# Cutting Access Hole in Stainless Steel Diesel Fuel Tank



## Ajay73 (Jun 13, 2011)

I have a 1980 Catalina 27 with a Universal 5411 diesel engine. I want to cut an access port in the stainless Steel fuel tank. I have good access to make the cut. I will have to drill a starter hole. Can stainless steel be cut with a jigsaw with a bi-metal blade? Has anyone done this kind of modification? What are the problems? I don't think there is an explosion risk in that the tank will be emptied and that it is a diesel fuel tank.


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## tommays (Sep 9, 2008)

As safe as diesel is cutting into a empty tank that still has some amount of fuel and a bunch of fumes is a high risk job 

If you go slow and kept the blades lubed and cool so the SS does not work harden it could be done on a tank that was cleaned OUT


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## kd3pc (Oct 19, 2006)

the bigger issue, is how to get all the metal shavings out of the tank....if you can stand the cutting long enough..

For small holes in stainless, I have used thick mechanics grease smeared on the top to help hold the shavings. I would at least use that, and a shop vac whilst cutting.

You will need a really good jig saw and top quality blades to cut the stainless, even then it will be time and blade consuming.

Access to good quality sawz-all or shears (air/hydraulic) would be the better choice...

Likely some bad smells and lots of fly back, so wear goggles and old clothes at least


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## TQA (Apr 4, 2009)

Steam clean the tank THEN then fill it FULL with water.

I would cut it with an angle grinder and suitable disc but a saw will work, albeit slowly and have plenty spare blades..

eg Bosch 2608600701 Cutting Disc, for Stainless Steel, 100mm

DO NOT ATTEMPT TO CUT IT WITHOUT TAKING THE ABOVE PRECAUTIONS - PEOPLE GET HURT OR KILLED EVERY YEAR DOING THIS.

Motor vehicle repair Repair of diesel tanks


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## kd3pc (Oct 19, 2006)

I assumed a "round" hole, which is all but impossible to cut with a grinder/cut off wheel....but if you can handle a square hole, then TQA's gear will be much quicker.

I have always been "assured" that drilling or small cuts in diesel tanks are safe, and have done quite a few as you are planning...and although you are not torching/brazing....but I would certainly err on his well documented side....and take the thing out, wash and rinse several times, then fill with water and do the cuts...

Or at least have a friend stand by with fire watch...

YMMV


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## Boasun (Feb 10, 2007)

In almost all shipyards and on commercial vessels, that tank would have to all of the fuel removed and steam cleaned before any modifications is done on it. This is for the safety of the people working on said tank.
You can rent small steam generators and Please use one for your safety along with an explosive meter to ensure that the tank is safe for hot work...And hot work does include drilling and metal saws.


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## sawingknots (Feb 24, 2005)

although diesel isn't highly combustible,heated fumes are,if you really want to do it safely run a hose from the exhaust of a small engine into the tank for a few minutes and during your cutting,the corbon deoxide and lack of oxygen will prevent an explosion[works on gas tanks too]


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## jrd22 (Nov 14, 2000)

We used to repair truck aluminum diesel fuel tanks using the method that sawingknots suggests. A jigsaw will work, generally the stainless is pretty thin on most tanks I've been around on boats. Good idea using grease to catch the chips.


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## ggray (Jun 18, 2011)

Can't be too safe.
Worst example --actually, the only bad one I know of -- was in a boat yard where they were cutting on a diesel tank. Plan was to fill tank with nitrogen, but gas company had mistakenly filled a nitrogen bottle with oxygen.
The worker burned to death before they could chop a hole through the hull. 
This was 25 years ago, and I still think about it.


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## hellosailor (Apr 11, 2006)

Boasun, steam gennies may be common in cow country but in the Northeast US you'd have an easier time trying to rent wooden false teeth. 

Ajay, an empty tank is now full of vapors and vapors are more explosive than liquid fuel. One trick to making that safer is to dump crushed dry ice into the tank, as the CO2 "melts" it will displace the air and fill the tank with CO2 which doesn't support combustion. You could use CO2, nitrogen, or any inert gas from a welding supply to do the same thing as well. It may be simpler and safer to just remove the tank, clean it out beforehand and afterwards where there's space to work.

