Paper (rolls)
| Infobox on Paper (rolls) | |
|---|---|
| Example of Paper (rolls) |  |
| Facts | |
| Origin | This table shows only a selection of the most important countries of origin and should not be throught of as exhaustive
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| Stowage factor (in m3/t) | 1.78 m³/t (paper rolls wrapped in 6 layers of packing paper). Package dimensions are variable, the important factor being that the rolls within one cargo stack must exhibit uniform dimensions, to prevent distortion. |
| Humidity / moisture |
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| Ventilation | Recommended ventilation conditions: air exchange rate: 6 changes/hour (airing), if the dew point of the external air is lower than the dew point of the hold air. On voyages from cold to hot climates (Scandinavian ports, Continental ports - tropical unloading ports in Africa, Asia), every possible opportunity for warming the paper must be used to avoid cargo sweat. |
| Risk factors | Self-heating / spontaneous combustion, contamination, wet damage, mechanical influences; see text. |
Paper (rolls)
Contents
Description
Paper (and board) are manufactured from paper pulp. This material is first repulped in water and, after passing through various intermediate operations, such as straining to remove particulate matter, the aqueous slurry of fibres (about 0,5% cellulose fibres) is deposited as a continuous film on a recirculating wire mesh or a moving felt band. The belt passes over suction boxes which removes water from the film to produce a continuous ‘paper’ strip containing about 35% of cellulose. This is sufficiently strong to be stripped off the belt and threaded through a battery of heated rollers where it is further dried so that the paper or board emerging from the end of the machine has a moisture content of about 5%. The warm paper is reeled and possibly slit simultaneously into predetermined sized rolls, by means of continuous reeling equipment.
There are a large number of different types of paper which can be produced by using different types of paper pulp and by various treatments during the paper making operation, such as sizing, opacifying, treatment to produce wet strength, polishing (calendaring), coating etc. It is evident that more complex papers are commercially more valuable than less complex papers. It is also evident that sophisticated paper products which are unacceptable for the intended purpose must either be sold for scrap or returned for repulping. The pulp produced will inevitably be used for low grade products.
Major uses of paper are for newsprint and the manufacture of corrugated fibre board. The paper products used for each application are similar in as much as they are almost always in large, very heavy rolls over half a tonne in weight. Unbleached kraft rolls used for carton board are only slightly less valuable. Because of their weight they must be mechanically handled.
Newsprint rolls are used on high speed printing presses. Any interruption in the printing process, due to a fault in the paper, results in a substantial financial loss. Users take particular care to ensure that only sound rolls which can easily be handled to make them sound, are accepted.
Although the users of kraft paper are not constrained by time in the same way as newspaper publishers, they also employ high speed machinery of high capital cost and take the utmost care to prevent any interruption on a production line.
Applications
Paper may be classified into seven categories:
- Printing papers of wide variety.
- Wrapping papers for the protection of goods and merchandise. This includes wax and kraft papers.
- Writing paper suitable for stationary requirements. This includes ledger, bank, and bond paper.
- Blotting papers containing little or no size.
- Drawing papers usually with rough surfaces used by artists and designers, including cartridge paper.
- Handmade papers including most decorative papers, Ingres papers, Japanese paper and tissues, all characterized by lack of grain direction.
- Specialty papers including cigarette paper, toilet tissue, and other industrial papers.
Newsprint, which belongs to the first group, is used for daily and weekly newspapers, magazines, catalogs, newspaper supplements, direct mail items and for advertising flyers.
Shipment / storage / usage
Newsprint is a machine-finished printing paper, predominantly for web offset printing. Its basis weight is 40 - 56 g/m2. Since damage to the rolls of paper leads to considerable losses, the demands made of transport and storage of such rolls are high.
Fewer demands are made of newsprint with regard to visual characteristics and printability, because, of all the types of paper, newspapers are the shortest-lived sources of information. To keep the retail price low, they must be inexpensive, which is why the Waste Paper or mechanical pulp content is high.
