GB2025594A - Storing and transporting fish under refrigerated conditions - Google Patents

Abstract

Fish or other aquatic food material is transported in a heat-insulated bulk load container (1) which is adapted to hold liquid cooled by a refrigeration system (9) to keep the fish in refrigerated but wet condition during transportation. The container preferably forms the tipping body of a vehicle. The fish is loaded in bulk into the container through sealable openings 2, 3 together with sufficient liquid to keep the fish wet and prevent crushing and the container is unloaded through an end closure wall 4 by tipping. <IMAGE>

Description

SPECIFICATION Method and apparatus for storing and transporting aquatic food materials under refrigerated conditions The conventional method of transporting fish from fishing ports to inland fish markets involves tempor ary storage of the catch in tanks at the fishing port and their eventual packaging with ice in boxes which are then loaded into vehicles for overland transpor tation. These procedures impose appreciable delays between the unloading of the fish from the fishing vessels and the arrival of the fish on the food market, and involve large handling costs which are necessar ily reflected in the market price of the fish. Apart from the labour involved in boxing up, the actual loading of the boxes onto transport vehicles is very expensive. For example, it often takes about 6 hours to load 18 tons of filled boxes onto a transport vehicle.An appreciable fraction of the transportation cost is attributable to the boxes. An 18 ton load includes about 4 tons of boxes.

A further serious disadvantage of the conventional procedures is that a substantial proportion of the tonnage of fish brought into port cannot be kept in prime condition for the period of time necessary for itto reach the inland fish markets where it would otherwise command a very good price. The period of time for which much sea food will remain in good condition while boxed in ice is strictly limited.

Pelagic fish for example are very prone to rancidity when boxed for one or two days, even when kept in modern refrigerated transporters operating between sea ports and inland markets. In consequence cer tain inland areas cannot obtain sea foods in top quality condition through the normal channels of distribution and supply and such foods are then available only at very inflated prices. the fish boxes themselves tend to harbour unhygenic conditions and this is often a contributory factor in the de terioration of the food prior to marketing.

The present invention aims to provide a method of storage and transportation by which aquatic farm material, particularly fish, can be available to food markets with less risk of deterioration and/or with appreciably lower handling costs.

According to the invention there is provided a method of transporting fish or other aquatic farm material for the food market, which method compris es providing a heat-insulated transportable bulk load container which is adapted to hold a bulk load comprising both solid and liquid material and which has an associated refrigeration system; loading that container with the farm material in bulk and with sufficent liquid to keep the farm material in wet condition; and transporting the said container while keeping the farm material therein in refrigerated wet condition by means of such refrigeration system.

In the nature of the invention, its potential benefits are best realised when using a large container having a load-carrying capacity say in excess of 15 tons.

The invention involves a quite radical departure from conventional practice in the handling of fish and other sea food between fishing ports or harbours and inland delivery sites. Tests have surprisingly shown that a load of fish of many tons in weight can be kept in good condition for some days in a bulk load container of a form suitable for overland transportation, when loaded together with a relatively small amount of water and transported in cooled condition in accordance with the invention as above defined. the liquid present in the container can relieve the food material from crushing when carrying large loads.

The length of time for which most fish can be kept in good condition under the conditions of this transportation method, in which the fish is kept refrigerated and wet, appreciably exceeds that which is possible in the conventional method of transporting the fish in dry-packed condition as hereinbefore described. The available load-carrying space in the container is utilised much more efficiently than it would be if the food were transported in boxes. In addition labour costs for loading and unloading are greatly reduced.

The nature of the liquid is open to choice within the limits imposed by the requirement that it remains in liquid condition at the temperature and pressures prevailing in the container during transportation. For transporting sea food the liquid can be and is preferably sea water.

An optional feature, which gives further important benefits, consists in oxygenating the water during transportation. This can be done by distributing air into the water, e.g. through perforated pipes at the bottom of the load container. the oxygen levels in the water can be maintained at a level high enough to sustain marine life. The transportation method can therefore be used for transporting and distributing fish, crabs and other aquatic farm creatures in the living state.

In preferred embodiments of the invention it is applied for transporting sea food which is loaded into the container direct from a fishing vessel.

