Patent Application
20230219679
The present invention relates to a system and method for fumigating a vessel. The invention has particular application to fumigation of roll-on/roll-off vessels. The present invention is also directed to an exhaust to assist with venting fumigant gases. Although the present invention is directed to roll-on/roll-off vessels, certain aspects of the invention are by no means limited to these types of vessels and may have broader application to cargo vessels and other types of sea-faring vessels.
The reader is also directed to our other coexisting application filed coincidentally: “System and method for fumigating a vessel with crew protection” concerning features described herein but not claimed. The entire contents of that coexisting application are incorporated herein by reference.
It is a requirement in many jurisdictions that cargo onboard a cargo-carrying vessel be fumigated prior to unloading. Fumigation of an infested vessel may also be necessary. The fumigation process involves releasing fumigant into a cargo area of the vessel to elimate, reduce, or avoid infestation of the cargo by insects or other undesirable pests. The fumigant may be provided in solid form and located in the cargo area, or may be provided in gaseous form and piped into the cargo area. The fumigation gases are usually toxic to human beings.
The fumigation process may be conducted en-route, when anchored, or when moored at quay, and is typically conducted by specially trained personnel with specialised equipment. In most instances, members of the crew of the vessel will be located on the vessel during the fumigation process, and thus it is imperative that the fumigation process is conducted in such a manner that ensures that the crew (and the specially trained fumigation personnel) are not exposed to the toxic fumigant. Access to parts of the vessel such as the engine room and mooring lines may also be required during fumigation.
A bulk carrier is a vessel specifically designed to transport unpackaged bulk cargo, such as grains, coal, ore, and other similar loose cargo. Bulk carriers typically comprise one or more separate cargo holds arranged fore to aft in the vessel. Grain or other unpackaged bulk goods may be loaded into and unloaded from the cargo holds by, for example, one or more cranes located on the deck of the vessel. Alternatively, conveyor loaders, shoreside cranes, or pneumatic loaders may be used to load and unload cargo. Each of the cargo holds typically also includes a hatch for closing the opening to the cargo holds.
In bulk carriers, the accomodation area of the vessel and the engine room of the vessel are typically located aft of the cargo holds, with the accomodation area provided above the engine room. The cargo holds are separated from the engine room by a vertically extending bulkhead. The accommodation area is physically separated from the cargo holds, by being physically removed from the cargo holds by the intervening engine room and furthermore by two physical barriers including the vertically extending bulkhead and the deck between the engine room and the accommodation area. Due to this physical separation, it has generally been relatively safe to fumigate each of the cargo holds of a bulk carrier, subject to inspection of the vessel.
A new challenge presents itself in safely fumigating roll-on/roll-off vessels, also known as RORO vessels. In vessels of this sort, the cargo area typically extends substantially the entire length of the vessel, and is arranged in decks within the vessel. The decks are interconnected by upright passageways such as staircases and ladders and the decks are joined by ramps. Further, the decks are grouped into watertight or gas tight zones, with typically 2 decks in each zone, although some vessels may include more than 2 decks per zone. Normally, RORO vessels are arranged into approximately 4 zones and each zone is independently ventilated. The cargo area is configured in this way so that breakbulk cargo such as wheeled cargo can be rolled onto or driven into the cargo area.
In a RORO vessel, the accomodation area is typically located upon the weatherdeck of the vessel, with only plate steel and a floor covering separating the accomodation area from the uppermost deck of the cargo area. Thus, any openings or small cracks within this plate steel structure could result in fumigant entering the accomodation area from the uppermost deck of the cargo area. Openings or small cracks are prevalent in seagoing vessels due to the stresses placed on the vessel during seafaring.
The arrangement of the accommodation area in a RORO vessel presents another challenge for exhausting the fumigant from the cargo area. Ventilation systems which service the cargo decks have been specifically designed to ventilate fuel vapour from the cargo area. Each zone (watertight or gas tight group of cargo decks) of the vessel is serviced by its own group of mechanical ventilators (supply and exhaust, as discussed below), wherein the ventilators may be controlled as a group or each ventilator in the group may be individually controlled independent of any other ventilators in that group. In general, the systems have been designed to typically achieve 20-30 air changes in each zone during loading/unloading operations and 10 air changes per hour during navigation.
RORO vessels typically have one of two types of ventilation systems for the cargo area:
1. Supply and Exhaust Mechanical Ventilators:
Supply and Exhaust ventilators are arranged around the perimeter of the weather deck. Some vessels may have as many as 70 or more mechanical ventilators. Mechanical Ventilators serve as either supply, exhaust, or reversable supply mechanical ventilators. Each zone of the vessel is ventilated by a group of supply and exhaust mechanical ventilators which work together to exchange air in the zone. Each zone has multiple ducts connected to the group of mechanical ventilators through which the air is exchanged (supply and exhaust ducts).
The ventilators may be dedicated supply ventilators and dedicated exhaust ventilators, as the case may be. Some fans can be run alternatively in supply and exhaust mode and the mode is controlled by the operator. Such ventilators are referred to as reversible supply ventilators. Depending on how many air changes need to be achieved during navigation or loading/unloading, some mechanical ventilators may be used/not used.
The mechanical ventilators are typically located very close to the accommodation area and the engine room supply ventilator or intake, sometimes barely a few metres. Type 1 is prevalent with new RORO vessels.
2. Supply Mechanical Ventilators and Vent Houses:
Supply mechanical ventilators are located around the forward and midship perimeter of the ship.
Fresh air is forced into each zone by the supply mechanical ventilators and the atmosphere is exhausted out through the vent houses.
In either case, the mechanical ventilators/vent houses are close to the engine room air intake and the air-conditioning intake for the crew accommodation. Thus, the relative proximity presents a risk to the crew if the mechanical ventilators/vent houses vent fumigant during fumigation.
In addition, the mechanical ventilators are designed with mechanically operated vents which open and close but which are directed downwardly in either case to avoid entry of rain. Therefore, the mechanical ventilators blow down onto the weather deck. Venting the fumigant from the cargo area through the mechanical ventilators creates a likelihood of fumigant stratifying and remaining on the weather deck. This poses a risk to crew requiring access to the engine room, moorings or in the case of evacuation.
Another special feature of RORO vessels as distinguished from bulk carriers is that RORO vessels sit proud of the water compared to bulk carriers due to the lower density of the cargo in RORO vessels. Thus, mooring lines will be lower down, typically on decks 4 or 5 and thus require stairwell access so that the crew can adjust the mooring lines to take account of tidal movement. In contrast, the mooring lines for a bulk carrier are arranged on the weather deck.
Other areas of the vessel may require access during fumigation. For example, the engine room, which is is sandwiched between cargo zones, may require access during fumigation. For example, auxiliary generators typically run during fumigation. Should an alarm condition arise, the crew will then require access to the engine room. Fumigant entering the engine room or accessways will be harmful to the health of the crew.
It is an object of the present invention to provide a system/method for fumigating a RORO vessel. It is also an object of the present invention to provide an exhaust for a cargo vessel. Another object of the present invention is to at least provide the public with a useful choice over known systems, methods and equipment.
As used herein, the term “roll-on/roll-off vessel” or “RORO vessel” refers to any vessel in which wheeled or tracked cargo is rolled onto or driven into the cargo decks of the vessel, typically via a stern ramp. Examples of such vessels include a pure car and truck carrier (PCTC), a large car and truck carrier (LCTC), and a pure car carrier (PCC).
