MATERIALS & MANUFACTURING
Figure 2 . Distribution of defects in valve commodities ( from 2018 till 2021 )
equipment deficiency reports ( EDRs ) in Europe with a focus on the last three years ; conducted a survey about welding processes for valve manufacturers ; reviewed the applicable specifications ; and made case studies to understand where improvements can be introduced . The study showed that the root causes of these failures are attributed to improper control of welding parameters , lack of competency of manufacturers ’ personnel , and misinterpretation of standard requirements . The methodology used included Six Sigma tools and focused on the identification of the main root causes to avoid reoccurrence in respect to Saudi Aramco applications . A schematic of the approach is presented in Table 1 .
Statistical data analysis
Aramco Europe collected and analyzed data from reported cases of welding failures observed during valve manufacturing , reported through manufacturer non-conformance reports ( MNCRs ) and material receiving inspection phases at sites , and reported through EDRs related to valves manufactured by Aramco approved European manufacturers . The failure ratio for the reported deficiencies was split into two populations representing two time spans , span-1 : from 2007 till 2017 and span-2 : from 2018 till 2021 . The results presented in Figures 1 and 2 reveal that welding defects recorded an increase from 2 % to 21 % in the overall distribution of the defect typologies between the two time spans , while the mix of valves sizes , types and quantities can be considered to be similar . It is clearly seen in the statistics of Figure 2 that welding related defects generate the highest rejection among the reported deficiencies . The prime reason for such an increase in the nonconformities since 2018 is related to the fact that Saudi Aramco valve specifications were updated with more stringent requirements based on valve class and design . A shift from the valve manufacturer ’ s usual manufacturing process was noticed , such as a switch from internal FBE coating to techniques requiring additional welding ; namely full or partial internal welding overlay , hard facing on critical areas , and welding on the sealing surfaces of the valves . Welding defects have been further split to categorize their nature and type , as shown in Figure 3 .
Figure 3 . Classification of welding defects
Root cause analysis of welding defects
To study the root causes behind all such issues related to welding , Aramco Europe conducted several analyses utilizing information received from source inspectors and liaised with the manufactures ’ quality assurance personnel , as well as with Aramco ’ s subject matter experts . After going through the identified root causes for all of the investigated cases related to welding defects of valves , the preliminary causes for such failures are illustrated in the form of sunburst representation , as shown in Figure 4 . It can be seen from Figure 4 that the primary reason behind the majority of issues was the lack of control of the welding process and parameters . The secondary reason of reported welding issues was related to the lack of competency of the manufacturer ’ s personnel . The tertiary reason was attributed to a lack of interpretation of standard requirements .
Process gap analysis
In addition to the statistical data analysis , Aramco Europe conducted a survey with 15 Aramco-approved European valve manufacturers covering most common valve types ( ball , gate , globe , check , butterfly and plug ) to assess their performance and compliance with applicable Saudi Aramco specifications and standards . The survey questionnaire requested information on the percentage of welding activities performed in-house versus outsourcing while focusing on Saudi Aramco specification , procedures , and inspection and test requirements . π www . valve-world . net Valve World September 2022
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