Neutron diffraction investigation of fluid end cracking in well stimulation pump fluid ends

This paper summarizes a study involving residual stress measurement in a cracked fluid end section from an industrial well stimulation pump. In order to withstand extremely high operating pressures, fluid ends typically are autofrettaged to introduce residual compressive stresses in stress concentration areas. In this study, neutron diffraction measurements were conducted on a cracked fluid end section to determine if these compressive stresses were still present or whether they had disappeared during the service lifetime of the component. Our work found that despite the fact that cracking had occurred, significant levels of residual stress were still present in the component. The cracking was attributed to a gouge in the suction inlet region, well away from the position of high compressive residual stresses.