Thanks guys. Looks like corrosion is also a major factor in this. Inspected a flapper that was broken from the hinge pin. Looks like corrosion is affecting the smaller parts like pin causing it to break. These are flow lines from high water cut wells and also only intermittent flow. So this...
I have come across frequent flapper (disc) failures on swing type check valves. The service in the flow line is oil+water mixture and the pressure is generally in the range of 30-40 psig. I assume the failure is due to pressure variations in the line and the continuous disc movement due to it...