First, I was not on the PRR -- I read this in a trade publication at the time.
Compressed air blew dirt _in_ as well as out.
Traction motors are cooled by air blown in from the car body through flexible duct connections. This puts some level of positive pressure in the motor. Air in the locomotive body is intended to enter through filters in the walls but locomotive bodies gt pretty leaky, so there is bypassing of filters. Filters are supposed to be changed with each 92 day inspection. That said, I ran locomotives for 25 years. I did not maintain them so my opinions here are based on various levels of hearsay and experience.
Locomotive in the 70's and later, maybe,have more specialized cooling systems that among other things can provide beter isolation from dirt in the cooling air.
I worked for the New York Central and know first hand that they used vapor degreaser tanks to clean disassembled traction motors when they received serious overhauls.
About 1958 a storm hit the Pennsylvania RR in the New Jersey area, with fine ice crystals that went through the linen air intake filters on electric locomotives and shut down the railroad with motor failures. The GG1 locomotives were the most affected due to the height of the intakes above ground. They were later relocated higher on the carbodies on some locomotives.
From: glenn brooks
Date: Wed, 22 Apr 2020 15:23:56 EDT
Any idea why they saw a reduced failure rate? In other words, what effect did not cleaning them out have on motor life?
We have 4 traction motor locos running at present. I’d like to pass on the info.
Date: Wed, 22 Apr 2020 15:40:43 EDT
Apologies for getting completely off topic here, but I can't resist it!
I too would be fascinated. I have worked on locomotive & multiple unit maintenance and consultancy for British Rail and its successors since 1973. We ran thousands of DC motors and generators, but new stuff has mostly been all AC for the last 20 years. The problems you get due to the dust are electrical tracking due to carbon brush debris build up and you also get build up of brake dust (rust) that tends to etch itself into the varnish, just like it does into body paint. We don't like blowing things through with compressed air because of health hazards, but making machines more reliable by not blowing the debris out is a new one on me! Perhaps they installed better air filtration and started wiping out the motors with solvent instead, not just stopped blowing them through? Those would certainly help.
We had a winter problem a few years ago with the "wrong sort of snow". We don't normally get fine powdery stuff here, just big soggy flakes. The powdery stuff got into a lot of motors, melted and they went fizz.