Ballast water is under scrutiny for its role in the spread of invasive species around the planet. However, recent legislation makes it compulsory for all ships to have an effective ballast water management system (BWMS) fitted, and properly certified components are an essential part of that. Jo Kirkbride, actuators & positioners product manager for ABB Measurement & Analytics UK with ABB, explains
Ballast water is pumped aboard vessels to maintain safe operating conditions throughout a voyage. It reduces stress on the hull, provides transverse stability, improves propulsion and manoeuvrability and compensates for weight changes as cargo is loaded and unloaded, and as fuel and water is consumed during the voyage. If the vessel is fully loaded, ballast water can end up being discharged in a completely different part of the world.
Water has been used as ballast and disposed of by ships in ports, harbours and coastal waters since the early 1900s. As a result, invasive species travelling the world in ballast water is not a new issue.
In fact, the spread of invasive species is recognised as a leading threat to biodiversity. International trade has led to a rise in shipping in recent decades and the transfer of ballast water has effectively opened up previously isolated ecosystems to one another. The resulting damage to the environment can be devastating and irreversible.
The rise of regulation
In the late 1980s, Canada and Australia were among countries experiencing problems with invasive species and they brought their concerns to the attention of the International Maritime Organization’s (IMO’s) Marine Environment Protection Committee (MEPC). The ensuing negotiations eventually culminated in the arrival of the Ballast Water Management (BWM) Convention, which entered into force in 2017.
The Convention requires all ships to carry a ballast water record book and they have to carry out ballast water management procedures to a given standard. Put simply, ships using a ballast water management system (BWMS) must meet a performance standard based on agreed numbers of organisms per unit of volume.
These guidelines were subsequently revised and converted into a mandatory Code for approval of ballast water management systems (the BWMS Code), which came into force in October 2019. This is generating a renewed focus on BWMS among vessels owners and operators globally.
A variety of technologies are available for treating ballast water on board vessels. Constraints such as space, cost and environmental friendliness can all be important when designing a BWMS.
Most BWMS combine two or three ballast water treatment technologies together, divided into different stages. A typical system would include a physical separation step, filtering out sediment and the larger organisms and returning them to the original ballast site, which is followed by another disinfection technology to remove pathogens and smaller organisms. valve positioners
Whatever the chosen design, it is essential to control the flow of ballast water throughout the stages of the system and ultimately to discharge ballast water following the regulatory guidelines. This is achieved by using a series of valves.
Valve positioners are therefore essential components of any ballast water management system. The systems often operate in tough, inaccessible environments in the ‘bowels’ of a ship and so need to be robust, reliable, space efficient and require minimum maintenance. In addition to the appropriate DNV GL certification, it’s therefore worth noting some of the features that make positioners a good fit for this important application.
Quality materials are important. ABB’s entry level TZIDC positioners have an aluminium housing, for example, while the top-of-the-range EDP300 uses stainless steel to offer the best possible long-term protection against what is likely to be a saline environment. Since it’s likely to be wet, choosing a positioner with a high IP rating is also a good idea.
The TZIDC-Remote and the EDP300-Remote allow the operator to use an HMI interface in a more accessible way, making it much easier and safer to monitor the system. The added benefit is the increased vibration immunity offered at (2g @ 300Hz) and the increased ingress protection (IP66) and ambient temperature range (-40°C - 100°C).
Resource efficiency is a key concern on long voyages. ABB’s pneumatically driven positioners offer the lowest steady state compressed air consumption on the market. At less than 0.03kg/h (0.015 scfm), this delivers large energy savings and a lower lifetime cost of ownership.
Similarly, design features that improve reliability and enable easy maintenance are very desirable when ships are operating far from their home ports. ABB’s positioners are modular in construction, making it straightforward to retrofit new parts if necessary.
Finally, it may also be advisable to choose a supplier who will be able to act locally – wherever in the world the vessel happens to be. ABB has a global network of partners that can respond if needed.
A brighter future?
Many invasive species have already arrived around the world via shipping, but the recent rule changes on BWMS will help prevent any further damage to biodiversity from ballast water – provided these front-line defence systems are properly certified, implemented and managed.