficient
Thread Content
GB 150 specifies that for pressure tests, the hydrostatic test pressure PT is equal to 1.25P, where P represents the allowable stress at the material’s test temperature compared to the allowable stress at the design temperature. For pneumatic tests, PT is equal to 1.1P, again based on the ratio of allowable stress at the test temperature to that at the design temperature. How are these coefficients of 1.25 and 1.1 determined? Can the voltage withstand test value be lower or higher than the calculated value, and how is it determined?
It can be high but not low. It has to meet the standards anyway.
In fact, the requirements specified in the major standards are higher than 150
This post was last edited by zhangjuhua on 2019-9-9 at 16:32. It may draw on some foreign standards and be adjusted based on engineering experience; abroad, values of 1.3 and 1.43 are considered too high or too low, which is not ideal
The 1.25 times factor is derived from the 1.3 times factor in ASME Section VIII-1; on one hand, it allows the vessel to withstand overstress tests at 1.25 times the design pressure, and on the other hand, it puts the tips of internal defects in a pre-compressed state. 1.1 times the pneumatic test value is used because pneumatic testing is relatively dangerous, which is why the multiplier for overstress testing is reduced. The pressure for the withstand voltage test can be higher than the recommended value, provided that the overall stress on the film is verified through stress analysis. Furthermore, it cannot be set unlimitedly high, as there are many areas on the container where the stress conditions are complex, and it is not possible to determine safety through simple stress checks. Such as flat covers subjected to bending stress, flanges, openings with edge stress, and the folded edges of elliptical heads.