Preferably the food is pumped in bulk from a hold or other storage space in the vessel into the container.

The refrigerated container can be transported according to the invention, either by road or rail.

For deriving the greatest benefit from the invention, the bulk load container should be capable of being easily loaded and unloaded and should be itself conveniently transportable.

In the most preferred embodiments of the invention, the bulk load container forms the tipping body of a road or rail vehicle, such body having at least one sealable filling hatch and an end closure wall which provides a liquid-tight seal and can be opened to allow the container to be emptied by tipping the body. The end closure wall is preferably hinted at the top. The vehicle is preferably a road vehicle. It can be self-motorised or designed for coupling to a haulage vehicle.

In an alternative embodiment of the method according to the invention the bulk load-carrying container does not form part of a transportation vehicle but is itself loaded onto such a vehicle before or after being itself loaded with the aquatic food material and water. In such a method, the cold generator or cold source of the refrigeration system may be associated with the container so as to form a unit th erewith, e.g. for handling by means of a crane and/o conveyor or other handling gear. The use of a bulk l(,ad container which forms the tipping body of a vehi-le is however much more advantageous in respe t of convenience and load-handling costs.

Coc ling of the contents of the load container is preferably achieved by a coolant which is caused to flow t lrough passageways in heat-conductive relationship with the interior of the container. Cooling of large bulk loads can be easily and economically effected in that way. Preferably the container has double-skinned walls incorporating coolant passages and heat-insulating material, the coolant passages being in contact with or in part defined by the inner skin. The refrigeration system may comprise a refrigaration plant of the compression and expansion type or a system employing a reservoir of liquefied gas, e.g. liquefied nitrogen, from which coola 7t is released and caused to flow in vaporised condition through such passageways.

In certain embodiments of the invention the contents of the load container are cooled at least in part by introduction of vaporised coolant into the container, above the surface of the bulk load. For example cooling may be achieved by flow coolant through passageways in the container walls and by the continuous or intermittent release of an amount of the coolant into the interior of the container above the Ic ad surface. The introduction of coolant into the interior of the container can be beneficial in order to establish an inert atmosphere which further con ducts to preservation of the load in good condition.

The invention includes a vehicle having a refrigerated tipping body and suitable for carrying out a method according to the invention as hereinbefore refer wed to.

A vehicle according to the invention is characterised in that it has a heat-insulated bulk-loadcarrying tipping body in the form of a container which has an associated refrigeration system and provides a liquid-tight storage space, such body having at least one sealable filling hatch and an end closure wall which provides a liquidtight seal and can be opened to allow the container to be emptied by tipping the body. The vehicle is preferably a road vehicle. The vehicle may be motorised or adapted for h lulage by a motorised vehicle.

In preferred embodiments of vehicle according to the invention, refrigerant passageways are formed in or tarried by a wall or walls of the load-carrying bodv and a refrigerant source or generator is supp Drted by the vehicle independently of the tippi 1g body and connected with such passageways so that the connections do not have to be broken when the body is tipped. Such connections can for example comprise flexible conduits which extend to and from the tipping body at a region adjacent its tipping axis, e.g. between that axis and the rear of the body. In such a vehicle, the refrigeration, e.g. a Freon or carbon dioxide, on a standard refrigeration cycle.At least the principal functional components of the refrigeration plant, and particularly the com pressor and condenser, can be supported for exam ple on a chassis or frame beneath the tipping body of the vehicle. Alternatively the refrigeration system may be one utilising a reservoir or reservoirs of liquefied gas refrigerant. If a refrigeration system of the latter type is employed, the refrigerant holder(s) can be carried by the tipping body itself instead of being supported independently of such body.

Preferably the vehicle is equipped with means for oxygenating water in the load-carrying body. For this purpose the vehicle may be provided with gas-distributing ducts having gas discharge orifices opening into the interior of the load container and a compressor for delivering air under pressure into such ducts.

Reference is now made to the accompanying diagrammatic drawings showing an example of a bulk load-carrying vehicle according to the invention and suitable for use in carrying out a method according to the invention. In these drawings: Figure 1 is a general view of a vehicle according to the invention; Figure 2 shows a detail of the vehicle body mounting; Figures 3 and4 are sectional views of details of the construction of the side walls of the vehicle body; Figure 5 represents the refrigeration system and Figure 6 represents the aeration system.

