Inspection hatch for stainless diesel tank

[prv]

We always knew that Ariam had some crud in the tank, but yesterday was the second time in not many days' use that a lump of it apparently got stuck in the dip tube. Fortunately without stopping the engine, unlike last time, but there was some nervous watching of the suction gauge until it suddenly cleared itself (the crud presumably passing into the filter). So the tank definitely needs a good clean out, and rather than keyhole surgery I want to get at the inside by hand.

The tank is relatively thin stainless steel, and the top is easily accessible. I'm familiar with the Wema plastic hatch (we had one on Kindred Spirit) but I don't think that would work as well on thin steel as it did on thick plastic. So I'm thinking of making a square version of the Seabuilt hatch - easier to fabricate in an unsophisticated home workshop and doesn't need clever tricks to fit through the hole!

I think I know how I'd go about building that, but any observations from other successful hatches on plate thickness, bolt spacing, and gasket thickness would be welcome.

Also, ideas on cutting into the tank? I'm not going to use an angle-grinder in a moderately confined space, quite apart from any fire risk. Jigsaw? Buy a nibbler? For some reason air ones seem to be much more common than electric, but are no good to me as I don't have a compressor. I've found one designed to be powered by a drill for £20 - are these ok for one job or complete rubbish?

How big a risk is igniting any diesel or fumes left in the tank, and what if anything to do to prevent it?

Cheers,

Pete

 

[Seajet]

Could you shut off the fuel feed and fill the tank with water, just to be on the safe side ? I don't fancy using cutting gear on any tank, even diesel...

If it's thin stainless chain-drilling the hatch outline then a hand padsaw ( if that's the term, the things which hold an extended senior hacksaw blade for one-handed use ) should be fine.

Or if you want an easier life and the fire risk is taken care of, a rechargeable Dremel with the optional cutting wheel is jolly handy; but about £90 so not an option unless you want it anyway or can borrow one !

As you already mention, it will be interesting to hear suggestions for diesel proof gasket / sealants.

 

[DownWest]

Just made one in ally.
Chain drilling followed by a jig saw is probably your best bet on thin SS. To get a good clamp with the bolts, make the hole oval and fab a thicker ring to hold the bolts from within the tank (this could be in 3mm ally with the bolts threaded in) I am using paper gasket material with a PU mastic glue. Spacing on the holes is 50mm. The hole is 200mm dia. ( The ally is thick enough not to need the internal ring, so hole is round)

 

[Graham_Wright]

I use Henderson hatches - five of them!

 

[Tranona]

Had an inspection hatch fitted to my SS water tank while it was out and being repaired. The fabricator welded a stainless ring plate to the top after cutting the hole. The plate is tapped to take M6 screws and the cover is a round SS plate and set in Fernox sealer - adequate for water, but diesel would probably need a better gasket. The screws are ss cap screws. Not sure whether this could be done with a tank in situ.

 

[Champagne Murphy]

Make sure the gasket is Nitrile! Dissolving rubber in the fuel won't help