I always see ships that seem to be shooting water from the hull, why do they do this?
Is it water sucked in by the engine for cooling purposes which is then pumped back overboard?
https://i.redd.it/ip5h2hn9qq791.jpg
In: 4419
Yes, it’s for engine cooling. Being submerged in water is too useful a source of coolant not to make use of. (Note that it isn’t pollution, it’s just warmed up water.)
There are several reasons that a ship used and then subsequently discharges water:
1) Ballast water – this is used to trim and stabilise the vessel. Usually (but not always) this is sea water taken in during loading/discharging cargo. Generally ships don’t tend to discharge ballast water at sea except in certain cases (where they may have to do a full ballast change having sailed from one area to another). Most ships will take on water during a passage to balance out the fuel they have consumed, and could discharge it for the same reasons if it was needed for keeping trim or staying upright. Normally you don’t see this as most ballast discharges are under water.
2) engine cooling water – the water is taken through a sea chest (or a hole in the hull as it is ELI5) pumped through the cooling system of the engine and engine room and then discharged back to sea. Normally you don’t see this as most systems discharge under water. However in some specialised vessel this may be preferable, but that is extremely rare.
3) free water clearance – when in rough seas or heavy rain, any water shipped on board will flow around the decks, in to the scuppers and flow back in to the sea. Scupper outlets are usually above the surface, so you see this discharge .
4) anchor wash – when entering shallow water areas, it is standard practice to have the anchor cleared from deep sea, ready to let go in the event of an engine failure, steering gear failure or other emergency requiring the immediate use of the anchor to stop and make the vessel safe. In this case most ships will also put on the anchor wash (which can also be the fire pump with an outlet in the spurling pipe) as standard. The same is also true (and arguable more useful) when weighing anchor to leave the anchorage. In this case water is seen running out the spurling pipe (where the anchors are) at a relatively high rate.
5) fire pumps – if the fire pumps are being run, in some systems it is not good to have the fire main pressurised with no outlet/flow through the system for long periods of time. In some cases there will be a designated discharge for this, but in most cases the anchor wash (see point 4) is used for this too.
Hope that helps!
Edit: first thanks for all the up votes, cheers!
It is now 8 years since I last sailed as a master on a cable installation barge, somethings have slipped my mind, so there are some errors in the above which other commenter have reminded me of either directly of indirectly.
A. When I wrote spurling pipe I should have written hawsepipe. The spurling pipe is the pipe that goes from deck in to the chain locker, whereas the hawsepipe is from deck down to sea.
B. We run the anchor wash when paying out the anchor so that you can see the chain markings denoting each shackle of anchor cable/chain paid out. The chain coming up from the locker is always dirty even when you wash it going back in, and you need to see these markings to properly anchor.
C. You need to wash the chain when recovering as it is very dirty with mud, sand and clay, which you don’t want to build up in the chain locker, which is where the chain is stored when not in use
D. For point number 2, the sea water is pumped through heat exchangers. The seawater takes heat away from the hot cooling (fresh) water which is used to cool the engine and other machinery. I am in no way a marine engineer, so I have a limited understanding there.
E. Bilge water is horribly oily, when I was at sea you could only pump it overboard when you had passed it through an “oily water sperator” which reduced it to 15 parts of oil per million. This may have changed now though due to constant law updates. It was really crap and risky to do so we just used to store it and pump it ashore to someone who could deal with it.
F. I worked on merchant ships. For military ships there are different rules, and lots of different equipment which may need water cooling.
Larger ships have [ballast](https://en.wikipedia.org/wiki/Ballast) systems to maintain stability, mostly using water in [ballast tanks](https://en.wikipedia.org/wiki/Ballast_tank).
The water in ballast tanks must be constantly managed to provide hydrostatic stability. They basically pump water into (and out from) the ship, and between various ballast tanks inside the ship.
https://www.marineinsight.com/naval-architecture/a-guide-to-ballast-tanks-on-ships/
when i used to work on large off shore fishing boats the hoses were always pumping water out of them, for the entire trip
u always need to hose the mess off during the trip, so an always on hose comes in handy
What is this ship? I love it and am terrified of it
The water you usually see spitting out of a ship is for engine cooling – it is usually raw water sucked in from somewhere else on the bottom of the ship, it goes through the engine (cooling), then it usually also goes to some heat exchangers which allow the heat put into the water by the engine to be used for other systems like hot water for showers, kitchen etc. before being piped out overboard, usually on the side of the boat but sometimes at the stern.
Water can also be from the bilges of the boat, or ballast. The captain or crew can turn on bilge or ballast pumps to either shift water within the boat or pump it overboard to raise the waterline (Or lower it) as required for stability or unsticking from a grounding incident. This water is usually not pumped overboard constantly – they’ll dump it for a bit then shut it off once it’s at the right level.
Water naturally seeps into many boat designs through the prop shaft seals. It typically comes in at a very slow drip, but if left long enough it can fill the bilge and require a long pump cycle to empty out. You can see some boats “peeing” at marinas even when no one is around, the bilge pump actuates via a float device like on a toilet. Failure of this system has sunk many a yacht just sitting at the docks waiting for the owner to come maintain it!
The purpose differs. The main reason is ease. A ship is surrounded by cool water, so if you need any of those properties for any purpose, why not use water.
Because of this, they generally leak water frequently
On boats that people own for fun, it’s the bilge pump. There’s a sensor that trips when water gets deep enough inside the hull. This can be for several reasons. The top deck isnt 100% water proof, so if they take a wave over the bow, some leaks into the hull. Some built in ice chests/bait wells are designed to drain inside the hull. Lastly, hull leaks, whether that be cracks in the hull or the drain plug.
> Is it water sucked in by the engine for cooling purposes which is then pumped back overboard?
This is the main reason, yes.
It’s done above the water line so people can check it’s working. If it isn’t working, the engine will overheat quickly.
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