Mr. Stamatis Fradelos, Director, Business Development, ABS, highlighted key technical safety issues related to the installation of Ballast Water Treatment Systems. His presentation provided an overview of the BWT Technologies and corresponding physical separation and different disinfection solutions that are currently available in the marine market.
Ballast Water Management Systems is a compliance method related with environmental regulations. However, when it comes for installation onboard the vessels, there are safety aspects that need to be considered. When selecting a BWMS, owners must carefully consider the risks associated with:
- Location aboard the vessel,
- Chosen technology,
- Vessel’s type.
A. Ballast Water Management Technologies
In general, ballast water treatment technologies fall into two groups: separation technologies or disinfection technologies. Separation technologies remove organisms from ballast water while disinfection technologies kill or render organisms incapable of reproducing. Depending on the chosen technology additional precautions might need to be taken due to possible hazards associated with that particular technology.
A thorough assessment would be required to ensure that any possible hazard has been mitigated to acceptable levels:
a. Inert Gas De-oxygenation Systems
For a BWMS treatment system supplying inert gas to ballast tanks, controls shall be in place ensuring that the ballast tanks will not be subjected to a pressure or vacuum in excess of the P/V valve setting. Suitable provisions should be in place in providing the protection measures for addressing the possible migration of hydrocarbon or flammable liquids or vapors from the cargo block ballast system to the non-hazardous area. Special consideration is also to be given to the design and location of scrubbers and blowers with relevant piping and fittings in order to prevent flue gas leakage into enclosed spaces.
b. Ultraviolet – Disinfection Irradiation (UV) Systems
Arrangements are to be provided such that the crew will not be exposed to excessive amounts of UV light during operation, maintenance or repairs of the system. Normally, a UV intensity meter and means to prevent operating the UV lamps without water in the treatment chamber (i.e. an interlock) are provided. This and means to prevent the accumulation of air in the top of the lamp enclosure or treatment chamber are provided by means of a high and high-high temperature alarm and automatic system shut down.
c. Prepared Chemical Treatment Systems
A Material Safety Data Sheet (MSDS) should be provided describing the proper storage and handling procedures as well as the information on the quantity to be added to the ballast water and the maximum allowable concentration of the substances in the treated water. The system should not exceed the maximum dosage and maximum allowable discharge concentration at any time to avoid any associated hazards and risks for the crew, vessel and the discharge of chemical substances to the sea. In particular the following aspects have to be considered:
- Design and installation of containment systems for all liquid chemicals stored and in use to prevent any chemicals from escaping under the maximum inclination conditions and implementation of a safe and secure means of transferring chemicals onto the vessel. Spill trays of ample size might need to be provided.
- An approved gas detection system is to be installed in all spaces housing the chemicals together with proper air supply and ventilation, and leakage detection. A high temperature and a high and low pressure alarm are to be provided, with its shutdown conditions identified.
- Chemical level indication, alarms, and automatic shutdown are to be arranged at remote and local control stations. An adequate system capable of self-monitoring and recording of chemical dosages is to also be provided.
- Adequate means are to be provided to prevent overflowing the ballast tanks and unintentional discharge of ballast water prior to completion of treatment or un-neutralized water exceeding the residual treatment chemical limits.
- All equipment, piping, components and coatings exposed to the chemical treatments need to be compatible with the chemical.
- Chemicals provided as a gas have to be placed in an open storage area or a storage room. The storage room is to be on or above the upper-most continuous deck, equipped with special ventilation arrangements, to be of steel and gastight and access to the room is to be from the open deck and the door is to open outwards.
d. Ozone Injection Systems
Ozone, due to its strongly oxidizing properties, is a primary irritant, affecting especially the eyes and respiratory systems and can be hazardous at even low concentrations. In this respect ozone sensors are to be installed in the immediate vicinity of the ozone generating unit and along the route of the ozone piping where ozone gas could accumulate and to activate an alarm at a manned location when a concentration of 0.1 ppm or more is detected. Furthermore the routing of the ozone piping is not to pass through accommodations or service spaces.
Provisions should be arranged for independent vents from the oxygen receiver safety relief valve and any ozone destructor unit are to be led directly to a place on the open deck where the discharges will not cause a safety or health hazard.
