Ballast Water Management Retrofits – 7 Steps to Selecting a Technically Suitable System
Selecting the most suitable ballast water management system for a specific vessel is a critical, and often, underestimated task. With over 50 commercial systems available, operating on numerous combinations of different technologies and treatment processes, the suitability of any one system to a specific vessel cannot simply be presumed.
This article provides a comprehensive, step-by-step guide to vessel owners and operators in the technical suitability of a BWMS, the first stage in the determination of the most suitable BWMS for a specific vessel. Armed with this guide, owners and operators can embark on an efficient and objective selection process, however, this guide is no substitute for a comprehensive feasibility study carried out by an experienced and competent engineering partner such as Cleanship Solutions.
Often the first question asked by shipowners and operators is; “Which technology is most suitable for our vessel?” The short answer to this is; there is no short answer .. !
Identification of the most suitable technology is driven by much more than just the vessel type or size, and has to incorporate a variety of key considerations, such as:
- Vessel trading patterns
- Required technology approvals I certification
- Existing ballast operations
- Installation location · Access for installation
- Power availability
- Existing pump capabilities
- Life cycle costs
- Availability & Logistics
- Manufacturer corporate viability & sustainability
This guide will identify these key considerations, and outline key discussions points of each.
Step 1 -Vessel Trading Patterns
The first step in determining the technical suitability of a BWMS is building an understanding of the trading patterns of the vessel, and any limitations on system selection that these may cause. Vessel trading patterns are a critical consideration for treatment system selection, for a combination of reasons, namely:
- Individual port state requirements or local legislation
- Specific water quality limitations
Of course in a global sense, the first geographical consideration is whether the vessel has, or is, trading to the United States – or if the vessel requires the ability to do so in the future. If so, then immediately the treatment system options are limited to either USCG Type Approved systems, or AMS approved systems with USCG Type Approval pending, or in the works. Installing a system without USCG Type Approval, and without any likelihood of obtaining it, on a vessel trading into the US, could have significant commercial consequences.
Water quality limitations are also highly important in the early stages of system selection. Water quality not only varies from country to country, but also from port to port. Various aspects such as turbidity, salinity, total suspended solids and silt contents impact the operation and performance of a BWMS -sometimes critically. It is important to understand any significant water quality issues associated with ports where the vessel conducts ballast water operations, and cross check these with the limitations of each BWMS independently.
Step 2 -Required Approvals & Certification
The second step in determining the technical suitability of a BWMS is understanding the required approvals and certification of the system itself. First and foremost, owners and operators must, of course, ensure that any BWMS considered hold appropriate IMO Type Approvals from a suitable Flag State. In general, most Type Approvals will be in accordance with either the G8 or G9 guidelines, and comply with IMO Resolution MEPC.174(58).
For vessels which have been identified as currently trading to the US, or requiring the ability to do so, will require suitable USCG approvals. The first consideration is whether the BWMS currently holds a valid USCG Type Approval. For those that don’t it is important that owners satisfy themselves that the manufacturer has a valid AMS approval, and is in the process of obtaining full USCG Type Approval. Long-term compliance with USCG legislation will require a fully USCG Type Approved system be onboard, beyond the 5 year grace period that AMS approval provides.
Alternatively, owners and operators trading into the US can utilise one of the other acceptable methods indicated by the USCG.
Step 3 -Existing Ballast Operations
The third step in the technical determination of a BWMS is ensuring a thorough understanding of the vessel’s existing ballast operations and the total treatment flow rate capacity required.
Understanding how, when and where the vessel currently, and historically, conducts ballasting f de-ballasting operations is crucial in determining the suitability of a system, and understanding the technical limitations these typical operations impose is of prime importance.
The total treatment capacity itself is a significant driver of suitability, particularly on the commercial side, as different technology types can immediately be discounted from consideration depending on the total capacity. Chemical based treatment systems, for example, are not cost efficient for lower flow rates, whilst UV based treatment systems, for example, tend to have significant operational costs at very high flow rates, due to their high power demand. Hence the importance in understanding the total treatment capacity required.
Vessels with high ballast dependency, such as bulk carriers, may also be sensitive to USCG Type Approved UV systems – which often have significant flow rate drops (up to 50%) whilst operating on USCG “mode.” This would have a dramatic effect on cargo operations.
In many cases, the operational approach of the vessel can drive the suitability of particular technologies or even individual systems, and in some cases, simple changes to the operational approach of the vessel can help widen the scope of suitable systems – such as dropping from two ballast pumps to one – halving the required treatment capacity immediately.
Some key ballasting / de-ballasting considerations to make include:
- Operational times – if during significant cargo operations this may have an impact on power availability and/or personnel availability to operate
- Operational locations – if the vessel tends to conduct ballasting I de-ballasting operations in deeper water prior to entering port, this may remove water quality issue limitations
- How many pumps? – Whether the vessel ballasts or de-ballasts with a single pump or two pumps will drive the total treatment capacity required
- Stripping procedures – if the vessel conducts stripping operations this will drive the selection of a system
Owners and operators should liaise closely with the vessel crew to establish a benchmark of the existing ballasting / de-ballasting operations, before embarking on the selection process. If changes to the operational approach of the vessel are being considered, it is important to conduct a thorough investigation, with all parties involved, into the impact of the proposed operational changes on the vessel’s efficiency, safety and, of course, suitability under its charter.
