ALMOST BLEW UP MY GAS TANK...READ THIS!

[ttmott]

If your run some simple numbers you will find that the energy in a 12 volt battery system (I used 300 amp hours) can no way heat up such a large aluminum tank let alone input enough energy to boil the fuel (consider the enthalpy of vaporization for gasoline; it's huge even for one gallon). The fuel is electrically non conductive so all heating would be through the tank being the heating element. There is simply not enough energy in the batteries to transfer the calories needed to heat the tank as a conductor; the battery will either fuse the tab connecting the shorting system to the tank or melt the battery cables of simply fail the battery. Are your batteries dead, wiring smoked, fuses and breakers blown/tripped? The tank is not the highest component of electrical resistance. So from an electrical aspect this is simply unreasonable.
"aluminum sludge" - there is no such element; how do you know what that liquid is? It looks as if you have a water problem in the fuel.....
Fuel tank is a "diode" - you need to find another "master electrician". Aluminum has no such properties to limit current flow to any one direction. By the way electrical current is always flowing through any metallic structure and it always flows from a higher potential to a lower potential; this is why the metallic structures are bonded.
Liquid gasoline is non-flammable.
Vapor gasoline is non-flammable.
Three properties are needed for fire - fuel, oxidizer, and heat. The flammability range of gasoline in air is 1.4% to 7.6%; outside of that range it will not burn.
So, for the sake of imagination, let's say there was a stochiometric mixture of fuel and air in the fuel tank. Something ignited that mixture and caused a "hot jet of gas" to discharge from the fuel tank vent fitting. There would be an instantaneous deflagration until the oxygen was consumed (below 1.4%) then it would extinguish. The pressure wave from the deflagration would permanently yield (bulge) the tank, extrude the sender gasket, and most likely blow off the fuel fill hose and possible the fill cap. There seems to be none of these effects / artifacts.

 

[Pirate Lady]

This is WAY too technical for me. Going to the bar for a few beers. I need mine replaced as stated near beginning but I think I will just let a pro do it.

 

[Thornton69]

The fuel tank acting as a diode doesn't fly and really shouldn't have taken up much time for those that know better. It is well known that current always flows from the higher potential to lower. I would have to assume someone got confused in a conversion with someone else which included suppression (flashback) diodes and what there function is. They are commonly used in the DC systems I work with across loads to protect the contacts in switches, not in fuel gauge circuits. As for the rest of this post, we will likely never know the whole story.

 

[FredM]

I want to thank everyone who has offered POSITIVE input to help me get to the bottom of this gas tank sending unit issue.

I have realized that I am at a serious disadvantage here. I have a 1990 250DA. Almost all those who have responded have much newer boats. ALSO, those who have responded who have a gasoline sending unit with a FACTORY GROUND ATTACHED to the ground connection of the sending unit, DON’T HAVE ANY EXPERIENCE with the issue. BECAUSE my 1990 DOES NOT have a ground wire!

I have an obvious question to ask those who don’t have any experience with the issue yet offer their 2 bits………

Those of you that troubleshoot for a living as I do, know that that you eliminate one variable at a time to determine the cause. In this issue, there are many variables:

1) The addition of a ground wire from the ground terminal of the sending unit to the ground terminal located on the gas tank, per the installation instructions of the sending unit.

2) The new sending unit possibly being damaged causing a spark inside the tank.

3) The float stem of the sending unit possibly touching metal inside the tank.

I have now received one response of a gentleman successfully using the same replacement sending unit. I agree with that gentleman that the unit appears not to be well made, but it does the job. The original unit doesn’t appear to be of higher quality yet worked for 30 years. As for each one, once they’re in, they’re in.

I reached out to SR Corp tech support and to Veethree, maker of the sending unit. Veethree ruled out the possibility of the sending unit on its own creating a spark. Of course they would.

Sea Ray tech support did NOT rule out the following:

1) The size of the tank POSSIBLY allowed the voltage to disperse to a point where it did not present a high amperage, therefore not burning the sending wire in two.

2) The jumper I installed COULD have made the sending unit part of the main ground allowing 12v to travel down the sending unit.

Chastise me all you want but disregard the use of the words “diode” and “backward voltage”. I am simply trying to brainstorm ideas. After all, I am the one that nearly got blown up.

I simply asked if this had happened to anyone. I had no idea my integrity would be questioned, or my intelligence. I am very thick skinned and wear egg well. But there is no way in hell that I will know what went on inside the tank. I asked for input. I got it. It’s good stuff from many. So be it.