Reference to any prior art in the specification is not an acknowledgment or suggestion that this prior art forms part of the common general knowledge in any jurisdiction or that this prior art could reasonably be expected to be understood, regarded as relevant, and/or combined with other pieces of prior art by a skilled person in the art.
1. System for Fumigation with Temporary Exhaust
In an aspect, there is provided a system for fumigating a RORO vessel, the system being ancillary to the vessel, the system comprising:
a fumigant delivery system for delivering fumigant to a cargo area of the vessel; and
a temporary flexible exhaust to assist removing fumigant from the cargo area, wherein the temporarily flexible exhaust has first and second openings, wherein the second opening has a smaller cross-sectional area than the first opening.
The exhaust may therefore comprise a temporary structure intended to remain in place only for the duration of the fumigation. The temporary exhaust may be removable from the vessel. Alternatively, the temporary exhaust may remain in position. Its configuration may change depending upon whether it is operational or non-operational. The exhaust may include a flexible conduit. The temporary exhaust may substantially comprise an upright exhaust. The temporary exhaust may comprise an inflatable conduit. Preferably the inflatable conduit inflates substantially vertically, preferably to provide an upright exhaust. In a most preferred form, the temporary exhaust may comprise a flexible conduit which is inflatable to provide an upright exhaust. The temporary exhaust may be configured such that it can be inflated by the exhausted air from the cargo area.
In a preferred form, the second opening with the smaller cross sectional area is intended to be disposed at an upper end of the upright exhaust with the first opening disposed at the lower end, or towards the lower end or to the side of the upright exhaust.
Preferably, the temporary exhaust is in fluid communication with an exhaust port (or an opening which is acting as an exhaust port) which is a permanent fixture or a temporary fixture on the vessel.
It will be understood by those skilled in the art that RORO vessels can have one of two different types of cargo ventilation systems as described above. In the first type described above, the air is supplied to the cargo area either by being forced through the supply ventilators or passively drawn in if the supply ventilators are switched off with the dampers opened. Air is positively withdrawn via the exhaust mechanical ventilators. Tests have found that the cargo area is pressurised in this system. Thus, pressurisation of the crew areas as described below will reduce and the risk of leakage to areas intended for human occupancy.
In the second type of ventilation system as described above, intake fans apply positive pressure to the cargo area and the vent houses allow passive outlet of the pressurised air. Thus it will be understood that such a system pressurises the air within the cargo area with a greater risk of leakage to areas intended for human occupancy.
The temporary exhaust may therefore be in fluid communication with a mechanical exhaust ventilator, in the case of the first system, or alternatively in fluid communication with a vent house, in the case of the second system. However, it will be appreciated that exhaust of fumigant from the cargo area using the second system is less desirable due to the pressurisation of the cargo area and other options for ventilation may be more desirable.
With this in mind, various alternative arrangements are possible including:
Example 1: one such temporary air extraction system relies upon using the existing escape trunks, of which there are approximately 8-10 on a RORO vessel, typically arranged along the perimeter of the weather deck. Approximately half of the escape trunks may be opened for use as air intakes and the other half installed with extraction fans. In such an arrangement, temporary exhausts may be attached in fluid communication with respective extraction fans.
Example 2: Another such ventilation system uses all of the escape trunks as exhaust trunks by installing extraction fans. The air may be positively or passively supplied by the mechanical supply ventilators. Temporary exhausts may be in fluid communication with respective extraction fans.
Example 3: In yet another extraction system, all of the escape trunks may be installed with intake fans, with the mechanical exhaust ventilators used to exhaust air from the cargo area. In such a system, temporary exhausts may be in fluid communication with respective mechanical exhaust ventilators.
Example 4: Escape trunks also have their own forced air supply and passive exhaust. A temporary flexible exhaust could also be fitted to an escape trunk without the use of temporary intake or extraction fans.
It will be understood that escape trunks may be known by various different terms including escape hatches, man ways and booby hatches.
While the foregoing describes the use of mechanical ventilators or fans at or adjacent the weather deck, it will be appreciated that additional fans may be provided in the cargo area, such fans disposed at the entry of conduits leading to the ventilators or fans at or adjacent the weather deck.
Thus, the exhaust port to which the temporary exhaust may be attached may comprise any one of the following: the mechanical exhaust ventilator, the vent housing, the extraction fan, as the case may be. The temporary exhaust may be attached to the exhaust port, either directly or indirectly. For instance, the temporary exhaust may be attached over the mechanical exhaust ventilator body, thereby being indirectly connected to the exhaust port. Alternatively, the temporary exhaust may be configured to facilitate venting through the service doorway of a mechanical exhaust ventilator or vent housing.
For example, in the case of a mechanical exhaust ventilator, the temporary exhaust may be attached thereto, either by enveloping the mechanical exhaust ventilator or by access through the service doors. In the case of the former type (Type I), the second opening of the temporary flexible exhaust is sized to accommodate a substantial portion of the mechanical ventilator. A typical size for a mechanical ventilator is L 2760 mm×W 1740 mm×H 3660 mm, being in the form of a vent body supported by a stem. The stem is the rising ventilation duct which opens into the vent body and is of approximately 1315 mm in height. The temporary exhaust may be fitted over the mechanical ventilator to accommodate a substantial portion of the mechanical ventilator, at least to the base of the vent body (positioned at the top of the stem). The substantial portion may encompass all of the vents in the mechanical ventilator. The temporary exhaust may be installed to extend below the vents and create a plenum chamber therebeneath to assist with inflation of the temporary exhaust. Preferably, the temporary exhaust is sufficiently sized to accommodate the ventilator housing with a gap between the ventilator housing and the temporary exhaust. The gap may be approximately 300 mm on each side of the ventilator housing.
The first opening may be disposed upstream for connection to the exhaust port and the second opening may be disposed downstream for exhaust of the fumigant. Preferably, where the temporary exhaust is in the form of a flexible conduit, the flexible conduit has a first open end for connection to the exhaust port and a second open end for exhaust of the fumigant. The first end may be sized to fit over the mechanical ventilator, with a cinch to secure the first end to the mechanical ventilator.
The flexible conduit may be conical in its inflated form. However, the flexible conduit may also be cylindrical in form with the second open end being adjustable such that the conduit is conical in its inflated form. The flexible conduit may have a first lower cylindrical portion and a second upper conical portion. The proportions may be two-thirds cylindrical and one-third frusto-conical. The second open end may be dimensioned to match the dimensions of the impeller in the mechanical ventilator.
The temporary exhaust may be fluidly connected to the exhaust port of the mechanical exhaust ventilator, through the service doors of the mechanical exhaust ventilator (Type II). The body of a mechanical exhaust ventilator typically houses the top of a ventilation duct from a specific cargo zone. The temporary exhaust may be configured to attach to the upper end of the ventilation duct, adjacent the opening thereof which ventilation duct opens into the vent body. Accordingly, the temporary exhaust may be shaped as an elbow with two portions, having a first portion which has a first open end for connection to the ventilation duct, the first portion configured to extend out through the service doors, and a second portion provided with a second open end for exhaust of the fumigant.
