Metal Radiographic and Ultrasonic Testing - Special Processes

[Sohail]

During AS9100 REV C audit, it was noted that radiographic and ultrasonic testing are not declared 'SPECIAL PROCESS'.

Auditee insists that where is it required in standard that these processes be declared as special processes?

Should the auditor raise NCR based on his own judgement, if yes, then on what ground?

Thanks

 

[Jen Kirley]

According to Note 5 to 3.4.1 (definition of process) of ISO 9000:2015:

A process where the conformity (3.6.11) of the resulting output cannot be readily or economically validated is frequently referred to as a “special process”.

Special processes have also been discussed on the Cove in this thread and also in this thread. Special Processes requirements are listed in 7.4.1 (suppliers must be approved by the customer when required) and 7.5.2 (special processes must be validated). These can only be done when the special processes have been identified (4.1).

 

[Sidney Vianna]

In addition to what Jen mentioned, I will say that this is EXACTLY the reason why organizations and their 3rd party auditors need to understand the context around the system and there are competence requirements for the audit teams in place.

Since this is AS9100 related I moved the thread to it's appropriate forum.

We had an interesting thread Welding - Is welding always a special process per ISO9001:2000 Clause 7.5.2 where I made the case that welding is NOT always a special process.

Now, this thread, being AS9100 related, I would be hard pressed to think of RT and UT in aerospace which would not be deemed special processes. As a hint if a process should be considered special or not in the Aviation, Space and Defense Sectors, have a look at the list of Nadcap processes. If they are listed there, very, very likely the processes should be treated as processes which need to be validated.

 

[howste]

Let's think about the logic of the requirement. AS9100 Rev C says:

7.5.2 The organization shall validate any processes for production and service provision where the resulting output cannot be verified by subsequent monitoring or measurement…

Some process results are easy to measure after they've been done. If a cutting process is done, and the characteristic I'm interested in is length, I could use a caliper or micrometer to measure the length. This doesn't sound like a special process.

Some process results are harder to measure. If a bonding process is done, and I'm interested in the strength/integrity of the bond, I may have a hard time checking it. I may need to do destructive testing on a sample to validate that the process worked as intended. This sounds like a special process. I can't do 100% destructive testing and still ship product. It makes sense that we should validate this process so that we're confident that the pieces we didn't test were done properly and have the strength/integrity that we need.

Now let's look at ultrasonic and radiographic testing. What's the intended result? A test report of the results of another process? Can the resulting output "be verified by subsequent monitoring or measurement?" Yes. I have a test report. By the way, is testing even a process for production? Does it change the part in any way, or does it just verify another process? This doesn't sound like a special process to me. If this is a special process, then the caliper measurement from the first scenario is too, because there is nothing I can measure on the product that will tell me if I've measured it before.

(I'm putting on my flame-proof underwear now.) Maybe I'm crazy, but since radiographic testing and ultrasonic testing are actually monitoring/measurement processes themselves, I don't believe that they're "processes for production" as referenced in AS9100C 7.5.2. As such I don't think they have to be classified as special processes. If a field failure occurred in a weldment due to a failed process, the root cause of the failure would never be "the test process wasn't done properly." The root cause would be "the weld process wasn't done properly." Many people point to the NADCAP list of "special processes" to show that UT and RT should be treated as special processes. We should consider that PRI financially benefits from having more processes fall under their purview and their NADCAP accreditations.

Having said that, I have been an AS9100 auditor for years. RT and UT are both important verification processes and proper controls should be in place to ensure that they're done correctly. Many times during an audit I've found that the client has identified RT or UT as special processes. In these cases I've audited them as special processes.

 

[Marc]

Howste - Has this changed in AS9100 Rev D? (I *assume* it has not, but...)

 

[Sidney Vianna]

Now let's look at ultrasonic and radiographic testing. What's the intended result? A test report of the results of another process? Can the resulting output "be verified by subsequent monitoring or measurement?" Yes. I have a test report.

Not necessarily. For example, if you did not have appropriate exposure, you might not have image quality to enable a proper reading of the film or digital media. There are many parameters in RT and UT that have to be properly managed. Obviously, even the reading of the results have to be done by properly qualified personnel. E.g., you put a radiography of a casting in the hands of a layman, s/he won't be able to properly read the results. That's why NDT processes have to be validated by ensuring that the techniques and professionals involved are competent/qualified/certified for the job. As for NDT not being a "production process", it is part of the product realization, so, in my estimation, despite the fact they are inspection processes, I would still consider them as being necessary for production.

 

[howste]

Howste - Has this changed in AS9100 Rev D? (I *assume* it has not, but...)

The short story is no. The criterion for determining what a special process is hasn't changed.

As far as overall changes, for ISO 9001:2015 instead of a separate clause, the requirement has been summarized to:

Controlled conditions shall include, as applicable... f) the validation, and periodic revalidation, of the ability to achieve planned results of the processes for production and service provision, where the resulting output cannot be verified by subsequent monitoring or measurement;

For AS9100 an additional clause has been added with the following:

8.5.1.2 Validation and control of special processes

For processes where the resulting output cannot be verified by subsequent monitoring or measurement, the organization shall establish arrangements for these processes including, as applicable:
a. definition of criteria for the review and approval of the processes;
b. determination of conditions to maintain the approval;
c. approval of facilities and equipment;
d. qualification of persons;
e. use of specific methods and procedures for implementation and monitoring the processes;
f. requirements for documented information to be retained.

