Loading of carriers
A carrier can be a: truck, container, railway wagon, etc., so all types of carriers on which we can transport a load.
It seems that the theory of load securing is different than the practice of load securing, but it is not!
Each load can be secured, regardless the size or shape.
Theoretical knowledge of movement, G-force and friction are always applied.
The first step is to unitize the goods and secure the load with load, specially for pallets and crates.
The goods are tightly loaded, starting at the front of the carrier.
If the goods do not allow tight loadeding, because of their weight or shape, the load has to be secured with securing materials.
In practice you will see that various types of securing materials are used or even combinations.
E.g. ratchet systems, antislipmats and timber.
The position of the load on or in a carrier is very important for the correct spreading of the weight. This is of influence on the pressure on the axles of a truck or the balance of a container in a crane.
During breaking, the load 10 tons of marble, shifted forwards.
Axle weights
In Holland the government wants to decrease the cost of repair to roads, caused by too heavy loaded trucks.
Since 1999 the wim-vid system (weight in motion video) is tested and now in use. This system checkes the axle pressure automatically when a truck passes the checkpoint, the licenceplate is recorded and the axle pressure is measured, the data is compared to the allowed axle pressure of the truck.
The maximum axle pressure is registered on the vehicle registration certificate.
The maximum axle pressure for Holland is:
11.500 kg. Driven axle.
10.000 kg. Non driven axle.
12.500 kg. Coupling between truck/trailer.
An important influence on the axle pressure is the location of the load on or in the truck/trailer and the distance between the axles.
We cannot change the distance between the axles but we can put the load in any position on or in the carrier. Therefore we cannot put every load against the headboard of the carrier. If there is any space between the headboard and the load you will have to pay extra attention to the securing of the load. Make sure that containers are always in balance, not more than 60% of the weight of the load in one half of the container.
When weight of the load on a truck/trailer not exceeds the maximum payload, there can still be a problem with exceeding the axle pressure. Sometimes this cannot be prevented.
The problem can be as follows:
Truck/trailer, maximum weight 40 tons, loaded with 24 pallets.
Max.weight 40.000 kg.
Load 26.000 kg.
Front axle truck 6.800 kg.
Driven axle 11.200 kg.
Coupling 11.100 kg.
Axles trailer 21.900.
All figures are lower than the allowed maximum, so no problem.
If the last 4 meters of the cargo are unloaded, the axle pressure is as follows:
Max. weight 40.000 kg.
Load 17.000 kg.
Front axle truck 7.150 kg.
Driven axle 12.500 kg.
Coupling 12.700 kg.
Axles trailer 13.300 kg.
The pressure on the coupling is increased so the pressure on the driven axle is exceeded, even when 30 % of the cargo is unloaded. There is no more balance, the effect of the counterweight no longer exists.
In this case the load has to be replaced backwards, than an extra securing is necessary.
LASHING AND SECURING MATERIALS
Many different materials can be used to secure or stow cargoes. It is, however, important to use materials which are especially designed for the job. Make sure you know the forces expected during transport and the strength of the material that you are going to use.
Certified systems, such as those manufactured and supplied by Easygu, will give the highest degree of safety.
Please find hereunder the description of the most commonly used stowage materials.
Timber
Timber is still often used to secure cargoes. Often cheap pine wood is used. Tropical hard-wood is much stronger, but also a lot more expensive. Only in special situations is this used.
Under the influence of moisture, wood will shrink or swell. How much depends on the type of wood used. The specific strength of timber is dependable on it's moisture content. In most cases the timber has a moisture content of 25%!
An average quality of pine wood is used for securing cargoes with timber.
The sizes of the cross sections are: 3"x4" / 7,5x10 cm. or 4"x4" / 10x10 cm.
To calculate an indication of the strength is simple. But it is only an indication!
Formula: size x size in cm. X 0,3
Size taken from the cross section.
For example: 7,5 x 10 = 75 x 0,3 = 22,5 Kn. = 2250 daN.
10 x 10 = 100x0,3 = 30 Kn. = 3000 daN.
The breaking strength of wood during bending, depends on the length and the moisture content of the wood.
