At TVRM we ONLY use water to flush out the pans. I was under the false impression early in my steam days that water was detrimental to the ash pan because that's what I had been taught and didn't know better. Just a garden hose can be sufficient to wash out the pan. I do wish those who currently use air to clean the pans would switch to water. It extinguishes the waste burning ash, kills the dust, and keeps everything clean.
On 630 the rear driver sits in the middle of the ash pan so it's very important to keep debris away from the driving boxes and crank pins. There is one instance when 630 was running mainline trips that someone blew the ash out with air, the rear crank pins got scored as a result.
John Hillier