Additional arrangements are to be provided to automatically shut down the system immediately when there is a high ambient oxygen concentration (25%) or a high ambient ozone concentration (0.2 ppm).
e. Electro-chlorination Systems
In addition to disinfecting chemicals such as hyper chlorides or peroxides, electro-chlorination process produces hydrogen (flammable) and chlorine (toxic). If the electro-chlorination unit (ECU) of a BWMS is installed in a dedicated space, the space is to be considered a Zone 1 space as defined in IEC Standard 60092-502 and is to be provided with non-sparking ventilation fans suitable for hazardous areas providing 30 air changes per hour with suitable interlock arrangements so that the fans will be in operation at all times when the electro-chlorination unit is in operation. The all welded exhaust piping vents for any gases generated in the electro-chlorination process that could be flammable or harmful to the crew are to be led directly to a place in the open deck where such discharges will not cause a fire or explosion hazard. The area within 3 meters (10 feet) around the vent outlet is to be considered to be a hazardous area.
Arrangements are also to be provided such that the ECU chamber is always filled with water to avoid creating an explosive atmosphere in the event of ingress of flammable fluid into the ECU chamber (i.e. Interlock arrangement such that the ECU cannot be energized if water level/flow is less than an acceptable limit) and also to avoid excessive surface temperature in the event of a water level drop (i.e. automatic shutdown in case of excessive temperature or pressure).
A fixed hydrogen gas detection system is to be provided in the space housing the ECU and arranged such that the activation of the gas detection alarm will result in an automatic shutdown of all electrical power to the ECU.
Furthermore the potential of any flammable or toxic gas released into the ballast tanks has to be assessed and if found in a concentration and/or volume that could present a hazard to the crew or the vessel measures are to be provided (e.g. venting arrangements, gas gauging system in tank, etc.).
B. Piping Components and Materials
Special consideration should be given to the compatibility of materials used in BWMS; The fire endurance and flammable spread requirements for BWMS non-metallic piping and components made of thermoplastic or thermosetting plastic material such as polyvinyl chloride (PVC), fiber reinforced plastic (FRP), etc.
The components of the ballast water treatment equipment are to be arranged on a skid and local firefighting arrangements and/or a metallic enclosure covering the non-metallic components may be required. The inlet, outlet and drain pipes connected to the skid-mounted unit are to be made of steel or equivalent materials or by fiber reinforced plastic pipe of approved type which has passed at least the level 3 (L3) fire endurance tests.
In case of emergencies, suitable remote operable bypasses are to be provided to isolate the complete non-metallic piping system on the skid- mounted unit from the rest of the ship’s piping system.
a. Damage Stability Consideration
BWMS piping, where installed within zones of the assumed extent of damage under damaged stability conditions, is not to lead to progressive flooding of spaces not assumed damaged. If it is not practicable to route piping outside the zone of assumed damage, then means are to be provided to prevent progressive flooding. Such means, for example, may be the provision of a remotely operated valve in the affected piping. Alternatively, intact spaces that can be so flooded are to be assumed flooded in the damage stability conditions.
b. Bypass Arrangements
Suitable bypass and interlocking arrangements are to be provided to isolate the BWMS from the ballast system piping such that the ballast system can be operated totally independent of the BWMS in the event of emergency. Any bypass of the BWMS should activate an alarm, and the bypass event should be recorded by the Control Equipment. Remote control valves, where fitted, are to be arranged so that they will close and remain closed in the event of a loss of control power or emergency shutdown.
D. Vessel’s Type (Oil/Chemical Tankers)
Additional provisions have to be taken to address the special requirements associated with the treatment of ballast water from tanks located adjacent to cargo tanks or other hazardous areas on oil or chemical carriers. The ballast water treatment and associated components could be installed:
- In a non-hazardous area (i.e. Engine room) provided that the arrangement of the ballast piping cannot permit the ballast water or vapors from the ballast tanks (hazardous area) to be returned to the space containing the BWMS (non-hazardous area).
- In a hazardous area (i.e. a void space in cargo area, ballast pump room, cargo pump room, etc) under special provisions.
- In a compartment in a hazardous area which is redesigned as a non- hazardous (i.e. an enclosure located above deck area)
For Gas Carriers ballast spaces in cargo area and non-hazardous spaces, may be connected to a ballast water management system located in a machinery space.
a. BWMS serving ballast tanks considered to be non-hazardous.
