[Real-Case Discussion] Issues in Weld Inspection of Pressure Piping
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Record dated August 29, 2018: Party A: Project owner； Party B: Design Institute ； Party C: Pressure pipeline inspection unit ； There is a formaldehyde pipeline with DN50, 0.5MPa pressure, and at room temperature. The design institute designated it as a GC2-class pressure pipeline, as formaldehyde is highly toxic. In accordance with the \"Code for Acceptance of Construction Quality of Industrial Metal Piping Projects\" GB 50184-2011, the inspection level for welds was set at II, which means that the proportion of non-destructive testing must be ≥20%. The pressure pipeline inspection agency was very dissatisfied upon seeing this; it contacted the design institute, questioning the high level required for weld inspection, and demanded that it be changed to grade IV, meaning a 5% ratio of non-destructive testing ； The reason is that the \"Code for Pressure Piping – Industrial Piping\" (GB/T 20801-2006) stipulates that for GC2-class pipelines, an inspection level of not lower than IV is sufficient. The construction party was completely confused throughout the process. I don’t know whose to listen to. Please share your opinions, thank you!
Personally, I believe that non-destructive testing should be carried out in accordance with the suggestions of the design unit. First of all, when there is a conflict in regulations, strict enforcement should be applied; and here it’s not a conflict of regulations, but rather different starting points for the provisions set out in the two regulations. One is to determine the inspection ratio based on the properties of the material. One is to determine the flaw detection ratio based on the pressure pipeline class and nominal pressure. From another perspective, one of these two standards is a recommended standard while the other is a mandatory standard; which standard should one follow according to you?
Non-destructive testing should be carried out in accordance with the suggestions of the design unit
The standard is the minimum requirement; when multiple standards have conflicting requirements, the higher standard shall prevail.
Non-destructive testing should be carried out in accordance with the recommendations of the design agency; the standards represent the minimum requirements, and the design agency may propose requirements that are higher than those specified in the standards, based on the actual circumstances.
According to the design institute, the inspection range cannot be determined solely based on pipeline pressure
For safety reasons, it is best to choose a high standard.
Our company acts as both the owner, the general contractor, and the supplier; in such situations, the only party with decision-making authority is the design institute. Of course, this is assuming that the owner does not give arbitrary instructions. I have encountered many such cases, and the usual response to the construction party is: Please construct in accordance with the drawings, as these drawings were designed and finalized by qualified professionals who carried out design verification, review, and other necessary processes； The contractor has no right to modify the drawings. If the contractor wishes to lower the standards or adopt different standards, it must negotiate with the supervisor and the owner on its own. The contractor should be reminded to have the corresponding costs deducted, and any subsequent responsibilities shall lie with the contractor, the owner, and the supervisor; the design institute will not be involved
The standards cover the most basic aspects... If higher standards are adopted, the cost will be higher... but the associated risks will be reduced as well... So there’s no right or wrong, only cost considerations to take into account!!!!