Newsprint must have good printability, good pressroom runnability (tear resistant), sufficient opacity (reverse must not show through), good recyclability, optimum water content 7% and good dimensional stability.
Newsprint is transported in rolls up to 300 cm wide and with total weight of up to 4.5 t.
The circumferential packaging for the paper rolls wound ultratightly onto paperboard or metal cores is up to 3,5 mm thick and, as a rule, consists of several plies of kraft paper. To provide protection from moisture, a waterproof ply (e.g. of asphalt paper) is often incorporated therein. The circumferential packaging is folded over the ends by approximately 20 cm. The ends of the rolls are protected with corrugated board covers. In many cases, the final kraft paper cover is plastic-coated and stuck to the folded-over circumferential packaging. Core stability is ensured by a wooden or metal plug driven in at each end.
As there is a risk of losses caused by swelling and tearing of individual layers, paper (rolls) should be protected from extraneous wetness and handled carefully resp. professionally (with special cargo handling gear and forklift trucks with paper roll clamps).
Incorrect cargo handling may result in distortion of paper rolls (ovalization). Rolls exhibiting marked ovality can no longer be used for printing and have to be rewound.
Cargo spaces must be clean and smooth, to prevent any possibility of damage to the ends. The goods must be protected from any possible leakage from hydraulic lines. In addition, paper must be protected from all moisture, such as rain, snow, condensation water, seawater, extremely high levels of relative humidity or damp stacking surfaces.
The most favorable travel temperature range is 0 - 25°C. Optimum travel temperature: 20°C ± 5°C (relative humidity 60-70%).
During cargo handling, temperatures below 0°C are also permissible for short periods. The goods must be protected from heat sources.
Paper rolls are very sensitive to mechanical influences such as pressure, impact and friction. The risk of damage is greatest during cargo handling (i.e. distortion / ovalization, telescoping, indentations, edge damage, tearing, chafing).
Rolls which are landed heavily may be flattened and in some cases the cores may be crushed. While it may be possible to force the core back into shape any flattening of the rolls can cause jerking during the printing operation. With high speed presses, jerking or uneven running of the roll results in breaks in the paper, thereby slowing down the operation. Where the cores cannot be pressed out it becomes necessary to rewind the damaged roll. This operation can only be carried out by a skilled operator as the roll must be rewound at the same tension as existed before rewinding.
Damage may take place during loading on board vessels but occurs chiefly during discharge due to careless handling of winches and cranes when lifting from holds. Damage can arise from bad stowage, e.g. with case goods or other sharp volumes, or by forcing rolls behind ladders, shaft tunnels or similar hindrances.
If wet, newsprint may be unfit for printing purposes but may possibly be used for pulp, manufacturing paper bags, shop wrapping paper, etc.
Should a roll come into contact with steelwork, be rolled over an uneven surface or dropped unevenly on its end, damage may be found in the form of cuts and tears on the face or edge of the newsprint. There are two methods of establishing the amount of damage to newsprint rolls. One is to have the damage cut off the reel and the amount of paper thus cut off weighed. The alternative is to measure the depth that the cut or tear has penetrated the roll, and calculate the amount of loss by use of a formula :
S = loss in %
T = depth of damage
D = diameter of roll
d = diameter of core
The two main forms of damage which cause problems with rolls of newsprint and kraft are:
Mechanical damage
This may take the form of tears, cuts or snags. Where such damage occurs, the rolls have to be unwound until completely sound paper is reached.
The second form of mechanical damage is distortion which may result from unsatisfactory use of clamp trucks or any form of impact. Where distortion occurs the paper web is subject to non-uniform tension during unreeling on a press or other machine. Because the web is under considerable tension, a non uniformity can result in rupture.
Wetting
Newsprint rolls are normally overwrapped with a wrapping system incorporating a waterproof barrier. Kraft rolls are not so protected. However, significant wetting even of newsprint, can result in the rolls themselves being damaged.
Wetted rolls, even after drying, normally present the same problems as distorted rolls and again must be stripped down to undamaged paper before they can be used. Due to swelling of the fibres, severely wetted rolls can split.
