Depending on the type of cut of the sheet and the transport system used, it is required to prepare the packaging of tin bundles or other material with the appropriate materials. The different ways of making this packaging and the necessary elements to carry them out are described below.
The materials to be described for use of the packaging in the drawings that illustrate this article, are applicable both for the packaging of packages of tinplate cut in rectangular form, as for the leaves cut in “primary scroll”, either in white or lithographed . Depending on the type of leaf, transport system – truck, train, boat – and distance to travel – local, long distance or rough handling – certain types of materials will be used. In general, a pallet, a cover, strips and edge protection angles will be used in all cases. In addition to these materials, in some cases, wood blocks with pads, anti-moisture paper, plastic and cardboard or corrugated covers will be used.
The transport classes already mentioned are defined as follows:
Local: Transportation by truck up to 100 km away, where there are roads in good condition and delivery is made on the same day.
Long distance: Transportation by truck with distances between 100 and 750 Kms, with or without night driving.
Rough or severe driving : transport by rail or ship without distance limit, and truck with distances greater than 750 Kms.
PRACTICAL PACKING CASES
A.- Local transport for rectangular sheets in white or lithographed
Consists of: pallet, cover or lower separator, protection angles and strapping. All of them arranged according to figure 1 and in the amount indicated therein. Later we will describe the characteristics of each of these elements.
Figure nº 1: Packing for local transport of rectangular sheets
Another option for this same case, is to wrap the package with stretch plastic film instead of the strapping. The film has to be applied tightly. In the case of varnished tin, the thickness of the film must be May, due to the danger of sliding of this material. Later on, characteristics of this film will be given.
The use of stretch film, although it is an interesting method because of the possibility of being automated with an inexpensive installation, and also giving good results from the point of view of fixing the sheets, has a possible high risk. If the package is covered with film in a warm and humid environment, as it can happen in the lithography ship located in the vicinity of the sea or large bodies of water, and later it is transferred to another cold and dry geographical area, condensations of water inside, with the consequent risk of oxidation of the material.
B.- Local transportation for leaves cut in primary scroll, in white or lithographed
The following elements are used as in the previous case: pallet, pallet cover, protection angles and strapping. All this as shown in Figure 2, and in the same amount as for the previous case.
Figure nº2: Packing for local transport of tinplate cut in primary scroll
Also in this type, the straps can be replaced by stretch plastic film.
C.- Long distance transport for rectangular white sheets
For this type of transport, harder because of the distance and time, it is necessary to use the following elements: pallet, pallet cover, anti-humidity covering paper or stretch film, strapping, protective angles under the straps at the corners and full angles. All this in the quantity and position according to figure 3.
Figure nº 3: Packing for long distance transport of rectangular blank sheets
As we have already indicated, to cover and protect the pile of sheets, it is possible to use anti-moisture paper or stretch film, so that all the faces of the package are well covered.
D.- Long distance transport for rectangular sheets varnished and / or lithographed and / or lubricated or cut in primary scroll in the same conditions.
In this case, the danger of sliding leaves is great, so the previous packaging has to be complemented by a crossed vertical strip, protective angles on all four sides of the base, horizontal straps and pads with angles at the four corners. Also, if the tin is cut in a scroll, you should take wooden blocks under the anti-damp paper in the two corners coinciding with the scroll cut. See figure # 4
Figure nº 4: Packing for long distance transport for rectangular sheets varnished and / or lubricated or cut in primary scroll.
E.- Transport and rough or severe handling for leaves of any type
When the treatment is foreseen hard and the complex transport, boat, rail or long distances by truck, it is necessary to improve the previous packing, adding a fourth vertical strip and above all resorting to the use of cardboard covers that protect the pile. Figure 5 describes this type of packaging.
Figure nº 5: Packaging for transport and rough or severe handling for leaves of any type
As in previous cases, we will add that it is possible to replace the anti-moisture paper with stretch film and add wooden blocks in the case of screened sheets. See example nº 6
Figure nº 6: Packing for transport and rough or severe handling for scroll sheets
We now enter to define each of the elements used in the packaging
The wooden pallets used for packing tin packages are two entries. In the drawing no. 2 a typical model is presented
Figure nº7: Palette for tin bundles
For larger dimensions of leaves, a more central skate is added to avoid warping of the boards.
The wood used in its construction must be economical but fulfilling a series of requirements. This can be made of pine, dried in the air or in a drying oven, with a maximum moisture content of 18% (+ 2%). Woods that contain oils, pitches or other products with a characteristic odor will not be used. Figure 2 shows the specifications and materials to be used in the construction of these pallets.
