In manufacturing, we do many processes . The product is a result of these processes. Every process adds some feature to the product. Some processes like cutting ,machining ,bending etc are processes leading to some physical attributes and we can see the result by making some measurements . But there are certain processes ,which add certain features but results are not measurable. That takes us to the concept of special process . 

What is considered a special process?

 Special Processes are those individual processes whose results on the product cannot be completely verified by measurements or objective checks, and where discrepancies can affect in service performance of the parts.

 I have been witness to a Turbo Generator inter turn failure problem at power station . The ventilation canals got choked because of flow of resin and spreading of insulation.

In this case ,baking is a special process . You may get reasonably good report even if process parameters are not met. Even in this case, insulation was hard, could be even filed off . The requirement of pressure was not met and result was such a big loss. A power station got out of service for a few months causing loss of generation, loss of man-hours and production from industry and agriculture. 

      Some thing more on  special processes ,

What is special process validation?

Regulatory and quality system requirements state that every process that cannot be verified by subsequent monitoring or measurement shall be validated. If you can't confirm the output with a direct test or measurement of the product – then you have a “special process” and must validate.

 For validation samples will have to me made my operators following certain set of parameters . The product shall be subjected to required destructive tests for qualification of the process. 

Once process is qualified , individual operators will have to be qualified following the specified process parameters . That means , once process is qualified , each and every operator can not be allowed to perform the process . Every operator has to qualify using the process parameters.

Is welding special process?

Welding is considered as a 'Special Process', which means that its quality cannot be readily verified and its successful application requires specialist management, personnel and procedures above and beyond those that are considered for general quality systems such as ISO 9001.

 Is painting a special process?

Yes. Properties like adhesion, corrosion resistance and light-fastness can't be verified unless the painted item is destructively tested. By definition, it's a special process.

Is soldering a special process?

Soldering is definitely a special process just like welding and brazing. You can't verify the integrity(strength) without destroying a solder joint.

 Similarly brazing , plating , impregnation , heat treatment  etc qualify as special processes. 

  In every special process always ensure parameters, mixing ratios, time duration / any preheating requirements are always met.

In my professional journey , I have faced many problems in special processes and understood how important it is to accept special process dependence on parameters only. I have experts failing because of over confidence. 

So for me the Mantra is , special process means process parameter control.