So AS9100 has added new requirements to determine "conditions to maintain special process approvals," to approve facilities, and to monitor special processes. These were previously implied, but are now explicit.

 

[howste]

Not necessarily. For example, if you did not have appropriate exposure, you might not have image quality to enable a proper reading of the film or digital media. There are many parameters in RT and UT that have to be properly managed. Obviously, even the reading of the results have to be done by properly qualified personnel. E.g., you put a radiography of a casting in the hands of a layman, s/he won't be able to properly read the results. That's why NDT processes have to be validated by ensuring that the techniques and professionals involved are competent/qualified/certified for the job. As for NDT not being a "production process", it is part of the product realization, so, in my estimation, despite the fact they are inspection processes, I would still consider them as being necessary for production.

If the x-ray image is a deliverable product, I can see the point. The process would need to be validated to ensure that it was done properly because no subsequent monitoring or measurement could be used to determine if it was properly done.

I don't disagree that these processes should be carefully controlled and done by competent, qualified persons. It's just that these justifications are not included in the criteria specified in the standard. Let me apply your logic to another monitoring process:

There are many parameters in caliper and micrometer measurement that have to be properly managed. Obviously, even the reading of the results have to be done by properly qualified personnel. E.g., you put a caliper or micrometer in the hands of a layman, s/he won't be able to properly read the results. That's why caliper and micrometer measurement processes have to be validated by ensuring that the techniques and professionals involved are competent/qualified/certified for the job. As for caliper and micrometer measurement not being a "production process", it is part of the product realization, so, in my estimation, despite the fact they are inspection processes, I would still consider them as being necessary for production.

Does this make caliper and micrometer measurements special processes?

 

[Sidney Vianna]

Does this make caliper and micrometer measurements special processes?

Not in my book. I think we differ on what is meant by validation.

As I said earlier, NDT techniques typically have numerous parameters to be managed, very differently from a dimensional inspection using calipers. For example, one of the parameters to be controlled during RT is exposure calculations. The following information concerning exposure calculation is copied from here.

Exposure Calculations
Properly exposing a radíograph is often a trial and error process, as there are many variables that affect the final radiograph. Some of the variables that affect the density of the radiograph include:
o The spectrum of radiation produced by the X-ray generator.
o The voltage potential used to generate the X-rays (kV).
o The amperage used to generate the X-rays (mA).
o The exposure time.
o The distance between the radiation source and the film.
o The material of the component being radiographed.
o The thickness of the materíal that the radiation must travel through.
o The amount of scattered radiation reaching the film.
o The film being used.
o The use of lead screens or fluorescent screens.
o The concentration of the film processing chemícals and the contact tíme.
The current industríal practice is to develop a procedure that produces an acceptable density by trail for each specific X-ray generator. This process may begin using published exposure...

 

[howste]

Not in my book. I think we differ on what is meant by validation.

As I said earlier, NDT techniques typically have numerous parameters to be managed, very differently from a dimensional inspection using calipers. For example, one of the parameters to be controlled during RT is exposure calculations. The following information concerning exposure calculation is copied from here.

I'm not even talking about validation. I'm talking about what qualifies as a special process. Special processes in AS9100 are "any processes for production and service provision where the resulting output cannot be verified by subsequent monitoring or measurement." There is nothing in the standard requirement quoted above about how many variables are involved in the process, how different one process is from another, or even how sensitive or critical the process may be. I read that there are two criteria: 1) the process must be for production/service provision, and 2) the process's output cannot be verified by subsequent monitoring or measurement.

If you interpret that criterion 1 means that NDT is a production process, then you must also interpret that caliper measurement is a production process. Then applying criterion 2, we find that neither test nor measurement can be verified after it is completed. The product can be tested again or measured again, but we will never be able to replicate the exact conditions of the original. Therefore both must be special processes. :mg: Without a qualified person and process, both NDT and calipers will fail to achieve the correct result. Calipers also have numerous parameters to be managed. Pressure applied, orientation of the jaws, parallax error, sine error, perpendicularity of the part surfaces, etc. But again, this is irrelevant to the requirement.

Let's look at the standard to see what evidence there is that inspection/verification processes are or aren't also production processes: AS9100 C clause 7.5.1h says: "evidence that all production and inspection/verification operations have been completed..." If inspection/verification were part of production, then it would just say "evidence that all production and inspection/verification operations have been completed..." AS9100 Rev D clause 8.5.1n says the exact same words as Rev C. The fact that they are listed separately indicates to me that they are NOT included in production.

The short story is that if NDT processes are special processes, then all measurement processes must be considered special processes. I believe that the standard makes a distinction between production processes and inspection/verification processes, and therefore NDT processes are not special processes. I think that they are best labeled as Special Requirements as defined in AS9100D 3.5 or AS9100C 3.2.