Simple questions for Engineers.. Appreciate it!

Galilee
26th March 2009, 16:23
Hi all,

So, I'm trying to study information on ballast systems...

What is the relationship between the pump (for intake of ballast water) and the eductor system (for the discharge) - Is it the same unit??

Are there individual eductors per ballast or is a unit assigned to several ballasts?? Where are these units typically located?
I'm sure each cargo's design varies but trying to get a general idea...

Appreciate any feedback, thank you kindly!!

Cheers,
DR

Fieldsy
26th March 2009, 16:49
Hi all,

So, I'm trying to study information on ballast systems...

What is the relationship between the pump (for intake of ballast water) and the eductor system (for the discharge) - Is it the same unit??

Are there individual eductors per ballast or is a unit assigned to several ballasts?? Where are these units typically located?
I'm sure each cargo's design varies but trying to get a general idea...

Appreciate any feedback, thank you kindly!!

Cheers,
DR


Unless things have changed in recent years - ballast pumps are located in the engine room, usually one port and one starboard, but they can be connected to ballast tanks on either side. The same pump is used to both fill and empty.
The largest pumps I ever sailed with could handle 1,000 tons per hour each.

Tmac1720
26th March 2009, 18:21
Fieldsy is correct, that was the arrangement on any H&W ship I worked on.

ROBERT HENDERSON
26th March 2009, 18:43
Fieldsy is correct, that was the arrangement on any H&W ship I worked on.

That obviously did not include the Titanic. [=P] [=P]

Regards Robert

Galilee
26th March 2009, 21:08
Hi Fieldsy,

So, the same pump unit can either be set to intake water or discharge (to create the ventury system), correct?

Appreciate all your feedbacks!

ccurtis1
26th March 2009, 22:17
On ore wagons in the 60's, the ballast pumps I sailed with had an attached vacuum pump fitted to the top of the motor to help with draining the dregs from the tanks. Later vessels were fitted with an independant vacuum system, again to assist with the last few tonnes of ballast water. The ballast had to be got out before going alongside in Seven Islands such was the loading rate, and deballasting was always fraught. Centrifugal pumps always needed help to drain DB tanks, and invariably the sea water intake was "cracked" open to asssist

Geoff_E
26th March 2009, 22:36
The originator here seems to have a problem with the conception of a pumping system.

In general, pumps "pump"; be that sucking liquid from the sea (ballast) and discharging into tanks, or sucking liquid from tanks (ballast or cargo) and discharging to sea, ashore or whatever.

On a dry cargo vessel or bulker the ballast system is just that; water in, water out. On most tankers the cargo pumps double as ballast pumps depending on the phase of operations.

The concept of an eductor system, while known, has not, to my knowledge been generally common. [BP's 60,000 ton "C" class featured ballast eductors, operating on a separate system from the cargo, but were unique in the company.]

The other concept discussed is an air evacuation system sometimes fitted to cargo/ballast pumps (generally centrifugal) to assist in draining tanks when the suction head was very low. On many older tankers the cargo/ballast pumping system was via reciprocating, positive displacement pumps, where suction might be adjusted by control of the pump speed.

Not a complete explanation, I know; and I'm sure there will be members who've sailed with all manner of variations on the above - including ballast eductors.

billyboy
27th March 2009, 04:56
That obviously did not include the Titanic. [=P] [=P]

Regards Robert


No, that was controlled by slice valves (or the lack of them...LOL) (Jester)

Ian J. Huckin
27th March 2009, 05:31
Ballast Pumps and Eductors:

Ballast pumps can pump water into ballast tanks or out of them. Dependant on time it would not be unusual to gravitate upper and wing tanks out, plus fore and aft peaks. If you were pumping then once the ballast pump suction started getting into negative territory it would not be unusual to crack open some sea suction to maintain the "prime" on the pump i.e. keep some water in the volute. Use of an air eductor helped.

Once the size of the ball. p/p suction capability defeated the flow of water back to the elephants foot in the tank then the duty eng would crank up a GS (General Service) or stripping p/p to pull the dregs or strippings out. Often this pump would be a positive displacement pump of a far lower capacity than the main ball. p/p. Most bulkers would have a cross over valve arrangement which would allow main SW cooling pumps to double duty as Ball. p/ps in emergency and visa versa.

