Installing New Hatches In Fuel Tanks

[Dockhead]

Thanks to everyone for the very useful input. But back to the original question: Can I cut a hole in my tank in situ, or not? I already have one "no". Is that it, then?

[s/v Jedi]

Originally Posted by Dockhead

Thanks to everyone for the very useful input. But back to the original question: Can I cut a hole in my tank in situ, or not? I already have one "no". Is that it, then?

No you can... I though Gord posted that already but see it is for a hatch, not a pickup. Just get the kit and do it. Use a vacuum cleaner to keep most of the aluminium out of the tank, ignore what goes in there. It will either stay there for ever or end up in you filter, no harm done in any way.

Don't be afraid of diesel fuel. You could throw a burning match in it and get away with it. Never touch a gas tank though.

[belizesailor]

Originally Posted by Dockhead

Thanks to everyone for the very useful input. But back to the original question: Can I cut a hole in my tank in situ, or not? I already have one "no". Is that it, then?

Have not done this myself but have pro welder friends who have told me..."no problem, just fill the tank w inert gas, like CO2, and cut or weld away". The idea being - no oxygen no risk of fire or explosion. Sounds reasonable on paper, but think I would pay them to do it while I watched from a safe distance just the same.

Cutting on diesel tank w a handsaw (not some high speed tool that would generate more heat) would worry me less. I have drilled small holes in diesel tanks for fittings w out event.

[Navatech]

Originally Posted by Dockhead

The problem with that, as I see it, is that if your main fuel pickup is properly designed, it will be located some distance above the lowest point in the tank, so won't -- by design -- pick up water, until the water level has become disastrous.

You can sleep restfully. My tanks are integral FRP tanks and the pickup lines have been placed at the lowest point (deep V hull). I can suck all but the last gallon or two from one (forward) tank and about double that from the other (rear) tank.

Originally Posted by Dockhead

My system already polishes fuel to the extent yours does -- the main engine fuel system is always pulling fuel through my quite good filter system and returning it to the tank.

No doubt. The advantage with the fuel purifier is that you don't have to replace filter cartridges. Had I done the same polishing based on the existing (double Racor 1000's) filters I would have gone through at least a couple of cartons of cartridges. I can now allow myself to put 1 set of 10 micron cartridges and not worry about them for a whole year.

Yes, having the fuel purifier and the Racors is somewhat of a belt and suspenders approach but mine is a big (46'6") SF boat and we're often over 20 miles offshore.

I carry eight 30 micron as well as four 10 micron Racor spare cartridges but that's just because I'm kind of anal on redundancy

[Navatech]

Originally Posted by Dockhead

Thanks to everyone for the very useful input. But back to the original question: Can I cut a hole in my tank in situ, or not? I already have one "no". Is that it, then?

Assuming your tank is aluminum, FRP or another plastic the answer is yes you can. The way I would do it is fill the tank with an inert gas (C02, Argon - both available from welding supply stores) and I'd make sure to use only air powered tools (explosion proof electric power tools are VERY expensive).

If your tank is steel (stainless or otherwise) the cutting could still cause a spark (blade on the tank). And, though diesel, as a liquid, is pretty safe (you really can throw a lit match into it without anything happening) diesel FUMES are another ball game altogether! That one I'd leave to a (well insured) professional.

As for the filings, regardless of the material, don't worry about them. Worst case scenario is that they end up in your primary filter.

[Cheechako]

Originally Posted by tamicatana

We're in the process. Had plates C&C'd up. Oval, to allow easy installation. Diesel tanks.

The plan is to shut the valve to the fuel line (to the engine). Empty tank. Fill tank with water. Use holesaw and grinder to cut hole. Clean tank. Install plate. Empty water and refill. Done.

I will not even consider anything more complicated than the sight tubes I now have.

Now what has been installed and did save our cross-Gulf trip is a second filter. Actually it's a primary filter. It got the nasty, and does catch water as well. I have it before the separator.

