Pump Discharge

[Steven Christian]

A question: Looking at some pics in another thread got me to wondering if ships like the Olympic class could ever use their various pump discharges below the waterline to say nudge the ship over when docking or leaving? Or were they just too big to consider that. I ask that because I saw in a movie once where carriers in the old days had used their prop planes tied down to use the thrust from their props to help dock the ship. The other thread was veering off from the original topic so I asked this here. Cheers all.

 

[Doug Criner]

Something comparable to your idea is bow thrusters often included on large, modern ships. Google for more info. I've not heard of the idea of using pumps, such as main circulating water pumps, normally used for condenser cooling, for this purpose.

 

[Doug Criner]

Long ago, yes, sometimes aircraft carriers, maneuvering into and out of port, would sometimes tie down aircraft on the flight deck, and use the aircraft. Not a real good idea, even then. Nowadays, large U.S. aircraft carriers would use multiple tugs, or just anchor outside a port, and use boats for liberty parties, etc.

 

[Steven Christian]

Thanks for the reply Doug. Yes I know about modern thrusters used today. And from what I understand back in the day when they used prop thrust of planes it was very hard on the piston engines. I was just wondering if in the older days if they ever used pump discharges to nudge a ship up next to the pier. Probably not as if they were that close the mooring lines would do the job. Was just wondering if it gave anybody some ideas. Thanks.

 

[Stephen Carey]

Thanks for the reply Doug. Yes I know about modern thrusters used today. And from what I understand back in the day when they used prop thrust of planes it was very hard on the piston engines. I was just wondering if in the older days if they ever used pump discharges to nudge a ship up next to the pier. Probably not as if they were that close the mooring lines would do the job. Was just wondering if it gave anybody some ideas. Thanks.

No, I doubt that that would happen as the overboard discharges are not regulated at all, they just discharge at constant volume. In any case they would push the ship away from the quay rather than towards it if the discharge was on the quay side of the ship. As a high volume low head system, there isn't much of a discharge force anyway - Olympic's system was around 5,000m3/hr at some 7-9bar head, which isn't very much, and it was on both sides of the ship, giving an equal force. No Master would ever ask the engineers to do something like that for fear of ridicule! If he can't get his ship alongside without "engineer assist", he's not a very good shiphandler...

 

[Steven Christian]

No, I doubt that that would happen as the overboard discharges are not regulated at all, they just discharge at constant volume. In any case they would push the ship away from the quay rather than towards it if the discharge was on the quay side of the ship. As a high volume low head system, there isn't much of a discharge force anyway - Olympic's system was around 5,000m3/hr at some 7-9bar head, which isn't very much, and it was on both sides of the ship, giving an equal force. No Master would ever ask the engineers to do something like that for fear of ridicule! If he can't get his ship alongside without "engineer assist", he's not a very good shiphandler...

Yes your probably right. Would be like a fly pushing on a building. It was just something I was thinking about. Metric values...grrr....LOL.