Now "eductors" were devices that used a venturi principle where, with the ship at speed, passing water through a "scoop" on the shell of the ship created a negative pressure in a pipe coupled to the ballast main. This enabled ballast tanks to be probably 90% emptied pretty much as quick as a ball. p/p but without the use of that extra energy required to operate the p/p. Might mean the difference between running one or two genies.

I stand to be corrected as I sure don't want to mislead anybody. (Thumb)

Satanic Mechanic
27th March 2009, 08:49
I'll dig out some system drawings for you (I'll need to sort of edit them slightly or some companies will get annoyed). But in addition and sometimes in contradiction to the above here are a few pointers:

1. Ballast pumps may be in the engine room or in oil tankers usually in the pump room with the prime mover, these days usually electric motor but steam turbine is not unknown, in the engine room

2. The system configuration is such that the ballast pump may be set up to pump into or out of the ballast tanks - just a simple matter of cross over valves.

3. Ballast eductors are normally fitted and while very inefficient at displacing water they are very good at stripping out the tanks once the pumps start losing suction. There are usually two fitted either in the pump room or in the engine room, they are set up on the ballast main and the tank (s) to be stripped are selected from there

4. The eductors require 'driving water' in order to function, this is usually available from a number of sources such as general service pumps etc as well as from the ballast pumps.

5. Cargo eductors are also used on oil tankers but usually only when the vacuum stripping/ stripping pump system isn't working. It takes ages to strip a vessel using eductors.

Ok let me see what I can find you in the way of drawings - they will be for a gas vessel but the principal is the same

Satanic Mechanic
27th March 2009, 08:54
The originator here seems to have a problem with the conception of a pumping system.

In general, pumps "pump"; be that sucking liquid from the sea (ballast) and discharging into tanks, or sucking liquid from tanks (ballast or cargo) and discharging to sea, ashore or whatever.

On a dry cargo vessel or bulker the ballast system is just that; water in, water out. On most tankers the cargo pumps double as ballast pumps depending on the phase of operations.

The concept of an eductor system, while known, has not, to my knowledge been generally common. [BP's 60,000 ton "C" class featured ballast eductors, operating on a separate system from the cargo, but were unique in the company.]

The other concept discussed is an air evacuation system sometimes fitted to cargo/ballast pumps (generally centrifugal) to assist in draining tanks when the suction head was very low. On many older tankers the cargo/ballast pumping system was via reciprocating, positive displacement pumps, where suction might be adjusted by control of the pump speed.

Not a complete explanation, I know; and I'm sure there will be members who've sailed with all manner of variations on the above - including ballast eductors.

Not since segregated ballast came in they haven't - not seen that arrangement for a long time

Pilot mac
27th March 2009, 11:06
The bulk carriers in which I served had centrifugal pumps as dedicated ballast pumps, these were used to shift the bulk of the ballast. Once the bulk of the ballast is removed then switch over to eductors/stripping pumps. The problem with centrifugal pumps is that once they draw air they will/should shut down unless you have the sea suction cracked open. The eductors should run all day (in theory anyway). When I was Mate I sailed with one Second Engineer that would use the ballast pumps only and he would get the tanks almost dry without using the eductors, the down side is that this is very time consuming and requires a lot of tinkering ie cracking / closing sea suction. Far simpler to leave it to us simple Mates with the eductor and turn in!

regards
Dave

Galilee
30th March 2009, 15:46
Greatly appreciate all your responses gentz!!

R798780
30th March 2009, 18:30
Energos, ex Mobil Refiner, had a dedicated ballast centrifugal pump in the pumproom for the double bottom ballast tanks which were beneath the centre cargo tanks. There was also a venturi eductor for final draining if/when the centrifugal pump lost suction. It was driven by the fire mains water with either the butterworth or fire pump pressuring.

Tmac1720
30th March 2009, 19:10
No, that was controlled by slice valves (or the lack of them...LOL) (Jester)

There was bugger all wrong with it when it left H&W (Thumb) and in any case if the iceberg had been ballasted properly and the sluice valves fully operational the ruddy thing still would have sunk (Jester)

If anyone is interested I have a genuine original CAD copy of the Iceberg's General Arrangement plan signed by Thomas Andrews in biro........any offers?(*))

Philthechill
30th March 2009, 19:36
There was bugger all wrong with it when it left H&W (Thumb) and in any case if the iceberg had been ballasted properly and the sluice valves fully operational the ruddy thing still would have sunk (Jester)

If anyone is interested I have a genuine original CAD copy of the Iceberg's General Arrangement plan signed by Thomas Andrews in biro........any offers?(*))Tmac! I'll give you 15/6d for the GA of the iceberg but you'll have to pay the postage! Salaams, Phil(Hippy)

david freeman
2nd April 2009, 19:36
Hi all,

So, I'm trying to study information on ballast systems...

