Product Failure Analysis
According to State Farm Fire and Casualty, washing machine hose failure alone accounts for over $100 million in losses in the United States and Canada. Such product failures can lead to numerous, costly claims.
Product liability involves investigating the malfunctions of consumer products, including appliances or toys that caused or could potentially have caused personal injury or property damage.
In product liability losses involving equipment and machinery, the investigating engineer will occasionally be asked to determine if the product or equipment contains an “inherent defect” arising as a consequence of poor design, faulty material, improper assembly or retrofit alteration. Often, the equipment did not malfunction; rather, operator error or poor installation may be to blame. This is an important factor to consider.
Leaking Water Heater
We recently were asked to determine the cause of a reported water heater failure that had caused extensive property damage. The water heater was only two years old, and the homeowner believed that the water heater was faulty.
Examination of the water heater interior through the hot and cold water openings revealed very little corrosion on the inside of the water heater. The homeowner stated that water was coming out of the top of the water heater from the anode plug area. The anode plug was rusted badly, but there did not appear to be any sign of leakage from the area.
The cold water connection threads were corroded and it was apparent based on our observations that it had leaked water over a long period of time. Based on the corrosion on the top surface of the water heater, water appears to have spurted toward the anode plug and the hot water connection. The sheet metal protecting the water heater had rusted out from the bottom side up between the cold water connection, the anode plug, and the hot water connection. Insulation held water between the sheet metal and the water heater.
The top sheet metal cover was not removed from the water heater because doing so would destroy evidence that needed to be preserved in the event that others need to examine the water heater. However, due to this need to preserve evidence, we were not able to see the actual hole in the water heater tank.
Our opinion, which was based on a reasonable degree of engineering certainty, was that the top of the water heater tank rusted through, from the outside top surface down into the tank. The water source was a slow leak at the cold water connection that spurted water toward the anode plug. The hot water tank and the insulation that held the water on the top of the tank provided a highly corrosive environment. The leak was slow enough that any water evaporated away before it drained to the floor. Water heaters are designed for corrosion protection on the inside, not the outside, which explains why this leak was so damaging.
The homeowners believed the tank was faulty because the water was coming out of the anode plug opening in the sheet metal, as this is what the problem appeared to be based on observation of the unit. However, the anode plug area corroded first because the water spurted toward it from the cold water connection.
Based on the results of our investigation, the product did not fail in this case. It is more likely that the cold water connection was not properly installed. It is also possible that, subsequent to installation, the water heater was disturbed by someone bumping it and causing the connection to fail.
Regardless of the cause of the damage, a professional can typically determine whether it is related to original product defect or an issue unrelated to product performance.
- Hot Water Heater Problems (answers.com)
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