Nails are commonly used to fix the timber while securing loads. 5 mm dia nails hammered 4 cm in wood (wood cut against the grain!) will give a shear resistance of approx. 400 kg. If this is done with wet wood the resistance will drop to 200kg.
When timber is used to block a load preventing movement, the nails should always be applied against the grain. They should be placed in the middle of the timber or wedge.
In the table below the number of nails required per wedge are shown in order to secure a certain weight of load.
| Weight | Qty. Of nails |
| 350 kg | 2 |
| 500 kg | 3 |
| 700 kg | 4 |
| 1100 kg | 6 |
| 1400 kg | 8 |
| 1800 kg | 10 |
| 2000 kg | 12 |
* The strength of timber is influenced by: the percentage of moisture, type of wood, thickness and the number of "knots: and "splits". It is difficult to calculate the exact strength of timber when securing a load.
Attention!
In a number of countries it is not allowed to use untreated timber, according to the international guidelines, as package and stowage material.
These countries are: New-Sealand, Australia, China, U.S.A., Canada, Mexico.
No rules in Argentina, but checking the timber.
It is expected that for containers coming into the E.G. the same guidelines will be applied.
Steel wire
Steel wire is being used less and less for securing loads. It is sometimes still used at the port for example on flat racks or in containers or in the industry to bundle steel profiles or coils. It used to be used frequently for rail transport but for safety reasons is no longer recommended.
Material: warm drawn steel wire
Dimensions: 5 mm dia
Linear breaking strength: 726 daN
Closure: twisting to form knot
Tensioning: wood or steel turnbuckle
System strength: 2.320 daN used double
The system strength is highly variable dependant on the quality of joint made.
Elongation: approx. 2%
Advantages: simple tooling, cheap, high corner strength
Disadvantages: rust forming, danger of injury due to sharp points where cut off, no definite system strength, hangs loose when load settles due to low elongation, time consuming
Steel strapping is still widely used in the industry to bundle and palletise goods and secure for example steel coils or plate in ships holds. However it is becoming less popular to secure loads on flats or in containers.
Material: USLM strapping (Signode) or equivalent
Dimensions: 31,75 x 0,8 – 1,45 mm
Linear breaking strength: 1.960 – 5.300 daN
Closure: Pneumatic – crimp seals
Tensioner: Pneumatic
System strength: Dependant on seal type and number.
For load securing only crimp seal allowed
Static tests 1.764 – 4.700 daN using 2 seals
Dynamic tests 1.176 – 3.180 daN using 2 seals
All values are single-pull tests!
Elongation at break: 9 – 11%
Handling: Heavy, air line necessary
Advantages: Defined system strengths (if used properly), high corner resistance
Disadvantages: Corrosion, danger of injury, time consuming, no elastic elongation so that hangs loose with volume reduction in load, can break under dynamic loads.
Wire rope
Wire rope was extensively used, mostly in port areas, to secure unit loads to flat racks and on board ships. The introduction of one-way Polyester lashing systems has made large inroads to this market and is gradually replacing wire rope for many applications.
Material: non-galvanised wire of 1.770 N/mm2
Availability: 10, 12, 14, 16, 20 mm
Linear breaking strength: 16 mm = 12.800 daN
Closure system: Bulldog clips
Tensioning: Turnbuckle
System strength: 16 mm = 8.500 daN (2 Bulldog clips)
= 17.000 daN (4 Bulldog clips)
The system strength depends greatly on correct application of the wire and proper tightening of the Bulldog clips!
Elongation: ca. 2%
Handling: Time consuming as has to be joined with steel tensioning bar and wires fastened with 4 Bulldog grips
Application: Seldom in containers, often for large, heavy units on board ship
Advantages: Used correctly = high strength
Disadvantages: Time consuming and often not used correctly = strength not reliable
Chains
Chains are mostly used to secure heavy loads. They can be either one-way systems made-to-measure for securing loads to flat racks, or multiple-trip systems often used for transporting special heavy loads by road.
