5.2 Steel pipe joints
5.2.1 Joints in steel pipelines may be made by:
• Screwed on or welded on bolted flanges.
• Butt welds between pipes or between pipes and valve chests.
• Socket welded joints (up to 60,3 mm outside diameter).
• Threaded sleeve joints (parallel thread), see also 5.5.
• Special types of approved joints that have been shown to be suitable for the design conditions, see also 5.4.
5.2.2 Where pipes are joined by welding a suitable number of flanged joints are to be provided at suitable positions to facilitate installation and removal for maintenance.
5.2.3 Where welded pipes are protected against corrosion then the corrosion protection is to be applied after welding or the corrosion protection is to be made good in way of the weld damaged area.
5.2.4 Where it is not possible to make good the corrosion protection of the weld damaged area, then the pipe is to be considered to have no corrosion protection.
5.2.5 Where backing rings are used for welding pipes, then the effect of the flow obstruction of the backing ring and erosion/crevice corrosion of the backing ring is to be taken into account.