Most welders will not weld any tank that has ever held gasoline. Could be a
big clue here!
"terry" wrote in message
...
washing and letting it vent will probably not work.

BE SURE TO INFORM SERVICE PERSONAL OF THE FORMER PRESENCE OF GASOLINE.
Otherwise you may face a costly lawsuit for wrongful death.

Only way to weld it is to leave it filled with water which will displace
any
air needed to create an explosion.

It just takes care. If you can, you wash out the tank. Regardless, you
purge it with air for many hours to guarantee it is dry. You fill the tank
with inert gas such as argon, then weld. Same process if you weld tanks of
unknown condition or which had unknown contents. Welders do it all the
time.

Brian


--
http://www.advantagecomposites.com/tongass -- My 22' Tolman Skiff project
http://www.advantagecomposites.com/catalog -- Discounted System Three
Resins products



"Dave W" wrote in message
...
Most welders will not weld any tank that has ever held gasoline. Could be
a
big clue here!
"terry" wrote in message
...
washing and letting it vent will probably not work.

BE SURE TO INFORM SERVICE PERSONAL OF THE FORMER PRESENCE OF GASOLINE.
Otherwise you may face a costly lawsuit for wrongful death.

Only way to weld it is to leave it filled with water which will displace
any
air needed to create an explosion.

"Brian D" wrote in message
news:9Qmfc.39212$wP1.153766@attbi_s54...
It just takes care. If you can, you wash out the tank. Regardless, you
purge it with air for many hours to guarantee it is dry. You fill the
tank
with inert gas such as argon, then weld. Same process if you weld tanks
of
unknown condition or which had unknown contents. Welders do it all the
time.

Once the tank is inerted, I would still be concerned about the residual gas
fumes in the bilges. An area where you can properly perge or inert.

If it doubt, or you can't test it before welding, then the tank should be
removed from the boat.

Steve
s/v Good Intentions

Steve wrote:
"Brian D" wrote in message
news:9Qmfc.39212$wP1.153766@attbi_s54...

It just takes care. If you can, you wash out the tank. Regardless, you
purge it with air for many hours to guarantee it is dry. You fill the

tank

with inert gas such as argon, then weld. Same process if you weld tanks

of

unknown condition or which had unknown contents. Welders do it all the
time.


Once the tank is inerted, I would still be concerned about the residual gas
fumes in the bilges. An area where you can properly perge or inert.

If it doubt, or you can't test it before welding, then the tank should be
removed from the boat.

Steve
s/v Good Intentions


why not inert those areas as well?

--
A significant part of courage is realizing that only you need to know
how terrified you are..

You're right. I was assuming the tank is out of the boat and in a shop.

--
http://www.advantagecomposites.com/tongass -- My 22' Tolman Skiff project
http://www.advantagecomposites.com/catalog -- Discounted System Three
Resins products


..
"Steve" wrote in message
...

"Brian D" wrote in message
news:9Qmfc.39212$wP1.153766@attbi_s54...
It just takes care. If you can, you wash out the tank. Regardless, you
purge it with air for many hours to guarantee it is dry. You fill the
tank
with inert gas such as argon, then weld. Same process if you weld tanks
of
unknown condition or which had unknown contents. Welders do it all the
time.

Once the tank is inerted, I would still be concerned about the residual
gas
fumes in the bilges. An area where you can properly perge or inert.

If it doubt, or you can't test it before welding, then the tank should be
removed from the boat.

Steve
s/v Good Intentions

sorry to reply so late but, do you not have a vent for the bilge? run
it for a while and then if yon are still worried get some canned
nitrogen and flood the bilge with the N2.

Rick

habbi wrote:
I have a 31 aluminum work boat with an under deck fuel tank which must be
leaking. The aluminum deck is welded in place. The tank is a 100 gallon
aluminum tank. The boat is only 1 year old. I removed the drain plug from
the back of the boat and about 2 gaollons of gas came out, this leads me to
believe that the crack must be on the top of the tank because the tank is
almost full and this is the only time I ever opened the drain plug. Before I
do any work I want to make sure I don't have an explosion. If I fill the
bilge area with dishsoap and water and then drain it will this remove all
dangerous vapours? Any other ideas?

We ended up steaming the bilge through several holes I drilled in the deck
and then had a "sniffer" check to make sure it was safe. We then cut out a
5' X 5' section of the deck and pressurized the tank to 3 psi and no bubbles
anywhere then up to 6 psi and bubbles started forming at the sending unit
only. Oh did I feel like an idiot, the tank and all connections were
perfectly air tight. I still can't understand how 2 gallon of gasoline came
out through the tiny leak at the sending unit. But then again every night we
topped of the tank and the head pressure from the fuel in the fill pipe must
have been enough that over 1 full year 2 gallons came out. We welded the
deck back down and I wasted $500.00. I guess it wasn't a complete waste
since we got all gasoline and vapour out of the bilge. Thanks to all.
"Rick" wrote in message
...
sorry to reply so late but, do you not have a vent for the bilge? run
it for a while and then if yon are still worried get some canned
nitrogen and flood the bilge with the N2.

Rick

habbi wrote:
I have a 31 aluminum work boat with an under deck fuel tank which must
be
leaking. The aluminum deck is welded in place. The tank is a 100 gallon
aluminum tank. The boat is only 1 year old. I removed the drain plug
from
the back of the boat and about 2 gaollons of gas came out, this leads me
to
believe that the crack must be on the top of the tank because the tank
is
almost full and this is the only time I ever opened the drain plug.
Before I
do any work I want to make sure I don't have an explosion. If I fill the
bilge area with dishsoap and water and then drain it will this remove
all
dangerous vapours? Any other ideas?

habbi says:

Oh did I feel like an idiot,

and few others here will admit to that, ever. Akthough we all are at some
point (someone back me up here - I'd hate to think it was just habbi and
myself)

We welded the
deck back down and I wasted $500.00

No, you spent $500 to ensure that you wouldn't blow up and/or burn up. Sounds
like a good deal to me. ;-)

Steve

habbi wrote:

We ended up steaming the bilge through several holes I drilled in the deck
and then had a "sniffer" check to make sure it was safe. We then cut out a
5' X 5' section of the deck and pressurized the tank to 3 psi and no bubbles
anywhere then up to 6 psi and bubbles started forming at the sending unit
only. Oh did I feel like an idiot, the tank and all connections were
perfectly air tight. I still can't understand how 2 gallon of gasoline came
out through the tiny leak at the sending unit. But then again every night we
topped of the tank and the head pressure from the fuel in the fill pipe must
have been enough that over 1 full year 2 gallons came out. We welded the
deck back down and I wasted $500.00. I guess it wasn't a complete waste
since we got all gasoline and vapour out of the bilge. Thanks to all.


You were careful. That is not being an idiot

and you are only an idiot if you fail to learn from your mistakes.

--
A significant part of courage is realizing that only you need to know
how terrified you are..

Guys,
Let's all go backto the original problem.......the boat is 1 year old. What
about the warranty?



"habbi" wrote in message
...
I have a 31 aluminum work boat with an under deck fuel tank which must be
leaking. The aluminum deck is welded in place. The tank is a 100 gallon
aluminum tank. The boat is only 1 year old. I removed the drain plug from
the back of the boat and about 2 gaollons of gas came out, this leads me
to
believe that the crack must be on the top of the tank because the tank is
almost full and this is the only time I ever opened the drain plug. Before
I
do any work I want to make sure I don't have an explosion. If I fill the
bilge area with dishsoap and water and then drain it will this remove all
dangerous vapours? Any other ideas?