Fuel tank inspection hatch

[donm]

I need to get inside my fuel tank to clean it, check the connections/pipework, and maybe install a dip meter. The tank is aluminium and completely sealed, and has tapped connections for inlet and return, spigots for filler and breather, and no other way in. Because it is in a deep bilge (Halmatic 30) it is a purpose wedge shape, is in good condition but takes some getting out. What I would like to do is fit a removable hatch to the top so that I can clean it without removing it. I thought maybe a plastic screw hatch bolted and bedded?

Is this type of hatch safe with diesel/ is this a good idea/anyone else done this?

 

[lpdsn]

I need to get inside my fuel tank to clean it, check the connections/pipework, and maybe install a dip meter. The tank is aluminium and completely sealed, and has tapped connections for inlet and return, spigots for filler and breather, and no other way in. Because it is in a deep bilge (Halmatic 30) it is a purpose wedge shape, is in good condition but takes some getting out. What I would like to do is fit a removable hatch to the top so that I can clean it without removing it. I thought maybe a plastic screw hatch bolted and bedded?

Is this type of hatch safe with diesel/ is this a good idea/anyone else done this?

Not fitted one, but got one and I can vouch for the usefulness of an inspection hatch.

Would certainly be wary of fitting a plastic one. Mine's stainless steel fitted to a stainless steel tank with, IIRC, about a dozen bolts. I remember the manufacturer of the hatch as Solimar.

 

[neil_s]

I have a hatch in the top of my stainless steel tank. I cut the hole and fitted the hatch with the tank in situ. The hatch is a rectangular s/s plate held down with bolts. The gasket is quite thick, made of cork and silicon rubber, like those under the engine rocker box. When I had a look inside the tank, there was loads of brown gunge. It needed long arms to reach into the corners to clean it all out!

 

[NormanS]

If you've got reasonable access to the top of the tank, I would cut out and fit a bolted alloy hatch, on a suitable joint. If you tap the bolt holes, and screw the bolts in from inside out, you will have studs for fixing down the hatch cover. It's not as if you need in very often, but you would need to be able to get all the cuttings and drillings cleaned out. You will never regret having an access hatch.

 

[pmagowan]

Just be very careful working on a tank which can have fumes in it. Explosions do occur and it is simple to avoid with care.

 

[GrahamM376]

I would stick to an aluminium plate. 2 options, either tank cutter for round access or, jig saw for a square or rectangular both of which makes it easier to fit a reinforcing piece underneath for screwing access plate down.

 

[lpdsn]

I decided to see if I could find mine on the web. Interesting result.

http://www.solimar.it/en/products/completion-fittings/water-fuel-waste-and-tiller-caps.html

It looks like the one in the photo and is unscrewed using a winch handle, but it is described here as a tiller cap.

 

[donm]

Thanks for the replies and advice. Looks like plastic is out.

I looked at a Solimar hatch lookalike on Ebay which comes in at £60!!!, so a plate (probably aluminium) fixed down with tapped studs backed up inside looks like the answer. I should have mentioned that I am going to remove the tank to do the job so cleaning out the swarf will not be an issue

Thanks again for all of the help

 

[Spyro]

How about the FLB-1 from WEma http://www.wema.co.uk/pg_other_prods.htm

 

[NormanS]

Thanks for the replies and advice. Looks like plastic is out.

I looked at a Solimar hatch lookalike on Ebay which comes in at £60!!!, so a plate (probably aluminium) fixed down with tapped studs backed up inside looks like the answer. I should have mentioned that I am going to remove the tank to do the job so cleaning out the swarf will not be an issue

Thanks again for all of the help

If you are removing the tank anyway, and if it's at all possible, consider fitting a dirt drain at the bottom of the tank.

 

[Latestarter1]

Thanks for the replies and advice. Looks like plastic is out.

I looked at a Solimar hatch lookalike on Ebay which comes in at £60!!!, so a plate (probably aluminium) fixed down with tapped studs backed up inside looks like the answer. I should have mentioned that I am going to remove the tank to do the job so cleaning out the swarf will not be an issue

Thanks again for all of the help

Your original plan is perfectly sound, not sure why plastic is perceived to be out. Older boats with glassed in GRP tanks can be problematic so it is normal practice to fit perspex inspection lid and I know of several vessels with this arrangement have passed MCA coding, in addition one competitor in Round Britain 2008 passed scutineering with this arrangement.

Having the ability to access as well as having visual check of tank contents makes total sense.

As to warnings regarding dangerous fumes and risk of explosion? We are talking about gas oil here...............

 

[jwilson]

How about the FLB-1 from WEma http://www.wema.co.uk/pg_other_prods.htm

I bought a FLB-1 to fit to a plastic diesel tank, leaked badly. Might work on a stiffer alloy tank but was not impressed. Binned it.

Ended up with a plate with multiple screws on cork/nitrile gasket plus some Hylotyte red, so far so good couple of years on.

