Can you provide a rule of thumb guide to selecting
and matching standard commercial pipe sizes to
API Spec 6A 10M flanges? 5M
flanges can be quite straight forward as the API specified weld neck
sizes match available pipe. I always have to think twice when using 10M
flanges as the specified weld neck size usually doesn"™t match pipe I can
find.
We know of no simply stated rule. Most API 5K flanges
fall into the category API refers to as 6B
flanges, these flanges seal with R or RX type ring gaskets. 6B weld neck
flanges, through 11" nominal size, have their weld necks specified in
API Spec 6A, and these weld necks correspond to standard pipe sizes and
schedules. Keep in mind that 6B standard weld neck flanges always have
restricted bores compared to the full bores specified for equipment with
the same size integral flanges.
When API introduced the current 10M, 15M, and 20M
flanges that seal with BX ring gaskets, API referred to them as
6BX flanges. These API 6BX weld neck
flanges all have full bores. API also specifies the O.D. of the weld
neck based on allowable stress levels of the flange material. Weld necks
on 6BX weld neck flanges do not correspond to any standard pipe size
except by coincidence.
Originally API specified weld neck "transition
pieces" to bridge the mismatch between the flange weld neck and
available commercial pipe, but API no longer specifies this component.
To see API Flange Weld Neck Dimensions and suggested
pipe or tubular material for attachment by welding,
Click Here.
For more information
about joining flanges to pipe by welding see:
Q & A 45 API Flange Weld Neck and Matching Pipe II.
Q & A 16 Weld Necks on 6BX Flanges.
Click
here for a caution about 6BX weld neck flanges.
Weld Neck Flange Attachment.
About Weld Neck
Flanges.
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