Corrective vs. Preventive: What is the Difference?


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When thinking about implementation of requirements, do not think about compliance, but about usefulness. If you strive to implement a useful tool, it will be compliant. If you first focus on being compliant, what you implement may not always be useful.

A particular quality system area where it is important to keep the above statement in mind is the area where ISO requirements are spelled out for corrective and preventive actions. If you look at these requirements separately, you would be hard pressed to identify the difference between the two; the requirements are almost identical. The main difference between the two actions is the word “potential” that is included within the Preventive Action mandate.

In preparation for an audit, an auditee will often take the time to pull out improvement actions and reaffirm what is “corrective” and what is “preventive.” If you find yourself going through this sorting process, then maybe there has to be a fundamental review of the purpose of your improvement activity.

I have always had an issue with some interpretations of “preventive actions.” To me, the entire ISO standard is predicated on preventive activity. To define a unique portion of the standard as “preventive” is counterintuitive to the stated purpose of the standard.

So, is there an alternative way to view both corrective and preventive actions? The distinctions and definitions given in the ISO guidance documentation are a good start to assist with your classification process. But even that guidance is purposely vague and sometimes confusing. Unfortunately, you can get caught up in taking way too much time figuring out the difference between the two.

Let’s look at this as a “best practice” use, not merely compliance. You have to be able to clearly distinguish between the two activities while maintaining clarity of purpose for your colleagues and yourself. The following offers one suggestion to supplement (or perhaps reaffirm) your current approach to corrective and preventive actions.

Corrective actions are the reactive measures taken in response to either product-related claims or service/system issues. They are the actions taken to immediately resolve an issue. In sports terms, think of corrective action responses as the “defense” of your process.

It is important to note that you are not being defensive, but rather you are reacting to an improvement opportunity from someone outside of the process involved. Evidence includes the development or revision of all documents and records involved.

Remember that corrective actions do not lend themselves to a “one size fits all” format. There are situations that call for customer-disciplined problem-solving processes (typically product-related claims) such as an 8D. There are also the more common nonconformance plans used in response to systems issues, as well as either an external or internal audit.
Don’t confuse the two – fitting information into an 8D where it does not lend itself to the discipline serves neither the customer nor your operation.
Preventive actions serve two purposes. The first purpose is the natural complement to the corrective actions. It identifies the actions that will be taken to prevent the nonconforming issue from occurring again.

Evidence of activity could be the implementation of a mistake-proofing activity; the training of personnel directly involved with the problem resolution; awareness provided to those areas of the organization where a similar occurrence could occur; and the verification audit after a defined period of time in order to confirm the effectiveness of all actions taken.
The second purpose of preventive actions is to react when data indicators fall outside your process parameters. For example, preventive actions could be taken if key product characteristics have a CPK of less than 1.33, if a gauge R&R is greater than 20 percent or if an FMEA Risk Priority Number is greater than your internally defined threshold.

Responses are not derived from a crystal ball. And they are not driven by a nonconformance. It is a way to improve without being required to do so by a customer or an auditor. Listening to the “voice of the customer” is often acknowledged as the means to improve processes. Think of corrective actions as a reaction taken to a voice external to the process. Think of preventive actions as the proactive response to the internal quality guidelines you set.

Precision Machined Products Association