In this Type II configuration, the temporary exhaust may include a plenum configured to encompass the upper end of the ventilation duct, in which the impeller is located. Preferably the plenum is of flexible sheet material. The plenum may project through the service doors of the mechanical exhaust ventilator upon inflation. Preferably, the plenum is fluidly connected to a flexible conduit, which is also of flexible sheet material. The plenum and the flexible conduit may be of different materials. The flexible conduit may be conical in form or cylindrical (with an adjustable second open end to provide adjustment to a conical form).
Due to the pressure of the exhausted air, this Type II configuration has a tendency to incline in use so that the flexible conduit leans away from the mechanical exhaust ventilator, the distance increasing towards the top. To counteract this tendency, a support structure may be provided to support the temporary exhaust. The support structure may comprise a U-shaped support assembly, the sides of which are mounted on the service doors of the mechanical exhaust ventilator with the base of U-shaped support assembly supporting the plenum.
Alternatively or additionally, the flexible conduit may be constructed such that it is angled relative to the outlet of the plenum. For instance, the plenum may have a circular outlet defining a first longitudinal axis perpendicular to the plane of the circular outlet, the circular outlet of the plenum being directly connected to a circular inlet of the flexible conduit. The flexible conduit may have a longitudinal axis which is inclined to the first longitudinal axis. The angle of inclination is towards the inlet of the plenum. Thus, in use, the flexible conduit will orient itself in an upright manner under the pressure of the exhausted air, the angle of inclination compensating for the pressure of the exhausted air.
A third form (Type III) is intended to operate with vent houses which allow passive outlet of the pressurised air. In this form, the temporary exhaust is connected directly to the service doorway of the vent house, with the louvred outlets from the vent house being temporarily blocked. Accordingly, the temporary exhaust may be configured as a tubular column with a peripheral branch to connect to the service doorway. Like the other embodiments, the upper end of the tubular column may be frustoconical. Optionally, the second open end at the upper end of the column is adjustable. The base of the column may be supported on the weatherdeck. The column may also be provided with ties to attach the column to the vent house. The peripheral branch having the first open end for connection to the service doorway is suitably commensurate in shape with the doorway e.g. typically oval.
Whichever the form, the temporary exhaust may have a height which exceeds the height of the accommodation block. The height range for the flexible conduit may be 4-10 m. With the various different types (type I, type II and type III), the preferred heights are as follows:
The idea of the flexible conduit is to get the airflow directed upward. Preferably the airflow is at high velocity.
The fumigant may comprise any substance for disinfecting or purifying the cargo area. The fumigant may comprise a fluid such as a gas, vapour, smoke or aerosol. Preferably, the fumigant is in a form which is removable from the cargo area by evacuation or exhaust of air from the cargo area.
The fumigant may be a pesticide. Alternatively, the fumigant may comprise an insecticide, disinfectant, purifier, bactericide, decontaminant, antiseptic, sanitiser, vaccine, anti-viral, or vapour.
RORO vessels likely carry untreated cargo that is likely to be infested. There is a risk that live insects could escape from the cargo decks and infiltrate an at-risk country like Australia. In order to mitigate this biosecurity risk, we have implemented several biosecurity safeguards to keep the insects contained in the cargo area.
Accordingly, the temporary exhaust may include an insect net. Preferably the insect net is located above the mechanical exhaust ventilator. The insect net may be located at the top of the temporary exhaust. However, it is preferable that the insect net is located closer to the first upstream opening than to the second downstream opening.
The insect net may be removable, for example by the use of hook and loop fastener. Alternatively, the insect net may be permanently affixed to the temporary exhaust, for example sewn into the temporary exhaust.
In another aspect, there is provided a RORO vessel including the system for fumigation as set out above.
Any of the features set out in connection with other aspects may have application to this aspect.
2. System for Fumigation with Inflatable Exhaust
In another aspect, there is provided a system for fumigating a RORO vessel having a cargo area and an accomodation block, the system being ancillary to the vessel and comprising:
a fumigant delivery system for delivering fumigant to the cargo area; and
an inflatable exhaust to assist removing fumigant from the cargo area wherein the inflatable exhaust is inflatable to a height exceeding the height of the accomodation block.
Any of the features described above in connection with the other aspects set out herein may have application to this aspect.
In another aspect, there is provided a RORO vessel including the system for fumigation as set out above.
3. Method of Ventilating with Temporary Flexible Exhaust
In yet another aspect, there is provided a method of ventilating a RORO vessel, the method including: providing a temporary flexible exhaust for exhausting fumigant from the cargo area.
Any of the features described above in connection with the other aspects may have application to this aspect. The method may include opening the doors of a service doorway to a mechanical ventilator and installing the temporary exhaust to the mechanical ventilator. The method may further include installing a support assembly to support the temporary exhaust from the service doors.
Alternatively, the method may include attaching the temporary exhaust to a vent housing by installing the temporary exhaust to fit the doorway and blocking any exit vents in the vent housing.
In particular, the method may include attaching the temporary exhaust to a positive exhaust provided on the vessel such as a mechanical exhaust ventilator or an extraction fan, as the case may be. The temporary exhaust may include an upstream opening and a downstream opening. The downstream opening may be of smaller cross-sectional area than the upstream opening. Alternatively, the downstream opening may have the same or a similar cross-sectional area as the upstream opening. Optionally, the downstream opening is adjustable in cross-sectional area. In an embodiment in which the temporary exhaust is attached to an extraction fan, the downstream opening preferably has the same cross-sectional area as the upstream opening. In another embodiment, the upstream opening may be sized to accommodate at least a substantial portion of a mechanical ventilator.
The method may include covering the mechanical exhaust ventilator with an insect net, prior to connecting the temporary exhaust. Alternatively, an insect net may be fitted over the exhaust duct intake in the cargo area. For example, an insect net may be fitted over the exhaust duct intake which supplies air to the mechanical exhaust ventilator.
The temporary exhaust may be configured to facilitate venting through the service doorway of a mechanical exhaust ventilator or vent housing. Accordingly, the method may include opening the doors of the service doorway to install the temporary exhaust. In the case of a mechanical exhaust ventilator, the method may include installing a support assembly to support the temporary exhaust from the service doors. In the case of a vent housing which passively vents, the method may include installing the temporary exhaust to fit the doorway and blocking the existing exit vents from the vent housing.
In another aspect, there is provided a method of fumigating including delivering fumigant to the cargo hold and the method of ventilating as per the aspect above. The temporary exhaust may have an adjustable downstream opening which is closed during fumigation and opened during ventilation.
In another aspect, there is provided a RORO vessel fumigated according to the above method.
4. Method of Ventilating with Inflatable Exhaust
In yet another aspect, there is provided a method of ventilating a RORO vessel, the method including: providing an inflatable exhaust for exhausting fumigant from the cargo area.
Any of the features described above in connection with other aspects may have application to this aspect. In particular, the method may include attaching the temporary exhaust to a mechanical exhaust ventilator or an extraction fan, as the case may be. The temporary exhaust may include an upstream opening and a downstream opening, the downstream opening being of smaller cross-sectional area than the upstream opening. Preferably, the inflatable exhaust is inflatable to a height exceeding the accommodation block of the RORO vessel.
The inflatable exhaust may be configured to facilitate venting through the service doorway of a mechanical exhaust ventilator or vent housing. Accordingly, the method may include opening the doors of the service doorway to install the inflatable exhaust. In the case of a mechanical exhaust ventilator, the method may include installing a support assembly to support the inflatable exhaust from the service doors. In the case of a vent housing which passively vents, the method may include installing the inflatable exhaust to fit the doorway and blocking the existing exit vents from the vent housing. The method includes inflating the inflatable exhaust.
