Home Forums General Discussion Shot Peening Process, Intensity, Coverage Intensity Check

Once a saturation graph has been produced and say the result is 7.25A @ 2.36 passes/ rotations etc. What is the recommended practice when peening single Almen strips before and after the part is peened, as you cannot peen @ 2.36 rotations. Is it better to either increase the RPM so that the strip will do three complete passes, decrease the RPM so the strip passes twice or stay with the current settings and peen it at three passes which will give a slightly higher Almen reading than is for your actual saturation point?

Do NOT change any of your machine parameters.

Evaluate your saturation curve for the curve's arc height at 3 rotations and then peen your confirmation strip for 3 rotations. The accept/reject criteria is normally ±0.0015" of the value originally displayed at the 3 rotations point on the graph.

Thanks for that Jack especially for the allowable tolerance.
Another question regarding saturation graphs. AMS 2430 states to check intensity verification periodically. I take it we would re run saturation graphs if we were getting abnormal results, after changing anything such as blast hoses, nozzles , valves etc, but what would be considered an acceptable time frame if non of the above has happened?
We also peen one off parts with radically different diameters throughout the day requiring individual saturation graphs. To reduce the amount of variables we attempt to peen using the same pounds, traverse rates, distance from part, etc and to allow for the different diameters we are using the same circumferential velocity.
Am I able to peen one graph to cover all the parts with the same intensity parameters to cover the requirement for periodical checking?

Roy,that's a tricky question. It depends upon your customer but may also be influenced by geometry of the parts. If the stand-off distances and angle of impingement are essentially the same for the various set-ups you could be ok. Be sure to document your set-ups, perhaps use digital cameras to illustrate the machine settings.