SEPARATOR OR PALETTE COVER
In order to protect the tinplate, a compact cardboard cover must be placed between the pallet and the tinplate. This compact cardboard must have a minimum thickness of 2 mm, with a grammage of 1200 g / m2, and its dimensions must be such that it does not protrude from the pallet, nor be less than 50 mm below the dimensions of the pallet.
The main purpose of wooden blocks, which must be placed in the corners of the leaves cut in primary scroll, is to allow horizontal strapping, the use of covers and outer packaging. Pads must be placed between the wooden blocks and the tinplate, which can be made of compact cardboard or corrugated cardboard.
Material: Must be made of pine wood or similar, free of resins, pitting and odors. Its moisture content will be a maximum of 18% (with tolerance of + 2%)
Size and labeling: These blocks should be rectangular section, with an approximate size of 3 mm. less than the cut of the tinplate in scroll to fill. The height of the block must be equal to that of the tin package with tolerances of + 0, – 6 mm.
The format for which it is suitable and its height should be labeled on the wooden block, in order to simplify its reuse. For example 73 x 340 (covers diameter 73 and height of the package 340.
The materials to be used as pads between the blocks of wood and tinplate are: compact canton with a minimum thickness of 1.5 mm, or double-sided corrugated cardboard. They must have a width of 125 mm., And with a length equal to that of the block and / or protection angles used. The pad should be folded in half, so that it is at a right angle with sides of at least 60 mm.
Compact cardboard covers must be used for the protection of tinplate in cases of transport by rail or ship. These covers must be manufactured with the following materials
– Compact carton type Kraft 2 mm thick or
– Corrugated cardboard double sided channel “B” (168 corrugations / meter), thickness 3 mm, 24 Kgr / cm2 of resistance in the Mullen test.
Types: One-piece covers can be used, die-cut as shown in figure “A”, or 4-piece covers, which are usually cheaper because they can be used for several different formats. See figure “B”
Figure No. A: One piece cover
Figure nº B. 4 piece covers
All the straps, in order to achieve maximum efficiency, must be placed parallel and / or perpendicular to the edges of the load and squared with it.
Type: The strap to be used must be Signode Magnus steel or similar, with dimensions of 16 mm x 0.6 mm and Signo type staples of 84 AMP or similar. The strip will have a breaking load of 820 kg minimum.
Strapping direction : The strapping should be placed as indicated in the different drawings corresponding to the different types of packaging shown in this article, which are a function of the type of material to be packed and the method of transport.
You can use cuttings of tin at least 0.24 mm caliber, with a corrugated cardboard pad, or pieces of angles of 40 x 40 x 4 mm of 75 mm in length, with its corresponding corrugated cardboard pad.
In some types of packaging, steel angles are used to protect the tinplate and have a rigid surface on which the strip can be tensioned. For most of the cases, angles of 40 x 40 x 4 mm should be used, although some times and depending on the state of the tables of the palette, angles of 25 x 75 x 4 mm can be used
The length of the angle is determined in the following way:
Protection angles Vertical corners: They must have a minimum length equal to the height of the tin stack plus 16 mm, so that they fit and overlap the wooden pallet.
Horizontal corner protection angles:
- Straight cut : It must have at least a length equal to that of the leaves, minus 6 mm. In no case should the angles protrude from the leaves.
- Scroll cutting: They must have at least a sufficient length to cover the entire scroll cut. Angles should not protrude from the edges of the leaves.
For tin bundles cut in primary scroll, and that will have a rough and prolonged handling, it may be advisable to protect the cuts in scroll with an additional cover; which can be constituted by two standard 4-piece cover elements, so that one of these elements protects a “scrolado” edge and the other element the opposite edge also “scrolado”. These cover elements must be placed before the strapping and must cover the scroll cut and part of the upper surface.
We have already seen that it is an alternative option in different cases, either to strapping in simple packaging, or to anti-moisture paper. Its use is simple, based on having a tensioning and application equipment. When the packages are subjected to abrupt changes in temperature and relative humidity, it is necessary to make some outlet holes to the occluded air to eliminate condensations, this limits its effect of protection against dust and contamination of the leaves.
When the packed sheets are varnished or lubricated, it is necessary to increase the thickness of the film so that it contributes more consistency to the sliding of the sheets between them, and reduces the risk of cracks. The characteristics of the ideal film in each case are:
Product: Stretchable polyethylene, 3 layers, without dyes. Single-sided adhesive, on the outside.
30 microns 23 microns
Longitudinal breaking load (Kg / cm) 480 390
Transverse rupture load (Kg / cm2) 360 305
Elongation at longitudinal break (%) 620 645
Elongation at transverse fracture (%) 910 915
Usage Varnished tinplate Tinplate blank