Northern California Failure Expert Witness Describes Tubing Failure

An interesting failure of steel tubing was observed when 1 3/4" diameter A513 Type 5 steel tubing was being bent in a tubing bender. In this case the tube was clamped into the bender in the wrong location. At this time the clamp bolt had made an indentation (nick) in the pipe surface. The pipe was released and moved. The "nick" ended up on the tensile surface (i.e. convex side of the bend) during bending. As the tubing was being formed it broke in a ductile manner. A513 Type 5 steel is work hardened and therefore has little ductility, and it cannot survive bending if the surface has been damaged. The appropriate tubing should have been made of C 1020 mild steel. Upper left is a photograph of the nick on the convex side of the bend. The failure is interesting because it is a progressive failure that was caused by non-cyclic stresses (i.e. it is not metal fatigue). In addition, there are faint crack arrest lines that show the progression of the ductile failure. The failure surface almost looks like metal fatigue. This fsailure did not occur when C 1020 tubing was treated in the same manner. This failure was the result of improper material selection. It is not the result of a manufacturing defect.

Plumbing Failure Analysis

Northern California failure analysis expert often performs plumbing failure analysis. In this case, the corrosion expert examines plumbing in numerous houses that was plugged due to brass dezincification of yellwo brass. In this case the zinc in the copper zinc alloy corrodes selectively and this leaves a white deposit on the interior of the pipe. The white material is a combination of zinc oxide and zinc carbonate. Above is an example of significant dezincification; however this pipe is still fairly open. One can see that the flow of the water is from the brass to the copper and the corrosion product is being dragged into the copper pipe from the corroding brass fitting that is soldered to it. As the brass contioues to corrode, the fitting can become clogged and its strength will significantly decline.