Threaded flanges to suit PTFE lined site fabricated piping

Companion flanges are used in conjunction with tight fit field flare pipe spools to enable the field fitting of a flange without welding which could serve to damage the liner inside the pipe. 

These flanges are specific to lined piping, as they are designed for threading onto the spool, but with a smooth radiussed transition from the pipe steel bore to the raised face. 

This is critical to prevent the liner becoming stressed when flared over this junction. It is important to thread the pipe sufficiently to run the flange fully home.

The table below shows the thread length on the flange and the amount by which to reduce the spool steel length to allow for the flange and lining – assuming flanges on both ends.