What Does Over Bend Mean?
An over bend can be defined as a bend in a pipe either in the high point or at the middle of a joint.
Trenchless construction methods such as horizontal directional drilling (HDD) requires the pipe to be pulled back in through the pilot bore during the reaming operation. Sometimes, the pipe is pulled through the hole at an angle causing an overbend at the highest point. If this over bend exceeds permissible limits it can cause damage or failure of the pipe.
Trenchlesspedia Explains Over Bend
Pipelines installed by HDD and other trenchless methods require the connection of the pipeline sections to the drill rods. While lifting the front end of the pipe, an over bend is created at the angle of entry of the pipeline. This over bend can be caused as a result of design or an error by the operator, who may assume that since the pipe did not break there was no over bend.
However, over bend may manifest as a small crack that may be invisible and may function for several bores until fatigue breaks the pipe without warning. The pipe should not be allowed to bend beyond the allowable bend radius, as most of the cracks form during the last 1% of the load cycle, making it difficult to detect damage due to fatigue before failure occurs.