Tuesday, August 29, 2006

It never occurred to me…

When we go out of town we turn off the water to the house. We once had a flush valve on a toilet fail and flood the bathroom. Fortunately we were home when it happened. I know people who had the valve on their icemakers fail when they weren’t home and have their homes flooded. So to avoid a potential problem we simply turn the water off.

We also unplug the coffee maker and toaster. A friend of ours had a plugged in coffee maker catch on fire. Fortunately it was on a tile countertop against a tile backsplash. The result was that it tripped the breaker and burned itself out leaving a gooey stinky mess on the countertop. So after hearing that story we have decided that prudence dictates we unplug the small appliances.

Coming back late at night from our vacation this summer we were greeted at the front door with a foul odor. We quickly discovered the source of the odor. We went into the kitchen and on the floor was a puddle of foul brown liquid that has oozed out of the fridge and onto the floor. We were somewhat baffled as to why the fridge had failed. It was only ten years old. New enough that it should not have failed yet.

We quickly got the kids in bed so as to begin dealing with the putrefying mess. We opened up the freezer on top and dumped its contents into the trash. Then we opened up the lower refrigerator compartment to deal with its contents. When we opened the fridge we saw that it had been turned off. We had a good guess as to what had happened.

We finally got ourselves into bed at two in the morning. The next morning my wife asked our three year old why he turned the refrigerator off.

He looked down at the floor, laughed, looked back at my wife and said, “I was going to turn it on when we got home.”

What can you do? Apparently, after seeing us turn off the water and unplug the small appliances, he thought he would help us get ready by turning off the refrigerator.

It never occurred to us to check that refrigerator was left on before leaving town.

When doing reliability reviews of equipment imagination is required to consider how equipment might fail or how users might abuse equipment.

Doing a quick informal failure mode and effects analysis (FMEA) on our refrigerator prior to our trip would have resulted in something that would have looked like this:

Item – refrigerator
Function – keep food cold
Potential failure mode – compressor fails due to age
Effect of failure – food spoils
Mitigation action – none, failure will occur at a random point in time

After our trip and our son’s action our FMEA would look like this:

Item – refrigerator
Function – keep food cold
Potential failure modes1)compressor fails due to age
2) refrigerator deliberately turned off
Effect of failure – food spoils
Mitigation actionfor failure mode 1, none, failure will occur at a random point in time
For failure mode 2, verify that fridge is on and plugged prior to leaving

From prior experience we have decided turn off our water and unplug our small appliances before leaving town. Before our trip it never occurred to us that our fridge might be deliberately turned off.

What failure modes are lurking in your equipment that you have not considered? Use your imagination. You don’t want to say to an injured employee or disgruntled customer is “It never occurred to me that….”

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