Reducing Human Errors with Maintenance Procedures

How many times have you heard from operations “You just fixed that last week, why is it breaking again?  You guys can’t fix anything.”?  This is an all too common occurrence in many organizations.  Why does this happen?  Often times, the issue comes down to well meaning maintenance, with a dose of human error.   

Human error causes many issues within maintenance.  Think of the 6 failure patterns as defined by Nowlan and Heap.  Infant mortality is the largest factor when considering failures at 68%.  Thankfully, many of these issues and failures can be reduced with proper procedures.

Human errors come in many forms, and one of the primary ones that we can address by using procedure are psychological factors.  Psychological Factors are related to the causes of which mistakes are made.  Psychological errors are divided into two types, unintended errors which occur when someone does a task incorrectly. 

• Unintended slips can be thought of as actions not carried out as intended or planned, e.g. “finger trouble” when dialling in a frequency or “Freudian slips” when saying something.

• Lapses are missed actions and omissions, i.e. when somebody has failed to do something due to lapses of memory and/or attention or because they have forgotten something, e.g. forgetting to lower the undercarriage on landing.

• An intended error occurs when someone deliberately sets out to do something, but what they do is inappropriate.   The intended error can be either be a mistake or violation.   A mistake is a misapplication of a good rule, or application of a bad rule, or an inappropriate response to an abnormal situation. 

• A violation is when someone knowingly and deliberately commits an error (Moubrary, 1997).   

As can be seen above, 3 out of the 4 types of psychological errors can be addressed with procedures, as they ensure work is done properly.  Procedures will help to address unintended errors and mistakes, but not violations (Moubrary, 1997).   But you may be wondering, how much do procedures help to reduce these errors?  In other words, is it worth the time to write good procedures and job plans?  The answer is yes. 

According to a study conducted by A.D. Swain, and H.E. Guttmann, a written procedure will reduce the error rate to 5%, while supplementing that procedure with a checklist will reduce the error rate to 1%.  Imagine reducing rework to 1%.  That is a lot less frustration from operations and your maintenance staff.  So where do you begin?

Procedures play a vital role in improving maintenance and reliability, and it is not just for PM activities. Corrective work orders should be written to the appropriate level of detail as well.  The goal of the procedure is to ensure that the task can be completed consistently regardless of who is performing the task, and enable a review to take place and identify where an error occurred.  You cannot easily determine where an error occurred when there is no procedure, nor can you eliminate it from occurring again.  

Developing these procedures is not a simple task, but it will be covered in the next article.  In the meantime, I want you to think about how many failures can be eliminated if you were to reduce the error rate of the work to 5% or less.  What impact would that have on your operation.  Please let me know at jkovacevic@eruditio.com.  Next week, we will discuss how to write good procedures, until then stay safe and reliable.