Intercargo Requests Changes to Ballast Water Requirements

ballast tank
ballast tank

Published May 14, 2017 9:22 PM by The Maritime Executive

Industry body Intercargo has highlighted some of the technical and operational difficulties faced by bulk carrier owners in meeting the requirements of the IMO Ballast Water Management Convention and U.S. legislation.

As a result of these concerns, Intercargo has submitted two papers to the 71st session of the IMO Marine Environment Protection Committee (MEPC 71) to be held in July. The organization's proposals include a revision be made so that:

"A bulk carrier constructed before 8 September [2017] conducts two sequential regulation D-1 ballast water exchanges for its topside tanks only, as an alternative to the standards described in regulation D-2 which shall be accepted as complying with the Ballast Water Management requirements of regulation B-3."

The organization has discussed it's concerns in an open letter to the industry. Some of the concerns are described here:

Availability of Type Approved Systems: insufficient

Currently there are 69 ballast water management systems (BWTS) that have received type approval certification by their respective administrations. It is important to highlight that this does not mean that a ship owner or shipyard has a choice of 69 different systems.

From a newbuilding perspective, not all the systems are suitable due to the treatment capacity of some of the systems i.e. a number of the listed systems are not able to treat the water at the same rate as required by the ship’s ballast system to enable normal ballasting operations. 

Compared to most other vessel types, bulk carriers together with tankers and gas carriers tend to have a larger ballast capacity with pumps of higher capacity.

The existing fleet is confronted with even greater challenges than those faced by newbuilds. Bulk carriers also have less choice due to the size limitations imposed by available space and also by the additional electrical powering requirements imposed by these systems compared to the available power on board.

Gravity Discharged Top Side Tanks: an inevitable sacrifice?

The world bulk carrier fleet is by far the largest single sector by deadweight tonnage and a significant portion of the fleet uses the highly energy efficient gravity discharge system for the topside ballast water tanks unique to bulk carriers.

On those vessels which use the gravity discharge system, the top side tanks are typically filled from the fire main, not from the ballast line and are discharged directly overboard, which is incompatible with the requirements for the obligatory discharge monitoring and secondary discharge treatment required to reach the performance standard or for neutralization of any chemicals used in the treatment process.

UV Systems generally require a secondary treatment phase at discharge to achieve the required IMO D-2 standard and thus to fit this type of system on bulk carriers with gravity discharged top side tanks is extremely challenging because of the technical obstacles and financial burden associated with altering the existing arrangements on board a vessel.

It is not possible to simply connect the top side tanks to the double bottom tanks as the structure of the lower tanks, particularly the hopper tanks, is not able to support the rise of pressure due to the additional head of water without additional strengthening of the tanks. 

It has been estimated that the additional weight, in the form of stiffeners, collar plates and brackets, would amount to between 50 and 200 tons depending on the vessel size. The considerable modifications, damage to and the repair of the ballast tank coatings also increases the scope of work that will need to be carried out.

Connecting the top side tanks to each other, via a valve, and then piping back to the engine room brings its own problems such as penetrating the engine room forward bulkhead and running ballast piping through fuel tanks. There will also be problems with effective emptying of tanks due to trim, which may lead to operational difficulties during loading and unloading.

A third possibility is to connect each top side tank to the ballast main in the double bottom/duct keel. In addition to modifications to existing pipework, fitting of pipe supports, new penetrations through watertight boundaries and repairs to the existing ballast tank coating system, isolating valves would need to be fitted to each new branch of the ballast line.

Fitting a common ballast discharge line through the top side tanks with cross valves to each tank is an option; however this would also lead to major modifications including penetrations through the engine room bulkhead, other tight bulkheads, fitting of pipe supports and damage to the ballast tank coatings.