What is the relationship between the pump (for intake of ballast water) and the eductor system (for the discharge) - Is it the same unit??

Are there individual eductors per ballast or is a unit assigned to several ballasts?? Where are these units typically located?
I'm sure each cargo's design varies but trying to get a general idea...

Appreciate any feedback, thank you kindly!!

Cheers,
DRI am like some of those other readers slightly confused as to your definition of an inductor, and again to what purpose you use it for?
I sailed on BP Tankers in the late 60,s & 70,s.
Steam eductors were used for gas freeing pumprooms (Ford, Aft and the Fore peaks and chain lockers.
Water eductors were used in the Air conditioning units retro fitted to the older steam vessels 28, 32, 35,s for the accommodation.
In the single skin tankers of the day, ballast and cargo when using the load on top method steam duplex upand downers (Stripping pumps where used to strip out cargo tanks.
In the engine room when pumping out bilges or engine room ballst tanks an air pump was fitted to the GS, Fire and Bilge pumps to help create a suction. The pumps where weirs rotatary impella types.
In the main pump room, on some of the later crude oil single skin tankers were fitted with an electrically driven air pump (usually 2(1 Port & 1 Starboard) driven by shafts through the engine room Pump room bulkhead) and this was connected to the Cargo Piping in the pumproom - so to each cargo/ ballast tank, and the necessary sealing mechanism for the air pump could be by cargo/Crude oil or water ballast. This is only as my memory serves me. This system was fitted where tankers had IG in the cago and ballast tanks, and was part of the load on top philosophy, and the start of crude oil washing plant. 70 and 80 thousand tonners) So it is over to you what is an eductor??. On large steam ships the main condensers where fitted with scoops, where the speed of the vessel through the water provided water movement to cool the main condenser.

thobshropshire
2nd April 2009, 21:32
Link below to a diagram showing an eductor used in a bilge sytem:

http://www.s-k.com/pdf/Ballast_Eductors.pdf

Regards
THOB

david freeman
5th April 2009, 17:11
Link below to a diagram showing an eductor used in a bilge sytem:

http://www.s-k.com/pdf/Ballast_Eductors.pdf

Regards
THOB Standard type of Eductor (Size to siuit application) The Pressure fluid can be water/staem/air/gas or fluid of any type compatable to the fluid to be pumped. I am not aware of any high capacities such as that over 1000tons per hour. Chemical Tankers due to their subdivision (HULL and Tanks-Grade 111/11 seperation/Construction or 1 according to the cargoes being transported). Maybe you are looking for a more powerful type eductor for a shore based purposes. Many thanks for the thought provoking ideas.

cryan
21st April 2009, 00:10
I've never heard of the external scoop type but sounds like a good idea if they work, Eductors are a section of pipe in a cone shape where the fluid passing through it expands and allows a suction on a smaller guage pipe at right angles to the flow near the small end of the cone. generally used when the process will involve a loss of suction on a normal pump by means of air ingress etc, also used to suck air out of a pressure vessel to pull a vacuum for example on an evaperator or for tank cleaning with a wandering hose etc. All work on the venturi principle. For ballast though its a way of emtying tanks without the loss of suction which may be caused by the size of the tank alowing time for water to drain though lumber holes etc into the suction well without having to stop pumps. Usually run off either ballast or GS pumps and sometimes fire main.

cryan
21st April 2009, 00:12
Not to be confused with bilge INJECTORS which are emergency direct bilge suctions.

stoker
4th May 2009, 20:35
Re eductors,
The only ship I sailed on which had eductors was a Cattle carrier, they were fitted in the bilges in the cattle spaces and were used when the Sailors cleaned out these spaces and hosed them down on the return ie empty, voyage. The foot valves were forever getting clogged with straw and could only be cleaned by a Sailor sticking his down into the bilge well, usually after trying to clear the blockage with a broom handle failed.The Deck crowd were on a very good bonus but only if we were ready to load the next cargo of cattle by the time we arrived at the next port and passed the Health inspector. The Eductors were supplied from the Fire main which seemed to be left running all the time.
On the ferries we were forever pumping the Heeling tanks when in port, on one ship it was done automatically, but this gave most trouble .As the valves were operated hydraulically it was not possible to "crack on" sea water, so you just opened and then closed the sea valve hoping it would pick up the suction, otherwise you had to go to the pump room or where ever the pump was and clutch in the air pump for a few minutes. Later ships had central vacuum systems which were much better.

david freeman
7th May 2009, 18:56
Hi all,

So, I'm trying to study information on ballast systems...

