Should Socket Welds Be Used In Sour Service Process Environments And What Are The Quality Control Requirements?

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Product Number: 51321-16536-SG

Author: Jan Baas

Publication Date: 2021

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Socket weld connections are frequently used in the petroleum and petrochemical industry for small bore carbon steel piping. These connections are allowed by piping codes such as ASME1 B31.3 (1) for process piping and are considered cost effective as they can be produced relatively quickly and they are to some extent tolerant regarding field fit up issues. The requirements for a socket weld are specified in the figures 328.5.2.A, B and C of ASME B31.3. These figures define the minimum size of the fillet weld in relation to the pipe and flange thickness and also specify a gap of approximately 1.5 mm after inserting the pipe in the socket before welding to allow for thermal expansion during welding. These socket welds are fillet welds and are normally made using the gas tungsten arc welding (GTAW) process. The objective of this paper is to explain that it is important to exercise caution in the use of socket welds in sour service process environments. This paper will explain the difficulty during socket welding in ensuring compliance to the ANSI2 /NACE3 MR0103/ ISO4 17945 (2) and NACE SP0472 (3) specification requirements. McDermott sets quality control requirements for socket welds to guarantee that socket welds are obtained with acceptable hardness figures that are resistant against Sulfide Stress Cracking (SSC).

Key words: Sulfide Stress Cracking, SSC, Socket Welds, Hardness, Sour Service