Riveting - special process
- Thread starter nath57
- Start date
John Predmore
Trusted Information Resource
In the aviation industry, a special process is defined as
"8.5.1.2 For processes where the resulting output cannot be verified by subsequent monitoring or measurement, the organization shall establish arrangements for these processes" [to verify or validate the quality].
Mechanical testing of an assembled rivet is probably considered a destructive test, so you can't do 100% test. Even if you do not pull test a rivet to failure, you can't be sure the rivet was not weakened by the test. The other case of a special process is when it is impossible to verify the quality of a component in an assembly before completing the assembly, which makes verification of the component impractical for the purpose of quality determination.
"8.5.1.2 For processes where the resulting output cannot be verified by subsequent monitoring or measurement, the organization shall establish arrangements for these processes" [to verify or validate the quality].
Mechanical testing of an assembled rivet is probably considered a destructive test, so you can't do 100% test. Even if you do not pull test a rivet to failure, you can't be sure the rivet was not weakened by the test. The other case of a special process is when it is impossible to verify the quality of a component in an assembly before completing the assembly, which makes verification of the component impractical for the purpose of quality determination.
First, thank you for your answers. I am little bit troubled because, in the case of a standard rivet, the aircraft manufacturer made a control procedure for the deformed head of the rivet after assembly (visual control, measure the diameter of the head). But according to the definition of a SP, the resulting output cannot be controlled. That why I asked why this type of riveting is considered as a SP.
In my experience, measuring the diameter of the head would be caliper checks done in between the pull tests. We would have to pull test a first piece and last piece, and caliper check the head diameter once per hour.
actually it isn't that the output can't be controlled. it most certainly can. the 'control' procedure you mention is a form of testing. the requirement for a special process is that it can't be confirmed or tested 100%. Rivets can't be completely tested.
The size of deformation of the head can be measured as Cari said. unless the head is in an unacceptable area. even more reason for it to be a special process. Of course measuring the deformation of the head is only ONE characteristic of the integrity of a rivet. it was the lowly rivet that brought down the unsinkable titanic...
it is a fully manual rivet installation on aircraft from the 70's
Randy
Super Moderator
Predates the 70's by at least 40 years, I've done hundred's of them.
Hi nath57, a bit more insight will help;
this takes me back a few to my undergrad course on airframes...good stuff, below some more thoughts:
- so this manual process/tool entails the rivet set tool is the rivet a universal, does the process entail using a bucking bar, or is the process a hand held pneumatic or semi-automatic tool? Manual to me is I insert rivet in said hole, set bucking bar in place and buck away until head is properly deformed or formed (depending on your terminology) with the rivet set tool usually pneumatic. Is this part of a repair, or retrofit operation?
- echoing Cari's above post, are there pre and post samples that can be verified dimensionally and or sectioned...depending on the application, I have seen destructive sectioning or x-ray of samples before the process is allowed to continue. These results and samples could become part of the device build book or history for later reference?
And to be certain when it is fully manual, there is a high degree of skill required, especially to do so on a repetitive basis
Below from the NADCAP website....it could be that this is a matter or semantics? Note: below it refers to creation of products, could be intended to address the end product, vis a vis an intermediate process or sub-assembly? I am not an AS9100 expert...hope this helps
"In the AS9100 series of standards, special processes refer to a set of linked procedures that lead to the creation of products and services whose end results would not otherwise be measured, monitored or verified before being released to the customer. Hence, these products and services require special attention during production to ensure that they are free of defects
this takes me back a few to my undergrad course on airframes...good stuff, below some more thoughts:
- so this manual process/tool entails the rivet set tool is the rivet a universal, does the process entail using a bucking bar, or is the process a hand held pneumatic or semi-automatic tool? Manual to me is I insert rivet in said hole, set bucking bar in place and buck away until head is properly deformed or formed (depending on your terminology) with the rivet set tool usually pneumatic. Is this part of a repair, or retrofit operation?
- echoing Cari's above post, are there pre and post samples that can be verified dimensionally and or sectioned...depending on the application, I have seen destructive sectioning or x-ray of samples before the process is allowed to continue. These results and samples could become part of the device build book or history for later reference?
And to be certain when it is fully manual, there is a high degree of skill required, especially to do so on a repetitive basis
Below from the NADCAP website....it could be that this is a matter or semantics? Note: below it refers to creation of products, could be intended to address the end product, vis a vis an intermediate process or sub-assembly? I am not an AS9100 expert...hope this helps
"In the AS9100 series of standards, special processes refer to a set of linked procedures that lead to the creation of products and services whose end results would not otherwise be measured, monitored or verified before being released to the customer. Hence, these products and services require special attention during production to ensure that they are free of defects
Similar threads