On top of the difficulties associated with the discharge, gravity discharged top side tanks are not filled by the ballast line serviced by the ballast pump but are filled using the fire main and general service pump. Therefore, a second treatment system would be required to treat the uptake of the general service pump, either that or a major modification to the fire main so that ballast water entering the fire main is passed through the ballast water treatment system.

Most chemical treatment systems require monitoring of the discharge and then a chemical neutralization phase and with these systems the same challenges faced with fitting a UV System would also apply. There are, however a limited number of chemical treatment systems which treat on the uptake only but modifications described previously would need to be carried out.

In addition to the major modifications that would be required, the advantages of gravity discharged tanks would be lost, these advantages include; a) Faster ballasting and de-ballasting; b) Less electrical energy used; c) Less wear and tear on the existing pumps and piping; and d) Effective tank stripping.

Powering requirements: prohibitively high

A significant portion of the existing fleet are geared bulk carriers. For these vessels, BWTS retrofit will create additional problems that will need to be overcome. The powering for newbuilding vessels is calculated at the design/construction phase and that these calculations are performed on the basis of the intended vessel operation and equipment/machinery fitted on board.

For the existing fleet there is little or no spare available power to run a BWTS. Geared bulk carriers typically have four cranes and four grabs which are used simultaneously during cargo operations. For these vessels, cargo operations will need to cease during ballasting or de-ballasting, or a major upgrade of the onboard power generation would be required. 

Cargo discharging capacity is often governed by the charter party and thus any reduction of the speed of cargo discharge could lead to failure to meet contractual requirements.

Electro-chlorination and UV Systems require significant power requirements which would compound the issues. It would be necessary to upgrade the onboard power generation and electrical systems. The increased power requirements of BWTS will lead to more fuel being consumed in the auxiliary engines resulting in an increase in air emissions.

Low treatment capacity compared to ballasting requirements

Not all the available BWTS have sufficient treatment capacity that is equal to the capacity of the ballast pumps. This means that the owners have to choose a system from the limited options available or have to fit additional treatment systems in order to operate under the conditions that the vessels were designed to. Additional systems would mean further modifications to the ballast and power supply systems, thus increasing the financial burden. This issue is even more complex when the large bulk carriers are considered.

Fitting BWTS will most likely incur significant ballast pump pressure drops due to the BWTS filters, which will cause a reduction in ballast pump capacity or the replacement of the ballast pumps with those of a greater capacity. The BWTS filters will also affect ballasting operations in sediment rich water, such as rivers, as additional time will be required to backflush the filters.

There is more… (coating, space, etc.)

The effects of chemically treated water on ballast tank and floodable hold coatings is not known and may have a detrimental effect on the coating. The coating system plays a fundamental role in maintaining the structural integrity of the vessel which is recognized by class and by the IMO Marine Safety Committee, which adopted the Performance Standard for Protective Coatings for Dedicated Seawater Ballast Tanks in all Types of Ships and Double-side Skin Spaces of Bulk Carriers.

The available space for fitting a BWTS also provides challenges for the ship owner which is especially true for the smaller bulk carriers where there is insufficient room to fit all the BWTS components in the engine room. This entails the BWTS being “broken up” and the components being installed in different locations in the machinery and deck areas which adds to the installation complexity, maintenance scope and is detrimental to the BWTS operation which could affect monitoring and safety.

Any modifications to the tanks and piping associated with retrofitting a BWTS will require class and flag appraisal. New connections between tanks may have significant impacts on stability, intact and damage stability requirements and would need to be re-assessed, documents such as the Loading Manual, Stability Booklet and Damage Control Plan would need to re-appraised and possibly amended.

Not so long ago, a big problem at terminals was ballast discharging speed and a bulk carrier’s capacity to load cargo at the rate the terminal wanted, so as to save loading time. Terminals black listed ships that delayed loading operations. It is entirely probable that such ‘swift’ loading times will no longer be possible if ballast discharge has to pass through the BWTS.


The opinions expressed herein are the author's and not necessarily those of The Maritime Executive.