Abstract
Piping systems are incorrectly designed when subjected to fatigue, and coatings are applied by preparing surfaces with grit blasting. Grit blasting is used on coated pipelines and steel structures to improve coating adherence, but this technique reduces the fatigue strength of in-service piping and structures. Grit blasting creates jagged peaks and valleys, or stress raisers, on metal surfaces, and at each of these sharp pointed valleys, the probability of crack initiation increases, where embedded shards of sand reduce the fatigue strength of metals to accelerate failures. As the primary conclusion of this paper, grit blasting reduces fatigue failure properties for piping designs, or any structural designs, that experiences cyclic loads. As an example of grit blasting effects, there are presently 250,000 water main breaks per year at a cost of 13 billion dollars per year, and a trillion dollars in damages are expected in the next 25 years(1). Previous research showed that water hammer causes nearly all of these failures, and slow operations of pumps, fire hydrants, and valves will stop water main breaks due to fatigue. In short, grit blasting is a major contributor to water main breaks, and grit blasting also contributes to other fatigue failures throughout industry.
