An important production line has been in the plant for about five years. During its first few months, there were several motor failures due to overheating.
To solve this recurring problem, the plant engineer had heat shields installed between the motors and the hot process. He designed a cooling system consisting of a shroud with ducted air. He explained it as being like a home roof venting system. Cool air gets drawn in through soffit vents as warm air flows out through the roof vents.
But recently, the motor failure problem started again, and the motors show signs of heat-related winding damage. That plant engineer is gone, but his shroud looks good. How would you solve this problem?
Possibly, the vent system of the shroud is clogged and/or the heat shield has deteriorated. Before checking either, conduct an “As Found” thermographic survey. Remove the shroud and clean the exposed area and the shroud as needed. Before removing the heat shield, conduct a thermographic survey. Remove the heat shield, and conduct another thermographic survey and compare to the previous one. Replace the heat shield if indicated.
Put the system back together, wait a day, and conduct another thermographic survey. If results are not greatly superior to the As Found, find a source of cool air; use an intake fan to supply the shroud with it.
Next, check for voltage imbalance. If it's more than 2%, address that issue; for example, put this system on its own transformer/panel. Measure power factor at each motor, add capacitors at each motor as needed.
