Diesel Fuel Leak - A Fire Hazard ?

[wsmurdoch]

This spring in the Bahamas I had a diesel fuel leak from the engine. It would completely soak the four paper towels I put under the leak in two hours of engine run time. It took me a couple of weeks to make temporary repairs that eventually stopped the leak. During that time I kept a folded wad of paper towels below the leak to catch the drips.

I know that it is difficult if not impossible to ignite a pool of diesel fuel, and I know that it is easy to ignite a wick soaked with diesel fuel. I also know that the paper towel confined the leaking fuel to a smaller area than letting it spill over the front of the hot engine, flow back across the bottom of the oil pan, and accumulate in the relatively open drip tray under the engine. The paper towel reduced the smell of fuel in the engine compartment, so it reduced the amount of fuel evaporated into the air.

From a fire safety standpoint, was I better soaking up the leaking fuel on paper towels, or should I have periodically mopped up the spilled fuel from the engine drip tray?

As background, the leak was from the joint between the high pressure fuel pump body and the aftmost 'delivery valve holder' of my Yanmar 3HM35F. I eventually (almost) stopped the leak by smearing JB Weld over the well cleaned joint, and we brought the boat back to North Carolina.

Bill

[S/V Illusion]

If it was me, I would have kept some water in the drip pan as a heat sink to ensure the diesel didn’t reach its flash point. Adding paper serves no purpose other than to concentrate the fuel and vapor to a limited area and certainly does nothing to “limit the amount of evaporation”.

[ttex]

Put a small container of kitty litter down there to soak it up as a better alternative to the towels.

My diesel drips fuel when on and this is what I am doing for the time being.

[tkeithlu]

The flash point, a confusing term that does not mean that it flashes, but that the diesel produced inflammable fumes, is about 150 F. The flashpoint of gasoline is about -40 F. or C. That difference is why you are allowed (ABYC, USCG) to tap diesel from the bottom of the tank by gravity but only by suction from the top of the tank for gasoline, aand I don't worry about rare sparks from non-certified alternators. As long as you keep it below 150 F. It will not produce those fumes. In a (in retrospect) spectacular goof, I released about 80 gallons of disesel into my engine room once. No problem. Anchored, pumped it through a filter and back into the tank, and went on.

The risk comes if you have a fire in the engine compartment for other reasons, and it heats the diesel above the flashpoint. Ergo, no plastic fuel lines. You don't have to insulate diesel from sparks, but you do from heat.

[GRIT]

In direct answer to the question asked. As a potential for fire, you would have been slightly safer to let it leak, without the "wick", and mop it up as you go.

I think, without a source of flame, the difference is minimal.

Woulda, coulda, shoulda...

Cheers.
Paul.

[RaymondR]

Sounds fairly low risk. However leaks in high pressure diesel fuel lines are very hazardous if they expunge a fine mist of diesel which could be exposed to an ignition source.

[thinwater]

Perhaps the drip tray, plus water and a healthy dose of Dawn Ultra. The diesel emulsifies into the water, becoming non-combustible. This is, to some extent, how firefighting foams work.


http://www.foamtechnology.us/Firefighters.pdf


Kitty litter sounds good too. Even if it burned, which is unlikely due to the mass of the clay, it would be simple to smother.

[Lepke]

I ran a variety of diesel military boats in Vietnam. A number took hits that caused diesel leaks. One filled the bilge with diesel, an a couple had brief flash fires that extinguished themselves. The bilge of diesel was like that for a couple hours before we could deal with it. It takes a lot to start a pool of diesel, even in a tropical climate and with engines running flat out. But in military vessel engine rooms, anything hot is well insulated.

I don't mean to play down the danger of fuel fires. Leaks need to be attended right away, but it's not like gas or propane.

[Compass790]

Found that loctite 518 flange sealant very good for leaks like you had /have . Use it on oil or water lines too. Just have to run motor immediately after installing to make sure that any squeezed out of joint gets flushed thru. It's anaerobic so only hardens in the absence of oxygen, i.e. in the joint. Smear it on both sides of copper washers if you dont have a new one.
I dont have any association with loctite btw

[roverhi]

Managed to power for over an hour with a leak in the high pressure injection pump spewing atomized diesel all over the engine compartment and condensing into a pool of diesel in the engine pan. Still here to talk about it.

When we hit the doldrums on the way to the Marquesas tried to tough it out and get through old style totally under sail. Unfortunately there were 10' swells rolling up from a storm in the Southern Ocean, air temp was close to a 100 matched by the humidity and we were floating in bath water. Tried jumping in the ocean but was little relief in the super heated ocean and the salt water wouldn't evaporate off afterwards leaving us feeling worse for the adventure.