In another aspect, there is provided a method of fumigating including delivering fumigant to the cargo hold and the method of ventilating as per the aspect above. The temporary exhaust may have an adjustable downstream opening which is closed during fumigation and opened during ventilation.
In another aspect, there is provided a RORO vessel fumigated according to the above method.
5. An Exhaust Conduit for a Cargo Vessel—Opening Size
In a still further aspect, there is provided an exhaust conduit for a cargo vessel, the exhaust conduit being a flexible conduit having a first upstream opening adapted to engage with an exhaust structure and a second downstream opening for exhausted air, wherein the exhaust conduit is inflatable due to the passage of exhausted air and the downstream opening is of smaller cross-sectional area than the upstream opening.
The inflation of the conduit may be solely by means of the passage of exhausted air.
In a preferred form, the exhaust conduit includes at least a portion in which the cross-sectional area progressively reduces along its length i.e. of tapering cross-sectional area. For example, the exhaust conduit may include a conical or frusto-conical portion. This provides a velocity cone.
The downstream opening may be adjustable to adjust the cross-sectional area. The downstream opening may be variable. For example, the downstream opening may incorporate a drawstring to adjust the cross-sectional area. The adjustment of the downstream opening may be achieved by initially drawing in the opening and allowing the pressure of the exhausted air to automatically adjust the opening. Accordingly, the preferred form has an adjustable velocity cone.
The exhaust conduit may take any of the forms described above in connection with the first aspect e.g. Types I, II or III.
The exhaust conduit may also include tether points to tether the exhaust conduit to the vessel.
The exhaust conduit may also include internal vanes or baffles to direct the exhaust. In another form, the exhaust conduit may include inflatable ribs to inflate the conduit or other structural components designed to keep the exhaust conduit in an upright configuration or in an open tubular configuration.
The exhaust conduit may be constructed from a fabric, preferably 30 to 130 gsm fabric such as Maxilite 150™ used as sail or spinnaker cloth. The fabric may comprise gas-proof ripstop nylon.
The exhaust conduit could incorporate its own fan. For example, the mechanical ventilator to which it is attached may be either active or passive.
Any of the features set out in connection with other aspects may have application to this aspect.
6. An Exhaust Conduit for a Cargo Vessel—Adjustable Opening
In a still further aspect there is provided an exhaust conduit for a cargo vessel, the exhaust conduit being a flexible conduit having a first upstream opening adapted to engage with an exhaust structure and a second downstream opening for exhausted air, wherein the exhaust conduit is inflatable due to the passage of exhausted air and the downstream opening is of adjustable cross-sectional area.
Any of the features described above in connection with other aspects may have application to this aspect. The exhaust conduit may take any of the forms described above in connection with the first aspect e.g. Types I, II or III.
As used herein, except where the context requires otherwise, the term “comprise” and variations of the term, such as “comprising”, “comprises” and “comprised”, are not intended to exclude further additives, components, integers or steps.
Further aspects and further embodiments of the aspects described in the preceding paragraphs will become apparent from the following description, given by way of example and with reference to the accompanying drawings.
Typical RORO Vessel
Referring to
The RORO vessel 10 further comprises a weather deck 18 located above an uppermost one of the plurality of cargo zones 14 and an accomodation area 20 located upon the weather deck 18 generally adjacent a fore end 22 of the vessel 10. The accommodation area 20 is arranged to provide accomodation to the crew or personnel of the vessel 10 and includes the various living quarters of the vessel 10. A bridge 23 is located above the accomodation area 20 and is generally fluidly connected thereto. The bridge 23 houses the various controls, navigation instrumentation, and other equipment necessary for the commanding of the vessel 10.
The cargo zones 14 of the RORO vessel 10 are located one above the other and extend substantially along the entire length of the vessel 10. In the illustrated embodiment, the vessel 10 includes four such cargo zones 14. As is described above, each of the cargo zones 14 is configured to be water-tight or gas-tight, and is further connectable to an adjacent cargo zone 14 via one or more moveable or sealable ramps. The moveable ramps are moveable between an open position and a closed position. In the open position, a ramp connecting adjacent cargo zones 14 enables the passage of crew members, other personnel, and cargo between the adjacent connected cargo zones 14. As will be appreciated, in the open position, the adjacent connected cargo zones 14 are fluidly connected to one another such that, for example, gaseous fumigant in one cargo zone 14 is able to flow into the adjacent connected cargo zone 14. In the closed position however, the ramp acts as a seal between adjacent cargo zones 14 such that the adjacent cargo zones are water-tight or gas-tight.
The uppermost cargo zone 14 may be accessed by crew or other personnel, such as specially trained fumigation personnel, via one or more escape trunks located in the weather deck 18. The RORO vessel 10 illustrated in
The opening or entryway into the uppermost cargo zone 14 via the weather deck 18 may be in the form of a hatch 29 (see
The RORO vessel 10 illustrated in
Mechanical Supply Ventilators and Exhaust Ventilators
The vessel 10 further comprises a plurality of supply mechanical ventilators 24 and a plurality of exhaust mechanical ventilators 26. Specifically, each cargo zone 14 includes respective dedicated supply and exhaust mechanical ventilators 24, 26. Each of the supply mechanical ventilators 24 are configured to supply fresh air from about the weather deck 18 into their respective cargo zones 14 via respective ducts 25 extending from the weather deck 18 to the respective cargo zone 14 (as illustrated by the direction of the arrows in
As is further illustrated in
The vessel 10 further comprises a engine room 38 located adjacent a lowermost one of the plurality of cargo zones 14 generally adjacent the aft end 34 of the vessel. The engine room 38 is physically separated from the lowermost cargo zone 14 via a vertically extending plate-steel bulkhead 40, and is further separated from the second lowermost cargo zone 14 by a plate-steel flooring of the second lowermost cargo zone 14. As will be appreciated, the engine room 38 houses the engines and other associated equipment used to power and propel the vessel 10, and is controlled by the various controls located in the bridge 23. Crew members may be located in the engine room 38 from time-to-time during operation of the vessel 10 and potentially during fumigation and subsequent ventilation. Exhaust gases produced during use of the engines is exhausted via a smokestack or chimney 42 located upon the weather deck 18 generally adjacent the aft end 34 of the vessel 10.
A travel tower 300 is located quay side to provide an alternative means of embarkment or disembarkment of the RORO vessel 10 during an emergency or fumigation operation when access to the RORO vessel 10 via the accomodation ladder water-tight door 36 is not possible. The travel tower 300 is a cherry picker style vehicle that is capable of raising passengers from the quay to the weather deck 18 of the RORO vessel 10.
