Weld prep routine

[Arc weld]

In the field I can see a lot more cleaning but inside a fab shop working with new steel, it is very rare to do any cleaning unless it is a more critical weld. All the vessel shops I worked in were 100% X-ray and of course the vessels and piping required lots of grinding and wire brushing. However for large skids and most other structural welding, other than cleaning up your cuts, you didn't do any cleaning before welding unless the steel was rusty or dirty. Some of the skids weighed over 10 tons and the section under the compressor engines was filled with concrete to help reduce vibration. The engines were Cat 3412's running on natural gas. The largest skid I worked on was 72' x 20' and was over 80 tons with the vessels and other apparatus attached to it. The main I beams called for 100% penetration and were x-rayed. They required grinding and cleaning but the rest of the welds certainly didn't need any special prep. It was even specified the checker plate had to welded on with 7018 so it certainly had a high standard to meet. Do you think anybody is going to take a grinder to clean new steel to weld the checker plate on? The web of the I beams required a 3 pass fillet weld with 7018. We didn't have to grind the joint before welding. The entire skid was rotated for flat/horizontal welding. I wasn't referring to repairing farm equipment and other welding on dirty steel.

 

[Gary Fowler]

It takes less than a minute to run a power brush down 10 feet of plate to clean surface rust, dirt and scale off and that time will be repaid in ease of welding and lack of porosity which might have to be ground out and repaired depending on severity. Some open porosity is allowed in structural welds but it sure shows lack of pride in the welder doing the work when his welds look like crap when finished due to improper cleaning. I clean the weld areas as best I can even on farm equipment repairs just because it makes for easier welding with less sparks flying about. Is that a requirement to make the weld strong enough to hold? In most cases no, but if it takes me 2 or 3 minutes to clean up and the welding is much better quality, then why not do it.

 

[k0ua]

but if it takes me 2 or 3 minutes to clean up and the welding is much better quality, then why not do it.

Since I have the wire wheel out anyway to clean off slag, why not hit it a lick before hand to clean off gunk.

 

[jwmorris]

As far as a wire brush is concerned, if you are welding aluminum you will likely have problems unless you are using a stainless brush that has never had contact with anything other than aluminum.