1. Threaded connections (pipe to pipe, fittings), slip-on flanges and mitred connections in excess of 3 degrees shall not be used in any part of the pipeline system.
2. “Pup” pieces should not be less than 0.3 m or one pipe diameter whichever is more.
3. All branch connections (except for pressure relief systems, see 3.12) should be provided with a valve to permit isolation of the branch from the pipeline.
4. For mechanical strength reasons, there should be no branch or instrument connections smaller than DN50 on pipelines. For pipelines smaller than DN50, the branch connections shall have the same diameter as the pipeline.
5. Weldolets larger than DN75 should not be used.
6. Gaskets for flanged connections should conform to the following:
7. Raised face spiral round gaskets for flanges class 1500 and below, for onshore or above water.
8. Ring type joints for subsea flanges, and for all flanges above class 1500.
9. The number of flanged connections in pipeline systems should be minimised, i.e. tie-in welds are preferred. In some situations (offshore pipeline tie-in to a PLEM or a pre-installed riser), a flanged connection may be used; one of the flanges should have a swivel ring for easy alignment. Subsea connections for large gas transmission systems should be realised by welding.