The only way I can prove the theories is to retest with a jumper wire. That I am NOT going to do. That would be ludicrous.

I have ruled out that the tank heated up and boiled the gas away.

So here in summation, is the best I can do for an explanation of the incident. I had piloted the boat the day before this incident without a problem.

Per the instruction manual of the Sierra sending unit, I added a ground wire from the sending unit to the ground terminal on the gas tank. IN THEORY, POSSIBLY, if the jumper made the sending unit part of the ground terminal, voltage traveled down the sending unit and heated or ignited the gasoline, but by the Grace of God the tank did not explode.

I cut off all power, battery switch to 0, and disconnected shore power, and left the boat for 24 hours. The tank was scarred inside and I flushed by hand pump 20 gal of gasoline to remove about a pint of aluminum colored sludge (oxidation) to clean the tank. I removed the jumper and the damaged sending unit.

I am starting the installation over with no jumper and cutting and bending the float stem of the sending unit to the exact length and size of the original 30 year old sending unit.

I will create a new thread with the notes regarding installation and to NOT use a separate ground wire if there is not one.

I don’t care what some may say or think of me. I don’t care if my story is called BS.

Have fun with it. Use it as fun conversation about what this “idiot said happen to him”. But keep this in your brain. Don’t let anyone add a ground to a gas sending unit they are replacing.

Done.

 

[Arminius]

A high power audio amp like the good one I found installed in my used boat has a circuit allowing it to maintain the volume even as the ship's batteries die. It does this by increasing amps being drawn on the input side while maintaining output wattage to the speakers. These amps will choke out your batteries when they are down. Just my Ohm's law anecdote for the morning.

 

[PlayDate]

I want to thank everyone who has offered POSITIVE input to help me get to the bottom of this gas tank sending unit issue.

I have realized that I am at a serious disadvantage here. I have a 1990 250DA. Almost all those who have responded have much newer boats. ALSO, those who have responded who have a gasoline sending unit with a FACTORY GROUND ATTACHED to the ground connection of the sending unit, DON’T HAVE ANY EXPERIENCE with the issue. BECAUSE my 1990 DOES NOT have a ground wire!

I have an obvious question to ask those who don’t have any experience with the issue yet offer their 2 bits………

Those of you that troubleshoot for a living as I do, know that that you eliminate one variable at a time to determine the cause. In this issue, there are many variables:

1) The addition of a ground wire from the ground terminal of the sending unit to the ground terminal located on the gas tank, per the installation instructions of the sending unit.

2) The new sending unit possibly being damaged causing a spark inside the tank.

3) The float stem of the sending unit possibly touching metal inside the tank.

I have now received one response of a gentleman successfully using the same replacement sending unit. I agree with that gentleman that the unit appears not to be well made, but it does the job. The original unit doesn’t appear to be of higher quality yet worked for 30 years. As for each one, once they’re in, they’re in.

I reached out to SR Corp tech support and to Veethree, maker of the sending unit. Veethree ruled out the possibility of the sending unit on its own creating a spark. Of course they would.

Sea Ray tech support did NOT rule out the following:

1) The size of the tank POSSIBLY allowed the voltage to disperse to a point where it did not present a high amperage, therefore not burning the sending wire in two.

2) The jumper I installed COULD have made the sending unit part of the main ground allowing 12v to travel down the sending unit.

Chastise me all you want but disregard the use of the words “diode” and “backward voltage”. I am simply trying to brainstorm ideas. After all, I am the one that nearly got blown up.

I simply asked if this had happened to anyone. I had no idea my integrity would be questioned, or my intelligence. I am very thick skinned and wear egg well. But there is no way in hell that I will know what went on inside the tank. I asked for input. I got it. It’s good stuff from many. So be it.

The only way I can prove the theories is to retest with a jumper wire. That I am NOT going to do. That would be ludicrous.

I have ruled out that the tank heated up and boiled the gas away.

So here in summation, is the best I can do for an explanation of the incident. I had piloted the boat the day before this incident without a problem.

Per the instruction manual of the Sierra sending unit, I added a ground wire from the sending unit to the ground terminal on the gas tank. IN THEORY, POSSIBLY, if the jumper made the sending unit part of the ground terminal, voltage traveled down the sending unit and heated or ignited the gasoline, but by the Grace of God the tank did not explode.

