Friday, November 1, 2013

Heinrich's Law. A Case Study


Frank was working on the B-2 assembly line and needed to use the restroom.  He called his team leader who covered for him while he ran to the can.

While walking to the can, Frank pulled out his smart phone to catch up on the latest football scores.  He crossed over the B-1 line and walked between a couple of stacks of empty material totes (boxes).  Stepping out into the aisle, he was hit by a tugger that had just come around the corner pulling three full material carts.

Frank's boot wedged between the front of the tugger and the concrete floor.  He tried to spring free but only succeeded in adding to his momentum as his body arched and the back of his head hit the concrete.

The human head is well armored against frontal impacts.  We have soft, squishy noses, lips and break-away teeth in front.  We have God's original air bags (sinuses) parked between our brains and the front of our skull.  We even have pressure relief valves, eyeballs, that can bulge outward and minimize peak pressures.

The human head is very fragile with regard to rear impacts.  No soft, squishy features.  No sinuses.  No pressure relief valves.  Obviously, there was far more selection pressure on the gene pool for frontal impacts (since we are typically moving forward and impact forward) than for rear impacts.

Frank was 52, a smoker and coffee drinker.  He had high blood pressure and cheesy arteries.  Several of those small arteries ruptured and created pressure within his skull.  That pressure jammed his brain stem (medulla) down into the top of his spinal column.  The brain stem controls involuntary body functions like breathing.

The Emergency Room surgeons sawed around the top of his skull at the level of his hair line.  The top of his skull lifted fifteen millimeters as the last of the bone separated.

Despite the heroic efforts of the Emergency Medical Technicians, the ambulance driver and the Emergency Room staff....Frank died.

So, what happened?

In flow-chart form

Red arrows are "Necessary Conditions" and arrow points in direction of causality

In the report:

The Five Whys:
1.) Why did Frank die?
----Frank died because he was struck by a tugger

2.) Why was Frank struck by a tugger?
----Frank was struck by the tugger because the tugger driver did not see him.

3.) Why did the tugger driver not see Frank?
----The tugger driver did not see Frank because he was not in a pedestrian aisle and did not wave.

4.) Why did Frank not wave to get the tugger driver's attention.
----The tugger driver reported that Frank was looking down.

5.) Why was Frank looking down>
----A smart phone was recovered at the scene that belonged to Frank.  It is believed that Frank was distracted and looking at his cell phone.

Root cause, Frank was looking at his cell phone.

Obviously, the report is a nice, tidy, straight line.  It was Frank's fault.  He was not paying attention.  But how do you prevent it from re-occurring?  Frank was acting no differently than many other employees and following a path he had walked hundreds of times before.

The rest of the story

Blue arrows are "Quenching Condition" like water on a fire.  This is a a take-off from TRIZ Problem Solving
Something had changed.  The empty totes obstructed the line of sight for the tugger driver.

The Material Department had recently changed over from fork trucks to tuggers.  A fork truck could only takes out one or two baskets at a time and then picked up the emptys or returned to the dock "dead-head".  The tuggers can pull up to four trailers and run a "race track".  A fully loaded train has no room for all the empties at the first station.  Room becomes available as more material is unloaded further along the race track.

The increased productivity of the tugger approach resulted in several people being "reduced out" of the Material Department.  The remaining employees were pushing back.  They saw the shortcomings of the new system but were alienated and had no interest in solving them.

Again, let me note that this is FICTION


Sidebar: Dry erase boards, blue and red pens and yellow sticky notes

While that nice, tidy, straight line of cause-and-effect makes for a good report, it is not a great way to solve problems.

A better way is to start writing the causal factors onto yellow sticky notes.  Place them on a dry erase board and connect them with red arrows.  Mitigating factors can also be written on sticky notes and they can be connected in with blue arrows.  As a general rule, the more "Necessary Conditions" going into an factor (hazard), the more vulnerable it is to mitigation

The advantage of using sticky notes is that they can be moved.  Additional layers of complexity can be inserted into the story as more information becomes known.

Unwinding the story

Let's unwind the story to highlight how Heinrich's Law plays into it.

If Frank had been genetically endowed with stronger blood vessels, or if he had practiced better health habits, he would not have sustained severe brain bleeding.  He would have had some memory loss and a broken leg.  (Very severe accident but not fatal)

If Frank had been wearing different footwear, his foot would not have become wedged beneath the tugger.  He would have sustained a broken leg. (Severe accident)

If Frank's favorite team had not been playing or he complied with shop rules regarding wireless devices, he would have seen the tugger and been able to move out of the way....either not getting hit or just getting brushed.  (Minor accident)

If the material totes were not allowed to stack up then the tugger would have been able to see Frank and stop in time. (Near miss)

If there were stop signs at the corner the tugger would have been moving slowly enough to stop or avoid Frank. (Near miss)

If Frank had not been in a hurry and had taken the pedestrian aisle way he would not have encountered the tugger coming around the corner. (No event)

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