In my last blog article I touched on this topic now, recently a customer brought in two 18 month old sewage grinder pumps that had failed. The motors in both pumps had burnt and open windings. The service plumber said they when they had a tank cleaner vacuum out the basin they had to scrape the walls of the basin with a shovel. (Please note the attached photo of the two grease caked pumps next to a new pump)
When I was asked why the pumps had failed I told the service plumber that the control floats were probably caked with grease too, and that they were not able to operate properly in such a greasy environment. My guess was that the pumps turned on at some point and the grease build up did not allow the pumps to turn off and they ran continuously until they burned themselves out.
My recommendation to the service plumber was to have the grease trap cleaned monthly and have the duplex system inspected and the floats cleaned quarterly. I also recommended replacing the control panel and floats as the original were over 15 years old.