The big trick is going to be making sure there are no metal particles of filings in the tank. Putting thick grease on the tool eldge will help that. If you can squeeze in a helper with a vaccum, that also helps. Either way you'll want to wipe out the tank afterwards and really try to chase out those cuttings.


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## ambianceack (Aug 27, 2006)

Obviously get as much fuel out as physically possible. Diesel is considered a combustible with a flashpoint over or at 300 F. Remember, diesels work on compression not a spark! Draw your cut line with an permanent marker. A jigsaw will be okay to cut with just use a new blade and cut slowly but efficiently. add oil along the cut line or as you are cutting the hole to help keep the blade cool for easy cutting. Clean the tank carefully! I wore nitrile gloves and used paper towels so I could feel the metal chips. I also vacumed via a standard shop vac. Installed the port 3 years ago no problem. Do the work in a well ventilated area. Be very diligent about cleaning out metal chips.


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## Hudsonian (Apr 3, 2008)

Wouldn't a nibbler do the work easier and faster?


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## rg500 (Jul 11, 2007)

SS, remember , low speed , high feed to prevent work hardening....


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## TQA (Apr 4, 2009)

ambianceack said:


> Obviously get as much fuel out as physically possible. .


This is not the correct thing to do. A full tank CAN NOT EXPLODE as there is no diesel vapour and no oxygen.

An empty tank on the other hand has both vapour and oxygen!

That is why I said to fill it with water after steam cleaning.

Also dont get too paranoid about cleaning out the debris, you have got fuel filters.


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## Ajay73 (Jun 13, 2011)

Thanks for all your replies. Well, this is a bit more complicated then I thought. I may have to reconsider this. To get the fuel out of my current tank I would be removing my fuel gauge which is about a 1.5 inch opening. Would that opening allow vapors to escape enough to not be a concern? Maybe I should just opt for replacing the tank. A new aluminum tank is $320 for the size (12 gallon) I want and if I want to add an inspection port that would be another $75.


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## Minnewaska (Feb 21, 2010)

Why aren't we just buying a large hole saw for cutting metal? Slow speed and cutting oil are good ideas. Fraction of the cost of a new tank. You will need to drill and tap holes for the cover too.

Filling with water is the simplest and safest idea. You will have a large inspection port when you're done, so you can vacuum up shavings and dry it out later. I'm betting you will end up scrubbing and washing it anyway. The inspection port must be for a reason. No big deal. Go for it. 

The dry ice idea is excellent, but without a current inspection port, you would need pieces small enough to fit in the fuel gauge hole. Again, I think you are going to use soap and water later to wash out the gunk and dead diesel bacteria anyway.

While not mandatory, this job would be much easier, if you you remove the tank from the boat.


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## TQA (Apr 4, 2009)

Fit a new tank if you can.


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## RichH (Jul 10, 2000)

tommays said:


> As safe as diesel is cutting into a empty tank that still has some amount of fuel and a bunch of fumes is a high risk job
> 
> If you go slow and kept the blades lubed and cool so the SS does not work harden it could be done on a tank that was cleaned OUT


... good advice from Tommy .... plus a good safety practice is to empty the tank, then totally fill the tank with WATER before any power cutting. All tanks need periodic cleaning/scrubbing anyway .... . Later, the water discharge from the tank can then be routed to a simple barrel with an 'opened' / unrolled "bilge pillow" to extract the oil from the discharge water.


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## hellosailor (Apr 11, 2006)

"Why aren't we just buying a large hole saw for cutting metal? "
That may even be available as a half-day or day rental from a large hardware store. They are used to cut holes in sheet metal ducts for home ventilation/heating systems, the only question is whether you can also get it in the right size that way.

"a 1.5 inch opening. Would that opening allow vapors to escape enough to not be a concern?" The vapors can be expelled through that or even smaller openings, the trick is to have enough of something inside the tank to flush it out.

