The Evaporator

Down in Auxiliary Engine Room #1 (AUX 1), was where I stood watch while the ship was underway. I was in charge of making the fresh water on board the ship. We had two huge flash type distilling plants (evaporators) that were super-heated by high pressured steam and would heat the sea water before it instantly flashes into vapor inside the first and second stages. The vapor then travels up through the demister pads filtering out any leftover brine in the water, producing fresh distilled water for the boilers and is also treated for the potable drinking water.

(Keep in mind that this ship was commissioned in 1977, so it’s old technology).

I would open the dump valve, then the brine water discharge valve, some valves to the sea chest, and open some valves for a seawater strainer, to filter out barnacles and sea life that would get sucked up into it. Then turn on a pump to get the EVAP primed until it causes a vacuum inside the first and second stage. Then it’s time to open up the steam valves for the heat exchanger.

The steam pressure was about 150psi in a ten inch pipe. It had some huge valves in the overhead that I would have to stand on top of the evaporator and put all my strength into just to open them. Once loose, the steam starts to hiss through the valve and it starts to warm up; when the valve begins to open up fully you can feel the steam rushing through the pipes, vibrating and shaking the whole pipe system in the overhead.

When I was new to the ship and I first opened a steam valve, I thought to myself, “is this steam pipe going to rupture and melt my face off next time I open it?” Then quite a few more steps and the EVAP was almost ready.

I would have to open about thirty to forty valves total. Then spend an hour or more fine tuning the valves by watching about fifteen different temperature and pressure gauges to make sure everything is in parameters. Then lift the dump valve when all the summery fault alarms stop flashing, then it’s time to light off the second one. I got so familiar to the systems after a while, to where I could light off an EVAP in about 30 to 45 min by myself without looking at the EOSS (Large manual that tells you step by step of the procedure).

When the ship rolls from side to side in turbulent waters, the summery fault alarms on both EVAPs would start going off from the water splashing around inside. I could spend an entire 6 hour midnight watch fine tuning both of the EVAPs, by adjusting valves open or closed millimeter by millimeter every couple of seconds, keeping everything in parameters by watching all the temperatures and pressure gauges.

Every couple of hours one of the four potable water tanks would get full and I would have to go to the forward or aft pump rooms and take a sample of water and find out how much bromine (water treatment chemical) was added to the potable water. Sometimes I would have to go to both pump rooms while switching over tanks. To get to the aft pump room, walk out from two levels of AUX 1, walk down the passage way to the aft end of the ship and then go down three levels, test the water then open some valves and turn on a pump, climb out three levels; then go all the way forward, to the forward pump room by climbing down a vertical latter five levels deep, with a few flimsy safety nets to catch me if I fall; turn off a pump and close some valves then climb out five levels and then head back down to AUX 1. Let’s just say you will sweat out any alcohol left in your system from a long night of drinking in port.

Before we went out on our Gulf tour, the ship went into repairs and we got a pre used Reverse Osmosis (RO) water purifier installed, which produced twice the amount of water as both EVAPs combined. This was easy; check some micron filters, open a few valves, turn on a pump, and let the water run through the membrane. But the Chief Engineer still wanted us to lite of at least one evaporator anyway, just for backup.

As much water the RO produced we always had to shut it down and clean the micron filters that filtered the sea water before it goes through the membrane. It got to the point that we went through fifty filters and couldn’t get any more on order, so we had to clean all the old filters by hand scrubbing the slimy, green algae in between the crevasses with tooth brushes. (classic military)