NO346652B1

NO346652B1 - An arrangement and a method for propagating bleed-out of fish

Info

Publication number: NO346652B1
Application number: NO20210558A
Authority: NO
Inventors: Leif Roger Gjelseth; Helge Birkeland
Original assignee: Mmc First Process As
Priority date: 2021-05-04
Filing date: 2021-05-04
Publication date: 2022-11-14
Also published as: WO2022233849A1; NO20210558A1

Description

Technical Field

[0001] The present invention relates to an arrangement for propagating bleedout of fish that has been cut and killed.

Background Art

[0002] Fish above a certain size is predominantly killed by cutting the throat of the fish. The killing is done this way not only to quickly kill the fish, but also to let out as much blood as possible from the fish. Blood remaining in the fish may discolour the fish meat. Discoloured fish meat results in a lower grade for the fish, and it may be regarded as unfit for human consumption. Hence, as soon as the fish has been cut, it is brought into a vessel containing preferably cold water. The cold water will delay the coagulation of the blood, so that as much blood as possible can be drained from the fish.

[0003] There are known a range of arrangements for propagating the bleeding of the fish:

[0004] EP 3367806 shows an arrangement where the killed fish is conveyed through a pipeline through different zones with different properties regarding air pressure and water flow.

[0005] WO 1997/01958 shows an arrangement where the fish is subjected to anaesthetics before being cut. The fish is conveyed between tanks with falling temperatures from 10°C to 1°C before cutting and into a tank with a water temperature 1,5 - 2°C after the cutting.

[0006] EP 3599872 / WO2018/173078 shows a bleeding tank with a paddle wheel to convey the fish therethrough.

[0007] NO 310951 B1 relates to an arrangement for propagating bleed-out of fish that has been cut and killed, comprising a cutting station, a receiving hub downstream of said cutting station and a bleed-out tank downstream of said receiving tub and a liquid and fish separator downstream of said bleed-out tank.

[0008] NO 314652 B1 relates to a device for bleeding of fish, with a bleed-out transporter, which is complete or partly surrounded by a vacuum tank, and where the bleed-out of the fish is propagated by the effect of the vacuum in the vacuum tank.

[0009] US 4826362 A relates to a solid transfer apparatus having at least one closed tank provided with a suction opening and a discharge opening, a suction valve communicated with the suction opening a discharge valve communicated with the discharge opening, a pressure reducer for introducing solids into the closed tank and a supply device for discharging solids in fluid out of the closed tank, whereby solids can be transferred.

Summary of invention

[0010] Although the prior known arrangements work fairly well, they have all one major drawback, which is the lack of sufficient and flexible capacity.

[0011] This problem is solved by the present invention by an arrangement according to the subsequent claim 1 and a method according to subsequent claim 8.

Brief description of drawings

[0012] The invention will now be described, referring to an exemplary embodiment illustrated in:

Figure 1, which shows an arrangement for bleed-out of cut fish.

Detailed description of the invention

[0013] Referring to figure 1, the intake of fish into the bleed-out arrangement is illustrated by a receiving tub 1, into which fish is fed immediately after being cut at the throat. A chute 2 or similar can be arranged between the cutting table (not shown) and the receiving tub 1 to facilitate the transfer.

[0014] There may be several cutting tables producing fish for the same tub 1 or for a multiple of tubs.

[0015] One or more lines 3 extends from the bottom (or close to the bottom) of the receiving tub 1 to at least one, but preferably at least two, bleed-out tanks 4’ and 4’’. The bleed-out tanks are commonly referred to by reference number 4. A valve 5 in each of the lines 3 controls the transfer of fish and water from the receiving tub 1 to the bleed-out tank 4. Each tank 4 may, e.g., have a volume of

[0016] The bleed-out tanks 4 are preferably arranged in an oblique position with the lines 3 coupled to the tanks 4 at an elevated end. In the shown embodiment, the tanks 4 are circular-cylindric, but they may also be shaped in other ways which result in a higher intake end 4a and a lower outtake end 4b.

[0017] At the lower outtake end 4b, each bleed-out tank 4 is coupled to a recirculation line 6. A strainer is arranged at the port of the recirculation line 6 to prevent fish from escaping into this line. Each recirculation line 6 has a recirculation pump 7 and cooler 8. The cooler is preferably an RSW (Recirculated sea Water) cooler.

[0018] The recirculation pumps 7 are conveniently equipped with frequency converters to adjust the pumping rate to the intake of fish into the tank 4.

[0019] At the exit from the cooler 8, the recirculating line 6 branches off to a tank return line 9, which extends to the intake end of the bleed-out tank 4, and a tub return line 10, which extends to the receiving tub 1.