The first time I pulled a fuel tank it was a 8itch. Disconnect the steering, move the battery cables, origami bodies into BOTH lazarettes to push-and-pull to get the damned thing out. But once it was out, the cleaning became REAL easy. And leaving it in the sun to make sure it was bone dry afterwards, also REAL easy. Which also gave us a chance to inspect the entire tank closely for pinhole corrosion, etc. in hidden areas.


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## MedSailor (Mar 30, 2008)

Ajay73 said:


> Has anyone done this kind of modification? What are the problems? I don't think there is an explosion risk in that the tank will be emptied and that it is a diesel fuel tank.


Yes I did it, and the job is not that bad. The explosion risk is minuscule since we're not talking about gasoline here. It's a messy job, but not dangerous and it sounds like it will save you a bunch of money.

Here is what I did and it worked great:

1: Remove and dispose of diesel fuel.
2: 1/2 fill tank with water and add biocide to water.
3: cut holes with high quality hole saw at slow speed 
4: scrub with toilet brush
5: remove and dispose of water
6: polish with paper towles
7: fit new inspection ports

I removed the fuel into 5gal jerry jugs and disposed of it at my marina for free. By far the most expensive, messy, and time consuming part of the job. The diesel had to be removed anyway in order to clean the tank and the fuel itself was grossly contaminated. If I were planning on "filtering" it, I would have spent more on Racor filters than new fuel.

To be extra safe, and out of fear of fumes I 1/2 filled the tank with water before cutting. At this point I didn't think a few droplets on the surface of a 1/2 water filled tank posed any risk. Also for good measure I added a shock-dose of Biobor fuel treatment to the water to help kill what was sticking to the sides of the tank.

With the fuel removed I bought a good quality, high carbon hole saw. (about $60)

Used a variable speed drill to keep the speed slow-ish and lots of cutting oil. If the metal got more than very warm, I would wipe it down with water to cool it. Nothing ever got very hot, and there were never any sparks.

Once holes were cut, I bought elbow length PVC gloves and a toilet brush and set about cleaning. I didn't use any detergent as I figured it would be impossible to remove. Once it was well cleaned I drained the water (and disposed of the water at the marina as diesel fuel) and I polished the tank walls with paper towels.

I never worried about the metal shavings. I got 99% of them out with a shop vac but honestly, they're too heavy to likely get sucked up into the fuel system, and even if they did, the filter bowl would separate them, or the filter element would catch them.

The only thing I would do differently would be to pick a hole-saw that was the same size as commercial, off the shelf, inspection port hatches instead of making my own out of plastic.

Medsailor


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## Ajay73 (Jun 13, 2011)

I really want to thank everyone for adding their experience. I really appreciate it. I think the best approach for me is to remove the tank from the boat which I can do with maybe just a little cutting of the fiberglass in the quarter berth. Then get it steam cleaned as some have suggested. Then I can work on the access port without risk. A hole saw at low rpm's is a good option. I can buy a Milwaukee bi-metal for about $50 around here or maybe take it to a welder/metal fabricator and see what they would charge. Anyway, removing the tank kind of takes care of everything. 

There's no reason I can't do the diesel pumpout during the cold weather months up here in Northwest Ohio, is there?


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## sawingknots (Feb 24, 2005)

it always amazes me that people ask for advice yet have no intention of taking any of it,why not just go with your first thoughts [instints]from the get go?


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## Ajay73 (Jun 13, 2011)

sawingknots said:


> it always amazes me that people ask for advice yet have no intention of taking any of it,why not just go with your first thoughts [instints]from the get go?


I won't go with my first thoughts because there are concerns I hadn't considered or even knew about. I got the information I wanted, i.e., what are the concerns(problems) and you all expressed them. Many expressed the concern of safety with vapors, etc. The vapors are something I didn't ever have a thought about. So my latest scenario with taking the tank out, etc, answers all the saftey concerns. I changed my course of action based on all the input. I'm sorry if there is some error on my part.


