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Subject: TWL: Scary incident with water flow alarms.
From: Joe Engel (joe@XXX.XXX)
Date: Mon Oct 01 2001 - 14:06:22 EDT
I have a story to relate regards raw water flow and alarm systems.
Another tale of "what were you pretending not to know - dummy?"
We've been working the boat pretty hard what with the CGAux patrols and
all since 9/11.
Last Tuesday evening I was running down the river pretty hard (14 kts)
to get to CG Group Portland where we sit all night on standby SAR
patrol. (Means that we moor up at the CG Group docks all night and
sleep aboard to answer any SAR call-outs so the regulars can get some
sleep.) I was running alone and driving from below because it was
raining like heck.
I was about 7 miles into the run when I began to smell burning rubber.
I quickly checked all the gauges and the temperatures were normal on
both engines. As I continued to run, the smell got worse, then really
worse.. I stuck my head out the side door thinking maybe some
industrial plant had caught fire and saw to my horror, that I was
trailing a huge plume of dark blue smoke from the starboard engine
exhaust. It looked like a WWII smoke screen. The engine gauges still
all read normal.
I shut everything down fast and after determining that flames were not
erupting, I opened up the main engine hatch, whereupon huge plumes of
acrid blue smoke filled the cabin. I could see no flames, but then I
couldn't see much at all. It drove me out on to the foredeck where I
stood waiting to see if we were going to burn up or what. I did note
that the big Halon extinguisher in the engine room had not tripped so I
figured we had some hope. After a while the smoke began to subside and
I could re-enter the main salon. I rigged up a couple of fans to start
to clear the smoke and eventually I could see enough into the engine
room to determine the problem. In the meantime my old-dear was
wallowing in the chop and dark clouds of smoke were still visible
wafting from every open hatch. I still don't know why no-one called in
a burning boat (which would have been very embarrassing as we were all
decked out in out full CGAux regalia with large flashing beacons and
patrol signs. We're supposed to be the givee not the receipee <G>.)
What had happened was that the end cap had come off the starboard engine
heat-exchanger. I had replaced these caps the week previous, in a
hurry. Obviously I did not secure one end correctly. The net result of
which is that the raw water pump was pumping merrily through the heat
exchanger and then out the other end, directly into the bilge. The
engine gauges did not show overheat because there was enough flow
through the heat-exchanger to keep the engine normal. What there wasn't
any of, was pressure to keep the flow of raw water running through the
wet exhaust system, which ran dry and then very, very hot.
There is a series of 4" diameter and 5" diameter rubber hoses connecting
the exhaust system to the muffler and ultimately out the stern. These
baked to a crisp. There is a large brass exhaust manifold arrangement
connecting these and the paint was cooked right off of this to bare
copper. There is a 5" fiberglass tube 90 elbow and a 6 foot long piece
of 5" fiberglass exhaust tubing that were burned black and crispy. The
smoke was coming from all of this stuff as it was cooking.
Oh yes, one other dumb thing. We usually run the boat from the
fly-bridge. Up in the fly-bridge there are audible alarms to indicate
overheat. There is an operating set of heat sensors on the exhaust
elbows and they work, but the alarm is only audible up on the bridge. I
had been planning to fix the lower alarms for a long time but hadn't
quite made it yet. If I had the lower alarm working, the exhaust
overheat would have announced itself in plenty of time to save the
exhaust components. I had assumed that I would notice any malfunction
on the lower engine gauges as I constantly scan the gauges. But in this
case, it didn't show on the gauges. The truth is, as soon as I shut of
the engines, I could hear the bridge alarm buzzing loudly, so it worked
great, except I couldn't hear it below, with the engines running.
This was a pretty expensive mistake. The exhaust components are
expensive and some of the fiberglass tubing is on back-order. I had to
tear a bunch of the boat apart just to get this stuff out. A long and
dirty job.
Dumb move #1 - Didn't take the time to make sure the heat-exchanger cap
was properly installed.
Dumb move #2 - Running the boat with inop alarms. Really dumb because I
knew they were inop. My only excuse is that I did not understand the
logic of the separate exhaust elbow heat sensors. It did not occur to
me that I could lose the exhaust cooling system but still have the
engine cooling system working. Lesson learned.
Good move #1 - Large capacity automatic bilge pumps that easily kept up
with the raw water flooding into the bilges.
Dumb Move #3 - No alarm or indicator on the bilge pumps either.
Boats - you gotta love em.
Joe & Debbie Engel
Marine Computer Services & JRE Consulting, Inc.
MV Freda Fly - 40' Tollycraft Tri-cabin
Portland, OR
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