Sunglasses bent out of shape again? Just bend them back and she’ll be right. Using force to straighten bent items is a natural response to most everyday situations.
But what do you do if someone has backed a forklift into a load bearing beam in your workplace? Or natural forces such as fire or earthquake have bent the only bridge in and out of your town? Nobody wants to tear down and rebuild.
Heat straightening is the art of strategically applying heat to sections of a piece of steel that has been bent out of shape. Put simply, an experienced practitioner can apply heat in specific areas to straighten load bearing steel whilst still in place, without adversely affecting its natural properties.
It started as an art…
Heat straightening began in the early days of welding with the earliest written information dating back to 1938. Considered a craft rather than a science, the heating procedures developed through the curiosity of welders, were handed down from one generation to the next. Those who practiced heat straightening as a repair method, also practiced heat curving as an aesthetic method, for example curved bridge girders.
And eventually became a science
The ability to repair damaged structural steel members in place eventually got the attention of the engineering community, but it wasn’t until recent years that official research was conducted to quantify the process. In fact, even in the late 1980’s the heat straightening repair of bridges was banned across half the United States due to a lack of understanding and appropriate scientific documentation of the process.
How we use it today
We recently applied the method to a bent load bearing beam at a client’s facility. The beam supported a small crane and became overloaded when the crane picked up a particularly heavy load. The result was a 30mm bend across approximately 3 meters of the beam.
After exploring the options, we went back to client with a heat straightening plan that their own experienced welders would be able to implement on site.
Below you can see the beam with yellow crane attached, bent slightly to the side. On the right, you can see the repaired result, nice and straight again. Note the interesting “V” shaped pattern of the heating method. The pattern and placement of the heat application depends on type of damage.
Basic heat straightening principle: