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The Latent Cause Analysis

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Schematic of Physical, Human, and Latent Causes

Schematic of Physical, Human, and Latent Causes


People sometimes have difficulty in trying to understand the difference between Physical, Human, and Latent Causes. The following information was developed to help clarify the distinctions between these 3 types of causes.


In essence, the following schematic infers that all Physical Failures have Physical Causes. Further, it infers that all Physical Causes are triggered by the human beings that come in contact with the physical system. Finally, it infers that all human interaction with the physical system is influenced by people that might not be in direct contact with the physical system.


Please read the text that accompanies each slide to help remember the difference between Physical, Human, and Latent Causes (as these terms are used by Failsafe).


Download the Schematic of Physical, Human, and Latent Causes (752 KB PPT)

A typical production-type business has physical equipment arranged in a specific manner in order to get a specific output.  Pumps, compressors, extruders, heaters, boilers, turbines, generators, piping, electrical systems, control circuitry, pressure vessels, heat exchangers, and similar equipment are parts of this production-related physical system.

However, production systems do not simply appear.  They are designed and then constructed.  Eventually, they are operated and maintained.  It is people (denoted by the red in the diagram) that design, construct, operate, and maintain the production system. 


It is important to note that these are the only people that come into direct contact with the physical production systemAlthough other people within a business can influence the people that "touch" the physical system, they themselves cannot "touch" it.

But the people that "touch" the system in a particular manner do so for a reason.  They are trained, advised, and encouraged to do specific things.  They are also provided materials for use within the physical system. 


The people that provide the training, advising, and encouragement -- as well as those who provide the materials are also a vital part of the business.  But they never interface directly with the physical system itself. 

As noted by the bold, dark arrows, the only people that come into direct contact with the physical system are those who have designed, constructed, operated, or maintained it.


This distinction is important in understanding Failsafe's definition of Physical, Human, and Latent Causes.

In other words, it is only the RED people that directly interface with the equipment or process.


The MAROON people can influence the RED people, but they cannot or do not directly "touch" the equipment or process.


Therefore, the RED people are said to be at the "sharp end" of human intervention.

The RED people, at the sharp end of human intervention with the physical system, are the doers.


The MAROON people are the influencers.

When something goes wrong on the physical production system, the first things that we need to understand are the PHYSICS of the problem.  For example, if a pump caught fire we need to understand the PHYSICS (or the HOW) of the fire.


We call these Physical Causes.


There are "rules" for describing Physical Causes.  The rules exist for a reason.  Please follow the rules.

However, all Physical Causes are also "caused by" something.  In the limit, PEOPLE trigger all Physical Causes.  People either do things to the equipment or process that they should not have done, or they do not do something that they should have done.


We call these Human Causes.


IMPORTANT NOTE:  Human Causes are restricted to direct actions or inactions imposed on the physical system.  All other human activity (or lack of activity) will be addressed when discussing Latent Causes.


There are different rules for describing Human Causes.  These rules also exist for a reason.  Please follow the rules.

But all human beings are influenced by one another.  We are influenced in beneficial ways, and unbeneficial ways.  When something goes wrong and we are able to define precise Human Causes, it is ultimately important to understand "why the people did what they did."  In Failsafe's approach to Latent Cause Analysis, this is done in two steps. 


First, an attempt is made to define Organizational Latent Causes.  Organizational Latent Causes are defined "as a group."  In other words, all the stakeholders suggest things aloud -- eventually agreeing on the most significant ones.


There are rules for describing Organizational Latent Causes.  These rules exist for a reason.  Please follow the rules.

The most important part of a Latent Cause Analysis is the identification of Personal Latent Causes.  Personal Latent Causes are defined individually, one-by-one -- after having defined the Physical, Human, and Organizational Latent Causes.


Personal Latent Causes are the most important to define because, it is each of us (not as a group, but individually) who cause problems.

The whole process is summarized on this chart.  It is vital that the Principal Investigator understands this chart in order to help clarify issues as they arrive during the Stakeholder Meetings.

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