The who, what, why and how of load restraint in the crane industry
Co-authored by Dashelle Bailey, Editor; Albert Smith, Chief Lifting Matters Sponsor and Nick Morris.
As vertical logistics enthusiasts, the crane industry is mostly focused on the exciting times when we get to lift and shift things up and down - but another significant component of our operations is road transport. We might be transporting major crane components, counterweights, shackles, chains, bridge beams, piping or even just some wood blocks on the back of a ute. You name it, we move it! Just as important as ensuring a vertical lift is carried out safely, is ensuring we transport all items to, from and around the site safely.
Why is it important to carry out adequate load restraint?
Because it’s unsafe if you don’t Did you know the weight of a load is not enough to hold it in place? In fact, heavier loads are subject to higher forces and have just as much chance (if not greater) of moving as a light load. The load can shift forwards, backwards, upwards or sidewards in response to even normal driving conditions.
Serious incidents, sometimes fatal ones, have occurred due to unrestrained loads shifting during transport. These are the three most common types of incidents:
The force from braking causes the load to shift forward at high speed, penetrating the cabin and seriously injuring or killing the driver or passenger.
The load shifts causing instability in the vehicle, often as the driver takes a corner, resulting in a vehicle overturn or serious road accident.
An item falls off the back of the vehicle and collides with other road users resulting in significant injury or death, or another road user swerves to avoid a fallen item causing a serious road accident.
In some instances injury or death is thankfully avoided, but serious property damage can occur. Don’t be fooled. There is a common yet false view that short, slow speed journeys to move counterweights around on site do not require proper load restraint. This is completely WRONG! The load needs to be restrained appropriately, no matter how short or slow the proposed journey is.
Serious accidents have occurred on many sites due to inadequate or non-existent load restraint of crane components on trailers for short distance on-site moves. This problem is always made worse by the steeper and changing grades on site roads which often add to the horizontal braking force applied to the load restraint system.
Because it’s the law
The law sets out Performance Standards for load restraints. More on that later when we look at the ‘how’ of load restraint. However, that does bring us to our next question.
Who is responsible for ensuring load restraint?
Every individual involved in packing, loading, moving or unloading a vehicle has a legal responsibility to follow load restraint laws. This means that in the event an incident does occur, any one of these individuals in the chain of responsibility may be found guilty of committing an offence. That includes the employer, prime contractor, operator, consignor of the loaded goods, the packer or loader, the packing or loading supervisor, or the driver. We are all responsible for ensuring properly restrained. The National Transport Commission’s Load Restraint Guide 2018 clearly outlines your legal obligations:
You are legally responsible for restraining your load so that:
It does not come off your vehicle under normal driving conditions, including heavy braking and minor collisions. If it comes off, this is evidence you have breached the law.
It does not negatively affect the stability of the vehicle, which can cause the vehicle to roll over or swerve uncontrollably, and cause an accident.
It does not stick out of the vehicle in a way that could injure people, damage property or obstruct others’ paths.
You must pick up any fallen load if it is safe to do so, or arrange for someone to retrieve it.
Source: Load Restraint Guide 2018
How do you restrain a load? A load restraint design must take into account the forces a load is subject to during travel. This includes forces caused by changes in speed, direction or slope. Key factors in these forces are braking, acceleration, cornering, travelling on uneven surfaces and effects of wind and air flow.
The law sets out Performance Standards for heavy vehicles that any load restraint design must meet. These standards ensure a load will not fall off or cause instability to the vehicle in expected driving conditions, including braking and minor collision. The standard states the load must be restrained to the following minimum standard:
Forward: 80% of the Load Weight
Sideways: 50% of the Load Weight
Reverse: 50% of the Load Weight
Vertical: 20% of the Load Weight
Provided the load restraint meets the Performance Standards, you can choose how to restrain the load. When transporting heavy items, like crane components, it is best to engineer the load restraint.
There are two key forms of lashing design; direct and indirect.
Relies upon blocking, containing or direct lashings between load and vehicle. An example of direct lashing is a blocked frame whereby a counterweight is positioned within the frame, preventing movement. Another example is a wheeled crane carrier, restrained by direct lashings between the crane and trailer.
Indirect (commonly referred to as tie-down) relies upon friction, whereby the load is tied down using lashings. An example of tie-down is where a clamping force is created; such as lashings direct over a counterweight biscuit positioned on load matting.
Lashing System Components
Several components are utilised in lashing design.
Load / Friction Matting
Load or friction matting is a product specifically developed to increase the friction force between a load and the support surface. The use of this matting, several types of which are issued with design data, can greatly assist a load restraint design in tie-down and combination design. It is important to note that without a friction mat, the coefficient of friction can be unknown, and therefore, conservative assumptions are often utilised. Whereas, the friction coefficient on a load mat could be as high as 0.6.
Load Chain & Binders
Within Australia, the industry will often refer to Grade 70 Transport Chain. This chain is inherently different from G80 and G100 Lifting Chain and is also designed only on a 2:1 Safety Factor (whereas Lifting Chain is 4:1). Note that G80, G100 and beyond can be used in a Lashing Design to increase capacity, and some manufacturers are providing specialist products of this nature. However, Grade 70 Transport Chain / Components should never be used for lifting. The chain, however, is only one component of the arrangement, and not usually the limiting factor. Special attention must also be paid to the load binder itself as this also affects the chain capacity.
Lashing pre-tension refers to the force within a lashing provided by a mechanical means, such as a load binder. The Load Restraint Guide 2018 states as a guideline that approximate pretension in a Load Binder 7mm and above is 1,000kg. However, several organisations will often complete their own testing to confirm they can achieve a pre-tension in excess of this figure. The available pre-tension becomes an important factor in a tie-down lashing design.
The tie-down force is the sum of the tensions on each side of a load, taking into account the angular effect. That is, multiple load binders can be used on one lashing, provided the overall lashing capacity is not exceeded. The angular effect adopts the same principles of rigging design, whereby if a tie-down lashing is not vertical, then its effectiveness will reduce below 100%.
We have looked at the why, who and how of load restraint mainly for heavy items that require engineered load restraint solutions, which in our industry is most often the transportation of crane components, counterweights and precast concrete or piping. However, the law and the principles outlined here are just as applicable to transporting smaller items such as furniture tools or on a ute tray. We look more into the National Transport Commission’s Load Restraint Guide for Light Vehicles specifically in another article in this issue of Lifting Matters, so be sure to check that out also. Never take for granted load restraint standards, even if you are transporting counterweights mere metres on a site. All of us are responsible at all times for ensuring loads are safely restrained.