Special Processes

In accordance with ISO9000:2015(E) 3.4.1 Process, Note 5: A process where the conformity of the resulting output cannot be readily or economically validated is frequently referred to as a “special process”.

So, a special process is when the output of a process cannot be verified without destruction of the product. Generally, if you cannot measure or confirm the output of a process (the resulting product or service) with calibrated tools or instruments and know whether it conforms to specifications, the process is likely a special process that requires validation.

A special process is when the output cannot be confirmed without destruction. If you can't verify conformity easily, the process needs validation.

• ISO9001 Requirements: Special Processes are referenced in ISO9001 8.5.1 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”.
• AS9100 Requirements for Aviation, Space and Defence: Specific requirements are listed in AS9100 8.5.1.2 Validation and Control of Special Processes including:
  • 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 people
  • e. Use of specific methods and procedures for implementation and monitoring the processes
  • f. Requirements for documented information to be retained

Special processes require a different approach to control. Instead of the output being directly measured for conformity, the process itself is 'measured' (validated). Validation takes the form of periodic testing and qualification against criteria detailed in specifications.

• Test pieces processed and destructively tested
• Qualified Operators are periodically evaluated or re-qualified
• Periodic monitoring, testing and system accuracy tests performed

All special processes must be validated and periodically re-tested to verify their ability to produce compliant product. For example, surface treatments like chemical conversion coating, electroplating, anodising, or painting involve periodic adhesion and salt spray (corrosion) testing of test coupons.

Some special processes require processing staff to be formally qualified and periodically re-qualified. Examples include coded welders and Non-Destructive Testing (NDT) Level II & III qualifications.

Special processes may require system accuracy monitoring. Examples include heat treatment system accuracy tests and temperature uniformity surveys (AMS2750 Pyrometry SAT & TUS) and NDT penetrant flaw detection evaluations using TAM panels.

If special processes are not validated or periodically tested, deficiencies might only become apparent after the product is in use. Examples include coating adhesion failures such as cracking, blistering, flaking, or peeling.