The vehicle comprises a tipping load.carrying body 1 constructed for carrying a bulk load. The body provides a single internally unobstructed loadcarrying space of large capacity, for example of the order of 1000 cubic feet. The body has two filling hatches 2 and 3 with hermetic sealing covers, and a top-hinged tail-gate 4.

The body is constructed almost entirely from sheet aluminium alloy of a specification within BSS:1470.

Each of the top, bottom, side and end walls (one of the latter being constituted by the tail gate) is doubleskinned and rigidity is imparted to the structure by a system of ribs such as 5 extending around the body in transverse planes, and ribs such as 6 extending along the horizontal corner edges of the body. The various ribs are hollow and formed by strips of aluminium, bent to channel section and welded to the inner skin.

The load-carrying body is welded to a tipping floor comprising cross-bearers to which bottom transverse ribs of the body are welded. The body is supported by a vehicle frame or chassis 7 to which the body is connected by rear hinges 8.

Within the subframe or chassis 7 of the vehicle there is mounted the refrigeration plant comprising a compressor, condenser and surge vessel. As will be further described with reference to Figure 4, flexible conduits such as 27 (Figure 2) connect this plant with five cooling coils one of these being disposed within the bottom wall of the load-carrying body and four of them being disposed in its side walls (two in each). The flexible conduits extend between the chassis and the tipping body at a region located adjacentto the tipping hinges 8 of the body.

The conduits impose no restraint on the movement of the body when it is tipped about the hinge axis by the body tipping mechanism (not shown) for discharging a load from the body through the tail gate.

The two cooling coils in each side wall are disposed one above the other. Figure 1 shows by dotted lines the path of one of the cooling coils (the lower one) in the nearer side wall of the vehicle body. The coil, designated 9, in fact comprises eight parallel straight reaches extending along the body side.

Figure 3 is a vertical cross-section of part of the near side wall of the vehicle body at a position where lengths of tubing 10 making up one of the cooling coils enter one of the vertical ribs 5. The tubing is formed of HE30 WP TB aluminium alloy (BSS:1470).

The tubing is of square or rectangular cross-section providing a flat face which is located in contact with the inner skin 11 of the side wall. The vertical rib is formed with cut-outs 12 to leave clearance for the passage of the tubing. At various local positions along the length of each side wall of the vehicle body the tubing forming the cooling coils is clamped to the inner skin 11 by a clamping strip 13 as indicated in Figure 4. The clamping strips are fastened to the inner skin by screw-threaded fasteners 14, e.g., fasteners comprising threaded pins secured to the inner skin and co-operating nuts which can be tightened onto the pins to exert the required clamping pressure on the strips.Between each clamping strip and the lengths of tubing bridged thereby there is elastically deformable material 15, e.g. rubber strip material, which transmits firm clamping pressure to the tubing while allowing small relative movements between the tubing and inner skin to take place due to differential thermal expansion.

Thermally insulating material 16 is disposed between the inner skin 11 and the outer skin 17 of the load-carrying body, including the hatch covers and the tailgate. Preferably the thermally insulating material is polyurethane foam. Such material may be applied in prefabricated sheets, slabs or other pieces or injected between spaced skins of the body or container and polymerised and foamed in situ. An example of alternative thermally insulating materials is polystyrene but polyurethane has much better thermally insulating properties. Quantities of such material 16 are also disposed within the hollow ribs 5. In the illustrated embodiment a layer 18 of wood is disposed between the outer skin 17 and the more highly insulating filling material 16 in the areas between the ribs of the vehicle body.

Figure 5 is a flow diagram of the refrigeration system. The diagram shows only two cooling coils connected to the refrigeration plant. Any number of additional coils can be connected to the plant in the same manner.

The refrigeration plant comprises a compressor 19 which is electrically driven by a diesel-operated generator 20, and an air-cooled condensing unit 21.