Step 4 – Installation Location
Exactly where onboard the vessel the BWMS components would likely be situated is a significant driver in the selection process, and has to be a combined effort in conjunction with Step 2 – existing ballast operations.
For conventional vessels with engine room ballast pumps and no hazardous areas, the location of the BWMS components is generally driven by space availability – not just for the BWMS components themselves, but also the associated pipework, fittings and maintenance access. In many cases, the lack of availability of suitable space, or the size limits of the space, can drive the selection of the BWMS.
For vessels with complex ballasting / de-ballasting operations and/or hazardous area limitations, the suitability of particular technologies becomes more obvious. First off, if the BWMS components are required to be installed in the hazardous area, perhaps due to the vessel utilising Framo pumps, then the BWMS selection process immediately requires systems that come with a suitable “EX” rating.
Generally, these vessels will also have limitations on where, within the hazardous area, the components can be installed – again driving the need for smaller components that can suit the space available. More often than not, vessels with hazardous area considerations will require a new, dedicated, deckhouse be design and installed to house the new BWMS.
This stage does tend to be somewhat iterative, but is crucial in selecting the most suitable system.
Stage 5 – Access for Installation
Once the vessels trading patterns are understood, the ballasting / de-ballasting operations have been investigated, and proposed installation locations identified, the next step is understanding the limitations on accessing the installation location onboard.
For vessels with conventional engine room ballast pumps, and hatch access directly from main deck into the engine room, access for installation is not an issue. However, for many vessel types and sizes, the proposed installation locations for the BWMS components may be somewhat difficult to access, and hence due consideration to the modularity and portability of the BWMS components has to be made.
Owners and operators should ensure that for complex installation locations, accessible only via watertight doors or small hatches, examination of the modularity of the BWMS components is undertaken. We have witnessed, on many projects, numerous BWMS be discounted from consideration simply due to their smallest components being too large to transport into the installation locations. Indeed, in some instances we have witnessed BWMS that claim to have been designed to be modular and fit through doors and hatches, be too large to do sol So owners and operators should be acutely aware of these limitations prior to selecting a BWMS.
The modularity and access for transportation internally is not the only consideration. Owners and operators should also pay close attention to the practicality and safety implications of transporting such heavy, and often unwieldy, components within vessel’s machinery spaces.
In many cases, cutting access holes to load components, either in various decks or in the sideshell of the vessel, may be the only course of action, but with some clever engineering and careful consideration during the feasibility and engineering phases, such drastic action may be able to be avoided.
Step 6 – Power Availability
Power availability is a critical consideration during the selection of a BWMS, and is an aspect that many stakeholders overlook.
Owners and operators have to conduct a detailed review of the existing power balance calculations for the vessel, reviewing the load conditions during which the BWMS would also be operating, and build an understanding of the power limitations, namely:
- Maximum free power available under current operating conditions prior to an additional generator being required
- Total maximum free power available
In many cases, the addition of the load of the BWMS will result in another generator running which will, of course, have implications on the operational costs of the vessel itself. In some critical cases, particularly on vessels with high ballast dependency (such as tankers and bulk carriers), vessels may not have sufficient power for the BWMS – and may have to examine more drastic alterations to the vessel’s powering.
The disparity in power consumption not only between different technology types, but also between different systems within a single technology branch, is astounding, particularly at higher flow rates. Vessels with limited power and high ballast flow rates will undoubtedly face the biggest challenge.
Understanding the numerical power limitations, and the commercial implications of exceeding them, is a key step in the selection of a BWMS.
Step 7- Existing Pump Capabilities
Step 7 involves the examination of the existing ballast pumps onboard, and their suitability to not only meet the hydraulic requirements of the BWMS, but also their ability to cope with the inherent pressure drop that BWMS create in the ballast system.
The majority of BWMS that incorporate a self-backflushing filter state very specific minimum inlet pressure requirements –typically around 1 bar- 1.6 bar. These requirements are to ensure that the backflushing process can be carried out efficiently and failure to meet these requirements can cause clogging or blocking of the filter elements. Indeed, very few BWMS manufacturers will guarantee their system if the inlet pressure of the ballast system does not meet these requirements during the commissioning phase.
Whilst many ballast systems will have been designed with pumps providing in excess of 1.6 bar, some systems, particularly on smaller vessels or older vessels, may struggle with reaching this requirement. Conversely, some vessels, such as PSVs and OSVs, which may have combined ballast / drill water pumps, may operate at a pressure which far exceeds the pressure limitations of the BWMS system-which tends to be around the 6 bar mark.
Ballast water treatment systems, by their very nature, also create an increase in pressure drop. The extent of the pressure drop varies depending on technology employed and specific system components, however pressure drops of 0.3 bar- 0.8 bar are not uncommon. Such additional pressure drops will have one of two effects on the existing ballast pumps:
- The pump flow rate will drop due to the increase in pressure drop
- The new system pressure demand will be unachievable by the pump, which will result in zero flow and/or erratic running
Whether the pumps are struggling to meet the inlet pressure requirements of the BWMS, or they are struggling to cope with the additional pressure drop, owners and operators may be faced with upgrading or, in worst case scenarios, replacing existing ballast pumps. Indeed, we observe this on many of the retrofit projects that we are involved in.
Analysing the capability and suitability of the existing ballast pumps is an important step in the BWMS selection process.