Dash 9 noises question

[ANDY117]

When im sitting down at Chenango street, or anywhere for that matter, and there's a later GE nearby (Dash 8 and on) i hear a few noises i can't identify.

While in idle, there's this occasional noise like a car revving up its engine, then the whole unit quiets down. Is this air pressure being regulated?

Second. There's this sputtering noise coming from the engine itself. I heard theses are pop valves, or some other part of the engine. Which is correct?

Im just wondering so next time either my dad, or one of my friends asks me, i can tell them what the noises are. I was up in DeWitt yesterday, and heard it on 2 CSX C40-8W's.

[LCJ]

While in idle, there's this occasional noise like a car revving up its engine, then the whole unit quiets down. Is this air pressure being regulated?

This is the AC motor-driven air compressor doing its job of keeping the main air reservoirs charged. It cycles on and off depending on the rate of usage of air for brakes, etc.. Older units had the compressor connected directly to the crankshaft of the diesel engine so that the compressor was always in motion internally. Cycling for these units was controlled by nullification (holding open) of the valves in the compressors.

Second. There's this sputtering noise coming from the engine itself. I heard theses are pop valves, or some other part of the engine. Which is correct?

These are valves that automatically expel moisture form the main reservoirs of the locomotive. In air brake systems, water is the enemy. It causes corrosion and other operational problems.

[ANDY117]

Wouldn't it also rust the pipes if it collected? Watching those 2 CSX units you could see the air being bled off between the air reservoirs.

[LCJ]

Wouldn't it also rust the pipes if it collected?

Yes -- corrosion (rust on iron/steel) is caused by water accumulation in the system.

In the air brake system, most of the moisture precipitates out when air passes into the #1 main reservoir after leaving the compressor. The automatic drain valves (that spitting, popping sound) expel it to atmosphere continuously/intermittently.

Many units these days are equipped with air dryers, as well, that help to get rid of water with greater efficiency.

Moisture content is also especially troublesome in very cold weather, for obvious, icy reasons.

[ANDY117]

Couldn't it also snap the air lines if it freezes in the hose itself?

[LCJ]

Well -- maybe if the hose were filled up completely with H2O (not bloody likely).

Mostly the problem (excessive water in the system at cold temps) causes problems with valve operation -- such as vent valves sticking open, or spool valves in the control body not moving as they should (brakes not working properly).

We used to inject alcohol (IPA) into the brake systems in really cold weather to decrease the problem of ice in the system.

[ANDY117]

thanks for the info. I think the NS Dash 9s are my favorite locomotives of all time. it's a shame they won't be made anymore. guess i'll have to get used to the ES40DC's (which haven't even run on the southern tier yet i think.)