Material: Hardened steel acc. to DIN 5687-8
Dimensions: 6 mm. – 20. mm
Linear breaking strength: 1.000 – 12.500 daN
Closure: Hooks
Tensioner: Turnbuckle or lever tool
System strength: Dependant on attachments and use
Elongation: Not known
Handling: Heavy and time consuming
Application: Most suitable for heavy loads by road transport
Advantages: Strength, resistance to sharp edges
Disadvantages: Handling, slow, damage to goods, stronger than lashing points, danger of coming loose due to links moving over corners (see diagram below)
When using chains, ensure that the edge of the carrier floor or edge of the load is always between the chain links and not on the chain links!
Rope, and Hercules rope
The use of rope to secure loads is not recommended. Linear breaking strengths are not known and the joint efficiency of knotting is very low. More than 50% is seldom reached!
Hercules rope consists of Polypropylene or sisal and a number of thin steel core wires. PP is commonly used as it is not influenced by weather conditions and aggressive chemicals. It is also twice as strong as Sisal.
The steel wires used in the rope do not improve the breaking strengths but it make it easier to use. Consistent system strengths are not predictable as the rope is knotted.
Material: PP rope with 3 wire cores
Dimensions: 10 MM dia (usual)
Linear breaking strength: 400 daN
Closure: knot
Tensioner: Turnbuckle/wood or metal bar
System strength: 1.200 daN when used double
The system strength is subject to large variations due to knotting!
Elongation: PP rope = 40%, wire 2%
Handling: Fast
Application: Securing light objects in containers (<1 ton)
Advantages: Inexpensive, moisture resistant, does not scratch
Disadvantages: No definite system strength, only for light loads
Re-usable Systems
Re-usable ratchet systems are commonly used to secure loads on lorry trailers and sometimes used to secure loads on flats or in containers.
These systems must conform to the European normation: NEN-EN 12192-2
This normation indicates the terms of production and only when production is in accordance whith tese terms the CE sign may be put on the label.
The most important terms are:
- Both parts of the system are seen as two different parts and must have their own unique number on the label. The tracebillity code.
- The strength is indicated with LC. Lashing capacity.
- The LC is indicated in daN.
- The LC is the result of safety margins of the ratchet and the strap.
- The safety margins are: factor 3 for the strap and factor 2 for the ratchet.
The label must show:
- Lashing capacity.
- Length in meters.
- Standard hand force.
- Standard tensioning force.
- Kind of lashing.
- Caution statement.
- Kind of webbing.
- Producer or supplier.
- Tracebillity code.
- The number of the European standard. NEN-EN 12195-2
- Year of production.
Systems are regularly offered without label, or with a label without the NEN normation. These systems are often sold as being 5 tons altough, without testing them you will never be sure. Many 4 tons systems are sold under price competition as 5 ton system.
In this case the security of the load will suffer!
One-way systems
One-way load securing systems are becoming more and more popular to secure loads on a variety of load carriers. Advantages are time and cost reduction as well as increased flexibility and safety compared to steel band and wire for both users and recipients.
Material: High tensile Polyester yarns in composite material or woven
Dimensions: 25 mm. – 50 mm.
Linear breaking strength: Dependant on supplier range (see Cordlash data sheets – 1.000 daN – 7.500 daN)
Joint: Steel buckle.
Tensioning: Hand or pneumatic tensioners
System strengths: Dependant on type of buckle used (see Cordlash data sheets (1.400 daN – 10.000daN)
Elongation: Elastic elongation ca. 7%
Elongation at break ca. 13%
Handling: Fast, safe and uncomplicated handling due to light and flexible material
Applications: From light to very heavy loads, in containers, on flats or on board ships, rail and road transport
Advantages: Fast, safe, light, defined system strengths (see Germanischer Lloyd Certificates), do not rust, shock absorbing, suitable for crimping loads cost effective
Disadvantages: Corner protection necessary around sharp edges
One-way systems are also available in Polypropylene material. However, the high elongation of up to 30% and a high "creep" factor makes it, as yet, not suitable for securing loads for transport.
Polyester one-way systems are never tensioned to their maximum but up to 50%. This allows the remaining elongation to be used to absorb any shocks during transport.
Linear and system strengths are supplied by the manufacturer. All one-way Polyester load securing systems manufactured by Easygu are tested and certificated by the Germanischer Lloyd and are printed with their type number and the linear breaking strength to comply with coming legislation.
This makes ensures that you will always be able to secure loads with the highest degree of security possible and conform accepted norms.
