Me and the SSMG

 "The world will ask you who you are.  And if you don't know, the world will tell you" - Carl Jung

 Story time again.  This is a sea-story, or since it happened while tied up next to the pier, maybe it should be called a harbor story.

Submarines use a lot of three-phase AC power.  Damn near everything on the ship runs on alternating current.  There are a handful of critical motors that operate on DC power - mainly for emergencies, when the ship's main storage battery might be the only thing with voltage in it...

But most of the ship runs on AC.  The main storage battery is there for backup power, in the event that both steam turbine generators - which produce AC power - come offline for some reason.  Perhaps a major steam leak, perhaps the reactor "scrams" or goes offline.  There are a few scenarios that could lead to losing both turbine generators.

For this reason, submarines have SSMGs or "Ship's Service Motor-Generators".  In the civilian world these are called "rotary converters".   An AC motor/generator shares a shaft with a DC motor/generator.  Energy can flow into the AC motor and out the DC generator to charge the battery.  If the turbine generators go offline, the SSMG can convert DC power from the battery by using the DC end of the machine as a motor to power the AC end as a generator.  Very flexible and very robust power conversion in either direction!

The SSMG looked roughly like this submarine propulsion motor.

 

That said, the SSMGs were maintenance-intensive, particularly on the DC end, which had a hellish number of carbon brushes - and carbon dust, and DC grounds due to carbon dust build-up.  

The machine built up a lot of heat, so it had a air-water cooler built into it.  On the class of ship I was on, all of the coolers for motors and generators were cooled by seawater.  Which meant every time the ship dove to test depth, hundreds of feet of supply and return piping and every cooler in every motor was exposed to the same seawater pressure as the hull of the ship.  Not a great arrangement.

In later submarine designs, they used a seawater-freshwater heat exchanger, and all the motors were cooled by circulating low-pressure fresh water, but my ship was from that transition era between shallow-diving WW2 submarine technology, and modern deep-diving ships... 

Back to the story at hand.  I was standing Shutdown Reactor Operator watch and had the 6 PM to Midnight watch.  Shortly after taking the watch, my roving watch reported that someone had left a flashlight in the starboard SSMG.  The flashlight had been left inside by the 2-4 guys who had performed the maintenance earlier in the day.  The flashlight was still turned on - and why it was so easily spotted. 

I had a few options at that point, and time to ponder them at length.  I could:

• Notify the Engineering Duty Officer, get permission to shut down the SSMG, and retrieve the flashlight.
• I could say nothing and hope that nobody would notice the flashlight until the next weekly maintenance.
• I could shut down the generator on the mid-watch when nobody else would be around, and start it back up without making notifications or getting permission, then retrieve the flashlight.
• I could remove the closest access panel and reach into the running machine and retrieve the flashlight. 

So I pondered these things and dismissed the worst of them offhand.

• If I notified the EDO, he would be compelled to tell the Engineer and the Captain, and it was likely that people above the Captain would get involved, because each SSMG is related to reactor safety.  My shipmates would get into a great deal of trouble over this.
• If I said nothing, it was likely that someone else would see the flashlight turned on in the inspection window of the machine, and then I would be complicit in a cover-up.
• I seriously thought about taking the SSMG offline in the middle of the night, but worried that maybe I'd screw up synchronizing it, or it would fail to start, and then where would I be with a shutdown SSMG in the morning?  With my luck, I'd cause loss of power to half the ship, then there would be some 'splainin' to do.
• The least bad option seemed to be popping the panel off and grabbing the flashlight with the machine running.  So that's what I did.

 Being the cautious guy that I am (LOL), after getting off watch, I stationed the roving watch who had spotted the flashlight at the reactor tunnel door to warn me if an officer was coming back aft to the machinery space.  Then I not so cautiously removed the wingnuts from the starboard SSMG access panel on the DC end.  The flashlight was right there, but there were DC bus bars at nearly 300 volts pretty close.  The noise was unbelievable and there was a lot of wind from the circulating fan.  

In any event, I was able to get the flashlight without getting shocked or caught up in the rotating part, and kept my buddies and my commanding officer from getting into a great deal of trouble with the Navy.

The only reason that I recalled all this today is because one of our guys replaced a mechanical seal on one of the condensate pumps, then closed it up and released the clearance - and left his flashlight on :)