Fitting an inspection hatch to stainless diesel tank ?

[Crowblack]

Please can anyone advise about doing this leaving the tank in place.

No hatch currently just a sender front corner which provides a hole of about two inches.

The tank is longer than it's deep and it's shallower at it's aft end - have not measured the tank but the sender is 30cm deep so with a hatch of about say 6 inches I could reach in quite easily.

The sender hole would enable either a probe or small mirror into the interior to establish location of baffles before making the hole for the new hatch.

Has anyone fitted such a hatch and can you recommend a manufacturer ?

Please also - method and tools for cutting the hole - obviously to avoid too much heat.

Thanks in advance.

 

[MagicalArmchair]

These get a good write up: http://tektankslimited.com/flb-inspection-hatch-flb-720-p.asp

I have the same problem with mine, I am attempting to clean mine through the sender hole! I PELAed out all the diesel and any water in there, filtered the diesel, and have a flexible fish tank cleaner to clean out the gunk. Bingo, no inspection hatch required. I also have a USB endoscope so I can have a good look around in the tank. If I were to drill it, I think a hole saw at very low speed.

My similar post was here: http://www.ybw.com/forums/showthread.php?441861-Fuel-tank-blues-(well-black-spots-in-fact)

 

[rogerthebodger]

I would cut a rectangular access hole big enough to get your head in so it can be inspected You can then get a stainless steel cover about 50 mmbigger in length and width to cover the hole and drill and tap holes at about 50 mm pitch around the edge in both the tank and cover. Screw set screws up from the underside through clearance holes in the cover fixing down with nuts and plain washers.

 

[prv]

I've done exactly this.

No manufacturer involved; I just went to Metal Supermarkets and got them to cut me two rectangles of stainless sheet about an inch bigger in all directions than my intended hole. In the shed at home I then cut out the middle of one of the sheets to make a square ring. I clamped the two together and drilled a series of holes around the edge, correctly sized for the thread I intended to use. Then I tapped all the holes in the ring plate, and widened the holes in the cover plate to 1mm larger than the intended studs (to allow for slight misalignment in fitting). I screwed machine screws into all the tapped holes, then tack-welded the heads to ensure they stayed in place (loctite, some kind of adhesive, or just doing them up very tight and galling the threads would probably do just as well if you don't have a welder). So I then had a square ring with protruding studs, and a cover plate with holes to match. I also made up a gasket out of nitrile sheet from eBay, using the cover plate as a template.

I tried several ways of cutting the tank - metal-cutting blades for a jigsaw went blunt after about half an inch of cut each, and the tip of the cheap nibbler broke off. So it had to be the angle grinder, which worked well. I started by pumping out all of the diesel through the sender hole, then tipped in plenty of soapy water to emulsify the dregs. I also hung wet cloths around the compartment to catch the sparks from the grinder, put on a damp cotton jacket and hat, and had a 10l foam extinguisher to hand. The actual cutting went very easily, along a line marked out using the stud plate as a template.

After filing down the edges of the hole slightly, I used the cover plate as a template to drill the bolt holes. The ring then went in through the opening and the studs passed up through the holes. The nitrile gasket placed over the top grips the studs (its holes are slightly undersize) and stops the plate falling down into the tank. So after vigorously cleaning the tank with a scrubbing brush and Scotchbrite, pumping out the soapy water, and thoroughly drying it with kitchen roll, I could then put the cover plate over the studs and do up the nuts.

Pete

 

[macd]

Neat job, Pete -- and certainly the way I'd go about a similar task. Sooner or later I'm going to have to bite the bullet and do it.

 

[rogerthebodger]

Nice job Pete

I did my water tank (stainless steel) and waste tank (GRP) in the same way but with Polycarb covers

My Diesel tanks are Mild steel so I could tap into the the tank and bolt the MS lids on using studs in the tank.

 

[prv]

My Diesel tanks are Mild steel so I could tap into the the tank and bolt the MS lids on using studs in the tank.

Yep, makes sense if the tank top is thick enough. Mine is quite thin stainless sheet, 1.2mm rings a bell, so it really needed the stiffening ring to take the studs and compress the gasket evenly.

Pete

 

[rogerthebodger]

My Diesel tank are welded into the hull and if I remember were 5 mm thk maybe overkill but my hull sides are 6mm and the bottom 8 mm.

My SS water tank is 1.6 so that's why I used the internal frame like you but I welded mine from 6 mm thk strip.

 

[Spyro]

http://www.wema.co.uk/pg_other_prods.htm
They do a product page down till you get to FLB flange

http://www.wema.com/publish_files/FLB_-_163110.pdf

 

[rogerthebodger]

IMHO that size access hatch is too small and it is easier to cut a rectangular than round.

 

[Crowblack]

Thanks to all for responses - think I'll go the route described by Pete.

Pete, can you advise - did you use two nitrile gaskets - i.e. one between internal ring and tank the other between tank and cover or just one between tank and cover ?

What thickness of Nitrile did you use ?

Also what centres do you recommend for the studs.

Thanks again.

 

[prv]

Pete, can you advise - did you use two nitrile gaskets - i.e. one between internal ring and tank the other between tank and cover or just one between tank and cover ?

No, just the gasket on top. I don't care if diesel manages to get between the reinforcing ring and the tank skin.

I did make the holes in the gasket slightly undersize, both in order to hold the reinforcing plate in place when the lid is off, and to ensure a good seal around the studs when the gasket is compressed. So far there's not been the slightest weep from the hatch even with about four feet of head in the filler pipe.

What thickness of Nitrile did you use ?

Checking my old ebay orders, apparently I used 3mm.

Also what centres do you recommend for the studs.

I don't have a figure for that, and I'm not going to be at the boat for a while to measure. But you should be able to get a good idea from the pictures.

Pete

 

[rogerthebodger]

I don't have a figure for that, and I'm not going to be at the boat for a while to measure. But you should be able to get a good idea from the pictures.

Pete

Mine are equal spaced with a maximum pitch of 50 mm

 

[prv]

Mine are equal spaced with a maximum pitch of 50 mm

Mine are probably about the same.

Pete

 

[Crowblack]

Thanks again to both - very useful.

 

[Crowblack]

Bit of a while ago but thought I'd update just in case any "unhandy" types like me are thinking of fitting an inspection hatch.

Followed the experiences passed on by forumites and it went well.

Was a bit apprehensive about cutting the hole in the tank but in practice it went extremely well - bought a 1.2mm plasma disc for the angle grinder from Machine Mart for just over a quid and it went through the SS like a knife through butter.

I used PRV's technique of surrounding the cutting with a dampened old duvet making sure the grinder was working towards it and pretty much all of the swarf ended up stuck to the duvet.

I'd already emptied the tank through the sender hole using a cheap submersible pump and also used a couple of doses of warm soapy water to get most of the rubbish out.

Not fitting an inspection hatch and using a pump will get most of the gunk out of the tank but it's surprising how much more you can get out by getting an arm and hand in to thoroughly scrub and dry it out.

Hopefully won't have to do it again for several years - but having the hatch now means it will pretty easy.

Couple of pic's of finished article.





Thanks again for the advice chaps.