I cut off all power, battery switch to 0, and disconnected shore power, and left the boat for 24 hours. The tank was scarred inside and I flushed by hand pump 20 gal of gasoline to remove about a pint of aluminum colored sludge (oxidation) to clean the tank. I removed the jumper and the damaged sending unit.

I am starting the installation over with no jumper and cutting and bending the float stem of the sending unit to the exact length and size of the original 30 year old sending unit.

I will create a new thread with the notes regarding installation and to NOT use a separate ground wire if there is not one.

I don’t care what some may say or think of me. I don’t care if my story is called BS.

Have fun with it. Use it as fun conversation about what this “idiot said happen to him”. But keep this in your brain. Don’t let anyone add a ground to a gas sending unit they are replacing.

Done.

Fred,

Generally speaking the folks at CSR are probably the most knowledgeable bunch you will find. If you had posted this at: the hull truth.......the comments would have been far worse.


I see that you believe now the gas did not boil off. For it to be gone do you believe it then flashed and continued to burn until it was all gone? For gas to burn inside a stored unit with no oxygen to feed it other than the vent seems as unlikely as a grounding wire. The internet has 1,000s of stories yet not one that I can find where the fuel flashed and didn't blow the tank.

Generally speaking when gas is ignited in a partially filled tank it explodes. It explodes because gasoline is present in the atmosphere inside the tank and any spark will set it off.

We still don't know what happened or what the ignition source was which should be of great concern to you. Hopefully you fair better with your next try. Just remember 1 gallon of gas in a confined space is equal to 4 sticks of dynamite.

 

[JimG]

I want to thank everyone who has offered POSITIVE input to help me get to the bottom of this gas tank sending unit issue.

I don’t care what some may say or think of me. I don’t care if my story is called BS.

Have fun with it. Use it as fun conversation about what this “idiot said happen to him”. But keep this in your brain. Don’t let anyone add a ground to a gas sending unit they are replacing.

There are some great members here that know allot about boats (and multiple other topics) and they really want to help. The problem is, you go off on these tangents and make assumptions, we dispute them but you don't seem to want to listen.

All that said, here's one possibility... your tank is somehow shorted to +12VDC. Simple test with a voltmeter... measure from the negative post on the battery to the aluminum tank. If you get 12 volts, look for a positive wire pinched somewhere around the tank.

 

[FredM]

There are some great members here that know allot about boats (and multiple other topics) and they really want to help. The problem is, you go off on these tangents and make assumptions, we dispute them but you don't seem to want to listen.

All that said, here's one possibility... your tank is somehow shorted to +12VDC. Simple test with a voltmeter... measure from the negative post on the battery to the aluminum tank. If you get 12 volts, look for a positive wire pinched somewhere around the tank.

Thank You......Like I said... I have a thick skin. I have deep respect f for thoseor most comments. But I had to get in a dig for those folks that were off the charts.
Will test the tank.

Fred,

Generally speaking the folks at CSR are probably the most knowledgeable bunch you will find. If you had posted this at: the hull truth.......the comments would have been far worse.


I see that you believe now the gas did not boil off. For it to be gone do you believe it then flashed and continued to burn until it was all gone? For gas to burn inside a stored unit with no oxygen to feed it other than the vent seems as unlikely as a grounding wire. The internet has 1,000s of stories yet not one that I can find where the fuel flashed and didn't blow the tank.

Generally speaking when gas is ignited in a partially filled tank it explodes. It explodes because gasoline is present in the atmosphere inside the tank and any spark will set it off.

We still don't know what happened or what the ignition source was which should be of great concern to you. Hopefully you fair better with your next try. Just remember 1 gallon of gas in a confined space is equal to 4 sticks of dynamite.

 

[FredM]

Fred,

Generally speaking the folks at CSR are probably the most knowledgeable bunch you will find. If you had posted this at: the hull truth.......the comments would have been far worse.


I see that you believe now the gas did not boil off. For it to be gone do you believe it then flashed and continued to burn until it was all gone? For gas to burn inside a stored unit with no oxygen to feed it other than the vent seems as unlikely as a grounding wire. The internet has 1,000s of stories yet not one that I can find where the fuel flashed and didn't blow the tank.

Generally speaking when gas is ignited in a partially filled tank it explodes. It explodes because gasoline is present in the atmosphere inside the tank and any spark will set it off.

We still don't know what happened or what the ignition source was which should be of great concern to you. Hopefully you fair better with your next try. Just remember 1 gallon of gas in a confined space is equal to 4 sticks of dynamite.