It will be appreciated that the RORO vessel 10 illustrated in
Ancillary Fumigation System
As is described above, there is a present need to ensure that the cargo 30 in the vessel 10 is properly fumigated prior to unloading, whilst ensuring the safety of the crew of the vessel and any specially trained fumigation personnel. To this end, the present disclosure provides a system and method for fumigating a vessel, embodiments of which are illustrated in
Referring initially to
The fumigant delivery system 50 comprises a plurality of first conduits 52 (shown schematically in
The fumigant may be any one or more of a pesticide, insecticide, disinfectant, purifier, bactericide, decontaminant, antiseptic, sanitiser, vaccine, anti-viral, or vapour, and may comprise any one or more of sulfuryl flouride, ethyl formate, ethane dinitrile, formaldeyde, methyl bromide, chloropicrin, iodoform, hydrogen cyanide (bluefume), nitrogen, and carbon dioxide. While the disclosure includes reference to sulfuryl flouride, it will be appreciated that other fumigants may be incorporated into the embodiments. Additionally, modes of delivery and levels of fumigant detected by the high range detection system and the low range detection system may vary according to the selected fumigant.
A second end of each of the plurality of first conduits 52 is fluidly connected to the cargo zones 14 via a fumigation bulkhead 110 located in the accomodation ladder landing water-tight door 36. The fumigation bulkhead 110 (see
In addition to the fumigation bulkhead 110 located in the accommodation ladder landing water-tight door 36, a plurality of other bulkheads are located throughout the cargo area 13. As is described above, there is a hatch bulkhead 115 (
The combination of the fumigation bulkhead 110, the door bulkheads 111, and the hatch bulkheads 115 used throughout the cargo area 13 enable the entire cargo area 13 to be fumigated substantially simultaneously, or alternatively, allow for a particular cargo zone 14 to be fumigated separately of any other cargo zone 14, or further alternatively, allow for a plurality of cargo zones 14 to be fumigated separately of any other cargo zone 14.
Mode of Fumigation
Fumigating the entire cargo area 13 substantially simultaneously is achieved in the following manner. Firstly, a plurality of first conduits 52 are fluidly connected at their first ends to the mobile fumigant-containing vehicle 56, and fluidly connected at their second ends to an external side of the fumigation bulkhead 110 located in the accommodation ladder landing water-tight door 36. Then, another plurality of first conduits 52 are connected at their first ends to the internal side of the fumigation bulkhead 110, and connected at their second ends to respective recirculation fans 33 located in the second lowermost cargo zone 14 (as is described above, the accomodation ladder landing water-tight door 36 provides direct access to the second lowermost cargo zone 14). The recirculation fans 33 are configured to disperse the gaseous fumigant throughout the second lowermost cargo zone 14. There are preferably two recirculation fans 33 located in each cargo deck 16 in each cargo zone 14 in order to disperse the gaseous fumigant throughout each cargo zone 14. In a preferred arrangement, there is a first fan 33 located generally at midship on a starboard side of the vessel 10, and a second fan located generally at midship on a port side of the vessel 10. The first and second fans 33 preferably face in opposite directions within the vessel 10. For example, the first fan 33 may face towards an aft end of the vessel 10, and the second fan 33 may face towards a fore end of the vessel 10 in order to disperse the gaseous fumigant fully throughout each cargo zone 14.
Each of the recirculation fans 33 are preferably direct drive axial fans. Preferably, each of the recirculation fans 33 are 7.5 kW direct drive axial fans. Further, each of the recirculation fans 33 preferably have a diameter of 760 mm, and a centreline located 1.5 m above the cargo deck 16 to ensure sufficient dispersion of the gaseous fumigant througout each cargo deck 16. The recirculation fans 33 may have an air volume flow rate of between approximately 4 to 16 m3/s. The preferred air volume flow rate of the recirculation fans 33 is approximately 10 m3/s.
In order to fumigate cargo zones other than the second lowermost cargo zone 14, another plurality of first conduits 52 are connected at their first ends to the internal side of the fumigation bulkhead 110, and connected at their seconds ends to recirculation fans 33 located in each of the other cargo zones 14. The plurality of first conduits 52 may be routed to a particular cargo zone 14 through one or more of the door bulkheads 111 (
To fumigate a single cargo zone 14 only, or a particular plurality of cargo zones 14 only, a plurality of the first conduits 52 are connected at their first ends to the internal side of the fumigation bulkhead 110, and connected at the second ends to the recirculation fans 33 in the particular cargo zone 14 or cargo zones 14 which are desired to be fumigated. Any particular cargo zone 14 which is not desired to be fumigated is fluidly sealed by closing the openings 113 and 117 in the respective door bulkheads 111 and hatch bulkheads 115 that lead into that cargo zone 14 via the escape trunk riser. As is shown in
As is shown in
High-Range Monitoring System
Other features of the fumigation system 50 will now be described. Referring back to
During the fumigation operation, the supply and exhaust mechanical ventilators 24, 26 are maintained in a closed position to prevent the escape of gaseous fumigant into the environment above the weather deck 18. Attached about each of the exhaust mechanical ventilators 26 are respective flexible temporary exhausts 58, described in detail below. The flexible temporary exhausts 58 assist with the safe removal of the gaseous fumigant from the cargo zones 14 after the fumigation operation has been completed. In the embodiment illustrated in
Overpressure in Crew Areas
As is described above, during the fumigation operation, the air pressure system 60 is configured to maintain an air pressure within the accomodation area 20 greater than an air pressure within the cargo zones 14. In the illustrated embodiment, the bridge 23 is also maintained a greater relative pressure than the cargo zones 14 due to the bridge 23 being fluidly connected to the accomodation area 20.
The air pressure system includes three second conduits 62 (shown schematically in
As is illustrated in
Differential Pressure Sensing
The air pressure system 60 further includes a differential pressure sensor 70 that includes a first pressure sensing end 72 located in the accommodation area 20 of the vessel, and a second pressure sensing end 74 located in the uppermost cargo zone 14 and adjacent the accomodation area 20. The first and second ends 72, 74 of the differential pressure sensor 70 are configured to sense the respective pressures in the accommodation area 20 and in the uppermost cargo zone 14, and transmit the respective pressures to the controller 41. The controller 41 is configured to determine a difference between the respective pressures, and to control the operation of the fans 66 connected to the conduits 62 to ensure that a predetermined desired pressure differential is maintained. Preferably, the pressure in the accommodation area 20 is maintained at least 50 Pa above the pressure in the cargo zone 14. More preferably, the pressure in accommodation area 20 is maintained between 50 and 100 Pa above the pressure in the cargo zone 14. As will be appreciated by those skilled in the art, if the pressure differential decreases below the predetermined desired pressure differential, the controller controls the fans 66 via the VSD 43 to increase the speed of the fans 66 to thereby increase the volume flow rate of air drawn into the accommodation area 20 via the conduits 62. Conversely, if the pressure differential increases above a maximum desired pressure differential, the controller controls the fans 66 via the VSD 43 to decrease the speed of the fans 66 to thereby decrease the volume flow rate of air drawn into the accommodation area 20 via the conduit 62.
Air Quality Monitoring
The air pressure system 60 further includes an air quality monitor 76 located quayside generally adjacent the fans 66 (and thus the intake ends of the conduits 62). The air quality monitor is configured to detect the presence of one or more of gaseous fumigant, carbon dioxide, carbon monoxide, and other volatile organic compounds (VOCs), and may report the presence of these gases to the controller and/or to an operator so that the air pressure system 60 may be shutdown if required. The air quality monitor 76 forms part of a low-range monitoring system which is used to detect fumigant gas comprising sulfuryl flouride in the range of 0.5 ppm-230 ppm, with a resolution of 0.1 ppm. Other sensors 37 forming part of the low-range monitoring system may be used in specific locations to detect gas leaks. For example, sensors 37 may be located in the engine room 38, passageways and crew access and accommodation area 20. The sensors 37 may be daisy-chained with cable feeds fed back to the control system. The low-range monitoring system is operated during fumigation and ventilation.