The refrigerant delivery line 22 frorn the condensing unit leads via a dehydrator 23, a solenoid valve 24, a sight glass 25 and a stop valve 26 to a flexible connection 27 by which the said delivery line is coupled to the inlet manifold 28 of the cooling coils 29, 30. The flexible connection 27 is formed by one of the flexible conduits which extend between the vehicle chassis and the tipping body of the vehicle, in the vicinity of its tipping axis, as hereinbefore referred to. Between the inlet manifold 28 and the cooling coils there are thermostaticaliy controlled expansion valves 31, 32 which operate automatically in dependence on the occurrence of predetermined temperature fluctuations in the refrigerant outlet lines 33, 34 from the coils.These outlet lines are connected to a common return line 35 which is coupled via another flexible connection 36 with the suction side of the refrigeration plant. The flexible connection 36 is connected to the compressor 19 via a suction line 37 in which there is incorporated a liquid trap 38.

The vehicle has an aeration system, shown diagrammatically in Figure 6, for the purpose of oxygenating water in the container, when required.

This system comprises a motor-driven air pump or compressor 39 mounted externally of the loadcarrying body 1, its outlet being connected to a duct 40 which passes through the top wall of the vehicle body ot its interior where it is connected to airdiffusing ducts 41 which extend along the vehicle body, in spaced parallel relation, near the bottom thereof.

An air vent 42 is provided the top of the vehicle body to avoid build up of air pressure over the load in the body.

The compressor 39 may be driven by a small internal combustion engine and an electrically driven compressor 43 may be provided for stand-by use, e.g. for a power pack on the vehicle or from an external power source.

The vehicle can have power coupling points at which both the aeration system and the refrigeration system can be coupled to an external power source or sources on a ship while the vehicle is being transported by sea.

When the hatch covers and tail-gate are closed the body is a liquid-tight container. It can be used to carry liquid, or solid material in wet state, in refrigerated condition. The vehicle is very suitable for loading with fish and sufficient water to maintain the fish in wet condition during transportation.

It is recommended to make the tail gate with a plug portion which fits into the end of the space defined by the top, bottom and side walls of the body. The tail gate should of course also have a face seal which seals against seating faces at the adjacent end of the vehicle body when the tail gate is closed.

Effective sealing can be promoted by providing the tail gate with sliding hinges which permit bodily movement of the tail gate against the seating faces under clamping pressure exerted by screw clamping means (not shown).

In addition to or in lieu of one or more passageways for regrigerant enclosed within a boundary wall or walls of the container, there may be one or more hollow coolers of plate or other form connected into the refrigerant circuit(s) and projecting into the load-carrying space so as to be exposed to contact by the load.

In a modified form of the illustrated refrigerated vehicle, the refrigeration plant carried by the subframe or chassis 7 is replaced by a pressurised liquefied gas holder or holders from which coolant can be released to flow through the cooling coils, and instead of recycling coolant, the coils vent coolant to atmosphere. Alternatively or in addition, there may be a connection between one or more of the coils and the interior of the vehicle body at a top region thereof to permit release of cold gas into a space above the load. Such release of coolant into the interior of the vehicle body can be under remote or automatic control. A suitable vaporizer may be interposed between the liquefied gas holder(s) and the said coils. Such vaporizer can itself be in heat-conductive relationship with the interior of the vehicle body.The liquefied gas need not be continuously released from the liquefied gas holder(s) during transportation of the load. Such release can be effected over any required period or periods of time depending on cooling demands.

The illustrated vehicle, while particularly intended for use in the bulk carrying of fish, including shellfish, in wet condition, can be used for other purposes, e.g. for carrying other foodstuffs, e.g. peas in water or animal foodstuff such as offal, in wet or dry condition; for carrying potable liquids, or for carrying substances in other categories which may benefit from storage at below ambienttempera- tures.

The foilowing is an example of a method according to the invention: Example Avehicle as described with reference to the accompanying drawings and having a load-carrying capacity of 18 tons is driven to a fishing port where 15 tons of freshly caught herrings are pumped from a trawler directly into the load-carrying body of the vehicle. Additionally 3 tons of liquid, e.g. ordinary water or sea water, are pumped into the vehicle body.