When the BWMS serves ballast tanks that are considered to be non-hazardous then the system may be installed in machinery spaces, void spaces or dedicated compartment unless specifically prohibited due to the treatment method involved. In case the BWMS is installed in the engine room or other machinery space it is to be located in a well-ventilated area.
Where the BWMS is installed in a separate space then an independent mechanical extraction ventilation system is to be fitted providing at least six (6) air changes per hour or as specified by the BWMS manufacturer, whichever is greater. The BWMS space is also to be treated as a machinery space other than a Category A in terms of the structural fire protection requirements.
The identification of fire risk of the BWMS, including the active substances or preparations used or generated (i.e. Hydrogen), and the provisions of effective means to detect and extinguish the type and scale of fire likely to occur in the BWMS space are to be considered.
b. Installation in a non-hazardous area
A piping system serving or having an opening into tanks or spaces that are considered to be hazardous is likewise to be regarded as contaminated and in general, is not permitted to enter machinery and other spaces normally containing sources of ignition due to the potential migration of flammable liquids or vapors from the hazardous area into the non-hazardous area. In this respect the following arrangements could be considered:
- The BWT sampling units are located in a non-hazardous area such as the engine room, which are connected to a ballast piping system serving a treatment unit installed in a hazardous area such as the cargo pump room.
- The BWT dosing units are located in a non-hazardous area such as the engine room, which serve a ballast system located in a hazardous area such as a cargo pump room.
- The whole BWMS is in a non-hazardous area and serves ballast tanks in a hazardous area such as the cargo area of tankers. The ballast pumps in this arrangement may be only used for filling the ballast tanks or for driving eductors to empty ballast tanks where the ballast water does not need treatment before it is discharged. The flow of ballast water is to be in one direction only from the gas safe zone to the hazardous zone.
c. BWMS sampling units located in a non-hazardous area
Suitable provisions should be in place in providing the protection measures for addressing the possible migration of hydrocarbon or flammable liquids or vapors from the cargo block ballast system to the non-hazardous area. The sampling system is to be located within a reasonably gas tight enclosure mounted on the forward bulkhead separating the hazardous and non-hazardous area provided with a gas and water leakage detection device to initiate an alarm upon detection of any gases and to disconnect all electrical power to the cabinet.
For isolation purposes sufficient stop valves are to be provided in each sample pipe supplemented by automatic fail-closed valves arranged to close upon loss of power or activation of gas detection or float level alarms.
Bulkhead penetrations of sampling piping, between safe and hazardous areas, are to be gastight and have the same fire integrity as the division penetrated while the cabinet is to be vented to a non-hazardous area in the weather deck.
d. BWT dosing units located in a non-hazardous area
The following provisions should be considered for all BWMS which are involving dosing units (i.e. chemicals, ozone, inert gas, etc) located in a non-hazardous area (i.e. engine room) and are interconnected to a ballast water system in a hazardous area (i.e. the cargo pump room) in addressing the safety concerns due to the potential migration of hydrocarbon or flammable liquids or vapors from the hazardous areas.
- The dosing piping is to pass through the bulkhead separating the safe and non-safe areas at as high an elevation as possible.
- Stop/check valves and fail closed valves that are closed at all times other than when the dosing system is in operation are to be provided to prevent back flow into the dosing unit.
- A reverse flow monitor with an alarm and system shut down is to be fitted in the dosing line.
- A passive in-line device capable of preventing the passage of vapors back through the dosing piping when the system is not operating is to be provided. This may be a loop seal, a water (liquid) seal, a block and vent arrangement, etc.
e. BWMS in a non-hazardous area serving hazardous ballast tanks
A BWMS may be installed in a non-hazardous area (i.e. engine room) serving non-hazardous ballast tanks (i.e. Aft Peak tank) and simultaneously serving hazardous ballast tanks in the cargo block incorporating special provisions which include but not limited the following:
- Remote control valves and stop check valves are to be provided to prevent hydrocarbon or flammable liquids or vapors to pass to the non-hazardous area.
- The ballast tanks are to be fitted with means of detecting hydrocarbon vapors if applicable, depending on the BWMS used.
- Remote operable valves are to be provided in the engine room and the cargo block, which together with the ballast water pump and the BWMS are to be automatically shut down / closed in the case of hydrocarbon gas detection in the ballast tanks and /or pump room.