The fumigation operation may last for several hours, such as around 12 to 48 hours or longer depending upon the treatment requirements. Throughout the fumigation operation, the air pressure system 60 is operated to maintain the predetermined desired pressure differential between the accommodation area 20 and the cargo zones 14, and is optionally operated beyond the end of the fumigation operation, at least until clearance of the gaseous fumigant from the cargo zones 14 and the cargo 30.
Ventilation Operation
After the fumigation operation has been completed, a ventilation operation is commenced in order to safely remove the gaseous fumigant from the cargo zones 14 and the cargo 30. The ventilation operation may last for several hours, such as around 10 to 36 hours or so. During the ventilation operation, the supply mechanical ventilators 24 are opened and their associated fans 24a are operated in order to enable a fresh supply of air to be drawn into the cargo zones 14. Additionally, the exhaust mechanical ventilators 26 are opened and their associated fans 26a are operated in order to positively remove air containing the gaseous fumigant from the cargo zones 14. This ventilation operation is illustrated in
Bulkheads
Referring initially to
Referring to
Referring to
As is shown in
The fumigation bulkhead 110 is similar in form and operation to the accomodation bulkhead 80. For example, similar to the accomodation bulkhead 80, the fumigation bulkhead 110 includes a body 82, a generally rectangular seal 84 extending generally about the perimeter of the body 82 on an outer face 86 of the body 82, a plurality of brackets 88 and associated T-shaped tubular rods 96, a plurality of generally circular apertures 98 extending through the body 82 of the bulkhead 110 configured to receive the distal ends of the tubular rods 96, and respective nuts 100 located about each of the distal ends of the rods 96 on the inner face of the body 82 in order to secure the rods 96 to the body 82. Additionally, the fumigation bulkhead 110 is sealed against the accommodation ladder landing water-tight door 36 in substantially the same manner as the accomodation bulkhead 80 is sealed against the opening 64 into the accomodation area 20. However, the fumigation bulkhead 110 is externally fitted to the accommodation ladder landing water-tight door 36, whereas the accommodation bulkhead 80 is internally fitted to the opening 64 into the accommodation area 20.
The fumigation bulkhead 110 also includes a plurality of generally circular openings or spigots 112 located generally in an upper half of the body 82, and which are configured to be fluidly and sealingly connected to respective first conduits 52 of the fumigation system 50 in order to deliver gaseous fumigant across the bulkhead 110. Specifically, the fumigation bulkhead 110 includes 36 openings or spigots 112 arranged in three adjacent vertically extending groups, each group including 6 rows of two openings 112 arranged side-by-side. Thus the fumigation bulkhead 110 can up to receive 36 first conduits 52 from the mobile fumigant-containing vehicle 56, and can distribute 36 first conduits 52 throughout the cargo area 13. As is shown in
The fumigation bulkhead 110 also includes a series of ports 119 located generally in a lower half of the body 82, and which are configured to receive power and/or data and transmit the power and/or data across the bulkhead 110. In the illustrated embodiment, the fumigation bulkhead 110 includes eight ports 119 arranged in two rows, one above the other. As is described above, it will be appreciated that the fumigation bulkhead 110 could include any number of ports 119 as required according to the particular vessel to be fumigated. In general, the fumigation bulkhead 110 will include enough ports 119 to enable at least one 3-phase power cable to be routed to each cargo deck 16. Each port 119 is preferably configured to supply a current of between 15 to 50 Amps.
The ports 119 may provide power to the recirculation fans 33 in each of the cargo zones 14, and may also provide a data connection between the sensors 35 of the high-range monitoring system and the controller 41. Specifically, one or more power cables may be connected between the first and/or second mobile generators 45 to the ports 119 on the external side of the fumigation bulkhead 110, and one or more other power cables may be connected between the ports 119 on the internal side of the fumigation bulkhead 110 and the recirculation fans 33 located in each of the cargo zones 14. The sensors 35 of the high range monitoring system may be connected to the controller 41 in a similar manner.
As is described above,
Fumigants
As stated above, different fumigant chemicals may be used which may require a variation on the fumigant delivery method described. As will be appreciated by the skilled person, fumigation chemicals such as ethyl formate, ethanedinitrile, and hydrogen cyanide can be flammable under certain conditions and concentrations that may be encountered if the above described method is used.
In the method above, this is most likely to occur during the vaporisation of the chemical from a liquid to a gas as the concentration of the fumigant will pass through the flammable region. This change in concentration occurs when introducing the fumigant to the recirculation fans 33 in the cargo zone 14 of the RoRo vessel 10. To avoid the risk of a fire starting in the cargo zones 14, an alternative method of fumigant delivery may be used for fumigant gases that present this risk.
It may be possible to safely perform a fumigation with a potentially flammable fumigant using the method for sulfuryl fluoride as described above. For example, liquid ethyl formate may be delivered to the cargo zone 14 via the plurality of first conduits 52 connected to the fumigant-container cylinders 54 of the mobile fumigation-containing vehicle 56 and one or more temporary bulkheads 110. The ethyl formate is supplied to a pump near to a recirculation fan 33 in the cargo zone 14. The pump increases the pressure of the ethyl formate to between 7 bar and 300 bar, and preferrably about 200 bar. The liquid ethyl formate may be expelled from the pump via a nozzle or restriction and into the air flow path of the recirculation fans 33. Due to the high pressure of the liquid ethyl formate it leaves the nozzle at a high velocity and is atomised into a fine spray, mist or fog. The atomised liquid ethyl formate is subjected to a decrease in pressure which causes the liquid ethyl formate to change into a gaseous state and disperse into the air. The air volume supplied by the recirculation fan 33 is such that the concentration of the ethyl formate rapidly drops below the flammable range. Using this method, the risk of a fire due to combustion of the fumigant may be low as only a small part of the atomised stream exiting the conduits 52 may be in the flammable range for a short period of time.
In an alternative fumigation delivery method, potentially flammable fumigant is directed to the cargo zone 14 under fumigation in liquid form via a plurality of conduits 52 in a similar manner to that described above. However, the liquid fumigant is not directed to the recirculation fans 33, instead it is directed to mixing equipment consisting of a vaporiser or heat exchanger and a high volume mixing apparatus located near the recirculation fans. The vaporiser or heat exchanger typically consist of a coil of copper tube in a hot water or thermal oil bath however many other suitable types of heat exchanger exist. As the liquid fumigant passes through the copper coil it is warmed and transitions from a liquid to a gas. The vaporisers are typically 1 kW to 15 kW, and preferrably 10 kW in power. The gaseous fumigant is then directed into a high volume mixing apparatus which draws in air and fumigant at the ratio required to create the desired fumigant concentration. The speed at which the mixing occurs is such that the flammable concentration of the fumigant is rapidly by-passed. The air/fumigant mix exits the mixing apparatus near the recirculation fans 33 so as to be evenly distributed around the cargo zone 14 under fumigation. Alternatively, the vaporised fumigant is delivered directly to the recirculation fans 33 to be mixed rather than entering the high volume mixing apparatus.
