Cutting an access hatch in a diesel tank

[jfkal]

Am thinking of cutting an access hatch (top) for my diesel tank. Any thoughts on how to do this safely without blowing the boat out of the water? I thought about loading dry ice into the tank in order to cool everything down and also displacing the air with the CO2 generated by the dry ice.
Would that be save enough?

/forums/images/graemlins/shocked.gif

 

[andyball]

Unless you're planning to use a gas cutting torch ( & even then...?) I don't see that you've any chance of igniting diesel fumes. Vapourised & mixed with air in an engine cylinder, diesel still needs very high temperatures to ignite,; rather more than jigsaw/holesaw will create.


Awaiting pasting from singed correspondents who know different.

 

[savageseadog]

A grinder would definitely ignite diesel in a tank. I'm not the most overly cautious type but I wouldn't risk sawing it without some precautions. The dry ice is an interesting idea and would probably work. Steam cleaning the tank would probably be OK as well

 

[boatmike]

That would certainly do it. However emptying out all diesel and filling the tank with water will suffice assuming you can empty it and dry out the interior thoroughly once the hatch is cut. Please do not take Andyballs advice and risk an explosion. Diesel is certainly less volatile than gasoline but the fumes can still ignite with a spark. If you fill it with water you can use a grinding wheel or cutting disc. Much quicker assuming safe environment. Best of course to remove the tank from the boat entirely first if you can. Will make cleaning it out easier too....

 

[capsco]

You need a tool called a "nibbler" you can get DIY type that fit in an electric drill wondrefull tool.

 

[tyce]

andyball what are you thinking, please dont take his advice.
boatmike is spot on empty diesel and fill with water.

 

[jfkal]

Thanks guys. Will revert back once job is done. Or else it may get reported in the news on TV :-0

 

[roger]

Sealing the hatch afterwards

I had to renew the seal on my diesel tank inspection hatch a year or two ago. I was recommended to use nitrile rubber as most rubber absorbs diesel and swells. As far as I remember I got it from Seals Direct.
As a back up I used a sealant of the type that goes in a sealant gun. I consulted Loctite who recommended one of their range which is apparently diesel proof. I used both thes product and so far have had no problems.

 

[John_Clarke]

What type of access hatch are you going to fit?

 

[Mudplugger]

Did it a few years ago, drained tank, filled with water, flushed it thru & repeated, used jig saw with metal cutting blade to make a nice large ole!, removed three buckets of black gunge from the bottom of the tank, made a new cover, drilled lots of holes, epoxied bolts in place, made a nice gasket from cork sheeting and bedded down on sealant...not too unpleasant! and no more problems!...would not have diesel tank that you cant get into!. HTH

 

[dodge]

Hi, this is a trick that I have used many times on petrol tanks so diesel will be many times safer, connect a pipe from the exhaust of a car to the tank and let it run for 5 minutes, then put a flame in the tank and it will just burn, there will not be enough oxygen to explode, then start cutting!! if you have a long break you will have to repeat the process as fumes will seep out from the metal and create enough fumes for a scary bang. TRUST me I have done this many time on petrol tanks and I am still here!! PS the first time i tried this I had a blow torch tied to a 20ft pole to ignite the tank as I was very sceptical of this tip /forums/images/graemlins/smile.gif

 

[BrendanS]

Nice one. Not often I see a genuinely new tip on here

 

[cliff]

[ QUOTE ]
Nice one. Not often I see a genuinely new tip on here

[/ QUOTE ]Brendan, that is an OLD trick usually performed with the exhaust from a diesel engine rather than the exhaust from a petrol engine. /forums/images/graemlins/grin.gif
--------------------

"Artificial intelligence is no match for natural stupidity"

 

[Avocet]

A variation on it is purging the tank with CO2 from a "pub" gas cylinder for 5 minutes or so.

 

[tugboat]

This is a variation of the system used on seagoing tankers for many years. The exhaust from the boilers is washed in a scrubbing tower them injected into the tanks on top of the oil. It is called 'Inert Gas' and creates a non-flammable atmosphere in the ullage space above the cargo. When the cargo is discharged from a tank, more inert gas is pumped in to fill the space created. When a tank is filled, the inert gas is vented to atmosphere from a mast up for'd. Looking back, and remembering how we loaded full cargoes of petrol (we called it Motor Spirit) with the gas venting off at deck level, I'm amazed we survived without it! I remember being gassed on Naptha once when topping off tanks. Aaahh, happy days! /forums/images/graemlins/crazy.gif

 

[boatmike]

Agreed. After over 30 years in ship and boatbuilding I have done it myself many times. In fact most welders would fill with co2 or Argon but for what this guy wants to do it's a damn sight easier and probably safer to just fill it up with water.