One product in the line of food-packaging machinery we manufactured used a large 12kW servo motor. It was very costly, and it was rated IP69 for use in this washdown environment. After a few years and some 30-plus motors in the field, we began to get warranty claims for failed motors. The motor manufacturer quickly identified water intrusion as the problem and cheerfully honored the warranty on the first two motors, but as more failures on these $10k motors came in, it became more reluctant to honor the warranty.
We examined the machine design, and the manufacturer's people also reviewed the application. We came up with no hint as to the cause. Then somebody at the motor manufacturer happened to notice, "Hey, these guys have bought almost 50 motors and drives from us but never bought a single cable. What's up with that?" It turns out that our local distributor of these motors and drives had a brother-in-law who was in the cable business. So every time we placed an order for motor, drive, and cables, the motor and drive order went to the manufacturer. The cable order, however, went to the brother-in-law.
Now a big motor like that is going to get hot, and since it's sealed IP69, it needs a vent. The motor manufacturer came up with a clever solution -- it ran a vent hose through one of the unused locations in the Cannon plug for the power cable and up into the cable some distance. This provided the necessary pressure equalization while protecting the vent hole from intrusion of water.
It turns out the brother-in-law's cables did not have this feature, which left the vent hole in the connector open. That was enough to allow it to suck in water when the hot motor was hit with colder water during the daily washdown. OK, so now we know the solution, but five years later, lawyers were still arguing over who pays for all of those bad motors, and the manufacturer no longer uses local distribution -- all sales are direct from the factory.
Our argument was that we placed the order for a complete package of equipment with the authorized distributor, and any problems arising out of how the distributor processed that order was between the distributor and the motor OEM. And furthermore, never having seen a "genuine" cable, how were we supposed to know that these were bogus cables, since they were delivered by the manufacturer's authorized distributor?
This entry was submitted by Kim Ground and edited by Rob Spiegel.
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