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Thursday, March 28, 2013

Fuel and Fire Prevention

These two seemed to go together so I'll put them in the same post. Our boat has six fuel tanks (forward port and starboard, aft port and starboard, keel forward, and keel aft) plus a 50 gallon day tank. This is a lot of tankage to keep track of and if you go back a ways in this blog (or search for "fuel") you'll find some posts describing our somewhat complicated fuel distribution system. Now that its all put together, we can transfer fuel between any two tanks, or to the day tank from any tank. Transferring from tank to tank allows us to trim the boat as necessary as we burn through our fuel supply. We can also directly feed the engine and the diesel furnace from any tank and return fuel directly to any tank. Most of the time we just transfer to the day tank as necessary and feed all machinery from the day tank. This makes it easy to monitor consumption (day tank is designed so that 1" on the site glass = 1 gallon). The transfers can be done with an electric pump, or with a hand crank pump. Either way, the fuel moves through a big Racor filter, and a fuel meter that counts gallons so we can keep track of how much we are putting where. So, the last part of the fuel system was the tank level gauges. As all our storage tanks are integral with hull and low in the boat, I opted for a Hart Tank Tender. This is a very simple and reliable system that uses a pressure gauge to read how many inches of liquid is in the tank. This is accomplished by running a thin nylon tube from the gauge panel in the wheelhouse to the bottom of each tank. To sound the tank, you pump some air into the tube with a mini pump on the gauge panel. The reading (in inches of diesel) from the gauge is then converted from inches to gallons using a chart  made up for each specific tank. When we built the tanks, I had this system in mind and installed 1/2" standpipes for the nylon tube fitting to enter the tanks. Here's some pics of some of the tank fittings that finished out the system. After a little tweaking with the distance between the end of the tubing and the tank bottom, everything seems to be reading correctly for how much fuel we estimated was in each tank from our first fill-up last fall.






I have also been working on fixed fire extinguishing systems for the engine room and the electrical cabinet. Both spaces now have fixed cylinders that will automatically discharge when the temp rises to 175 degrees or so. They can also be manually discharged with a pull cable from outside the compartment, which is a much safer way to deal with a fire in a confined space. The extinguishing agent FM200 does not leave any corrosive residue like dry-chem so is safe for all electronics and machinery. This means that you have a good chance of getting underway again at some point after fighting a fire with this stuff. I still have to hook up some parts of the electrical portion of the engine room system. This is a little black box full of relays that takes a signal from a pressure switch on the extinguisher and automatically shuts off all the machinery in the event of a discharge. This is so the running engine, diesel burner, etc. don't suck up all the extinguishing agent into the air intakes. Also you don't want to keep pulling fuel through the lines with a running engine, potentially continuing to feed the fire. The rest of our extinguishers are hand-helds which are spread throughout the boat. 
I'll probably get back to cabinetwork again this weekend and post some more interior shots...




2 comments:

  1. Is the FM200 what they came up with to replace the Halon ?

    Bill Kelleher

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    Replies
    1. Hi Bill,

      Yes, FM200 or HFC227ea (same stuff) is the more environmentally friendly replacement for Halon. I think you can still get Halon systems serviced and recharged (until existing Halon gas supplies run out), but all new systems have to be Halon free. As I understand it, about 80% of FM200's effectiveness comes from rapidly dissipating the heat from the fire and 20% from chemically breaking up the combustion process. It's also supposed to be less toxic- but I don't ever want to test that.
      -PB

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