Diesel Tank Inspection Hole

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SURWAYA

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My boat has a 110 gallon stainless steel diesel tank which unfortunaltely doesn't have an inspection hatch. I intend to drain the tank and cut out a 10" diameter hole in the top using a jigsaw/drill. Can anyone advise me on safety concerns i.e. is this approach going to result in a loud bang? Is there a better way? Thanks
 
10" would seem to be excessive - try 5" don't forget you will not be bale to use the normal plastic inspection ports as are sold at the chandler's. You will need to also ensure you use proper gasket material for diesel when you make the cover
 
Thanks. I've played around with hole sizes using a gash piece of plywood and to be honest 10" is the smallest practical size for cleaning what is quite a deep tank. I'm going to make a stainless hatch that can be bolted down into captive nuts with a thick rubber gasket. My main worry is igniting diesel/fumes with hot metal when drilling/cutting. Any thoughts?
 
Buy some dry ice, fill the tank. Make sure the pressure cannot build up:= leave the filler cap open. Dry ice will sublimate, tank is then filled with CO2. At least it will minimise the explosion chance.
 
I used a drill and jigsaw, slow cut and drilling fluid - about the size you are contemplating. I didn't bother with captive nuts, but tapped the tank and put a series of bolts through the cover plate and gasket at about 50mm intervals. The likelihood of producing enough heat or a spark was miniscule IMO.

The reason for the access hole was that although there was already one at one end of the tank, there was a baffle halfway which prevented access to the sludge in the other half /forums/images/graemlins/frown.gif - so make sure you don't need TWO hatches!
 
Excellent information thanks. That's exactly how I intended to approach it. I also have a baffle mid-tank and I'm hoping to place the hole mid-way across the baffle giving me a 5" radius semi-circle access on either side. Thanks again.
 
Explosion risk is minimal with the tools you are using, as the flash point of diesel is quite high. I have welded diesel tanks after draining the tank and flushing with soapy water. If you really want to be certain partly fill the tank with water to minimise the air space at the top.
 
Cheers for that. I must admit I had been considering that option but was wrestling with the old water in diesel thoughts. At the endof the day the whole reason for this hatch is so that I can give the tank a thorough clean so any water will be completely removed and on balance I think I will do as you suggest. thanks
 
hi dont you guys over there have diesel addative??? ive not had s...t in tank in 15 yrs i use what we got here every time i fill up . as for your little jod i used drill and jig saw. filled tank with water . to get all water out of tank after . i use the addative as it kills water and algee dave
 
It depends very much on the source of the fuel. Many ports and marinas in UK and northern Europe have bunkers that are refilled by barge. Barges can be used for a variety of purposes that may introduce contamination, especially water. Many bunkers have a very slow turnover which can also attact moisture long-term with the fluctuations of temperature around the dew point.

Refuelling from road tankers, as many people in the eastern Med do, brings big advantages as their turnover is much faster, general temperatures are well above dew point and fuel condition is therefore better. I have had no contamination at all since moving out there, whereas I did have a few isolated problems in UK and Holland.
 
Been there only with a 30 gallon petrol tank that was well flushed with a hose over night. Then drilled it with a box of 6mm bits. Might be worth having a look in the vetus catalogue because I fitted one of their tank inspection hatches afterwards with complete success.

Pete
 
Like others above we have done this. Cut the hole with a jigsaw - used up 2 or 3 blades as I recall, slow cutting speed. Nothing exploded. Drained the tank of diesel beforehand but did nothing else. The central baffle may give you problems with the jigsaw blade. Then had a hatch made (6mm thick stainless rim with nitrile gasket and countersunk bolts clamping this to the tank top. The rim was tapped and a stainless lid is bolted to it, with another nitrile gasket). Good luck.
 
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