Thank you. The knowledgeable comments steered me away from the boil off idea.

 

[bracketracer]

... If you had posted this at: the hull truth.......

This would have gone from zero to epic in 15 minutes at THT

 

[ttmott]

I edited out my derogatoryness; Hopefully it is more helpful and appetizing. Sorry about that....
As a qualifier my company develops propellant storage and transfer systems for space launch systems; we support most of the launch providers in the US as well as the government. One thing we do understand is flammable materials and environments they exist in. Just here trying to input some logic.

 

[FredM]

If your run some simple numbers you will find that the energy in a 12 volt battery system (I used 300 amp hours) can no way heat up such a large aluminum tank let alone input enough energy to boil the fuel (consider the enthalpy of vaporization for gasoline; it's huge even for one gallon). The fuel is electrically non conductive so all heating would be through the tank being the heating element. There is simply not enough energy in the batteries to transfer the calories needed to heat the tank as a conductor; the battery will either fuse the tab connecting the shorting system to the tank or melt the battery cables of simply fail the battery. Are your batteries dead, wiring smoked, fuses and breakers blown/tripped? The tank is not the highest component of electrical resistance. So from an electrical aspect this is simply unreasonable.
"aluminum sludge" - there is no such element; how do you know what that liquid is? It looks as if you have a water problem in the fuel.....
Fuel tank is a "diode" - you need to find another "master electrician". Aluminum has no such properties to limit current flow to any one direction. By the way electrical current is always flowing through any metallic structure and it always flows from a higher potential to a lower potential; this is why the metallic structures are bonded.
Liquid gasoline is non-flammable.
Vapor gasoline is non-flammable.
Three properties are needed for fire - fuel, oxidizer, and heat. The flammability range of gasoline in air is 1.4% to 7.6%; outside of that range it will not burn.
So, for the sake of imagination, let's say there was a stochiometric mixture of fuel and air in the fuel tank. Something ignited that mixture and caused a "hot jet of gas" to discharge from the fuel tank vent fitting. There would be an instantaneous deflagration until the oxygen was consumed (below 1.4%) then it would extinguish. The pressure wave from the deflagration would permanently yield (bulge) the tank, extrude the sender gasket, and most likely blow off the fuel fill hose and possible the fill cap. There seems to be none of these effects / artifacts.

In 1976 I began a water based chemical company in Greenville, Sc. One of our basic products was a high alkaline floor cleaner and oven cleaner. Basically lye, detergent, and a coupler. Restaurants were our niche. Our basic demo was to take a dirty aluminum potato pan, pour some oven cleaner on it, roll it back and forth, and the burnt grease would lift off the pan. The high ph of the cleaner reacted with the aluminum. The grease came off because the cleaner took off a layer of the aluminum. It would form a "sludge" in the potato pan.
When I removed some of the "sludge" from the tank, some dropped on my hand and burnt me even though it had been 24 hours since the incident. I googled the ph of hot gasoline vs cold gasoline. I learned gasoline doesn't have a ph. I have a ph meter I haven't used in years. Thought about cranking it up and seeing what the ph of the "sludge" is.
I totally respect what you have written. But the bottom line is ...this happened. And thanks to you and some other good posts, I am being extra cautious. I just don't know what else to say. I'm sure I could have been more definitive if I had more time while the incident happened, but I was getting the hell off the boat. Reread the gasoline burner explanation from the the gentleman in BC. Do you agree with that?

 

[Woody]

But keep this in your brain. Don’t let anyone add a ground to a gas sending unit they are replacing.

You don't know what happened but your assigning the blame to that ground wire as if you do.

 

[FredM]

Fred,

Generally speaking the folks at CSR are probably the most knowledgeable bunch you will find. If you had posted this at: the hull truth.......the comments would have been far worse.


I see that you believe now the gas did not boil off. For it to be gone do you believe it then flashed and continued to burn until it was all gone? For gas to burn inside a stored unit with no oxygen to feed it other than the vent seems as unlikely as a grounding wire. The internet has 1,000s of stories yet not one that I can find where the fuel flashed and didn't blow the tank.

Generally speaking when gas is ignited in a partially filled tank it explodes. It explodes because gasoline is present in the atmosphere inside the tank and any spark will set it off.

We still don't know what happened or what the ignition source was which should be of great concern to you. Hopefully you fair better with your next try. Just remember 1 gallon of gas in a confined space is equal to 4 sticks of dynamite.