There are various precautions which should be taken by a ship’s command to ensure the above-mentioned problems are minimised.
All rolls should be examined at the time of loading for evidence of damage. As paper frequently originates from countries which are very cold in winter, they may sometimes be coated in a thin layer of ice, which is not detectable without careful checking. Where possible, damaged rolls should be rejected. If this proves impractical, Mate’s Receipts should be claused giving details of affected rolls, including the nature of the damage.
Obviously, Bills of Lading should be claused in the same terms as relevant Mate’s Receipts.
Ship’s holds should be clean and dry before loading commences and preferably, the tank tops should be covered with kraft paper.
Great care should be taken in order to ensure rolls, which are always stowed vertically, are not subject to uneven pressure from such fittings as horizontal cargo battens or dunnage. Any objects which can snag rolls, such as projecting nails, should be removed. Other projections should be cased in dunnage. Rough sawn dunnage should not be used in contact with rolls. The most suitable contact material is plywood sheets. Rolls should never be secured in a way which results in direct contact with wires.
Bearing in mind rolls of differing widths are often to be loaded in one hold, special care must be taken with stowage to ensure a stable stow. Care should be taken to prevent wetting on board. Hatch covers should be closed when rain is threatened.
The ship should, of course, be watertight and if ventilation system is used, ventilators should be closed whenever bad weather threatens. Paper rolls originate from the same areas as paper-pulp i.e. often from ports where the temperature is very low in winter. Masters should either check temperatures of rolls, which is difficult to do, as there may be significant variation through a roll, or assume the rolls are at the same temperature as the ambient atmosphere and ventilate accordingly. Rolls loaded at ports where the temperature is low, do not normally require to be ventilated at any time on a subsequent voyage. There have been massive claims for damage to rolls of paper which have been damaged by cargo sweat resulting from ventilation of cold cargo with warmer air.
Conversely, there have been claims due to wetting of relatively warm rolls by ship’s sweat when atmospheric temperatures are falling, or when ventilation is interrupted during a period when the outside air temperature is lower than the dew point of the air in the cargo compartment: i.e. the ambient air surrounding the rolls which is influenced to a degree by the peculiarities or characteristics of the actual cargo.
Another problem which has given rise to massive claims is taint. This is discussed in relation to paper pulp. It is not always easy to detect taint to paper rolls, particularly when this originates from residual odours from previous chemical cargoes. A case is known where bleached board was used for the manufacture of milk cartons and no taint was detected until complaints were received from the public who consumed the milk. The taint was traced to an earlier cargo of herbicides. Masters should obviously check, or arrange for surveyors to check that holds to be used for paper products are not only scrupulously clean but also odor free. Because detection of odors is very difficult when the atmospheric temperature is low, when loading takes place under such conditions, it is recommended that known properties of earlier cargoes are reviewed.
Wetting and mechanical damage can occur at the time of discharge. Masters should obviously supervise discharging operations. Where damage is seen to arise as a result of mishandling by stevedores, the occurrence and nature of such damage should be reported in writing to the stevedoring company and recorded in the ship’s log book.
Coated Paper
The term coated paper usually indicated paper that is pigment-coated or gummed. Due to the presence of water soluble binders in the coating formulation, they tend to stick together if moistened and then re-dried.
Corrugated Paper
Is extremely brittle. If damaged may not be possible to cut and re-roll. May then only be disposed of for scrap value.
Kraft Paper
Usually shipped in rolls without packing. Rolls should be loaded in an upright position and protected from any kind of moisture. Liable to tearing and flattening during loading and transshipment. A misshapen roll cannot be used and must be rewound with subsequent loss and re-winding costs. Damage to ends of rolls may cause total loss. Unless paper is split, damp patches do not necessarily.
Risk factors
- Self-heating / Spontaneous combustion
- Moisture
- Odor
- Contamination
- Mechanical influences
- Distortion
- Shrinkage / Shortage / Theft