What you select as a means of securing a load on a tray truck or trailer platform will depend to a large extent on the type and construction of the load to be carried. Clamps, special bolts, steel wire rope, chains, webbing straps, rope and cordage made from natural and synthetic fibres, and shoring bars used in vans are all suitable devices. Rope, cordage and webbing straps, whether made from natural or synthetic fibres, should be used with caution as their strength cannot readily be assessed and can be seriously weakened by age, wear or incorrect use.
In view of the continuing proliferation of various grades and quality of rope on the market, prospective purchasers of rope should, for their own protection, insist on the following information, provided by the supplier, in writing:
Where the above information is not available or there is doubt, samples should be tested by either the supplier or an independent party that is acceptable to both purchaser and supplier.
Rope should be 12mm in diameter and manufactured from one of the following fibres:
The list shows the materials arranged in their order of preference. Light (UV) stabilised material should be used where there is a choice. If rope is sold as light stabilised grade, the supplier should be able to substantiate such a claim.
Ropes should preferably be manufactured and supplied in accordance with AS/NZS 4345.
Manila ropes and 12mm sisal should not be used other than for securing tarpaulins and loads less than 0.5 tonne.
Ropes made from any material are liable to wear. They can be weakened by various agencies such as chemicals, heat and light or by excessive knotting, bending or chafing. Regular inspection is necessary to ensure that the rope is still serviceable.
Examination at intervals of about a metre at a time is desirable, the rope being turned to reveal all sides and the strands being untwisted slightly to allow examination between the strands.
To define a standard of acceptance or rejection is much more difficult than to describe the method of inspection. There can be no well-defined boundary between ropes that are safe and those that are not because this depends on the stresses placed on a rope. The decision whether to use a rope or to replace it must depend on an assessment of its general condition. If, after examination, there should be any doubt about its safety, it should be withdrawn from service.
Fibre rope is easily damaged and this potentially dangerous condition is not always visible. Constant vigilance throughout the life of the rope is therefore essential in the interests of safety.
Purpose-made clamps are suitable for loads, eg containers where special lifting pockets, brackets or attachments are fitted to the loads. In most cases, it will be necessary to reinforce the platform of the vehicle in the vicinity of the clamp position. The design of the clamp and reinforcement should be carried out in accordance with sound engineering practice. It must meet the strength requirements of the necessary load restraint and be compatible with the structure characteristics of the vehicle. Where clamps are used, a minimum of four should be fitted and three of these must be strong enough to restrain the load if one clamp fails to function correctly.
Steel wire ropes made up into special straps or slings are suitable for securing a load when used in conjunction with other suitable devices, eg shackles or thimbles. They are not as commonly used as steel chains. The strength of the steel wire rope will depend on the quality of the steel used, the number of strands, the number of wires in each strand, the diameter of the rope and the method of construction. The rope should be free from rust and there should be no broken wires or strands. Apart from the risk of injury to personnel from contact with broken wire strands, if 10 percent or more broken wires are visible in a rope length equivalent to 10 rope diameters, the rope is unsafe and should be condemned. There is a risk of unseen internal corrosion with steel wire rope and it can be easily damaged if driven over or bent around a sharp corner, etc. Therefore, the use of chain is preferable.
Those responsible for the purchase of wire rope and fittings for use in load restraint systems should ensure that they comply with AS 3569 or BS 302.
Chains may also be used for lashing loads. A number of factors determine the strength of chain - size and grade of material, link dimensions and heat treatment. Chain used for load restraint purposes is required to possess special mechanical properties for this demanding application. For specifications refer to appendix B.
All chains must comply with AS/NZS 4344 or BS 4942.
Load binders and turnbuckles should be at least as strong as the chains to which they are attached. The use of grab hooks reduces the strength of chain by 25 percent and, as such, the lashing capacity of this type of system must be reduced by 25 percent. Clevis claw hooks do not reduce chain strength and should be used in preference. The hook of the binder should not be spread or distorted. The attaching pin should not be bent, worn over 10 percent of its thickness or inadvertently secured to the hook. The binder parts should not be bent, repaired by welding or so worn or distorted that the chain cannot be tensioned properly or retain tension when in the secured position.
All chains used for load restraint purposes should be clearly identified with links quality marked at regular intervals, to provide protection against the use of chains of unknown quality. Chain should be of 'short-link' formation because it is more resistant to deformation than other formations. When turnbuckles or load binders are used in conjunction with chains they should correspond in strength with the chain used. Any distortion of load tensioning devices clearly indicates that severe overloading has occurred and such items should be removed from service. Welded repairs to turnbuckles or load binders are not permitted as this can result in subsequent failure. When tensioning devices are not capable of applying or retaining tension, they should be removed from service.
The following safety precautions must be taken when using and inspecting chains:
Figure 8 Detail of load binder
Hinge pins should be parallel or have a positive locking means employed to prevent link spreading.
Commercial webbing and strapping, specially designed for lashing loads to vehicles, are available. These incorporate quick-fastening release hooks and tensioning devices, and occasionally include anti-chafing sleeves (see figure 9).
Webbing made from synthetic fibres is slightly elastic in use. This prevents the load from working loose.
Where webbing is used as a means of primary restraint it must show no signs of damage, chafing, fraying or stitching failures.
The following points should be considered when selecting webbing type restraint equipment for use with palletised loads:
When webbing is used, the vehicle should have at least one lashing every 1.5 metres along the length of the load. Complex loads are likely to require additional lashings. Each part load or load that is not loaded against a headboard or baulked must have a minimum of two lashings.
Where rope is used, knots must be correctly made and the lashing scheme arranged so that failure of one length of rope does not lead to failure of the entire lashing. It should be borne in mind that rope made of natural fibres will stretch when dry, allowing the load to move. When wet it is liable to shrink with the risk of damaging the load and jamming the securing points.
In general, the method of securing any load must be decided by the type of load.
It is therefore strongly recommended that owners equip themselves with the correct type of securing equipment for the type of load carried. Where general cargoes are carried, various types should be made available.
The following illustrations indicate some of the more common knots used with ropes and cordage for load securing purposes.
Figure 10 The sheepshank
The sheepshank or truckie’s hitch is used for tightening ropes used to secure loads.
Where a tie rail is used to attach a rope, the anchor point should be adjacent to a cross member.
Figure 11 Truckie’s hitch
Double shank/double hitch.
Figure 12 Single sheet bend
This is used to join two lengths of rope together, eg if a belly rope is required on a load
and the ropes are too short and where the knot itself will not bear on anything.
Figure 13 Clove hitch
This is most commonly used by truck operators for fastening the end of a rope.
With this knot, a stopper (ie two half hitches) should be used.
Figure 14 Round turn and two half hitches
This is a safe knot for fastening the end of a rope.
Figure 15 Timber hitch
This can be handy for fastening when an object requires moving
Figure 16 Towing hitch
This is handy if the vehicle requires towing for a short distance by rope
as it will not or should not jam, and a jerk on the end will release the tow.