MATERIALS & MANUFACTURING
The results of the distributed questionnaires revealed that 12 manufacturers had the capabilities to perform the welding process in-house , but a major portion of their welding activities were handled by outsourced welding suppliers . This can be seen in the representation in Figure 5 . The questionnaires further revealed that the valve manufacturers usually do not carry out and implement proper controls as required by applicable specifications . Among the reasons behind such a lack of control by the manufacturers , we identified a lack in requirements in the applicable international standards , but also in Aramco specifications to mandate surveillance of the welding process or to mandate notification of customer ’ s inspection representative for such activities . Similarly , the level of control and approval from customers regarding welding procedure specification ( WPS ) and procedure qualification record ( PQR ) is relatively low , if not nil in most of the cases . In regards to weld overlay thickness , the generally accepted practice of three random thickness readings often proved to be insufficient , especially when the manufacturers failed to identify and conduct these measurements in the most critical areas , depending on the valve geometry and welding equipment limitations . Managing different requirements for different projects , customers , specifications or types of valves often led to confusion or adoption of the wrong requirement for the ongoing job .
Conclusion and recommendations
Based on the provided data and conducted analysis , it is concluded that the welding process is extensively applied to valves in various forms such as overlay welding , hard-facing and joining process by utilizing outsourced partners . The criticality level of the majority of the valves supplied in the oil and gas industry is between a high to severe
Figure 5 . Welding process outsourcing volume adopted by manufacturers
Figure 4 . Preliminary causes of welding defects
criticality . The service ambient is also considered as high to critical . During the past three years , the demand for valves with internal welding overlays has been dramatically increased , and the results of non-conforming outputs have also been observed to be increasing . Some of the identified recommendations are indicated below .
• One of the proposals refers to the replacement of the minimum threereadings requirement for the weld overlay thickness with the requirement for the valve manufacturers to have a dedicated procedure for weld overlay inspection to ensure that the minimum overlay thickness is met at any point on the surface . The procedure shall be process specific and shall include tools , sample size , and reading locations for all manufactured valve sizes .
• It is also recommended to mandate valve manufacturers having in-house
or outsourced welding activities to have a certified welding inspector or technologist to monitor the welding process .
• Adding a sampling plan in applicable specifications for valve manufacturers ’ and customers ’ inspection representatives to witness the in-process welding activities may eliminate some of the non-conformities covered by this study .
• Finally , it is suggested to consider adding an approval / control mechanism by the customer ’ s representation on valve related WPS ’ s and PRS ’ s , and to include non-destructive tests on the first welding pass on similar valves .
About the author Dragos Chetroiu is a Mechanical Engineer with 25 + years of experience in manufacturing and inspection of various types of equipment used in oil and gas industry . After joining Aramco Europe HQ in 2007 , Dragos worked in several areas with the Technical Services Department and is currently the Supervisor of the Quality Control Unit , responsible for Aramco operations in Europe and Africa .
32 Valve World September 2022 www . valve-world . net