"Docking plugs" is this a UK or common term?

[Larks]

My last course module (Surveying of Super yachts) states that, when preparing to dry dock a vessel - "the docking plan will show the position of any projections from the hull and the position of the docking plugs".

This is in regard to larger vessels (Super Yachts) rather than yachts that may have a drain plug in the bilge, so what are "docking plugs"?

Rather than opinions, is it a term that anywhere here is familiar with in commercial vessels?

Are they a "below waterline" fitting that needs to be clear when locating blocks and slings or perhaps simply deck level service points that need to be accessable for hooking up water and power to keep vessel systems operating when the vessel is in dock?

The term is not something that I am familiar with despite having run a commercial slipway and having been involved in building, refitting and maintaining/docking commercial vessels.

[Hwyl]

I'm guessing (an informed guess because I speak the vernacular) shore power connections. No minor item on a big boat

[JimConlin]

Google finds lots of references to 'docking plug' that describe temporary electrical or electronic connections.

There's an ASTM standard that sorta indicates that docking plugs are drain plugs in bilge plating and other places you might want to drain.
http://www.astm.org/Standards/F991M.htm

[Larks]

Gareth, that was what I suspected but my "Google" searching bought up quite a variation in results so couldn't really pick one from the other,

HOWEVER.......................................

Jim, I hadn't found the ASTM standard site but that does seem to hit the nail fairly smack on the head and is completely relevant to the context, so thank you very much for that:

"This specification provides design, construction, and purchasing criteria for docking/drain plug and boss assemblies. Assemblies are intended for installation in shell, rudder, and tank bottom plate. Assemblies shall be installed at the lowest point of a tank or rudder for draining during dry docking. Docking plugs and bosses shall be classified as follows: type I - docking plug and bosses for plating from 8 to 15 mm, and type II - docking plug and bosses for plating greater than 15 to 38 mm. The procedure for installing docking/drain plug and boss assemblies are presented."

[Dryfeet]

Actually, a docking plug is literally a drain plug in the bottom of the hull. The blocking needs to be clear so that the plug can be removed and the compartment can thus be drained. Seems a bit unnecessary what with bilge pumps and all but 1000' tankers had them as the tanks could not really be stripped dry without a bit of water left in them. For instance the suction bells may have been 3-8 " above the tank bottom. But theoretically the tanks are dead level in dry dock and don't drain back to the suction. Work done inside the tanks might include sand blasting and/or coating and painting. A dry tank would obviously be necessary and this is much easier than sending smaller pumps and mops down into the tank. Of course, on chemical tankers carrying ethanol we did just that each time before loading to get ALL water/moisture out of the tank.

[Larks]

Do they actually look like a through hull fitting or are there cover plates over them?

[Dryfeet]

The ones I've seen were threaded plugs right into the plating. Apply square bar to the plug and unscrew it. No different really than a threaded plug on the end of a pipe except it's flush with the steel plate.

[Andrew Craig-Bennett]

I can add nothing to that.

Bet your next item will be "gas freeing"...:)

[Torna]

Knowing absolutely nothing about what I type, but imagining the reference above to rudders: On a large vessel you might imagine that the rudder is hollow and normally filled with water. But if you were to drydock that vessel, the full rudder might be too heavy for its supports. It might need to be drained as the water level is lowered - so the "docking plugs" will need to be removed beforesuch.

-leif

[Larks]

I can add nothing to that.

Bet your next item will be "gas freeing"...:)

This is actually the last module before the exam next week, we'd already done a bit on tank inspections, safe entry and so on. So this "new term" threw me a bit as it hadn't been mentioned before and it was in reference to docking Super Yachts rather than general commercial vessels.

Thanks again for your help guys.