Saturday, May 9, 2009

Mechanical Issues

Shot water impeller

Between the watermaker and the generator, we've experienced a few mechanical problems.  Unfortunately, they're been in the two systems most conducive to anchoring out.

Firstly, the watermaker.  Last we left it, I'd briefly mentioned that it had become bio-fouled while we had been in Ft Lauderdale.  Sea Water has lots of little organisms in it.  They're at the bottom of the food chain and allow for the huge diversity of life we see in the oceans.  This life thrives in warmer weather and after leaving Biscayne Bay the temperature must have warmed up enough to allow the little critters to blossom.  The watermaker automatically replaces the sea water with fresh water at the end of each watermaking session and then replaces it every five days.  This had proven effective at preventing bio-growth since I installed the watermaker last September.  However, I guess the temperature had warmed up enough to overcome this.  I've since reduced the fresh water flush interval to three days, but the damage has been done.  Despite many attempts to clean the membrane, there must still be critters in there.  Unless we run the watermaker at least once a day, it struggles to desalinate.  Eventually the salinity will come down, but it takes time.  If we run it everyday, it's only about 15 minutes.  Miss a day and it can take over an hour.  If that wasn't enough, the diversion valve is sticking.  This is a relay operated valve that diverts the product water (the desalinated water) into the water tanks once the salinity comes down enough.  Fortunately, our unit has a switch that allows me to manually operate the valve.  So now I go down and move the switch once salinity has come down to around 800 ppm.  It's a pain and I need to remember to turn it back after the run, but we're able to make water and that's the important thing.  When we get back to the east coast, I'll be able to order a replacement valve and membrane and these issues will be behind us.

Secondly, the generator and the reason behind our unexpected return to Nassau.  It stopped working the day we arrived at Normans Cay.  When it errors it blinks a light with the reason why.  In this case, seven blinks meaning raw water flow impeded.  Unlike car engines, whose coolant is cooled by air passing through a radiator, marine engines use raw water (the water the vessel in floating in) passing through a heat exchanger.  Not only does this water cool the coolant (and hence the engine), but it also passes into the exhaust and  cools that down as well.  Losing raw water flow is worse than losing air flow over a car's radiator and the engine shuts itself down quickly.  At first I thought it was the same issue we experienced in Allen's Key - something sucked up the intake.  Not to be.  The strainer and hoses were clear all the way to the raw water pump.  I even got a mouth full of sea water when I sucked on the end of the hose, just to make sure.  So I took the impeller out.  The impeller spins inside a sealed housing and pumps the water through the system.  As you can see, ours was shredded.  It was near it's end of life and the shock of being run dry must have been enough for it to give up the ghost.  I didn't have any spares for the genset (yeah, yeah.  I know...) so back to Nassau it was.  The only other alternative was to head down to Georgetown, which was even further away.

We arrived in Nassau, refueled and docked.  We immediately headed over the bridge and hit all the marine stores.  It was looking grim when we hit success in this small "hole in the wall"  repair shop called Albert's.  I also took the opportunity to get a few Raycor primary fuel filters for the generator as well.  After lunch I descended into to heat of the engine room - the engines were still over 120 degrees from the run up - and got working.  After replacing the impeller I was still getting the same error.  So I checked downstream from the pump.  There's always the possibility that pieces of the impeller get stuck in the heat exchanger and impede water flow.  The exchanger has end caps that can be easily removed to check for this, so I did.  No bits of impeller, though there were a few pieces of zinc from the zinc anode protection.  I removed them and then checked flow by blowing through the hose leading into the exchanger.  No blockage and I could hear faint gurgles as the air I was blowing through percolated through the water still in the exhaust.  I put everything back together and tried again.  No go.  Rechecking the impeller, I noticed it was dry, which implies it wasn't spinning up at all.  watching the strainer carefully during another attempt confirmed it.  No water was flowing at all.  So the pump is broken.  I called Cummins and they gave me the address of the local authorized dealer and service outfit.  I called at 5:55 and, not surprisingly, they're closed.  Someone answered and I arranged for the mechanic to call me first thing Monday morning.  Hopefully that doesn't mean 2pm Tuesday afternoon.  If I've not heard anything by Monday afternoon and calling back isn't helping, I'll give Albert's a call and see if they can come down to look at it.  Albert's say they can get any part in 48 hours, so I'm optimistic we can get it fixed before we leave for Staniel Cay this weekend. 

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