6. SPECIAL CONTAINERS

6.1 Choice of Containers
6.2 Standards for Simple Containers
6.3 Containers for Road Transport
6.4 Container Standards
6.5 Calculation of Required Capacity for Refrigeration Unit

In the fishing industry there are a great number of containers in use designed for special purposes and uses.

They fall into two categories:

1. Insulated containers
2. Uninsulated containers

Generally their application is mainly within the following areas:

• storage (onboard vessels, in plant, with wholesaler, retailer)
• transport (sea, rail, road, air)

6.1 Choice of Containers

The main function of the container is to keep the fish in good condition while being stored or during transport.

Before deciding on type of container, special considerations should be given to the following points:

• main aim of using container;
• type of fish which will be held in the container;
• average storage time;
• type of storage (frozen, chilled, dry, etc.);
• means of handling and transport of the container;
• economic considerations.

The important qualities to consider when choosing a container are durability, suitability for the intended purpose and standardization for mechanized handling and transport. Long life and versatility will ensure maximum use of such equipment.

Insulated containers, by keeping out unwanted heat will preserve the quality of chilled or frozen fish. The use of appropriate ancillary equipment will facilitate handling, cleaning and maintenance.

The technology is available for manufacture of simple containers and also complex refrigerated units. Many types are in use around the world and a few of these will be described here. Those listed are practical, economical and cover most needs.

6.2 Standards for Simple Containers

The standards used are often a result of cooperation between the producer and consumer. The general requirements for chemical/physical properties of the materials are that they should be non-toxic and easy to clean.

In Scandinavia and parts of Europe the base measurements used are often similar to the Euro-pall Modul, which is 800 x 1 200 mm². This size is easy to accommodate on transport equipment for the best utilization of area/volume.

Wooden containers

Wood is not a very suitable material to use because it easily absorbs and retains water which makes it heavier and difficult to clean unless the surface is sealed. Wooden containers suffer damage relatively easily with rough handling and transport.

One advantage of wood is that it is available in most countries throughout the world. It is relatively cheap and can be worked with simple tools by local craftsmen.

Figure 13 HD-polyethylene containers (when filled they can be stacked 3 on top of each other)

Table 11 Dimensions of polyethylene containers

Containers of different shape and volume can be made and repaired locally. Wood has a relatively good insulation effect, but is fairly dense.

Aluminium containers are solid and easy to clean but require specialized construction equipment and are more difficult to repair. Aluminium has poor insulation qualities. Containers made of seawater resistant aluminium will be quite expensive, but durable.

Steel containers are sometimes used for bulk fish transport. These are very durable if galvanized or painted with a rust proof paint. Sometimes steel containers have an inner GRP lining with the space between liner and steel filled with polyurethane foam.

Glass reinforced plastic (GRP) containers are simple to use and durable. GRP containers can be built to any shape and volume. The technology is much the same as used for GRP boat production.

HD-polyethylene is the material which is most commonly used for containers. This type can be double walled with air as insulation or have the hollow space filled with polyurethane foam. This "sandwich" construction gives good insulation and a stronger container.

Insulation. Most insulated containers will have polyurethane or similar foam as insulation material. It has high insulation effect and is very durable.

6.3 Containers for Road Transport

The basis for chill/cold container road transport is the lorry chassis, as shown in Figure 14. These types of containers are insulated and built for fast fixing to/removing from the chassis.

Figure 14 Lorry chassis

Containers may be built to satisfy any carrying capacity

The load carrying capacity is of course not only dependent on the size of the container; due consideration must also be given to the capacity and stability of the vehicle, loaded and unloaded. It is also necessary that engine power and braking power are compatible with total weight of loaded vehicle and in accordance with international and/or domestic regulations.

Figure 15 shows the construction principle for an insulated pre-fabricated container for road transport.

The container is made of insulated laminates fixed to an aluminium profile bearing system for walls and roof. The bottom frame is made of steel profiles costomized to fit the lorry chassis in question.

Tested and approved steel fittings should be used for fixing the container's bottom frame to the chassis. It is the manufacturer's responsibility to fulfill this requirements.

Table 12 gives a number of standardized inside dimensions and combinations of dimensions which are normally offered by container manufacturers.

