A special process is one where the resulting output cannot be verified by subsequent monitoring or measurement — meaning any deficiency becomes apparent only after the product is in use, or would require destroying the product to detect.
ISO 9001 addresses these in clause 8.5.1, which requires validation and periodic revalidation of such processes.
Common examples
Welding, heat treatment, plating and surface finishing, adhesive bonding, soldering, sterilisation, casting, forging, painting and coating, and many software and analytical processes.
The test is not whether the process is difficult. It is whether you can confirm the result by inspecting the finished item without destroying it. You cannot check the internal grain structure of a heat-treated part without sectioning it — so heat treatment is a special process.
What validation requires
- Defined criteria for review and approval of the process
- Approval of the equipment and qualification of personnel
- Use of specific methods and procedures
- Requirements for records
- Revalidation at defined intervals or after changes
Operator qualification is the part most often missed
For special processes, it is not enough that operators are trained. They must be qualified — demonstrably able to perform the process to the required result, with records. In welding this is formalised through recognised qualification schemes; in other processes organisations must define their own.
Outsourcing does not remove the obligation
If you send parts out for heat treatment or plating, that process remains inside your quality management system. “Our supplier is certified” is a control, but rarely a sufficient one on its own.