McMaster 9875K216, 80 mesh screen (Impact resistant nylon clear bowl)

Why the water?

[Navatech]

Originally Posted by Cheechako

Why the water?

The water would displace the diesel fumes (explosive) thereby creating a so called "gas free" (i.e. explosion proof) environment. That's how older (metal) automotive tanks were/are repaired.

The little water remaining after a thorough pump out will be caught by the primary filter (which is also a water separator).

[Cheechako]

Yeah, suprised it's thought necessary with diesel.

[Navatech]

Originally Posted by Cheechako

Yeah, suprised it's thought necessary with diesel.

Diesel fumes can be explosive (after all, that's what happens to the fuel on the power stroke in the cylinder)! Better safe then sorry!

[Dockhead]

Originally Posted by Navatech

Diesel fumes can be explosive (after all, that's what happens to the fuel on the power stroke in the cylinder)! Better safe then sorry!

I don't think they can be explosive at all, unlEss finely atomized and injected into superheated air at 1 million bar. I'm really not worried aboutnthis. I'm worried about the metal chips. Jedi is encouraging.

[Dockhead]

Originally Posted by Navatech

Assuming your tank is aluminum, FRP or another plastic the answer is yes you can. The way I would do it is fill the tank with an inert gas (C02, Argon - both available from welding supply stores) and I'd make sure to use only air powered tools (explosion proof electric power tools are VERY expensive).

If your tank is steel (stainless or otherwise) the cutting could still cause a spark (blade on the tank). And, though diesel, as a liquid, is pretty safe (you really can throw a lit match into it without anything happening) diesel FUMES are another ball game altogether! That one I'd leave to a (well insured) professional.

As for the filings, regardless of the material, don't worry about them. Worst case scenario is that they end up in your primary filter.

A spark? But why would I worry about that? Diesel fumes cannot be ignited by a spark! Unless I am grossly misinformed.

[David_Old_Jersey]

Just an idea - not a recomendation! - how about using tinsnips or a nibbler to make the inspection hole?....for the initial hole, if you have access from an existing hatch drill into a bundle of rag........useful if the tanks are not topped up to full! Might also want someone nearby with a video.........

Of course you likely to have baffles in the tank - which means that even if you had good top access might need more than one inspection hole.

[Navatech]

Originally Posted by Dockhead

I'm really not worried about this.

You're free to chose what to worry about. What the heck do I know?!... After all, I've only spend 4 years in a nautical school, 3 years in a navy and another 3 years in the merchant marine.

Frankly, it's no skin off my nose if your boat goes boom! Good luck. BTW, just keep in mind that we're talking about fumes (equivalent to the finely atomized fuel coming out of the injector) and that no cylinder achieves "1 million bar" on the compression stroke. Indeed, the heat generated by the compression is required for ignition. A spark would be a quite suitable alternative. Look up old marine diesel engines that had "glow plugs" and read up on the Diesel Cycle...

Originally Posted by Dockhead

I'm worried about the metal chips.

That's the one thing you do not have to worry about! That's what your existing filters are for. You do have a primary and secondary filter for each engine right?

[Navatech]

Originally Posted by Dockhead

A spark? But why would I worry about that? Diesel fumes cannot be ignited by a spark!

You're possibly taking the piss with me but as this might mean lethal danger for other people. Steel on steel could result in a spark. A power tool will most certainly cause sparks (around the brushes). Add to that diesel fuel fumes and you might be in for a nasty surprise...

Originally Posted by Dockhead

Unless I am grossly misinformed.

You have now been correctly informed. What you do with that information is up to you. Good luck.

[Navatech]

Originally Posted by David_Old_Jersey

about using tinsnips or a nibbler to make the inspection hole

Those tools are predominantly for rather thin plate. I have yet to see such a tool sized for the plate thickness of fuel tanks. In addition, there's still the internal sparks (in the electric motor, around the brushes) to worry about. Explosion proof mobile power tools exist but are extremely expensive. The very acceptable alternative is a pneumatic tool.