[0020] The recirculating line 6 has a valve 11 upstream of the pump 7, as well as a valve 12 in the tank return line 9 and a valve 13 in the tub return line 10. These valves control the recirculation of cooled seawater.

[0021] In the embodiment illustrated, there are separate recirculating lines, pumps and coolers for each bleed-out tank 4, but there may also be a common line, pump and cooler for two or more tanks 4.

[0022] The outtake end 4b of the bleed-out tank 4 also has exit lines 14 that extend to a strainer 15, 16. In figure 1 two strainers 15, 16 are illustrated, but there may be just one or there may be more than two.

[0023] The exit lines 14 have each a valve 17 that control the flow. The port leading to the exit line 14 allows for fish to pass therethrough.

[0024] In figure 1, the exit lines 14 merge into a single line 14a downstream of the valves 17. They may alternatively extend as separate lines to the strainers 15, 16.

[0025] The single exit line 14a branches off into separate lines 18 for each strainer 15, 16. Valves 19 are also arranged in the lines 14a and 18 to control the flow.

[0026] In the strainers 15, 16, the fish and water are separated. The fish is conveyed to further processing, such as filleting and freezing, while the water flows to a water collecting tank 20 (only illustrated for one of the strainers 15, but there will be a similar tank for the strainer 16). A line 21 extends from the water collecting tank 20 to the pumps 7. The line 21 has a valve 22 to control the return of the water from the tank 20.

[0027] In addition to the above components, the arrangement is also equipped with at least one vacuum/pressure pump 23 for each bleed-out tank 4 via a pneumatic line 24. The vacuum/pressure pump 23 provides vacuum or air pressure in the bleed-out tanks 4. This will be explained further below.

[0028] In the following, the function of the arrangement described above will be explained. In the following the term “water” is used to denote the liquid being circulated. It should be understood that the preferred liquid is seawater. The liquid may, however, also be a brine having a higher salt concentration than seawater.

[0029] The receiving tub 1 is more or less continuously filled with fish. The fish has been cut, and possibly gutted, before transfer to the receiving tub 1. The fish may come from a fish farming facility or be caught wild fish, such as by trawling. The tub 1 preferably contains cold water, such as seawater. Most of the blood of the fish runs out of the fish either at the cutting table or in the receiving tub 1.

[0030] The fish is drawn out of the receiving tub 1 through the lines 3 and into one of the bleed-out tanks 4’. The bleed-out tank 4’ that is receiving the fish, is at this stage subjected to a vacuum and is preferably filled with water to about 40%. The vacuum has been created by the associated vacuum/pressure pump 23, which creates a sufficient vacuum to draw a predetermined volume of water and fish out of the receiving tub. The vacuum may also partially be created by the associated pump 7.

[0031] When the predetermined vacuum in the tank 4’’ has been obtained, the valve 5 is opened. Fish and water will now flow out of the receiving tub 1 and into the tank 4’’. Figure 1 shows the bleed-out tank 4’ after it has received the predetermined volume of fish and water. The tank 4’ is now filled to its maximum capacity and the pressure in the air pocket shown above the water level is approximately at atmospheric pressure. The ratio of fish to water in the tank 4’ is preferably 4/10 based on volume.

[0032] While the tank 4’ is being filled, the associated pump 7 is circulating water from the downstream end 4b of the tank 4’ to the upstream end 4a. Some of the water is also diverted back to the receiving tub 1.

[0033] The water level in the receiving tub 1 is constantly monitored, and the valve 13 is adjusted to ensure a minimum water level in the receiving tub 1.

[0034] The continuous circulation of water through the pump 7 and the cooler 8 ensures a constant low temperature of the water.

[0035] At the same time as the tank 4’’ is being filled with fish and water from the receiving tub 1, the valves 22 and 13 may be opened, so that the pump 7 also can draw water from the water collecting tank 20 and pump this through the cooler 8 and into the tank 4’ and also to the receiving tub 1, to replace the water that has been drained to the bleed-out tank 4’.

[0036] The pump 7 continues to circulate water from the downstream end 4b to the upstream end 4a also after the tank 4’ has been filled and during the retention time of the fish.

[0037] After the bleed-out tank 4’ has been filled with fish and water and a prescribed retention time, such as 30 - 60 minutes, has been reached for the first fish that entered the tank 4’, the vacuum/pressure pump 23 is reversed and will now pressurize the air pocket above the water level in the tank 4’. The valves 5 and 17 remain closed during this stage, but the pump 7 continues to circulate water through the tank 4’. When a sufficient pressure has been reached, the valve 17 is opened, and the fish and water in the tank 4’ is expelled from the tank due to the pressure and transferred to one of the strainers 15, 16, where the water is separated from the fish and collected in the collecting tank 20 for reuse. The air pressure in the tank 4’ may be increased as the tank 4’ is emptied to compensate for the lower water level in the tank 4’. The pump 7 continues to circulate water, which ensures that the fish is forced towards the downstream end 4b of the tank 4’. Due to the inclined position of the tank 4’’, the tank will be completely drained of fish through this process, and the filling and emptying of the fish will be approximately first fish in – first fish out. Hence, the retention time will be about the same for all fish.

