DOSSIER

 

A simpler way to treat aft  peak tank ballast?


Techcross has developed a way to treat aft peak tank ballast water in your main vessel ballast water system without mixing - with a different flow system

Treating aft peak tank ballast water is a headache for tanker operators. Aft peak tanks are small tanks in the stern of the ship used to ensure the propeller is immersed, to dampen propeller vibration, and to cool the stern tube bearing, which carries the propeller shaft.

The water in them needs to be put through a ballast water system like any other ballast water on the ship, to make sure that any foreign organisms are killed before the water is discharged to the ocean.

Regulations state that the aft peak tank ballast water cannot be mixed with the main ballast water tanks. This is because of perceived risks that oil from cargo in an adjacent tank could leak through corroded tank walls into the main ballast water tanks. The aft peak tank is located in a ‘gas safe zone’ so there cannot be any possibility for it to contain oil.

This means that tanker operators have been forced to consider a separate ballast water system just for the aft peak tank.

But Techcross, a ballast water system manufacturer in South Korea, has developed a different option, where the water from both aft peak tank and main ballast tanks could be handled by the same ballast water system, by structuring the flows in a clever way.

In Techcross’ system, the ballast water system treats the water after it has been stored in the aft peak tank, but before it is loaded into the main ballast tank.

So during the ballast voyage, the water in the main ballast water tank is already treated, and afterwards it can be discharged to the ocean.

This process was approved by DNV in 2018.


In more detail, the steps are like this.
Step 1 - the Aft Peak Tank is filled with untreated water.
Step 2 - The ballast water in the Aft peak tank is transferred across the deck, in a ‘non-return connection’, to the ballast water treatment system, and then to an empty ballast water tank in the cargo area. The ballast water treatment system is in a hazardous area.
Step 3 - the water is held in the cargo ballast water area
Step 4 - the water is discharged using ‘neutralisation’.
This is shown in the diagram.

                          
Altogether, this arrangement can save customers the over $100k cost of an aft peak tank system, the company says.

Since the Techcross system is electrochemical rather than ultraviolet, it does not need any filter, Techcross says.


Filters
This layout would not work if a filter was needed because of other complexities.

In a normal ballast water installation, the water is both filtered and treated before entering the ballast water tank. This means that any organisms caught by the filter can be discharged into water in the same place they came from, as required under the regulations. However, it is not allowed to be discharged in a different location from where it originated.

If you have a filter upstream of the aft peak tank (as it is filled with water), and a ballast water treatment system downstream of the aft peak tank after voyage (as the water is discharged), that is not considered equivalent to the type approved process, because organisms not separated by the filter can grow in size and volume during the voyage.

This would also make it harder for this water to be then flowed into the main ballast tank.

But with the Techcross system, no filtering is needed, all the killing of the organisms is handled by the electrochemical process.


Submerged pumps

Techcross also has a system for tankers with submerged pumps, such as a Medium Range (MR) tanker, where there is no pump room.

The normal way to install ballast water systems on these vessels is in a specially designed room on deck.

This involves safety concerns and a high cost of installation. Being on deck, the systems need to be explosion proof, which increases the cost.

The Tech Cross system can be installed in the engine room, which is not considered a ‘hazardous’ environment, so the system does not need to be explosion proof, and welding is much easier. This is possible because its systems are small.

The system has a modular design and small footprint.

This enables customers to save 20 per cent of the price of the system, and 30 per cent of the installation costs.
The submerged pumps are used only for de-ballasting. A different pump - a fire pump or general service pump - is used for loading the ballast tank.

This solution has been applied to over 50 newbuild medium range tankers at Korean shipyards, and a number of retrofits.


EPA’s VIDA

The US Environmental Protection Agency (EPA) Vessel Incidental Discharge Act (VIDA) National Standards of Performance are new proposed ballast water regulations which could apply to small vessels (less than 79 feet in length) and fishing vessels of all sizes. Vessels above 79 feet are covered by existing legislation.

Techcross makes a very small ballast water system, ECS-150, which is supplied mounted on a skid, as a ‘one size fits all’ system for easy installation.

Techcross is currently researching ways to reduce the footprint and cost of this system.

 

About Techcross

Techcross supplies an electrochemical based ballast water system. It has 3762 systems installed in the maritime industry, as of July 2021.

It claims that its systems have a lower operating cost but the same performance as others in the market.

 

 

 

  LMB-BML 2007 Webmaster & designer: Cmdt. André Jehaes - email andre.jehaes@lmb-bml.be