I very appreciative and respectful of the folks that gave good information. As you know, there is a group that has decided my story is invalid and has made it their mission to shoot it full of holes. Those replies I will not dignify with a response.
I can't be more definitive what happened. If I stuck around, maybe I would have more input. But I was trying to get the hell off the boat.
I am cautiously beginning the process. Just finished sizing the new sending unit today.

 

[Arminius]

In a structure subject to the electrical code, all electrical appliances have both a white return path completing the circuit and a green ground or "bonding" lead linking them to the ground bar in the service panel which is attached to the ground from the transformer, a water pipe and a copper rod driven 10' or more into the earth outside the structure. Electricity flows through the black wire through the energized appliance and returns through the white wire (and the appliance if intentionally or inadvertently attached) also energizing it unless the charge is diverted into the bonding network.

Tanks of flammable liquids must be bonded because of the additional hazard of ignition by discharge of static electricity.
https://www.greatamericaninsuranceg...uid-containers-1-16-web.pdf?sfvrsn=667f77b1_6

West Marine writes:
"On a boat, things are considerably more complicated. In addition to the AC ground, we need a DC ground or return line, a lightning ground, and a RF ground plane for the radio systems. Our first thought might be to simply make the ground connection to a metal thru-hull, propeller shaft or other underwater metal. This underwater metal will be grounded by connection to the seawater will serve as our water pipe. Unfortunately, a connection between any of these systems and underwater metal can, and probably will, give rise to serious electrolytic corrosion problems. This article will discuss the particular requirements of each system, resolve the contradictions between the systems and present a consistent and correct solution for a complete, integrated, marine grounding system.

Figure 1. The boat's electrical system should be connected to seawater at one point only, via the engine negative terminal or its bus.

DC Ground
Every light or appliance should be wired with its own DC return wire. Never use the mast, engine, or other metal object as part of the return circuit. The DC load returns of all branch circuits should be tied to the negative bus of the DC distribution panel. In turn, the negative bus of the DC distribution panel should be connected to the engine negative terminal or its bus. The battery negative is also connected to the engine negative terminal or its bus. The key factor here is that the yacht's electrical system is connected to seawater ground at one point only, via the engine negative terminal or its bus."
https://www.westmarine.com/WestAdvi...al system should,negative terminal or its bus.

 

[blaster]

This would have gone from zero to epic in 15 minutes at THT

It would have been deleted with haste!

 

[Pirate Lady]

Sitting back and observing I see a lot of very knowledgeable folks offering help. I also notice they weren’t there. My son, professional mechanic, has a credo, won’t diagnose problems over the phone. Fred, I would strongly suggest you hire a pro to fix this. Just pay the man and be done. 116 posts and nobody can know what really was the cause. HIRE A PRO! Or the next thread may be “Remember that guy Fred with the gas tank? He got toasted”.

 

[Pirate Lady]

PS. And before y’all knock my dik in dirt about maintaining our boats is half the fun, this ain’t that, this is entering dangerous territory best fit for a pro.

 

[PlayDate]

Sitting back and observing I see a lot of very knowledgeable folks offering help. I also notice they weren’t there. My son, professional mechanic, has a credo, won’t diagnose problems over the phone. Fred, I would strongly suggest you hire a pro to fix this. Just pay the man and be done. 116 posts and nobody can know what really was the cause. HIRE A PRO! Or the next thread may be “Remember that guy Fred with the gas tank? He got toasted”.

I believe that CSR exists because it helps people. The advantage of owning a Sea Ray boat is that the long-term members of CSR have probably seen 99% of the problems the boats can have. Some of us have businesses that have been working on these boats for the last 20 years and generally speaking we don't have to physically see the boat to help the owner diagnose the issue. Once diagnosed.....the solution can be addressed by the owner or if they aren't comfortable with it they can hire someone.

I know a few great mechanics and a lot of mediocre ones. The difference is the working knowledge, experience and having a wide range of diagnostic tools.

All Fred has heard is that most of us don't agree with his conclusion. He has tried to make arguments to support it but they just don't pass the test as an ignition source. Something happened to be sure but some of us have replaced dozens of fuel level sensors without any issues.....so understanding what happened still remains a mystery.

 

[Pirate Lady]

Some of us have businesses that have been working on these boats for the last 20 years and generally speaking we don't have to physically see the boat to help the owner diagnose the issue.

Hey Fred, listen to the internet mechanics.. go for it, i sure they 20 years of experience fixing SR problems on the 'net. Good luck.