In another alternative fumigation delivery method, the mixing equipment is located on the quayside and not in the cargo zone 14 of the RORO vessel 10 to be fumigated. The fumigant is vaporised in the vaporiser or heat exchanger and mixed with air in the high volume mixing apparatus. The gaseous air/fumigant mix is then delivered to the cargo zone 14 under fumigation via flexible ducts and a temporary bulkhead configured to accommodate the flexible ducts in a similar manner to the air pressure system 60 described in detail above.
It is possible that the liquid fumigant does not require vaporisation using the vaporiser located in the cargo zone 14 or on the quay. In this instance, the liquid fumigant can be vaporised inside the high volume mixing apparatus located either in the cargo zone 14 or on the quay side. Alternatively, the liquid fumigant can be pressurised with a pump and then ejected from a nozzle to create an atomised spray, mist, or fog that can be mixed with air on the quay side. The fumigant is either delivered to the cargo zone 14 as a liquid as described above, or as a gaseous air/fumigant mix via flexible ducts as described above.
In another embodiment the gaseous air/fumigant mix can be delivered to the cargo zone 14 to be fumigated via the ducts 25, 27 which connect the cargo zone 14 to the supply mechanical ventilator 24 or exhaust mechanical ventilators 26 on the weather deck 18 of the RoRo vessel 10. The gaseous air/fumigant mix may be prepared in any manner previously described or may be delivered to the ducts 25, 27 or mechanical ventilators 24, 26 as a liquid and vaporised inside the mechanical ventilator 24, 26 or ducts 25, 27.
In a further alternative method, the fumigant may be mixed to the desired concentration quayside with a non-flammable gas other than air such as carbon dioxide or nitrogen and then delivered to the cargo zone 14 to be fumigated via flexible ducts in a similar manner to the air pressure system 60 or the mechanical ventilators 24, 26 as described above.
It may also be desirable to mix the fumigant to the desired concentration with liquid carbon dioxide and deliver the fumigant mix to the cargo zone 14 as a low temperature liquid which could then be safely vaporised using a vaporiser, heat exchanger, or atomisation as described above.
It will be appreciated by those skilled in the art that a combination of the above described fumigation methods could be utilised based on the configuration of the vessel and the fumigation to be conducted.
Temporary Flexible Exhausts
The remaining figures provide detail relating to the flexible temporary exhaust that is configured to assist with removing the gaseous fumigant from the cargo zones 14 during the ventilation operation.
Type I Temporary Flexible Exhaust
Referring initially to
Referring to
The first opening 122 is fitted over an an exhaust mechanical ventilator 26 (or a similar conduit could be fitted over a vent house, described below) and is mechanically secured thereto via a length-adjustable flexible strap 126. Once the first, or lower, opening 122 is secured to the mechanical ventilator 26 via the strap 126, the flexible exhaust 58 is in fluid communication with the mechanical ventilator 26, and is thus configured to exhaust the air exhausted from the mechanical ventilator 26 via the upper opening 124, which is located downstream of the lower opening 122 (as is shown by the direction of the arrows in
As is shown in these figures, the flexible exhaust 58 is substantially conical when in use and inflated, and includes a lower generally cylindrical portion 128 (which appears somewhat rectangular in
Referring to
As is shown in
The particular ventilation arrangement, such as the number of mechanical ventilators 26 employed may depend upon a large variety of factors such as the design of the RORO vessel, the ventilation requirements for the particular kind of cargo and fumigant and a safe level of dilution as determined by the cargo, fumigant and relevant regulations, the flow capacity of each mechanical ventilator 26, and the zoning arrangements of the cargo decks 16. Prevailing wind another conditions may also have a bearing on the ventilation requirements. These factors can be taken into account in designing a suitable ventilation plan for a particular vessel concerned.
In one embodiment of a ventilation arrangement, illustrated in
Type II Temporary Flexible Exhaust
The flexible temporary exhaust 58 described above may encounter a limitation wherein an air-tight seal cannot be formed at the stem or rising duct of the mechanical exhaust ventilator 26 due to pipework or other obstructions.
The fumigation operation of
As can be seen in
The substantially horizontal portion 246 is an inflatable plenum 247 which is a generally elongate cuboid but may be cylindrical. It has a circular connection 250 which is about 1 m in diameter, slightly larger than the axial flow fan 26a to accommodate and enclose the top of the exhaust duct 27 and which is secured using a tension/ratchet strap 252 creating a gas tight seal. The exhaust duct 27 affords a clean surface free of obstruction to which the plenum 247 may be attached. When inflated, the plenum extends out of the maintenance doors 244 and beyond the housing 242 so that the substantially vertical portion 248 is clear of the ventilator housing 242.
The substantially vertical portion 248 connects to the plenum 247 distal to the circular connection 250. The substantially vertical portion 248 tapers to a frustoconical velocity cone 252 with an upper downstream opening 124 and a drawstring 134 to vary the diameter of the upper downstream opening 124 to modify the velocity of the exhausted fumigant. The velocity cone 252 may be adjustable.
The velocity cone 252/substantially vertical portion 248 is inclined at an angle of about 12° to the horizontal, towards the ventilator housing 242 to allow for the force of the exhausted fumigant acting on the internal faces of the inflatable plenum 247 and/or the substantially vertical portion 248. As can be seen in
To further support the alternative flexible exhaust 240, a support assembly including at least one bracket 254 including cross members, as shown in
Compensatory Over Pressure System
As is described above, the air pressure system 60 is operated throughout the fumigation operation and preferably throughout the ventilation operation, until all or substantially all of the gaseous fumigant has been removed from the cargo zones 14 and cargo 30. The gaseous fumigant is considered to have been removed or substantially removed from the cargo zones 14 and the cargo 30 when the sensors 35 of the high-range monitoring system detect a concentration of gaseous fumigant in the form of sulfuryl flouride in concentrations equal to or less than 5 ppm.
As will be appreciated, during the ventilation operation, the pressure within the cargo area 13 may increase due to the supply of fresh air being provided by the supply mechanical ventilators 24. The air pressure system 60 accordingly operates to maintain the desired pressure differential between the cargo area 13 and the accommodation area 20 in light of any increase in pressure in the cargo area 13. It has been discovered that the air pressure system 60 is able to deliver air to the accommodation area 20 such that the accommodation area 20 is at a pressure of up to between 300 Pa and 1 kPa above mean sea level atmospheric pressure without significantly affecting the livability or usability the accommodation area 20 (whilst maintaining the desired pressure differential of at least 50 Pa above the pressure in the cargo area 13). However, the preferred maximum pressure in the accomodation area 20 is about 300 Pa above mean sea level atmospheric pressure.
If the pressure in the accommodation area 20 is close to or above 300 Pa above mean sea level atmospheric pressure, an alarm may be triggered to notify an operator to reduce the pressure in the cargo area 13. This may be achieved by adjusting the operation of the supply mechanical ventilators 24, and/or by opening one or more of the hatches 29 in the weather deck 18.
Alternative Ventilation Arrangements
The above described RORO vessel with supply, exhaust, and reverse mechanical ventilators is the most common arrangement, especially in the case of new RORO vessels. However, other arrangements can also be found in RORO vessels which present additional challenges for ventilation.
