Another thought. Make your weld on the existing pipe, test against the existing pipe. Cut out portion of pipe to have flange communicate with existing pipe. This is a great technique on smaller fittings. I've never had to do it on a 20" line.
The process I am working on is preheat of natural gas prior to pressure reduction. Peak Process load is 385,000 btu. Target gas temp is 175 F. I am looking for some guidance to understand the differences in controlling gas temp with a 3 way valve for bypassing the hex and keeping constant hot...
