Importance of maintaining the ballast water will provide the vessel a seaworthiness and safety to the structure and human, Hence, each vessel type has its own procedure to manage the ballast water in various conditions , however, the ballast water capacity rate can be determined by two main factors the first one is loading/unloading cargo capacity weight and the second factor is the speed of cargo operation , for instance, the ballast water uptake or discharge has to be capable to response with cargo capacity loading/unloading rate and its speed in order to stabilize the vessel . Therefore, selection of BWTS on board vessel must be considered carefully and must be synchronized with existing ballast operating plan and future requirements.
6-2 FACTORS OF SELECTING AND INSTALLATION BWTS
A – Flow rate:
The selection of BWTS capacity rate must be capable to response in certain period to be aligned with capacity rate of cargo operation, otherwise, delay in operation might occur or effect on the vessel stability. However, evaluate the vessel ballast capacity in various condition will help to select appropriate system. Therefore, it is very important to choose BWTS that capable to produce a higher capacity rate than the existing ballast capacity to sustain the current and future growth demand. Additional to this, Risk Assessment must be conducted to ensure under any circumstances the vessels stability will be maintained.
B – Pressure drop:
The difference pressure between inlet flows form the ballast pumps and BWTS, created by BWTS components to be kept at minimum. In this respect, increases in difference pressure would result in longer time to fulfil the ballast plan, thus, this might cause delay in loading/unloading cargo operation (29).
C- Operational Power:
Power requirement on board the vessel was closely predetermined during the vessel construction , in order to meet the operation demand in various conditions such as vessel voyage, loading/unloading, at anchorage or at port and a redundant extra KW were considered during the design stage in order to avoid black out following sudden changes in the power load and permits to serve only additional small appliances that their power consumption will not affect the vessel power supply. However, Retrofit vessel with current power management system, despite the BWTS operating in low power range, it might cause blackout, especially during the discharging with several equipment’s are operating at the same time. Consequently, prior to final selection of BWTS, it is worth to recalculate the load power analysis on board the vessel to determine the available power in various conditions with consideration to ensure a sufficient redundant in the power system to be able to response in case of unexpected change in vessel load and for future growth. The outcomes evaluation will assist the vessel owner to support their decision in either to utilise the existing power system or new generator with redundant power is mandatory.
Different makers have developed different treatment technique, however, throughout the uptake ballast water treatment some of the outcome products are generated in this process such as active substances or formed gases are entering the ballast tank, in long term operational might cause a sever corrosion in ballast tank coatings or ballast pipes. Therefore, it is required to obtain a long-term corrosion test from the maker and after the installation a regular inspection must be conducted.
E – Cost:
The cost has been classified in this project as a capital cost refer to one-time payment for procurement and installation such as installation and pipe modifications, second cost is the operating expense includes the consumption of fuel to power up the system, consumables spare parts, interventional maintenance and inspections. Thus, the operating cost is considered the most important factor. Some of the BWTS Systems are designed to consume a high chemical dosing which ultimately will lead to decrease the CAPEXP and increase the operating expense due to high necessitates chemical consumption. In other hand, low power consumption is achieved and vice versa (29).
The footprint requirements can vary from 1 to 50 m² (29). An appropriate site has to predetermine in order to select a proper dimension (footprint) that would be easily fitted and pipe modification arrangement. Retrofit vessel would essentially require an assessment of the existing structure, thus along with a trim and stability assessment, incline experiment and an updated watertight integrity plan would need to be carried out and submit to class for final approval. Systems can be fitted close to ballast pump in engine room or on main deck if the propose system has granted Explosion-proof Certificate especially for oil tanker.
BWTS uses a chemical or high voltage would be essential to conduct a risk assessment identifying the potential risks of transport and storage chemical, operating sequence, maintenance and risk following expose to high voltage. Each vessel type must be dealt with individually case by case, depends on the discharge capacity, cargo type, the nature of operation in various conditions, power suitability, available space and costs.