Gary, Martinsitic Cast Shot does NOT work harden more than 1.5 HRC. The AMS Range for new shot is 7 HRC points, thus a minimal gain during life is not likely the cause here. Air pressure, size and flow control limits are the reasonable issue here. Joe
Loc: Corpus Christi Army Depot
Gary: Adding small portions of new shot to the existing batch should not have a significant impact in Intensity variation. Even though AMS 2430 and AMS 2431/1 do not cover media conditioning, you are not prevented from having an internal conditioning procedure when a batch is completely replaced with new shot. We will certainly recommend to the committee adding a paragraph to the AMS specs related to this topic. Conditioning of new shot will add quality value and consistency to the process.
Loc: Corpus Christi, TX
Thank you for the link, Walter. I did mistakenly say that we were using a +/- 10 psi range but in fact we are using +/- 10% on air pressure. The machines maintain a very even pressure and are maintained and tested by the manufacturer. I have no reason to belive that air pressure is the problem. The screens kick out any under/over size pieces and our shot checks always turn out very good. It seems that when our new machines were installed we just did not know about this variable.
Gary, Why not trying to get a substantiation for switching over from Cast Steel Shot towards SCCW shot (high hardness) ? I also had always lot's of problems with my newly bought Cast steel shot and went over to SCCW shot and got full approval of the Aircracft Engine OEM to use it always where-ever Cast Steel shot was mentioned. Since then (1994) we never had any issues anymore around shotmedia quality and related shotpeen-problems with our computerized shotpeen machines and shot sieve systems. Marcel