Low-temperature impact work
Thread Content
For low-temperature equipment, low-temperature materials are used; the material standards specify that these materials have been tested for their low-temperature impact strength at the lowest operating temperature required for that type of steel, prior to leaving the steel mill. 1. Does the impact energy required by GB150 refer to the low-temperature impact test that must be conducted on the steel before it leaves the factory, or does it mean that the manufacturer conducts the impact test on the material after purchasing it (which is equivalent to a retest)? 2. If it’s a re-inspection, I’m a bit confused – since the inspection was already done before leaving the steel plant, is there really a need for another one?
The impact energy required by GB150 refers to the low-temperature impact energy that steel mills need to achieve. It does not refer to the retesting of materials by the manufacturer who uses them.
Thank you for your answer. You mean that 150 is actually a requirement for versatility, but if the material standard selected already specifies the low-temperature impact value, then there’s no need to mention it in the document, right? Since it’s already specified in the standard, purchasing will go smoothly without any mistakes
This standard does not state it explicitly; as the moderator said, it should be done by the steel plant. However, the welds also need to undergo impact testing
The impact test temperature specified in the standards is not necessarily the design temperature of the equipment itself; there is a difference between the two. Moreover, as mentioned above, the impact energy required for welds is generally lower than that required for the base material. Therefore, in order to ensure that the welds also meet the standards, higher requirements are set for the base material than those specified in the standards.
As mentioned above, the impact energy required for steel plants is determined in accordance with the standards for specific steel grades; generally, there is a discrepancy between this value and the actual conditions. Therefore, design requirements call for retesting, which is carried out under the design conditions, including testing of the welds as well. Re-inspection is necessary for important equipment. Additionally: The possibility that the purchased materials are of inferior quality is also a reason for requesting re-inspection.
Where GB150.4 5.1.1 specifies requirements for re-inspection of materials, reliance solely on the purchased materials is not acceptable. Of course, this is another matter if the design documents do not require it and the owner has no objections
It’s actually a matter of recognition – the quality certificate certainly contains the data from tests conducted by the steel mill. According to the regulations, retesting is only necessary when there are doubts; you can have doubts about everything, or you can have no doubts at all
The main issue is that the standard impact test temperature does not match the design temperature of the specific equipment; it is therefore necessary to specify the impact energy value at that corresponding design temperature.
If it is a low-temperature steel, according to the standards, the impact energy value corresponds to the lowest operating temperature of that steel. The design temperature indicated on the chart is definitely greater than or equal to this lowest operating temperature. Therefore, if things are done in accordance with the standards, all requirements are already met, and there’s no need to indicate it separately on the chart. Of course, this does not apply to ordinary low-alloy steels, as the standards assume an impact energy value at 0 degrees Celsius; if it’s at -10 degrees Celsius, then it needs to be specified separately