The Basics of Field Welding Repair on Construction Equipment

In the construction industry, nothing cripples a jobsite like a broken machine. When it comes to fixing broken steel in the field, there are three steps to master:

* Cutting and removal of the failed component.

* Preparation of the new joint/part.

* Welding and cleanup.

This article discusses these three stages and helps guide you to the right combination of equipment to meet your field repair needs.

Stick welding, or SMAW, is the most commonly used process for field repair

Cutting and Removal of the Failed Metal

The first step in welding repair is removal of the damaged metal.  This can be done with oxy-fuel, plasma cutting or carbon arc gouging. Oxy-fuel and plasma are typically better for cutting through metal, whereas carbon arc gouging is better for gouging out a crack or defect without completely severing the part.

Oxy-fuel torches are one of the most common tools for cutting and are found on most service trucks. Plasma cutters, however, produce a smaller kerf (cut width), a smaller heat affected zone (HAZ), and are typically faster than oxy-fu el torches. Plasma cutters also cut through all electrically-conductive metals, whereas oxy-fuel won’t cut through aluminum or stainless steel.

Carbon arc gouging is another option when using welding generators with 250 to 500 amps of output and a high duty cycle. This process uses a carbon electrode to melt the defective area, and blast away molten metal with a focused, high-pressure stream of air.

To begin: cut away the damaged area and remove all rough edges to ensure proper fit-up of the replacement part. It is extremely important to fully grind out all cracks—even beyond what’s visible—because the slightest remnant of a defect will continue cracking even after a weld is laid over it.

Engine-driven welding generators feature 5,500 to 20,000 watts of generator power , depending on the model, for running grinders (pictured), drills and other tools.