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.
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.
a good quality carpenter's level that can check vertical as well as
the pipe (or body) in a stable, level orientation. Check with the
carpenter's level as illustrated.
or check, vertical orientation of both end flanges using the
carpenter's level, as illustrated.
two equal diameter pins located in two adjacent bolt holes, orient
the flange on one end so that the carpenter's level resting on the
pins indicates level. Move the pins and level to the opposite flange
and, without any rotation of the pipe (or body), position or check
the orientation of the holes in the second flange in the same manner
as the first. The level should indicate level while resting on the
pins on both flanges without any rotation of the body.
the pipe (or body) 90°, check both flanges again for vertical
orientation. This step will assure parallel flange faces.
inspect the external weld surface for uniform appearance, and
inspect the internal area for excessive burn through or
lack of full penetration.
checks made with a level in the field have an approximate nature,
so fabricators must take care to execute careful craftsmanship.1
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.
more information see: About Weld Neck Flanges and
Weld Neck Dimensions.
To view a
catalog page on Weld Neck Flanges, Click Here.
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