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Weld Neck Flange Attachment
Operators often have to make field attachment of weld neck flanges to pipe in order to complete field assembly of pressure systems. To facilitate the fit-up of field welded, flanged equipment, flanges must have parallel orientation at the time of attachment. And, unless engineering considerations require otherwise, flanges at opposite ends of pipe should have the same bolt hole orientation as well. See the illustration below for a suggested setup for installing or checking the installation of weld neck flanges on straight pipe using a carpenter's level.
The following outline of steps supported by the above illustration will provide a useful guide to set-up or check field-fabricated units of straight pipe with 2 weld neck flanges.
Operators should always use Qualified Welding Procedures, supported by Procedure Qualification Records, performed by Qualified Welders, on flanges and pipe of known material chemistries. Flange weld necks and pipe diameters, O.D. and I.D., should match. Successful, safe use of API Weld Neck Flanges requires sound full penetration welds.
1 Words in bold italic indicate they have subjective meaning and persons using this information must use experience to improve the reliability of their judgement when the meaning of these words can have impact on performance