There are multiple reasons why you can’t get a tight fit-up for every joint every time. Often times during tower mods we run into this problem because we are fitting new pieces of steel over existing pieces of tower, and there are only so many sizes of pipe commercially available for the engineer to choose from. I have inspected so many fitups on these towers that 1. didn’t meet the code requirements, and 2. the welder didn’t understand or have the tools to fix it correctly and in compliance. I thought I’d share how we do it at FinishLine Certified Welding;
- OPEN ROOT without access to the back side is NOT ALLOWED by AWS D1.1.
- AWS D1.1 Clause 5 (Fabrication) has allowances and instruction for how to deal with fit-up issues. Don’t worry, your not the first welder to run into a fit up issue
- BACKING – Always pack some A36 with MTRs in your welding truck to aid in mis-fits. You can’t run to Home Depot on the job and buy their steel, or grab some off the ground, you need to know its weldable and won’t impact weld deposit strength/integrity.
- Add a BACKING BAR to close the root gap. In this photo due to pipe sizing, the root gap was 1/4″. AWS D1.1 allows you to do this up to 5/16″..any larger and you have to get Engineer/EOR approval. We have done this many times and typically the Engineer approves (get in writing).
- INCREASE the fillet weld size by the now filled root gap. So a 1/4″ fillet weld now becomes a 1/2″ fillet weld after adding a 1/4″ backing bar.
- PROBLEM SOLVED, in compliance with the code, high quality weld deposited, everyone is happy. Make sure to keep the CWI in the loop, and make sure redlines are submitted, other than that; keep on keeping on!