[0038] When the tank 4’ is emptied of fish, the pump 7 ensures that it is about 40% filled with water before the vacuum pump 23 is operated and the process is repeated.

[0039] The two bleed-out tanks 4’, 4’’ will be set to operate in counter-phase, i.e., while the bleed-out tank 4’ is being filled with fish and water, the other bleed-out tank 4’’ is drained through the line 14 and valve 17, and vice versa. This ensures that the receiving tub 1 is emptied at regular intervals and that fish is almost continuously delivered to the further processing. The retention time can be used to adjust delivery of fish according to the capacity at the cutting station upstream of the receiving tub 1.

[0040] The pumps 7 will pump continuously and circulate water through the tanks 4‘, 4’’. A continuous circulation of water through the pumps 7 and the coolers 8 ensures that the water will be kept at the prescribed temperature. The temperature is conveniently 0°C or lower.

[0041] The pump 7 will also pump water from the collecting tank 20 and into the receiving tub 1 or into the bleed-out tank 4 depending on the fill level of the tanks 4, 20 and tub 1. Level sensors in the tanks and tub are coupled to a control system that regulates the valves of the arrangement to adjust the level.

[0042] The total water volume in the arrangement will be the same at any given time, but fresh seawater may be supplied to replace water that is lost due to clinging to the fish, evaporating or otherwise escaping the system. This supply of seawater is conveniently regulated by the same control system that regulates the valves of the arrangement.

[0043] It is also possible to intentionally replace a proportion of the water by fresh seawater during the processing, especially of a large quantity of fish is to be processed and to avoid a too high concentration of fish blood and debris in the water.

[0044] When the processing of fish through the arrangement is finished, water can be circulated through the tanks 4 to ensure that all fish has been expelled from the tanks 4 and for cleaning the tanks 4. Fresh seawater can be used for this cleaning.

Claims

1. An arrangement for propagating bleed-out of fish that has been cut and killed, comprising a cutting station, a receiving tub (1) downstream of said cutting station and a bleed-out tank (4) downstream of said receiving tub (1), a liquid and fish separator (15, 16) downstream of said bleed-out tank (4), characterised in that said bleed-out tank (4) is coupled to a vacuum source, that there is a valve (5) arranged between said bleed-out tank (4) and said receiving tub (1), that said bleed-out tank (4) is coupled to an air pressure source, and that there is a valve (17) arranged between said bleed-out tank (4) and said separator (15, 16).

2. The arrangement according to claim 1, characterised in that an outlet from said bleed-out tank (4) is fluidly coupled to an intake side of a recirculation pump (7), and an output side of said recirculation pump (7) being coupled to said receiving tub (1).

3. The arrangement according to claim 2, characterised in that said intake side of said recirculation pump is also coupled to a collecting tank (20), said collecting tank (20) being coupled to receive liquid from said separator (15, 16).

4. The arrangement according to claim 2 or 3, characterised in that the output side of said recirculating pump is also couple to said bleed-out tank (4).

5. The arrangement according to any of the claims 1-4, characterised in that said bleed-out tank (4) has a receiving end (4a) that is at an elevated position relative to an outtake end (4b).

6. The arrangement according to any of the preceding claims 1-5, characterised in that said pump (7) is coupled to a liquid cooler (8).

7. The arrangement according to any of the preceding claims, characterised in that it comprises at least two bleed-out tanks (4’, 4’’).

8. A method for propagating bleed-out of fish that has been cut and killed, characterised in that a bleed-out tank is subjected to vacuum, said vacuum being used to suck killed and cut fish and liquid into said bleed-out tank, circulating cold liquid through said tank to propagate bleed-out of said fish, emptying said tank after a prescribed retention time by pressurizing said tank and letting said fish and liquid flow to a strainer to separate fish and water.

9. The method of claim 8, characterised in that cold liquid is circulated continuously through said tank.

10. The method of claim 8 or 9, characterised in that said liquid that is separated from said fish is returned to said tank or to a receiving vessel upstream of said bleed-out tank.

11. The method of claims 8, 9 or 10, characterised in that two bleed-out tanks are arranged to work in counter-phase.

12. The method of any of the claims 8-11, characterised in that said liquid is seawater or brine at a temperature of about 0°C or colder.