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
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.
Obtain a good quality carpenter's level that can check vertical as
well as horizontal orientation.
Position the pipe (or body) in a stable, level orientation. Check
with the carpenter's level as illustrated.
Position, or check, vertical orientation of both end flanges using
the carpenter's level, as illustrated.
Using 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.
Rotate the pipe (or body) 90°, check both flanges again for vertical
orientation. This step will assure parallel flange faces.
Visually inspect the external weld surface for uniform appearance,
and inspect the internal area for excessive
burn through or
lack of full penetration.
All checks made with a level in the field have an approximate
nature, so fabricators must take care to execute careful craftsmanship.1
Operators should always use
Qualified Welding Procedures, supported by
Procedure Qualification Records, performed by
Qualified Welders, on flanges and pipe of known
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.
For more information see: About
Weld Neck Flanges and
Flange Weld Neck
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