 

[pmagowan]

As to warnings regarding dangerous fumes and risk of explosion? We are talking about gas oil here...............

So what do you think happens to gas oil when you use an angle grinder or a cutting torch (or any other power tool that can heat up) when it is confined to an enclosed space? Oil drum explosions are a serious and all too common risk of working on a tank containing diesel. I would rather the OP took the simple precautions necessary to avoid the risk. I personally have been involved in a diesel drum explosion which sent a bit of metal flying about 2 inches away from my brothers head. We were being stupid and hadn't checked that the drum was washed out.

 

[NormanS]

So what do you think happens to gas oil when you use an angle grinder or a cutting torch (or any other power tool that can heat up) when it is confined to an enclosed space? Oil drum explosions are a serious and all too common risk of working on a tank containing diesel. I would rather the OP took the simple precautions necessary to avoid the risk. I personally have been involved in a diesel drum explosion which sent a bit of metal flying about 2 inches away from my brothers head. We were being stupid and hadn't checked that the drum was washed out.

I shouldn't think that any sane person would attack an aluminium tank with a cutting torch. The dangers in drilling, and jigsawing said tank are minimal. Anyway, the OP is proposing to take the tank out of the boat before starting the work, so not difficult to flush out with water.

 

[rob2]

I think the problem of a metal hatch on a plastic tank is that the plastic flexes and the flange doesn't, so it can't maintain a seal. On an aluminium tank it should be fine. I was just thinking that you should mark exactly where you want the hatch before you remove the tank so as to ensure you get the best access once it is all in situ. With the tank out and thoroughly washed you can do a really good job of fitting a hatch. If the tank is close fitted to the hull, you probably don't have room to fit a sump for future muck collection. Many tanks pick up from above the bottom to deal with this, but another option would be to fit an agglomerator (sp?) to the fuel line as close as possible to the tank and with the bowl below the bottom of the tank.

Rob.

 

[vyv_cox]

If you mean the type of hatch that people fit in cockpits or on the buoyancy tanks of dinghies I suspect you would have to be very careful about selection of any seals or O-rings. They are likely to be EPDM, which although excellent at resisting water and UV, are hopelessly non-resistant to hydrocarbons.

 

[GrahamM376]

I shouldn't think that any sane person would attack an aluminium tank with a cutting torch. The dangers in drilling, and jigsawing said tank are minimal. Anyway, the OP is proposing to take the tank out of the boat before starting the work, so not difficult to flush out with water.

Explosion risk depends on temperature. http://www.forestoperationsreview.org/index.php/news-issues/item/329-diesel-fuel-vapor-hazards

 

[pmagowan]

I shouldn't think that any sane person would attack an aluminium tank with a cutting torch. The dangers in drilling, and jigsawing said tank are minimal. Anyway, the OP is proposing to take the tank out of the boat before starting the work, so not difficult to flush out with water.

You would be surprised what apparently sane people do. Yes, using a cutting torch would be silly and ineffective but many people use angle grinders and other tools that can get very hot very quickly on tanks. I don't think a word of caution is unwarranted, I did not give a lecture, and much of the detail has appeared after my post. Simply put, you should always take care when using power tools on a metal tank that has contained a volatile substance. Explosions can and do occur and preventing them is incredibly easy, requiring, as you say, a simple flush-out. I am not sure why the matter requires any debate or further comment, just a simple bit of advice.

 

[moonshine]

Here is another source of Fuel Tank hatches :

http://www.seabuilt.com/pricing.php

They come as a kit including gaskets, fasteners and can be purchased from an agent in Scotland. I have fitted 8" alu to the sides of two steel tanks and am really pleased with the result. PM me if you want pictures.

A

 

[prv]

I think the problem of a metal hatch on a plastic tank is that the plastic flexes and the flange doesn't, so it can't maintain a seal. On an aluminium tank it should be fine.

Depends what we mean by "plastic tank". A welded 10mm polyethylene tank as made by Tek Tanks will work very well with the FLB clamp-on hatch. A thin roto-moulded tank probably not. A stainless steel one I'd expect to be a bit marginal due to flexing. Not sure about aluminium as I've never had an ally tank and not sure how thick they typically are.

Since it's not the sort of thing you need to open in a hurry, I reckon a simple ring of bolts and drilled plate, in the same material as the tank, is the way to go. It's what I did on mine.

If the tank is close fitted to the hull, you probably don't have room to fit a sump for future muck collection. Many tanks pick up from above the bottom to deal with this, but another option would be to fit an agglomerator (sp?) to the fuel line as close as possible to the tank and with the bowl below the bottom of the tank.

If the tank's sitting in the bilge, I doubt there's room to have an agglomerator below it.

A closer equivalent to the gravity drain would be a second pickup tube reaching right to the bottom of the tank, whereas the normal fuel supply one stops an inch or two above it. Then a pump can be used to suck out any water and loose crud in the same way as the traditional drain cock. Might be worth making the tube a size or two larger than the supply one, to prevent blockage.

Pete