Maximum permissible outside width is in many countries limited to 2 500 mm.

Figure 15 Principle of construction

Table 12 Standard measurements for lorry containers (mm)

a/ Aluminium floor plate with raised edges reduces the inside width by 10 mm
b/ Has to do with max. standard measurements. Larger inside height can be produced on request.

Insulation

The majority of containers for modern road transport are made of pre-fabricated sandwich elements, usually hard polyurethane (PUR) foam laminated between sheets of aluminium or gel-coat finished GRP.

Figure 16 Insulation thickness for chill and cold containers

Doors are made of PUR insulated elements cast in one piece with cast-in reinforcement for fixing of hinges, locks. etc .
The floor is normally reinforced with an anti-slip aluminium sheets, bent up 200 mm along the sides and front wall. On top of a 15-21 mm plywood flooring.

6.4 Container Standards

General

On an international level there is a growing trend toward standardizing of structural details, surface finish, insulation and dimensions for food transport containers.

To optimize quality preserving conditions for perishable food-stuffs during transport, particularly in international commerce, discussions have been held at international levels. This has resulted in an agreement called "Agreement on international transport of easily perishable food-stuffs - and special equipment for such transport" (ATP).

The ATP agreement was developed in order to give transport container manufacturers a Code of Practice, or a norm for the design of their products. Thus it would also be possible to classify the containers with respect to standards and suitability for various transport needs.

The transport container can be insulated only, with its own refrigeration equipment or insulated and heated. They are classified in different categories according to capacity, cooling system, K-value (measure for = insulation property), etc.

Testing of Containers

In order that new equipment may be approved for use, the ATP requires the equipment to be tested. Approval of a tested model or type is valid for three years, or for 100 container units.

Full tests for certificate of approval can be carried out in Germany at:

TECHNISCHER UBERWACHNUNGS VEREIN BAYERN EV. MUNIK (TÜV) .

in France at:

CENTRE TECHNIQUE DU GENIE RURAL DES EAUX ET DES FROIDS, ANTONY

Certificate

New containers that are already approved through tests on a "prototype" model, are awarded a performance certificate valid for 6 years.

For later tests and tests on used containers, the validity of the performance certificate may be extended for 3 years at a time if the test is passed.

Marking of equipment Tested and Passed in Accordance with ATP Regulations

Marking shall be in accordance with the regulations Dark blue Latin lettering on a white background shall be used. The minimum height of the lettering being 120 mm. The marking shall be easily visible, preferably fixed high up on the forward ends of both side walls.

If the equipment is fitted with a removable temperature sensitive control unit, the asterisk "*" is added after the mark.

The certificate expiry month and year, is indicated immediately below the marking.

Example

FRC denotes a container with extra thick insulation, mechanically cooled with temperature choice ranging between +12°C and -20°C. 05-1983 indicates that the equipment certificate expires May 1983.

The marking letter code is as follows:

The first letter indicates cooling (or heating) and type of cooling agent:

I - no cooling agent used
R - cooling agent is eutectic plates or liquid (Nitrogen)
F - mechanical cooling is used
C - heating can be (is) applied

The second letter indicates the highest permissible K-value:

N - normal insulation with highest permissible K-value = 0,7 W/m² °C
R - extra thick insulation with highest permissible K-value = 0,4 W/m² °C

The third letter indicates class and internal temperature range :

1. cooled equipment at external temperature +30°c

Class A +12 °C to 0 °C
Class B +12 °C to -10 °C
Class C +12 °C to -20 °C
Class D less or equal to +2°C
Class E less or equal to -10 °C
Class F less or equal to -20 °C

2. heated equipment capable of keeping internal temperature at least +12 °C when

Class A outside temperature is -10 °C
Class B outside temperature is -20 °C

6.5 Calculation of Required Capacity for Refrigeration Unit

The calculation formula used is

Q = A x t x k x 1.75 where

once the required cooling capacity (Q) needed for the container in question has been computed, one must choose a refrigeration unit with cooling capacity equal to, or larger than this.

(Note: the refrigeration unit must also be certified).

Figure 18 Lorry with container and refrigerator unit