What is the relationship between the pump (for intake of ballast water) and the eductor system (for the discharge) - Is it the same unit??

Are there individual eductors per ballast or is a unit assigned to several ballasts?? Where are these units typically located?
I'm sure each cargo's design varies but trying to get a general idea...

Appreciate any feedback, thank you kindly!!

Cheers,
DR I think you have had all your answers, since you posted the original question? some time ago. Who is poking your cage now? I respectfully suggest you have no conception of any ideas of what you are looking for? either maritime or shore based. If you require more gentle advice how about quoting your knowledge base, and or books of learning which have put you in such a postion, that you appear not to recognise the responses you are getting?

Satanic Mechanic
9th May 2009, 16:57
This thread went in a sort of odd direction didn't it.

Ok - Ballast eductors are used to get the last of the ballast out when the large pumps used start to lose suction. They can use driving water from a number of source, the ballast pump is the normal or the GS pump. There are usually 2 and they are located in the pump room or the engine room depending on the type of vessel

Cargo eductors are the same but used for finishing cargo - but not by preference - very slow see. The vacuum pumps talked about earlier are part of a vacstrip system which is a method of keeping pumps primed at low levels using a vacuum chamber on the suction side of the pump.

Stripping pumps are reciprocating pumps used to do the last of the line clearing etc.

Scoops have nothing to do with eductors but are a large hole in the bottom of the vessel - not proud of it - through which the condenser cooling water enters. As the vessel slows the main circulating pump takes over (large capacity low pressure) and the scoop is closed.

Feel free to pm me if there is anything else

Beartracks
9th May 2009, 20:22
Hi all,

So, I'm trying to study information on ballast systems...

What is the relationship between the pump (for intake of ballast water) and the eductor system (for the discharge) - Is it the same unit??

Are there individual eductors per ballast or is a unit assigned to several ballasts?? Where are these units typically located?
I'm sure each cargo's design varies but trying to get a general idea...

Appreciate any feedback, thank you kindly!!

Cheers,
DR

One can get lot in terms. It's all concerned with the "Delta"p. That is the pressure difference between the air acting on the surface of the fluid to be pumped from a bilge well.tank top.tank. flooded compartment etc,etc etc.This pressure is normally atmospheric and is the purpose of vents being fitted to tanks and void spaces. The water or other fluid leaves the tank and is replaced by air. This is why it is a good safety policy to fill a ballast tank that has been empty a long time because once filled all air is displaced from the tank and replaced with fresh air when the water is pumped out again. If the tank were to be entered prior to doing this there is a chance that oxygen in the tank may have been diminished by rusting (oxidation) of the structure of the tank.

Now that we covered this the pressure at the suction eye of the pump impeller or the valve chest if the pump be of the positive displacement type MUST be less than atmospheric and the lower the pressue at the pump eye the heavier the flow in the suction line. This is why all total head pump calculations are done with absolute pressure. A priming pump or Venturi type converging diverging educter connected to the suction chest or pump casing will assure this "Delta" p is efficient.

Having gone through this explanation I'll relate a personal experience. I was Chief Engineer of a 50000 ton Tanker fully loaded with a cargo of casing head crude from Constanzia , Rumainia for San Diego. Once through the Panama Canal I decided to Butterworth the Port Aft Settling Tank in order to enter same and put a cold patch on a leaking stem heater return in side the tank. I went out on deck and saw the Pumpman and a Wiper standing by the open ullage hatch peering into the tank. I asked them where the Second Engineer was and was told he was in the tank. I asked was it tested and was told no. I started to call the Second from the opening at the Ullage Hatch and when I received no answer I went down into the tank WITH NO AIR PACK. I guess if this sea story has a motto the motto is this......."Regardless of one's position and grasp of abstract physical and technical minutia...........IF YOU LOOSE YOUR HEAD YOU"RE ASS GOES WITH IT" The good Lord was watching over the Chief as well as the Second that day as "only the good die young".

Respectfully;
Hugh Curran aka Beartracks