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Unformatted text preview: HIDDEN DEFECTS IN FITTINGS Reported by: Shell Chemicals, SNC Moerdijk Large bore flanges and fittings that were delivered in a critical phase of a multi-million project had to be rejected because of unusual and possibly concealed manufacturing defects. In this stage, the project can only be continued at the expense of very high cost and effort. Currently SNC Moerdijk is implementing a 10 million+ project in the MSPO-2 unit. For these projects numerous piping materials have to be supplied, diameters ranging up to 56”. Most materials are made of AISI 316L stainless steel. Initially some issues were encountered on a shipment of 40” flanges, where cracking was observed visually. Follow-up inspections with dye penetrant testing further revealed that 10 out of 60 flanges had crack indications. Metallurgical investigations confirmed that cracking was caused by forging defects. Moreover, the investigations showed that cracking was concealed by welding! (see figure 1). The whole shipment had to be rejected. The manufacturer of the flanges is: Wenzhou Fada Flange Co Ltd, Wenzhou PRC. In parallel, another shipment was received of fittings, sizes 8”and larger, including longitudinally welded fittings Since materials certificates and test reports were incomplete, additional acceptance tests were performed. These tests not only revealed that unacceptable welding defects were found on welds that were approved by the notified body, there were additional welds too! (see figures 2 and 3). With further investigation it became clear that the majority of the fittings appeared to have additional welds, as if they were assembled by pieces. The certificates did not mention any additional welds, nor repairs and were witnessed and approved by the NoBo (!). Also, while the longitudinal welds were visible, the additional welds were so well concealed that they could only be found by eddy current testing. Again, the whole shipment was rejected. The manufacturer of the fittings is: Shanghai Want Industry Co Ltd, Shanghai, PRC. Although further investigation would be needed to detect all backgrounds and causes, the findings are striking and the impression of intentional deception is hard to avoid in both cases. Needless to say that it is very unfortunate that these issues become evident in a critical stage and jeopardize the whole project, since finding replacement parts of this diameter on the very short term is extremely difficult. Furthermore, some fittings and flanges were already installed and had to be cut out. Nevertheless, if these materials would have been installed without detection of these defects, consequences would without any doubt have been disastrous: potential of very serious process safety incidents and loss of production of months! Actions taken: • All rejected materials have to be replaced at the expense of very high costs and efforts. Failing to install correct materials on time, will stop the project with multimillion regret cost. • The issue will be included in a Business Control Incident that will be submitted. • Liability of the supplier will be established and followed through (again at the expense of cost and time). The above incident triggers existential questions on the effectiveness of the procurement process, quality assurance and the policy to rely on the QA system of manufacturers and suppliers: • How effective is the quality assurance system of our supply chain? • What actions do YOU take to prevent this from happening? Figure 1. Weld covering defect in flange Figure 2. 24”elbow, with dotted line indicating additional weld as detected by Eddy Current and confirmed by metallography. Figure 3. More additional welds, besides the longitudinal. ...
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This note was uploaded on 03/12/2010 for the course MECHANICAL M768501 taught by Professor Prof.han during the Spring '10 term at Institut Teknologi Bandung.
- Spring '10