After sealing the covers on the hatches 2 and 3 the vehicle is driven from the port to an inland destination while operating the refrigeration plant to keep the load at a temperature a little above the freezing point of the liquid. The plant incorporates a com pressor, an air cooled condenser, expansion valves and a surge vessel disposed between the return lines from the cooling coils and the compressor. The refrigeration system can utilise any suitable vapor ous refrigerant, e.g. Freon 12. On arrival at the destination the load is discharged by opening the vehicle tail-gate and tipping the vehicle body. During tipping, any liquid refrigerant which drains from the cooling coils enters the surge vessel and does not pass directly back to the compressor.

Instead of introducing sea water as the liquid, ordinary water can be used provided the refrigera tion temperature in the vehicle body is above O"C.

When using ordinary water it can be pumped into the vehicle body prior to its arrival at the sea port and cooled on route.

The full load of herrings transported as described in the foregoing example was found to be in excellent condition after storage in the vehicle for several days. The same method was used for transporting in one test mackerel, in a second pilchards in a third sprats. In further tests the method was used for transporting a load of different kinds of fish including crabs. The method was found to be equally satisfactory for these purposes. It was found that by operating the aeration system to deliver air into the water, e.g. at a rate between 100 and 300 cubic feet per hour, a load of fish could be kept alive during transportation over a similar period of time.

The amount of water introduced into the load container should of course preferably not exceed or not substantially exceed what is required for keeping the fish or other food material wet and preventing crushing of material under the superincumbent weight, in order to utilise the carrying capacity of the container as profitably as possible. The minimum weight of water which should be used per unit weight of food material depends in part on the nature of the food material. Fish with a high oil content seem to require more water than others.

Generally speaking it is appropriate to use from 10 to 25% by weight of water based on the weight of the fish, depending inter-alia on the time for which the fish are to remain in the container. The temperature of the liquid during the storage and transporation period may be just a few degrees above the freezing temperature of the liquid, e.g. between 32 and 38"F when using ordinary water and between 25 and 38"F when using sea water.

Claims (11)

1. A method of transporting fish or other aquatic farm material for the food market, which method comprises providing a heat-insulated transportable bulk load container which is adapted to hold a bulk load comprising both solid and liquid material and which has an associated refrigeration system; loading that container with the farm material in bulk and with sufficient liquid to keep the farm material in wet condition; and transpoerting the said container while keeping the farm material therein in refrigerated wet condition by means of such refrigeration system.

2. A method according to claim 1, wherein the container is loaded with live fish or other aquatic farm creatures, and water, and the water is oxygenated during transportation sufficiently to sustain life.

3. A method according to claim 1 or 2, wherein the aquatic farm material is sea food which is loaded into the container direct from a fishing vessel.

4. A method according to any preceding claim, wherein the bulk load container forms the tipping body of a road or rail vehicle, such body having at least one sealable filling hatch and an end closure wall which makes a liquid-tight seal and can be opened to allow the container to be emptied by tipping the body.

5. A method according to any preceding claim, wherein cooling of the contents of the load container is achieved buy a coolantwhich is caused to flow through passageways in heat conductive relationship with the interior of the container.

6. A method according to any preceding claim, wherein the contents of the container are cooled at least in part by introduction of vaporised coolant into the container, above the surface of the bulk load.

7. A refrigerated load-carrying vehicle having a heat-insulated bulk load-carrying tipping body in the form of a container which has an associated refriger ation system and provides a liquid-tight storage space, such body having at least one sealable filling hatch and an end closure wall which makes a liquid tight seal and can be opened to allow the container to be emptied by tipping the body.

8. A vehicle according to claim 7, wherein re frige ant passageways are formed in or carried by a wall (Jr walls of the load-carrying body and a refrigerant source or generator is supported by the vehicle independently by the tipping body and connected with such passageways so that the connections do not have to be broken when the body is tipped.

9. A vehicle according to claim 8, wherein such conn3ctions comprise flexible conduits which extend to and from the tipping body at a region adjac ent its tipping axis.

10. A vehicle according to any of claims 7 to 9 and Equipped with means for oxygenating water in the Is ading-carrying body.

11. A vehicle according to claim 10, wherein the said oxygenating means comprises gas-distributing ducts having gas discharge orifices opening into the inter or of the load container, and a compressor for deliv ring air under pressure into such ducts.