When revision “U” of AMS 2430 was published in April of 2018, one of the most notable changes was that manual peening requirements had been included. Previously, the standard had been titled “Shot Peening, Automatic” which limited its scope to processes where the part or the nozzle, or both, were manipulated by the automated machine. But because the manual technique of shot peening is applied in some cases, it needs a standard to assess consistent performance against industry-agreed requirements. So the new title simply became “Shot Peening” and it included the requirements for manual peening and batch or tumble-barrel peening.
The inclusion of manual or batch peening does not mean that shot peening processors now have the option of using these techniques instead of the automated technique. The automated technique has to be used unless the use of manual or batch peening has been explicitly authorized as part of the purchasing information. This authorization must come from the cognizant engineering authority for the part; an intermediate supplier does not have the authority to decide this.
The requirement for documented authorization is made in section 1, “Scope”, and in the Appendices A & B giving requirements for the manual and batch peening processes. It has also been added to the list of items in “Ordering Information” at the beginning of the standard.
If the required authorization mentioned above has been received, then the peening must be carried-out to the requirements of Appendix A, for Manual Peening, or Appendix B, for batch peening.
The requirements for manual peening are focussed on operator training and qualification. As this is a manual process, the operator must have a record of demonstrated competence in achieving the engineering requirements for the part on a repeatable basis.
The training and qualification requirements for all techniques of peening, automation, manual and batch operation are specified in section 4.3.4. This identifies twelve items for which all operators must receive training and demonstrate proficiency. Appendix A then gives further requirements to qualify an operator for manual peening.
The process company must have a procedure for training and qualifying manual peening operators, and the procedure needs to include the items specified in Appendix A. In addition to the general training requirements listed in 4.3.4, the operator must have received instruction in manual peening techniques and use of the manual peening equipment. As a demonstration of competence, the operator must produce saturation curves for two different intensities and at one of these intensities, produce complete, uniform coverage on test specimen pieces. These test specimens have flat plate, angle and hole geometries and two different material types. The details of the geometries and alloys are listed in Appendix A.
The training and qualification must be accurately recorded for each individual operator and evidence maintained for audit and review. Operators must be requalified every twelve months, so this should be included in the documented training procedure. It is advisable that the document recording the operator qualification for manual shot peening has an expiration date no longer than twelve months after the issue date.
Appendix A also requires that the manual peening machine can propel media at a controlled rate and consistently reproduce the required intensities. The AMS does not detail further machine requirements, but in practice, achieving process repeatability may entail the use of special fixtures to control nozzle stand-off and angle, and calibrated timers or guides to control the exposure time on Almen strips and peening areas.
It is also a requirement of Appendix A that if the operator is changed during the manual peening of a batch of part, then a conforming Almen strip verification test must be undertaken by the new operator before peening any of the parts. 
A shot peening processor should also check if their customer requires that they are Nadcap-certified for manual shot peening. In this case the requirements of AC7117 and AC7117/5 will be applicable. AC7117 section 7 has a list of proficiencies to be demonstrated by a qualified operator. The manual peening checklist AC7117/5 adds further requirements, principally that there is a specific qualification for manual peening. These checklists are available to registered users of the Eauditnet website. Nadcap qualification also requires that the operators are requalified within a twelve-month period.
If a processor is going to undertake manual shot peening, careful consideration must be given to all these requirements. Copies of the relevant, current AMS 2430 and Nadcap checklists need to be acquired and fully reviewed.
The requirements for qualifying manual shot peening operators in AMS 2430 and Nadcap are very similar; it is not difficult to devise procedures which satisfy both criteria. The use of proven, qualified trainers and the guidance of an experienced specialist in the process is recommended.

For questions contact paul@mfn.li

Standards Forum
by Paul Huyton,
MFN Course Director World Wide
more information at www.mfn.li/trainers