Single or double shot peening for sucker rods?

For most sucker rods, single shot peening already delivers a significant gain in fatigue resistance and is sufficient. Double shot peening is reserved for the most demanding rods —deep wells, high loads or corrosive service— where the maximum possible service life is sought.

The difference is a second pass with finer shot, which raises the residual compression in the outermost layer and improves the surface finish, without removing the deep compression left by the first pass. (For the process detail, see the FAQ “What is double shot peening?”.)

In rod production, the double process is implemented with two machines arranged in line: the first works at high intensity and the second at low intensity, each with its shot under control. It is the configuration that ensures repeatability in both stages without stopping the line.

The decision is made according to the failure mode and the actual demand on the rod; for the engineering criteria, see the double shot peening report, and for the machines, the sucker rod shot peening page.

CYM designs and builds single and in-line double shot peening machines for sucker rods.