Failures in Fracking - From Fatigue to Temper Embrittlement

Hydraulic fracturing (fracking) plays a major role in oil and gas production worldwide, and involves the use of very high pressure (on the order of 10-15 thousand psi) slurries of produced water and sand. Due to the high pressures and flow rates involved, the piping that carries these slurries is of critical importance for the safe operation of equipment, as failures can produce extremely high-pressure jets that can pose a significant danger to personnel and other equipment. This paper reviews three failures in these pipe components with three different causes. The first case concerns piping components that were improperly installed, resulting in higher than designed loading leading to rapid fatigue of the connections between different components with cracks initiating at geometric stress risers. The second failure concerns a poorly designed valve where the design appears to fail to account for one of the key principal loading stresses, resulting in unacceptably high loads at geometric stress risers that culminated in the rapid fatigue failure of the valves in under one day of service. The final failure concerns faulty manufacturing and apparently falsified MTRs that resulted in a sub-standard quality material being used for the manufacturing of parts, and ultimate failure of the parts due to tempered martensite embrittlement. The number and variety of causes of failures in these components serves to stress the importance of proper engineering of components, care in installation, and supply chain control and quality management.