By 803056
Date 05-17-2019 13:11
Edited 05-17-2019 13:22
I'm confused as well. Exactly what is it you are struggling with.
For starters T = the thickness of the test coupon and the total thickness qualified for production.
t = the thickness of the weld deposited with particular welding process. This comes into play if electrodes having different f numbers are used or if multiple welding processes are used. Thus, if the root is deposited with GTAW, one must record the thickness of the weld deposited. If the remainder of the groove is deposited with FCAW, a second process, the thickness deposited must be recorded separately from the root.
The final thickness qualified is separate for the GTAW and FCAW (t1 and t2). The thickness used for production welds is typically the sum of both the ranges qualified for t1 and t2. However, if the processes are used separately (not in combination) the thickness T qualified is that qualified for t1 or t2.
Take a look at the graphic I have attached. It shows a test assembly welded with two different SMAW filler metals (w/ different F numbers) and a second process (could be GTAW, FCAW, GMAW, etc.). It may clarify the ranges for which the WPS can be qualified. In this case, each filler metal or each process can be used individually thereby reducing the total thickness range qualified for production to the deposited thickness range of each F number/process. The thickness range can be increased by combining the processes or the filler metal F numbers to get the full range.
Al