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## MedSailor (Mar 30, 2008)

Sorry to see that you're making a medium project into a huge one out of fear of diesel vapors. I can tell you from my experience using a dickinson stove, where you try and light a puddle of diesel to start the stove, diesel is not that easy to light. 

I NEVER was able to light the stove by dropping a lit match into the 2" diesel puddle. Every time I tried it, the match would burn, floating on a puddle of pure diesel and then go out. The only way to light the stove was to make a little wick out of a paper towel and drop that in. Then, reluctantly, the diesel would start to burn. NO vapors exploding even though it was a lot of diesel for the small enclosed space of the burning chamber.

Diesel is just not propane, diesel is not gasoline, diesel is just not that dangerous. I would say that cutting into the tank with it full wouldn't even be manifestly unsafe if you used a hole saw and were slow about it. Certainly an empty tank is safe, weather you fill it with water, nitrogen from dry ice, or just empty as is. 

Also I don't see why manhandling the tank out of the boat, and then having transporting it and finding a place to work on it, is easier than working on it where it lies. You said you had good access right? 

Sailnet is a place full of good advice and wisdom, but it also can be a groupthink culture where the trend is for overkill on all things safety related. 

Medsailor


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## Omatako (Sep 14, 2003)

One of the most sensible suggestions has been completely ignored.

Use a nibbler - no heat, no cuttings/swarf, just a clean, safe, accurate hole.

With the "cost" of removal of the tank and making it nuke-safe as suggested, you could afford to buy a new nibbler, use it and sell it used on E-bay and get most of your money back.

Or keep it for 100 other uses down the years to come.


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## rg500 (Jul 11, 2007)

LOTS of swarf with a nibbler.....


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## Minnewaska (Feb 21, 2010)

Whether removing the tank is more or less work, will depend on the degree of difficulty to remove. Presumably, this access port is being installed for a reason and I suspect the first will be to clean the tank. Whatever you clean it with will have to be repeatedly drained out the fuel line connection into a container and transported to a hazardous waste receptacle, if you clean it aboard. That will be an effort. Cleaning it at home should be a walk in the park.

OP will just have to decide whether the effort to remove is worth it.


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## Ajay73 (Jun 13, 2011)

The tank is under the starboard rear berth. There is a large access panel in the berth and the tank is under that panel. The tank measures 13" wide by 30" long and is 8" deep on one side and 11" deep on the other. The berth access panel is 18" wide by 28" long. I may be able to get the tank through the opening without cutting any glass but if I did have to cut it would be very minimal. The tank is near the front of the berth with the front edge of the tank where you have standing head room. It should be an easy take out if I should decide to.


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## ewoden (Mar 30, 2011)

Built a lot of barbeques out of heating oil tanks. Lots of cutting on some hefty steel to do those. Never a vapor ignition issue after draining and a quick rinse with the hose. But that was out side not in a confined space.

I used a 30 dollar Home Depot fuel transfer pump to empty my boat tank of diesel into jerry cans. Filled it with water to do the cutting on board with a nibbler. Hole saw was not an option for me as the clearances proved almost impossible to keep purchase on the drill. When I was done with cutting, same afore said transfer pump was used to remove the water, rinse and repeat. Did a final scrub down with acetone and lint free rags. Put my shop vac hose on exhaust side and blew into tank until acetone was evaported. Then used shop vac to remove and cuttings remaining in tank.

Thirty bucks for the pump, which I now use for lots of stuff, 5 bucks worth of acetone, 3 bucks for the lint free cloths.

Doesn't seem worth pulling the tank to me.


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## Omatako (Sep 14, 2003)

rg500 said:


> LOTS of swarf with a nibbler.....


Yep, I guess if you buy the wrong type of anything it will not work as expected. There are two types of nibbler, see extract below

A nibbler is a tool for cutting sheet metal with minimal distortion. One type operates much like a punch and die, with a blade that moves in a linear fashion against a fixed die, removing small bits of metal and leaving a kerf approximately 6 mm wide. Another type operates similar to tin snips, but shears the sheet along two parallel tracks 3-6 mm apart, rolling up the waste in a tight spiral as it cuts

So look around and buy the tool that does what you want it to.


