ENGINEERING/DESIGN

Problem Solving

Engineering & Design

An engineering firm requested that Touchstone perform an examination of the failure of brazed fire hydrant pipe samples.

The following examples illustrate some of our contributions to this business sector:

  • Prior to installation in a large housing development, fixtures for doors and lighting fixtures were evaluated to determine the most durable product from among several suppliers. Testing included UV/humidity exposure, resistance to residue from fingerprints, mechanical strength, and salt fog exposure.
  • An engineering firm requested that Touchstone perform an examination of the failure of brazed fire hydrant pipe samples. Four samples, cut at 90 degree angle intervals, around a circular section of a cast iron water pipe which supplies water to a fire hydrant were examined. Although mechanical damage could have shortened the life of the brass/cast iron interfaces the differences in appearance between the brass surface of the fresh fracture and the as-received fractures indicates a variation in brazing quality around the pipe.
  • Touchstone was contacted regarding a problem that involved the failure of a cast iron steam boiler assembly. TRL concluded that the failure seen in this boiler was most probably the result of an initial failure of at least six of the internal stay bolts and a portion of the corner of the casting. The final failure would have occurred when the remaining section thickness could no longer sustain the loading on the internal surface. The presence of stay bolts indicated some understanding of the forces present during use but the overall design did not appear to allow for the rather unique properties of gray cast iron. The final report stated that the use of internally cast-in-place staybolts was inadvisable because of the mechanical properties of gray cast iron, particularly, low elongation. There was no evidence that this design had been approved by the ASME section VIII committee.
  • The purpose of this investigation was to determine the cause of cracks which were seen to develop at the flame cut radius of a wide flange steel I-beams during hot-dip galvanizing. TRL was asked to examine one of the specimens to determine the cause of the cracking problem and to recommend a procedural change, which would eliminate the problem. The evaluation found the cracking problem was due to a combination of factors: residual stresses in steel beam which remained from manufacture, a brittle zone at the flame cut surface, and the effect of thermal shock which occurs as the I-beam is lowered into the 850 degree F zinc bath. It is also possible that liquid metal embrittlement may have had some effect here.

The above examples are only a sample of our work in this area. We would be pleased to provide any additional information you may require. We also invite you to review examples on our website of work that we have performed in support of other business sectors.