Liberal supplies of clean, dry, unstained and appropriately adaptable dunnage to the cargoes lo he loaded should be available and handy. Specialized dunnage and packaging of a synthetic nature should he in good condition. With all cargoes which require dunnage it is essential dial the latter is clean, dry and free from slain or odour.
Bagged cargo requires widely sized boards for dunnaging, for two main reasons, firstly in order lo provide a reasonable floor between tiers of hags such that sagging will not lake place and so that by laying the boards at about four lo six inch intervals between edges, air circulation is maintained between the tiers.
Laying dunnage is not a haphazard function. Dunnage has the purpose of assisting in the solidarity of slow and also preventing undue damage to cargo in proximity lo itself. It must therefore be laid with thought and attention lo the purpose for which it is being used and its size and adaptability filled where this can best serve the total slow.
The main contributory factors towards damage lo cargoes whilst in vessels are: crushing; dampness; contact with ironwork of the ship or other cargo; and lack of systems of ventilation specifically suited to the cargoes.
In view of this it is essential to give due attention lo dunnaging needs. In terms of the materials which can be used for dunnaging it must he such as will provide protection to and from any or all of the above font factors and could be seasoned wood of different size and shape; pieces of cordwood; bamboos; mats; rattans and ply-board. Modern practices use quantities of blocks of expanded polystyrene and also air tilled hags.
In refrigerated compartments permanent steel corrugated dunnage is used with a high degree of success. It allows a sufficiency of air flow and has the strength to carry the load/weight of fork I ill trucks.
Double dunnage, that is one layer on top of another, is preferable at all times but particularly so with the bottom layers adjacent to the decks. Modern synthetic dunnaging materials, which serve as packaging as well, tend to lessen the need for an overabundance of oilier forms of dunnaging such as wood.
Laying dunnage in preparation for a cargo depends largely upon the type of consignments in the load(s). With most bagged cargoes a complete tier of dunnage is first laid over the floor of the space on to which a complete covering of bags is laid. General cargo, by virtue of its different shapes and sizes, would break up any previously laid dunnage and it is therefore better in such cases lo 'dunnage' as the stow goes along.
Sweepings . . . torn or split bags are a common form of damage with bagged cargoes. The extent of the damage depends largely on the handling of the bags during loading and the care taken to prevent their coming in contact with projections in the space or compartment, such as stringers or angle backets. The weight of the layers of hags also, in some cases, causes those in the lower tiers to split and the contents seep down to the bottom of the space where, alter discharge, a considerable quantity of the commodity may be found. It is for this reason that separation cloths, or tarpaulins should he completely spread over the bottom dunnage in order to retain this residue on discharge, and to keep it as clean as possible. Sweepings are part of the consignment, and must be discharged as such.
Spar ceiling, or cargo battens as they are called in some trades, comprise portable wooden battens lilted to the inner edges of the frames of the ship's structure so to form a sheathing to the ship's side. Normally spar ceiling is made up of 1½ in boards of about 6 in wide and arranged horizontally in convenient lengths attached to the frames by angle brackets and spaced about 9 in apart. In some cases vertical sections are made up to lit in between the frame spaces. The purpose of this wooden sheathing is to prevent packages of cargo protruding beyond the inner edges of the frames and so becoming damaged by moisture which may collect on the side of the ship. The space so formed between the spar ceiling and the ship's side helps to provide a complete air space around the cargo and thereby improves ventilation. The spar ceiling should always be kept in an efficient state of repair.
With a coal cargo it is advisable to remove the spar ceiling before loading, so as to prevent any possibility of "through ventilation".
More frequently it is the practice to fit vertical spar ceiling throughout hold and tween decks and this usually takes the form of 6 in x 2 in battens, three to each frame space, all of which are bolted to 2 in x ½ in iron brackets.
The advantage of this type of sparring is that it results in less broken stowage than the horizontal battens fitted on the inner-side of the frames.
Specialized Arrangements. Spar ceiling fittings in roll on/roll oil vessels take on an additional purpose. Cargo is usually loaded quickly into these vessels and can be of considerable variety and size in the main deck/hold stowage. Prevention of movement becomes of paramount importance here and it is necessary to provide this feature as well as ship side condensation effect.
To this end, spar ceiling units are fitted in 15 ft x 15 ft sections, hinged to attachments at the ship side and capable of being pressure-forced to the cargo bulk, thus providing an overall tying effect.