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## sawingknots (Feb 24, 2005)

i have to ask,why do you even need to cut another hole in a fuctional fuel tank,don't you already have a filler,vent,fuel level indicator and supply to the engine hole?


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## arf145 (Jul 25, 2007)

sawingknots said:


> it always amazes me that people ask for advice yet have no intention of taking any of it,why not just go with your first thoughts [instints]from the get go?


How is he not taking the advice? OP heard a lot of different views, learned that it was more involved than he thought, and is reacting by removing tank and, as suggested, having it steam cleaned, and then, as suggested, using a hole saw.


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## sawingknots (Feb 24, 2005)

its not involved at all,and after he has removed it he still needs to cut the hole and someone is right diesel isn't that cumbustable but i wouldn't take that chance,rinsing out with water won't prevent an explosion,comepletely filling with water would but then how to comepletely remove the water,i'm not all that sure about steam cleaning either, i just don't see how removing the tank is going to be of any partcular benefit


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## hellosailor (Apr 11, 2006)

The guy just hasn't gotten any good advice yet.

OK, so you take an empty coffee can and tack it down (couple drops crazy glue or hot wax) to the fuel tank where you want the access hole to be. Now carefully make ONE wrap of detonex or other light primer cord around the base of the can where it meets the fuel tank. Fill the fuel tank and coffee can both with water.

Following normal safety procedures, detonate the primer cord.

Voila, neat hole in side of tank, no grindings or metal filings to worry about. Polish or paint as necessary. This is a ten minute, nothing more.


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## sawingknots (Feb 24, 2005)

nah just use a torch right after you get lots of life insurence,if your boat survives someother sailor will enjoy it


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## Ajay73 (Jun 13, 2011)

Well, my apologies to everyone. Tank is aluminum, not stainless steel. I will still take it out to clean it and take a look for any corrosion. The tank has been sitting on plywood for its 31 year life so I'm sure there has been a lot of trapped moisture between the bottom and the plywood. Everything I read on aluminum tanks is that they have a life of 15-20 years. Tank is .090" aluminum. The one quote I received for a replacement is .125 inch aluminum.


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## tommays (Sep 9, 2008)

.090 tanks were one of those things they did for a short amount of time and there life was much less than the .125 tanks

FWIW my 1970 Cal just got its third tank in 2011


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## CapnBilll (Sep 9, 2006)

Aluminum is a soft metal and non sparking. Cutting is easy. The dry ice tablets are a good idea though, I'll have to remember that.


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## GaryHLucas (Mar 24, 2008)

We cut holes in Stainless electrical panels and tanks all the time. Big holes, lots of cutting just using a jigsaw. You want one with variable speed, AND blade oscillation. 

Blade oscillation on a jigsaw is an unbelievable improvement when cutting stainless and even plastics. With oscillation the blade cuts on the upstroke and clears the cut on the downstroke so the teeth don't drag, or kick the saw back up. Ussually the middle of three oscillation settings works best on stainless.

On our Bosch saws we use a coarse tooth blade, distance between teeth should be slightly less than the material thickness so that at least two teeth are in contact at all times, but not many more. Fine teeth take lots more power. Fine teeth pack with chips then break off. Coarse blades have more set, making a wider kerf and it is easier to cut a curve.

Set the speed slow, use a little lubricant, a wax stick lube works very well. Hold the saw firmly and keep moving forward. If you have it all right it will work like a nibbler, producing thick relatively cool chips. We cut about 4 to 5 feet of cut with a single blade.

You know the most powerful non nuclear bomb in the US arsenal is a fuel air bomb, that detonates a cloud of kerosene vapor. All these tricks to clean the tank MIGHT work, but a tank full of water leaves no space for any fuel and air to combine, so its safe even if the tank contained gasoline. If the tank is completely full the water will cool your blade too, and the tank will be heavy and much quieter too. Your ears will appreciate the difference!

One of my coworkers was an airplane mechanic. He was first on scene and found two guys knocked out cold by an aluminum airplane tank they had carefully washed out!

