Most Memorable Files Series – Part 4

From runaway garbage trucks to flying water tanks

Whenever someone first meets one of our engineers, they are inevitably asked, “what’s the craziest thing you’ve ever seen?” and, while we obviously won’t share identifying details, every engineer has a story! In part four of our series, we chatted with three of our mechanical engineers, Andrew Happer, MBA, M.Eng., P.Eng., CFEI, from Edmonton, Hugo Julien, P.Eng., from Montreal, and Kenneth Cowie, P.Eng., from our Moncton office, to ask them about the memorable files they’ve encountered throughout the years:

It’s a bird, it’s a plane…

Being woken up in the middle of the night by the sound of an explosion is certainly concerning, but that was what happened in this file. The homeowners went to check on the boom and were astonished to see the stars through a gaping hole in their roof. Looking for the origin of the damage, they noticed that the hot water tank was no longer in its place. Taking off through a major pressure leak, it smashed through a floor, a stairwell and the ceiling before landing on a neighbour’s property, more than 60 feet away! Our engineer examined the part that caused the damage. He discovered a failure in the security measures; the thermostat had incorrectly sensed the temperature of the water, causing a continuous increase in heat, and, consequently, the pressure in the tank. The pressure relief valve, which should have opened to maintain adequate pressure, also failed. It was this double failure that allowed an incredible amount of gas to escape through an opening, transforming the tank into a rocket. Fortunately, no one was injured.

The truck got stuck…

Sometimes, we are called in to look at damage that doesn’t appear consistent with the story. In this case, our engineer was examining a pickup truck that had hit the ditch. The insured was confident that the transmission had failed and caused the accident… However, the damage was to the differential, and was not something you might normally see in that type of collision. Our engineer was able to download the vehicle’s infotainment unit and determine the insured had gotten the vehicle stuck, and while attempting to dislodge it had overspun the tires in 4wd low, causing the failure of the differential, not the transmission. Often, negligence or misuse is what causes mechanical failures… If you are not using the tool/vehicle/machine correctly, it greatly increases the likelihood of it failing.

One man’s trash is another’s flattened garage?

A few years ago, an interesting mechanical file came across our engineer’s desk… A garbage truck had rolled backward down a slope and through, yes through, a home. CEP was called in to investigate exactly how it happened. The initial thought, in cases such as these, is that someone didn’t properly apply the brakes, but they actually had been applied! Large trucks like this usually have two brake systems, a standard one where a pedal is pushed and the brakes activate and an airbrake system, so when the truck is turned on, air pressure is created in the lines pushing back a spring and releasing the brake. This truck had an additional system installed by the manufacturer, which used an air system as well, and was intended to apply the standard brakes during short intervals while the operator is out of the truck. However, that system had a leak! When the driver exited the truck to load up some garbage from the street, the brakes didn’t properly engage, and the truck began rolling… Straight down a hill and into a home. So, in reality, this was a combination of errors resulting in a giant mess. The driver used the brake incorrectly, and a mechanical fault resulted in a catastrophic event.

From explosions to breakdowns, our engineers have seen a huge variety of losses related to mechanical systems. It isn’t always the most obvious answer that is the cause, and usually in mechanical systems, multiple things have to go wrong for things like this to happen. But, CEP is always there to comb through the evidence and figure out what really happened!

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