Ballasting and deballasting are very essential in ships. It is an operation keenly supervised by the ship officers to maintain the vessel’s stability.
This is very crucial. It keeps the ship upright by compensating for the distribution of weights.
What are ballasting and deballasting?
In the simplest definition, de-ballasting is removing water from the ship to the sea. In contrast, transferring water from the sea to the vessel is called ballasting.
The (sea) water is stored in specific tanks on board called water ballast tanks (WBT) or simply called ballast tanks.
These tanks are dedicated to carrying only seawater which is now called ballast water.
By gravity or pumps?
There are two methods used in this operation. Using gravity is one economical way to make ballasting or deballasting.
You just open the right valves and let the seawater find its way to the ballast tanks or vice versa (tanks to the sea).
However, this method has limitations. They are only effective when the ballast tanks are full or empty and then slow down gradually.
Whenever the ship’s ballast in the tank levels with the waterline, the gravity method stops.
This is where ballasting or deballasting by pump comes in. They are fast, reliable, and usable at any stage of the operation.
Water Ballast System
The ship’s ballast system consists of three main parts: the ballast tanks, the piping system, and the high-capacity ballast pumps.
The ballast tanks are segregated from each other and only connected by pipes and valves. They are only meant to carry ballast water and nothing else, hence they are also called Segregated Ballast Tanks (SBT).
The piping system connects the tanks, the ballast pumps, and other peripherals. You can choose which tanks you want to pump water in or out by opening the right valves.
Ballast pumps are the “heart of the system”. There are usually two of them which are designed to “catch up” with the maximum rate of cargo operation.
Other components of equal importance are the sea chest, ballast stripping ejector, and the various sensors and alarms used to monitor the ballasting/ de-ballasting operation.
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Ballast Stripping Ejector
High-capacity ballast pumps are normally used to load or discharge the bulk of seawater. However, these pumps are not efficient in pumping out the few remaining ballast water inside the tank.
This is where the ballast stripping system comes in. During the last stage of deballasting, they use an ejector to discharge the remaining ballast water in the tank.
Using Fire Mains
Stripping the ballast involves using the fire pump. Lining up the valves and pipes is important so that water from the fire line goes to the ejector, which is also connected to the ballast tanks.
The ejector creates a vacuum on the pipeline thereby “sucking” the remaining water in the tank.
You can visibly tell when the ship is stripping her ballast tanks.
If you see water coming out from her anchor wash and another on her seaside, she is probably in her final stage of de-ballasting operation.
Who is in charge?
The Chief Officer (C/O) plans the ballasting and de-ballasting procedures in line with the cargo operation. He takes into account the ship’s stability, draft, vessel’s stresses, bending moments, and many other factors.
But due to the rules on working hours, the Chief Mate can not do this on his own. Therefore, he delegates this activity to the Officers-on-Watch (OOW).
The OOW follows what’s written in the cargo plan. Remember that the cargo plan also includes the ballasting and deballasting plan.
The C/O then supervises the whole operation until completed.
There is news regarding the development of unmanned ships but the intricacy of this operation is still debatable whether machines or artificial intelligence (AI) can handle ballasting/ de-ballasting safely.
Why Do Ships Engage in Ballasting and De-ballasting Operation?
There are many factors why vessels engage in ballasting and de-ballasting activity. The bottom line is to keep her safe, upright, and stable.
A ship is subject to internal and external forces while at sea or in port. Even if she is made of steel, these forces could break her putting the crew and cargo in complete danger.
Ballasting and deballasting help avoid those risks.
1. Cargo Operation
Cargo operation is the process of transferring the cargo from the shore facility to the ship- called loading, and from the ship to the shore terminal called unloading or discharging.
Ballasting and de-ballasting are simultaneously involved.
During loading, cargo transferred on board adds weight to the vessel. De-ballasting removes some of the ship’s weight to lighten her, thus counterbalancing the added cargo weight.
You can see this happen on some ships in port pumping out water from their seaside. They are most likely engaged in deballasting operations.
Ballasting usually happens during the discharging operation. When the ship is transferring her cargo to the terminal or shore facilities, she becomes lighter due to the movement of weights.
Adding ballast water into her tanks compensates for the loss of weight. This process maintains the vessel’s stability and structural integrity.
2. Entering Ports, Channels, or Canals
Ports, channels, and canals have draft requirements before vessels can pass, cross, or enter. This is to avoid grounding or touching her bottom into the seabed.
Adjusting the ship’s draft is possible with ballasting or deballasting operation. Sometimes, it’s a mix of both just to reach the required draft for entry.
3. Emergency Heavy Weather Ballast
For ballast ships (ships carrying no cargo), one of the purposes of ballasting is to keep the propeller and rudder submerged.
But there are times when the sea is very rough and the ship’s stern throws into the air thus over-speeding the propeller.
Scenarios like this happen even if the ship makes all speed adjustments and ballasting procedures to keep her upright.
In this special case, the vessel performs an emergency heavy weather ballast where she fills a cargo tank with ballast water.
This added ballast increases the ship’s stability, weight, and therefore her draft, giving more immersion to the propeller.
4. Ballast Exchange
A ship’s water ballast tanks contain microorganisms and other marine life which got sucked in during ballasting operation.
These creatures get a “free ride” from one port to another depending on the ship’s voyage.
When the vessel deballasts her tanks, these marine species are also transferred to their new environment. Sometimes, they pose a threat by actively invading its new territory.
These invasive species disrupt the balance of the new ecosystem. To avoid this from happening, ships perform a ballast exchange procedure.
A vessel conducts ballast exchange in the open sea, usually a few nautical miles from land before arriving at the port. She pumps out the current ballast water and replaces it with the water in that area.
Another procedure involves diluting the current ballast by overflowing the ballast tanks on deck.
5. Emergency Inspections
One time, our vessel got involved in an incident where the rudder touched the bottom while performing a turn.
After that event, there was a creaking sound whenever the rudder made certain angles.
We decided to see as much of the rudder so the Chief Officer made the vessel trimmed by her head (forward draft is greater than aft draft).
This was possible by ballasting the fore peak tank and the tanks forward of the tipping center. Furthermore, deballasting the aft peak and tanks aft of the tipping center also helped.
6. Grounding
When a ship runs aground, a portion of her weight rests on the seabed.
Deballasting on the right tanks while keeping the propeller submerged may help free her with the help of her engines.
Or she can completely empty her ballast tanks and ask assistance from salvage tugs if the latter doesn’t work. If all those fail, she may need a dredger to remove the seabed around her.
7. Hull Breach
Ballast tanks are not only meant for carrying seawater. They are also the first line of defense that protects the ship from hull breaches.
A design called double walls and double bottoms safeguards the cargo holds or tanks avoiding further damage to the ship’s stability.
Since ballast tanks are segregated from each other, a hole from one tank is only contained in that part. The right mix of ballasting and deballasting may still be able to keep the ship afloat.
What’s your experience with ballasting and deballasting operations?
May the winds be in your favor.