Gary H. Lucas


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## MedSailor (Mar 30, 2008)

GaryHLucas said:


> You know the most powerful non nuclear bomb in the US arsenal is a fuel air bomb, that detonates a cloud of kerosene vapor. All these tricks to clean the tank MIGHT work, but a tank full of water leaves no space for any fuel and air to combine, so its safe even if the tank contained gasoline. If the tank is completely full the water will cool your blade too, and the tank will be heavy and much quieter too. Your ears will appreciate the difference!
> 
> Gary H. Lucas


Gary, this is just fear-mongering and bad information. Lets look at the facts:

Fuel air bombs don't use kerosene, they use ethylene oxide. Even if they did use kerosene, we're talking about diesel here. Fuel air bombs rely on a complex system to create a POWDER of explosive in the air at a specific concentration. From the Fedaration of American Scientists: CBU-72 / BLU-73/B Fuel/Air Explosive (FAE) - Dumb Bombs

#2 diesel fuel is not even considered flammable on it's MSDS, it is combustable. http://www.marathonpetroleum.com/brand//content/documents/mpc/msds/0281MAR019.pdf

It's flash point is 130-190F. (reference the link above) For those that need a brush up on what "flash point means" read below.

"Flash point This is the minimum temperature at which the vapor above a liquid fuel will first support a combustion transient or "flash". The flash point is measured by a standardized test using a small quantity (50 cc) of liquid that is slowly heated (about 1 deg C/minute) until a flash is observed when an open flame is dipped down into a covered vapor space. The legal description of flammable is used for all liquids with a flash point less than 100 deg C, and the term combustible is used for liquids with a flash point in excess of 100 deg C." EDL

Now to apply it to the case at hand. Diesel will support a transient flash if a flame is applied to diesel that is heated to 150F. (I've done this trying to re-light a stove). Diesel will not explode, flash, or even burn if a spark is applied to a tank that has been drained and has water sloshing around in it. What about every boat's bilge? It is essentially a very weak diesel solution ( <1% by volume much as a tank would be). Nobody is taking extra precautions "just in case" there.

As long as you don't use an oxy-acetylene torch to cut into a full tank, you're really not at risk. Again, the MSDS lists diesel as combustable, (#2 on a scale of 0-4) it's not even called flammable.

Medsailor


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## chuck711 (Dec 25, 2002)

*The 3 best times of a Boat Owners Life*

My Company, Power and Sail Boat Repair does a lot of Fuel Tank Issues in
Eastern North Carolina.

I've found after cutting an access area, wiping out the tank and putting back a suitable cover plate you'll find it leaking shortly afterwards due to the fact
you've cleaned out the crud from the bottom that was keeping it from corroding thru ( or you accelerated the process ).

The 3 Best times of a Boat Owners Life:

You buy a Boat

You sell a Boat

You have a Brand New Fuel Tank that doesn't Leak 
and has nothing in it but Fresh Fuel !


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## MikeinLA (Jul 25, 2006)

FWIW, I recently had my Catalina 36's fuel tank cleaned out in place. The guy drained the fuel, removed the sender unit to provide ventilation, cut two large square access holes (one on each side of the baffle), drilled and installed a 1/4" plug/cap so I can check fuel with a dipstick, hand cleaned and polished the inside of the tank, fastened two SS plates over the access holes, added 5 gals fuel...DONE. Took about 5 hours with a helper. He's been doing this daily since 1979, he's still alive. 

Mike


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## GaryHLucas (Mar 24, 2008)

MedSailor said:


> Gary, this is just fear-mongering and bad information. Lets look at the facts:
> 
> Fuel air bombs don't use kerosene, they use ethylene oxide. Even if they did use kerosene, we're talking about diesel here. Fuel air bombs rely on a complex system to create a POWDER of explosive in the air at a specific concentration. From the Fedaration of American Scientists: CBU-72 / BLU-73/B Fuel/Air Explosive (FAE) - Dumb Bombs
> 
> ...


Hey, you are right and I am wrong. I'm not sure where I got the idea they were using fuel oil.

Gary H. Lucas


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