Re: Purpose of various steam locomotive parts

A blowdown is to rid the boiler of dissolved solids,and to occasionally rid the boiler of excess water. I usually use the blowdown every 5-7 miles or so. If you blow down while sitting,you can see the foam and solids on the ground afterwards. Many blowdowns are muffled to blow the water down toward the ground.Others are set up to blow straight out from the mudring of the firebo as the narrow guage engines are)
Engineers can make many running repairs on the road,according to their skills and experience. Anything from doping a hot pin to taking down a rod,blocking the ports to come in on one side if necessary.
Oil cans usually carry air oil for the compressor,valve oil for the lubricators,and journal oil to oil shoes and wedges,crossheads,or any sliding or rubbing part the engineer feels he needs it.
Generators power the headlight and cab lights,occasionally the cab radio. I hope I have answered your questions.