Cutting Out a Fuel Tank

[Mike Sibley]

I have to replace the 30-year old steel fuel tank in my Pearson 365 sailboat. Unless I remove the engine first (Boooo), the only way to get the old tank out is to first cut in in half and then remove it through the cockpit locker. I plan to use a reciprocating saw. Although I can remove almost all the diesel fuel from the tank, some will undoubtedly remain at the bottom. What can I do to the remaining fuel or to the tank to insure that it doesn't all go up in flames when I start cutting and a few sparks fly?

(I plan to replace the old 50-gallon tank with two 25-gallon tanks that can be installed through the cockpit locker.)

[Chief Engineer]

You might want to pull the engine....after the busted knuckles with a reciprocating saw...as well as the pulled muscles and pranged up blades $$$$$$. Pulling the engine might me the easier softer way.

[lorenzo b]

If you can disconnect the fuel lines, you could just flush the tank out with water a few times until you no longer smell gas or diesel. You can cut steel with a sawzall, but if it's thicker than 1/32 inch it will take forever. If you can get a 4 1/4 grinder with a razor blade you can chop the tank up in pieces, but it will still take some time. The best way to cut steel is with a torch, but you'll have to be really careful not to burn your boat down.

[Kefaa]

I am reminded of the joke - there are a 100 ways to do this and all of them end badly.

Depending on the state you are in (or country), you are required to use special handling including getting a permit to do this. Presuming none of that applies, then here is the start of what you need to start:
1. If you can flush it with a degreaser to start, that will help. However, I cannot think of a place in the US where the outcome of that is legal to dump anywhere.
2. oil-dry absorbents - these are chemicals you can pour into the tank to dry it out. That should not be confused with "dried out." You hit a spark, even with absorbents, and its way 99 of a good start to a bad day.
3. oil-dry pads - put these under it. No matter what you do, something is going to spill and the CEO is going to smell it for a month and you will hear about it for a year. Put the pads where they can absorb anything that drops.

Now it may seem logical to fill the tank with absorbers and vacuum it back out. Rethink that. Oil laden material thrown into a high speed electric arc (way 98 to get a bad day started). I have seen guys repair fuel tanks by putting dry ice in them. The CO2 is supposed to dampen the possibility of a spark. The theory is good, but bad execution.. (way 97)

Now I am sure someone will say you can just cut the tank because diesel fuel does not burn easily. And - they are correct. However, if you happen to vaporize some while you are cutting, well - that would be way 96...

So, given the legal, permit, EPA and explosive ramifications, this is one you may want to leave to professionals (or take out the motor).

[6string]

I removed a 110 gallon diesel tank this past winter. It was empty when I bought the boat but it still had some fumes. I did some research about the volatility of diesel. You could throw a cigarette or match into it and it won't light. I just took my sawzall and cut away at the tank. I removed the top first and then wiped out the tank so I wouldn't have as much of a mess in the boat. I then proceeded to cut the rest of the tank with the sawzall. I had 2 spots that I took a right angle grinder to because the sawzall wouldn't work there. The tank was well cleaned up by then and there wasn't any concern of problems.

Good luck

Jeff
SV/Mezzaluna
Baba 40

SV

[Mike Sibley]

I finished the job of removing the tank, and it wasn't too bad. First, I drained almost all of the fuel using the fuel supply hose and an electric fuel pump. Then I poured in a gallon of degreaser and an equal volume of water. I tested the resulting mixture and it refused to burn, so I began cutting with a reciprocating saw. The actual cutting went quite fast using a heavy duty bimetal blade with 14 teeth per inch. First, I cut out the sides before and aft of the baffle. Then I removed the "soup" that remained inside the tank. Given poor access to the front and back of the tank, I finished the cutting with the saw inside the tank. Overall, it is a task one person can complete from start to finish in a day. In my case, however, temperatures of 95-104 F led me to spread the work over two days.

[Randy]

NICE!!
I read the first post and thought there's no way that there's enough room for a sawzall to do it's work.

Nice job on the back yard version of testing lower explosive limit too.

By the way, what's up with the heat down south?