In many companies, product quality is checked at the end of production: dimensions are measured, visual inspections are performed, and test reports are completed. But for some processes, that is not enough. In certain cases, the quality of the result cannot be fully confirmed through ordinary post-process inspection. Some defects may only become visible later — during use, under load, or after time has passed.
In quality management practice, such processes are usually referred to as special processes. In ISO 9001, this exact term is not explicitly used, but the logic is clearly present: if the result of a process cannot be fully verified by subsequent monitoring or measurement, the organization must ensure the validation and periodic revalidation of the process’s ability to achieve planned results.
This is an important topic for any quality management system, especially if a company is involved in manufacturing, assembly, repair, material treatment, or services where the final result depends heavily on the technology, equipment, and competence of personnel. Weak control of special processes often leads to hidden defects, customer complaints, product failures, and significant losses.
What a Special Process Is
A special process is a process whose result cannot be fully verified through subsequent inspection or measurement, or whose defects may only become evident after the product is in use or after the service has been delivered.
In simple terms, if a defect cannot be reliably “caught” through normal inspection after the process is completed, then the process itself must be controlled in a special way.
Typical examples of special processes include:
- welding
- soldering
- bonding
- cladding or overlay welding
- impregnation
- heat treatment
- casting
- plastic forming
- hot forging
- coating application
- sterilization
- special inspection and testing methods such as radiography, ultrasonic testing, magnetic particle inspection, and thermography.
The actual list will vary by industry. In mechanical engineering, common examples are welding, heat treatment, coatings, and special inspections. In electronics, soldering and potting are often special processes. In healthcare, sterilization is a classic example. In service organizations, a process may also be considered special if the quality of the result cannot be fully checked after the service is completed.
The key characteristic of a special process is that quality must be built into the process itself. It is not enough to rely only on final inspection.
Requirements of the Standard
In ISO 9001, there is no separate formal definition of a “special process,” but in the section on production and service provision, the standard includes an important requirement: the organization must operate under controlled conditions and, where applicable, perform validation and periodic revalidation of processes whose outputs cannot be verified by subsequent monitoring or measurement.
From a practical point of view, this means the organization should:
- determine which processes fall into this category
- establish rules for how those processes are carried out
- define acceptance criteria
- confirm that the process is capable of delivering consistent results
- control equipment, personnel, materials, and environmental conditions
- periodically confirm that the process remains under control.
For QMS implementation, this is a very important issue. If a company has not identified its special processes, it often overestimates the effectiveness of ordinary inspection and underestimates the risk of hidden defects.
How It Works in Practice
In practice, management of special processes is usually organized in stages.
1. Identifying the list of special processes
The first step is to determine which processes in the organization truly qualify as special.
Useful questions include:
- Can the result be fully verified after the process is completed?
- Is there a risk of hidden defects?
- Could a nonconformity appear only during use?
- Does the result depend strongly on operator competence, equipment setup, environmental conditions, or process parameters?
The result should be an official list of special processes.
2. Establishing process requirements
For each special process, the organization should define:
- how the process must be performed
- personnel qualification requirements
- equipment requirements
- material and component requirements
- environmental condition requirements
- process parameters
- how records and results must be documented.
For welding, for example, this may include:
- an approved process specification
- welder qualification requirements
- qualified equipment
- approved welding consumables
- current, voltage, and travel speed parameters
- surface preparation requirements
- environmental conditions
- records by batch, operator, and parameter set.
3. Validating the process
Validation means confirming that the process is actually capable of consistently producing the required result.
In simple terms, the company must demonstrate that when the process is performed under defined conditions, it produces a conforming output.
Validation usually includes:
- review of documentation
- verification of equipment suitability
- confirmation of personnel competence
- trial execution of the process
- assessment of the resulting output
- completion of records and validation reports.
It is important to understand that validation is not just a formality or a one-time document. It is evidence that the process works.
4. Revalidation
Even a good process can lose stability over time. That is why revalidation is needed.
Revalidation is usually required when:
- equipment changes
- the process method changes
- materials are replaced
- the operator changes
- environmental conditions change
- new product types are introduced
- recurring nonconformities are detected.
5. Ongoing process control
Once a process has been validated, it must not be left unattended. Continuous control is necessary over:
- compliance with process discipline
- process parameters
- equipment condition
- calibration and verification status
- personnel authorization
- environmental conditions
- materials used
- completion of required records.
This is how a special process becomes part of the daily quality management system, rather than a purely technical issue.
Practical Example
Let us imagine a company performing heat treatment of parts.
After the operation, hardness can be measured, but that alone is not enough to fully guarantee the quality of the process. The result depends on factors such as:
- temperature
- holding time
- heating uniformity
- furnace condition
- sensor accuracy
- loading configuration
- operator competence.
The company includes heat treatment in its list of special processes and introduces the following controls:
- approved process instructions
- defined acceptable operating parameters
- qualification requirements for operators
- a furnace inspection schedule
- control of materials and loading methods
- temperature charts and records for each batch
- periodic revalidation of the process
- analysis of nonconformities and test results.
As a result, the company controls not only the final measured characteristic, but the process that creates that characteristic.
What Measures Can Be Used to Control Special Processes
In practice, the best results come not from one or two controls, but from a connected set of measures.
The main measures usually include:
- an official list of special processes
- approved technological or process documentation
- clear criteria for proper execution
- personnel authorization and competence confirmation
- qualification or approval of equipment
- monitoring of process parameters
- control of environmental conditions
- control of materials and consumables
- mandatory execution records
- initial validation and revalidation
- internal audit of special processes
- nonconformity analysis and corrective actions
- change management for the process.
The more critical the process is for quality and safety, the stronger the controls should be.
Common Mistakes
During audits, several recurring problems are often found in organizations.
No defined list of special processes
The company is actually performing welding, soldering, or heat treatment, but does not formally recognize these as special processes.
Relying only on final inspection
The organization believes that output inspection is enough, even though hidden defects may remain undetected.
No validation or only formal validation
The process has “always been used,” but there is no documented confirmation that it is capable of consistently achieving the required result.
Weak control of personnel qualification
An operator performs a critical activity, but there is no proper system for authorization, training, or requalification.
Changes are not controlled
A material, parameter, tool, or operator is changed, but the process continues to be treated as validated without further review.
No root cause analysis of nonconformities
When deviations occur in a special process, the organization may only apply a correction and fail to eliminate the underlying cause.
Practical Tips
First, create a list of special processes and review it regularly. That is the foundation of control.
Then make sure that each of those processes has clearly defined requirements: who performs it, on what equipment, according to which parameters, and under what conditions.
After that, verify whether real evidence of validation exists. Not just an old approval record, but actual proof that the process is capable of producing stable results.
Next, strengthen recordkeeping. For special processes, it is particularly important to keep data on parameters, operators, equipment, materials, and results.
Finally, include special processes in the internal audit program. This is one of the best ways to determine whether the process is really controlled, rather than simply well-described in documentation.
Conclusion
Special processes are one of the most sensitive topics in a quality management system. Their main characteristic is that the quality of the output cannot be reliably guaranteed by subsequent inspection alone. That is why the main focus must be on controlling the process itself.
For organizations working according to ISO 9001, this means they need to:
- identify special processes
- establish requirements for their execution
- perform validation
- control personnel, equipment, materials, and environment
- carry out revalidation
- analyze deviations and support process improvement.
When special processes are controlled systematically, the company reduces the risk of hidden defects, increases production stability, and strengthens customer confidence. That is one of the key goals of a mature QMS.