Steel tank labelling

I have over 3000 gallons in eight integral steel fuel tanks, and a hell of a lot of pipes coming out, some are labelled with a welded letter, some are not. The ones that are labelled have the following letters, with my best interpretation without taking off the lid from each tank yet:

V = Vent
F = Fill
H = ?
S = ?
L = ?
I = Input to keel cooler (confirmed)
O = Output from keel cooler (confirmed)

Is there a convention to this? I think H, S and L are fuel pick-up pipes. L is possibly "Low" for sucking up fuel from the lowest point (uncomfirmed as yet), and S or H are possibly "Short" or "High", I imagine for picking up fuel from higher points so that the muck at the bottom isn't pulled into the filters.

I discovered that the builder of my boat put in extensive keel cooling in at least two of my tanks which hold about 500 gallons each, yippee!

 

Heineken, Scotch and Lemonade. ?

 

How did you get on Ray?

Lettering is shown on the piping diagram and there is no standard. If you don't have the plumbing plans and the building yard has shut then you'll have to pull the lids off.

From your list you need to assign the fuel return and the main feed line out. The fuel return line usually feeds into a volume limited day tank. The other tanks then transfer into the day tank.

Keel cooling as in flooded keel tanks ?

 

Not quite down to getting pipes ready yet, just working on getting my two 25kW generators mounted... yes, without being able to contact the tank welder, looks like I'm down for lifting the ports! Pity, they are beautifully sealed with internal pressure. Hope I don't muck up bolting them all down again.

Return is just going to my 500 gallon "day" (!) tank, that's no problem.

The tanks are integral to the outer hull plate with the keel cooler "radiator" piping welded to the hull. Lovverly.

 

Have you posted any Pics of the boat?

Tank lids are usually lifted 5 yearly or so for inspection and should be easily accomplished. Re-sealing shouldn't be an issue. A full re usable gasket is the best solution if it's well bolted, but if stuck down with Polysulphide it might be hard to get off.

If you use a tube of sealant you need to incorporate a 'release' so the lids can be removed easily later and aren't stuck down.