After a day of going nowhere, the boat rolling like a drunken pig in the swells and sweating our hearts out felt the need for the engine. Unfortunately decided to reroute a fuel line that was chafing and managed to twist off the bleed screw on he high pressure pump after I did it. Another day of rolling and slatting and my wife was threatening to walk home. Went through all the storage compartments looking for a fastener that would replace the bleed screw. Miracle of miracles found a metric Phillips head machine screw that was the same size. Unfortunately it was a #3 Phillips and my tool box only had a #2 screw driver. Used that screw driver to get the screw as tight as I could and got the engine running. At idle there was a little, very little fuel weeping from the screw which wasn't enough to be of concern. Closed up the engine compartment and throttled up to normal cruise. After an hour or so began to smell diesel in the cockpit so had my wife take over the helm, no autopilot, and went below to check out the source of the smell. Discovered a cloud of atomized diesel and a pool of diesel in the engine pan when I opened up the compartment. Couldn't have created a more combustible combination if I'd intended. Apparently the pressure at the bleed screw went way up at cruise rpm and had atomized about a 1/2 gallon of diesel in an hour at cruise rpm. Fortunately nothing ignited it. Shut down the diesel and went back to sweating, rolling and slatting which got real old in a hurry.

Without a #3 Phillips screw driver there was no way I was going to get that screw tight enough to seal off the leak at the high pressures generated at cruising rpm. After slatting and rolling around for the rest of the day developed a lot of sympatico for Coleridge's sailor. Going crazy in the cockpit, suddenly remembered that, literally, as we were backing out of the slip to head south, one of our well wishers had handed me a screw driver. With everything involved in getting the boat underway had even looked at it and chucked it on one of the cushions and forgot about it. It had rolled to the back of the cushion and down in the crack at the back which is why I hadn't found it in my previous searches. Lo and behold it was a huge #3 Phillips screw driver. Armed with that and a crescent wrench to put additional torque on it got the screw tight enough so it no longer leaked even at high rpm. Voila, all was good and screw stayed in place till we got back to the States.

If you do any work on the engine, run it up through its full rpm range and let it run for a while checking to see if everything is working like it should.

[a64pilot]

I have had to turn a many a Phillips head screw into a straight slotted head screw with either a dremel or a hacksaw blade to remove it.
That and if it’s a pan head screw usually a pair of vise grips can grab the head very well, also you can use a scouring powder on the screwdriver bit and that will really help get a bite on a screw to loosen or tighten it without slipping.

But yes, Diesel will burn and burn very well indeed, especially if atomized or put on a towel or rag etc.
Even things that can’t normally burn at all if atomized will burn or explode, hydraulic fluid for example will make a horrible flash fire, and just plain dust will explode.
Please don’t motor with any leak or spilled fuel, fire scares me worse than bad weather.

[wsmurdoch]

Thank you all for the comments.

As I said, I collected the dripping fuel on paper towels as it leaked from the engine rather than letting it pool in the catch tray under the engine. After thinking about what I did, I had some doubts that I had done the best thing. After reading your notes, perhaps the best thing I could have done (aside from stopping the leak) would be to collect the liquid in a bowl placed under the drip with either kitty litter or a water/detergent mix in the bowl to reduce the flammability of the fuel.

Adding a bit more background to the story...

The leak was from the low pressure side of the high pressure fuel pump, so there was no spraying of fuel.

Shutting off the electric fuel pump and using only the engine fuel pump reduced the leakage.

I was unable to turn the 'delivery valve holder' on the top of the fuel pump to tighten the leaking connection with any of the tools I had aboard. The service manual also has a severe warning about over tightening the part beyond the initial 30 ft-lb.

The seal between the "delivery valve holder' and the high pressure pump body was made with a copper crush washer, and we ordered a replacement in Marsh Harbour on May 21 with an expected delivery time of three weeks. To my knowledge it has not yet arrived.

Talking to other cruisers in Marsh Harbour about my leaking fuel problem, I was amazed by the number who said that they had small diesel leaks in their fuel systems; ones that they could either see or smell.

Last year's leak of diesel fuel from our corroded fuel tank put fuel in our bilge. Thankfully, I did not have the additional problem of people firing at me at the time.

This year's Bahamas trip was beset with problems. Aside from this fuel leak and the usual things, the output flange fell off the transmission twice, the forward disk pack in the transmission had to be replaced, our cutless bearing went from nearly new and tight to badly worn and vibrating, I poked my hand through the mainsail where a two square foot area had chafed against the sail cover, we bought water contaminated fuel in George Town, and I had an eye blackened and a pair of glasses bent up by a wayward genoa sheet. My wife's view of it all is in her blog Irish Eyes to the Bahamas

Bill

[GeneM]

Spontaneous combustion happens around 500 deg F, so an engine running normal at 200 deg F should be OK. Keeping the space well ventilated should prevent ignition sources from going off on vapors.
I have and many others have operated with diesel leaks. They usually don't ignite.
However, be aware of the risk and keep the vapors down. I agree with often mopping. Also, oil pads are good at locking in the liquid.

[B23iL23]

For those interested in how easy (hard ) diesel it to ignite...

You can take a blow torch to it and it just sits there (for a while at least). Diesel part starts at 3:27 into the video



https://youtu.be/7nL10C7FSbE?t=207