Body (girth) flanges have
distinct advantages in small columns (Part 1)
by Matt Gertz
Small-diameter columns (typically smaller than 36” diameter) can impose unique equipment design and installation constraints compared to larger columns. Installers cannot easily enter these columns to perform installation, and limited access makes hardware connections difficult to complete. Furthermore, internal supports tend to block an increasing percentage of the column cross-section as the diameter decreases, and it becomes more difficult to install them. In these situations, an effective approach is often to divide the column itself into smaller segments through the use of body (or girth) flanges at strategic elevations along the height of the column.
Using body flanges makes the full column cross-section accessible without the use of manways, removing many installation constraints that would otherwise be created by the small column diameter. Because the flanges break the column into segments, the column itself may be erected one segment at a time rather than all at once, potentially reducing the lifting equipment requirements and the amount of space required for column set-up. Depending on the method of securing the equipment in the column, it may be possible to install it in the vertically oriented column segments at ground level and then raise the segments into place. NOTE: Once the internals and/or packing are installed, the column segments must remain vertical. Equipment installation time can be further reduced by performing simultaneous installation of the equipment in each column segment. Thus, body flanges can significantly increase the speed and safety of installation while reducing its cost.
With a body flange design, it is often possible to reduce the number of internally welded tower attachments, as the equipment can be made either to be sandwiched in the flanged connections themselves or to rest on separate rings made to mount in the flange joints. This is a particularly useful approach for structured packing installations, which often use single-piece packing layers for small diameters and require a completely open cross-section. Future changes in equipment configuration are also easier to accommodate and tend to require less column rework if body flanges are used.
Read Part II
to learn more about the design advantages to using body flanges.