- The valves to and from the ballast tank are to be arranged so that they remain closed at all times except when ballasting.
- The ballast water piping penetrations are to be gastight.
- A loop seal of at least 1,5m height or a liquid column of at least 1,5m tall or a block and bleed arrangement with a reverse flow sensor is to be provided in the hazardous area as a safeguard to prevent hydrocarbon or flammable liquids or vapors to pass to the non-hazardous area.
f. Installation in a hazardous area
Where a BWMS involves electrical equipment, the acceptance of placement in a hazardous location (i.e pump room) and the associated arrangements will be subject to special considerations according to Class Rules and Regulations, Chapter II-1, Regulation 45.11 of the 2004 Amendments to SOLAS, the requirements of IEC 60092-502 (1999) “Electrical Installations in Ships – Tankers – Special Features”, as referenced by SOLAS for ships constructed on or after 1 January 2007 and the concurrence of the vessel’s flag Administration.
The installation of a BWMS which requires electrical current of more than 20 milliamps in a pump room of a tanker would not appear to be in compliance with the above mentioned Class Rules and Regulations. However the international standard IEC 60092-502 is in general less restrictive on the certification of electrical equipment than traditional class rules and the installation of a ballast water treatment system in a pump room may be possible provided the tanker is operated and maintained in accordance with the IEC standard.
The normal provisions would include the following:
- The electrical equipment intended for installation in hazardous areas is to be of the certified safe type and is to be selected based on the class of hazardous area at its location of installation.
- An Interlock is to be provided for the pump room ventilation such that the electrical power supply to the BWMS cannot be energized while the ventilation is not in operation.
- An interlock is also to be provided such that any detection of hydrocarbon gas (or other flammable gases associated with the cargo) in the Ballast Water Tanks or in the Pump Room will immediately shut down the BWMS.
- The circuit feeding the BWMS in the pump room is to be monitored continuously for ground faults and is to give an audible and visual alarm at a manned location.
- Equipotential bonding is to be provided for the BWMS, i.e., the BWMS is to be earthed to the metal hull (see 5.4 of IEC 60092-502).
- All cables, installed in the pump room, other than those of intrinsically-safe circuits are to be sheathed with a non-metallic impervious sheath in combination with braiding or other metallic covering.
- The failure of pressurization where applicable for certified safe type components of a BWMS is to result in the shut-down of the power supply of the BWMS
g. Installation in a hazardous area which is redesigned as a non-hazardous
When some of the components of the BWMS are not suitable for installation in a hazardous area they may be installed in a separate compartment which can be designed to be non-hazardous (i.e. installation of a BWMS in a room located above the upper deck of a tanker) subject to the provisions of the following arrangements:
- There are no portions of the BWMS’s ballast water piping or sources of release (i.e., cargo piping with flanged connections, valves etc.) within the compartment.
- The external surface of the floor of the separate compartment need to be at a height of 2.4m above the main deck or alternatively the enclosure arrangements should include an air-lock capable of maintaining an over-pressure and a cofferdam should be installed between the floor of the separate compartment and the main deck tank top. The relative overpressure or air flow is to be continuously monitored with an audible and visual alarm and the electrical supply of all equipment is to be automatically disconnected in case of a fault.
- All ventilation inlets and outlets are to be routed outside of the hazardous area.
- The mechanical ventilation system is to have at least twenty (20) air changes an hour or as required by the BWMS manufacturer, whichever is greater.
Systems that treat ballast water are to be designed and installed to achieve operability and measurable efficacy levels while not impacting vessel safety.
A ballast water treatment system must meet all the normal requirements for shipboard materials, effects on other ship systems or structure (corrosion), equipment protection and hazardous space safety, acceptability of any active substances and preparations aiming to ensure the health and safety of those responsible for operating the equipment and handling the materials, as well as the risk of unintentional discharge into the environment. The skill and training of the crew and their ability to manage this safety risk should be considered when selecting a treatment system. In other words safety should never take a back seat to operability and biological efficacy
Above article is an edited version of Stamatis Fradelos’ presentation during the last SAFETY4SEA Conference.
View his video presentation herebelow:
The views presented hereabove are only those of the author and not necessarily those of SAFETY4SEA and are for information sharing and discussion purposes only.