Welding Ti Pipe

Ladies and others

I have some existing 100NB GR12 Ti pipe that I want to add a flange pair to. The pipe spool consists of flange-straight-bend-straight- bend-straight-flange; one piece. I want to add a flange pair to the middle straight in order to simplify descaling; currently using 30,000 psi water blaster. By adding the flange pair, we will have good access to each straight portion, and can use a lance instead of a rat.
The pipe has been in service for 4 years; no apparent corrosion. The process fluid is a metallurgical slurry with dilute sulphuric acid in the carrier liquid.
However I have not welded new flanges to old pipe before (only new to new).
I envisage a thorough clean/linish/pickle (to remove iron traces) , thickness check, dye check and then prep, weld, NDT and hydro as for new pipe using prequalified procedures and experienced qualified welding operators.

However given the brittleness of Ti,the criticality of this spool (not a good one to fail), and the uncertainty of NDT, I wondered if anyone has any experience or advice on welding old Ti to new Ti.

Especially interested to know if any other pre-weld conditioning of the old pipe is recommended.

Cheers

Steve Received on Wed Jan 05 03:46:00 2005