Passive Ventilation Through Vent Houses
In a first case, a RORO vessel may have no exhaust mechanical ventilators and instead rely on passive ventilation of the cargo zones by vent houses located upon the weather deck. Vent houses are commonly found on Pure Car and Truck Carrier type vessels (PCTC). Such a RORO vessel is illustrated in
As can be seen in
Alternatively, temporary flexible exhausts (not shown) of a type similar to temporary flexible exhausts 58 could be attached about the vent houses 39 in substantially the same manner as described above in relation to the exhaust mechanical ventilators 26 (see
During the fumigation operation (shown in
Type III Temporary Flexible Exhaust
An alternative temporary flexible exhaust 262 is now presented in connection with
However the ventilation of the fumigant relies on the mechanical supply ventilators 24 to draw air into, and raise the pressure of, the cargo zone 14 being fumigated to expel the fumigant via the passive exhaust ducts 27.
Shown in
Referring to
The second alternative exhaust 262 comprises a plenum 268 that extends away from the access doorway 258 when inflated, a lower portion of the plenum 268 that extends downwards and towards the weatherdeck 18 to provide support to the second alternative exhaust 262, and an adjustable velocity cone 270 that extends upwards from the plenum 268 to direct exhaust fumigant away from the weatherdeck 18. The plenum may be an elongate cuboid or a generally cylindrical shape. The velocity cone 268 is frustoconical in shape with an upper downstream opening 224 at the uppermost point and a drawstring 234 to vary the diameter of the opening to modify the velocity of the exhausted fumigant.
To install the second alternative exhaust 262 to a vent house 39:
1. All supply ventilators are switched off;
2. The duct leading to the vent house is closed via its lid.
3. The maintenance door to the vent house is opened.
4. Plastic sheeting/corflute/other sheeting is fitted or taped over the ventilation louvres from the inside of the vent house.
5. The exhaust 262 is fitted to the access doorway 258.
6. The supply ventilators are turned on.
7. The vent house duct is opened to allow inflation of the second alternative exhaust 262.
Additionally, the exhaust 262 may be provided with ties to secure it to the vent house 256.
Ventilation Through Escape Trunks
In a second example, the preferred method is not possible due to incompatability of the flexible exhausts described above due to the arrangement of the mechanical ventilators or vent houses or due to other circumstances.
In this case, ventilation could be achieved by use of the escape trunks. As is described above, the escape trunks may be in the form of hatches 29 (
As will be appreciated by the person skilled in the art, this alternative method of ventilation could also be used with the RORO vessel 10 illustrated in
Referring initially to
In an arrangement, approximately half of the total number of escape trunks (either hatches 29 or staircases 31) are fitted with flexible temporary exhausts 58, and the remaining half of the total number of escape trunks (either hatches 29 or staircases 31) are fitted with respective temporary bulkheads and axial or mixed flow fans 164 for use as supply ventilators during the ventilation operation.
Once the concentration of gaseous fumigant in the uppermost cargo zone 14 is at or below 5 ppm (for gaseous fumigant comprising sulfuryl flouride), the specially trained fumigation personnel enter the uppermost cargo zone via the hatches 29 or staircases 31. The specially trained fumigation personnel then open the hatches 19 that lead into the second uppermost cargo zone 14 from the uppermost cargo zone 14. The specially trained fumigation personnel then route the flexible ducts 159 of the supply hatches 29 into the second uppermost cargo zone 14 such that the downstream openings of the flexible ducts 159 are located in the second uppermost cargo zone 14. In this manner, fresh air may be supplied into the second uppermost cargo zone 14. It will be appreciated that
After the flexible ducts 159 have been routed to the second uppermost cargo zone 14, the specially trained fumigation personnel then exit the cargo area 13. Once clear of the cargo area 13, the ventilation operation is recommenced and the second uppermost cargo zone 14 is ventilated. Specifically, fresh air is drawn into the second uppermost cargo zone 14 via the opened hatches 19 and the hatches 29 that include the axial or mixed flow fans 164. The supply of fresh air to the second uppermost cargo zone 14 causes air containing gaseous fumigant to be exhausted from the second uppermost cargo zone 14 via the opened hatches 19 and the hatches 29 and staircases 31 that include the flexible temporary exhausts. Once the concentration of gaseous fumigant in the second uppermost cargo zone 14 is at or below 5 ppm (for gaseous fumigant comprising sulfuryl flouride), the specially trained fumigation personnel enter the second uppermost cargo zone via the hatches 29 or staircases 31 and the internal hatches 19.
Then, the specially trained fumigation personnel open the hatches 19 to the second lowermost cargo zone 14 and route the flexible ducts 159 such that their downstream openings are located in the second lowermost cargo zone 14. The specially trained fumigation personnel then exit the cargo area 13. Once clear of the cargo area 13, the ventilation operation is recommenced and the second lowermost cargo zone 14 is ventilated. This process is repeated until all of the cargo zones 14 have been ventilated. Thus, as is described above, in this alternative method of ventilation, the cargo area 13 is ventilated by fresh air positively drawn through the hatches 29 and/or staircases 31 by axial or mixed flow fans 164. In essence, the hatches 29 and/or staircases 31 that include the axial or mixed flow fans 164 act as supply ventilators and perform a similar function to the mechanical supply ventilators 24.
Any of the foregoing arrangements which result in passive exhaust of air from the cargo zones are less desirable in view of the potential pressure buildup in the cargo zones which could conceivably exceed the positive pressure applied to the accommodation and other crew areas.
As will be appreciated by a person skilled in the art, a combination of methods described above could be used to achieve the fumigation of a RORO vessel 10. For example combining the alternative methods to draw fresh air into the cargo area 13 via mechanical supply ducts 25 during ventilation and to exhaust fumigant via hatches 29 or stairs 31 in the escape trunk is also possible.
Assessment as to an appropriate arrangement may include an inspection of the ship. For example, a ship which is in poor condition due to fatigue resulting in hairline cracks in metal sheeting between various compartments would be unsuited to such an arrangement. However, if the ship is in good condition such an arrangement may suffice.
Insect Net
As is shown in
Alternate safeguard methods include: a) first covering the exhaust mechanical ventilator with an insect net and fastening at the base of the exhaust mechanical ventilator, and then covering the net-covered exhaust mechanical ventilator with a flexible exhaust 58; or b) fixing an insect net over the intake (exhaust duct) in the cargo zone, to prevent insects from being sucked into the exhaust duct and from being exhausted into the atmosphere (in this example, no insect net is present in the flexible exhaust 58).
Type II and type III flexible exhausts 240, 262 may also be fitted with insect nets as per above.
Adjustable Upper Opening
The use of a velocity cone is intended to narrow the shape of the conduit 58 from the first opening which is intended to be large and fit over the structure of the exhaust mechanical ventilator 26 to the upper second opening which is intended to be of a size which keeps the flexible conduit 58 in an inflated configuration. Additionally, the outflow from an exhaust mechanical ventilator 26 is downward and the flexible conduit 58 needs to be shaped to create a plenum chamber below the exhaust mechanical ventilator 26. Additionally, adequate clearance around the exhaust mechanical ventilator 26 is required for the upward passage of exhausted air. These factors determine a large base for the flexible conduit 58, thereby requiring a frustoconical tapering to a smaller second upper opening 124.
As is shown in
It will be understood that the invention disclosed and defined in this specification extends to all alternative combinations of two or more of the individual features mentioned or evident from the text or drawings. All of these different combinations constitute various alternative aspects of the invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2020901707 | May 2020 | AU | national |
| 2020901708 | May 2020 | AU | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/AU2021/050504 | 5/26/2021 | WO |
