The Importance of Proper Lifting Practices for Precast Concrete

//The Importance of Proper Lifting Practices for Precast Concrete

There are many material benefits associated with concrete, such as its strength, durability, thermal efficiency and resistance to weather. Another key characteristic of the material is its weight.

Concrete weighs 2400kg per cubic metre, over three times heavier than the equivalent volume of timber (700kg). A 450x450x450 standard precast concrete pit (SVC’s smallest stock pit) weighs 280kg, which is more than enough to cause significant damage if dropped. When such heavy items are involved, it is imperative for customers to abide by the correct safety procedures when handling, lifting or transporting the product.

What are the risks involved?

Ample safety precautions are required at all times when working with heavy concrete products. Failure to use the appropriate lifting tools or techniques may lead to product failure, breakages, damage to products or machinery or, in the worst case, accidental injury to staff.

During transport, concrete products are typically loaded onto delivery trucks where the height of the truck trays can range from 1m to 1.5m tall. Any products dropped from this height are unlikely to survive the fall.

SVC concrete products loaded on a delivery truck.

What are some appropriate lifting techniques?

There are several different methods to lift heavy concrete products and each method involves the use of a particular type of lifting apparatus. Sometimes, more than one technique may be suitable for a specific product, and the final method is selected based on the best fit for the project. The types of lifting methods are outlined below:

Manual Lifting: Some smaller products such as pavers and civil accessories are light enough to lift by hand. There are no set rules as to the maximum weight that an individual can lift by themselves, but SVC recommends that anything above 15kg should be lifted by two people. When lifting by hand, it is important for the person lifting to use the proper techniques such as keeping their back straight, bending their knees and keeping both feet firmly planted on the ground.

Proper way to lift by hand

Image: Employsure

Lifting with Forklifts: In a factory environment, products are easily loaded onto pallets for transportation via forklift. Standard pallets are typically load-rated to accept up to 2 tonnes of weight, and once products have been secured, the pallets can be loaded straight onto the delivery truck via forklift. When placing products on pallets, they should always be centred in the middle of the pallet and properly secured onto the pallet.

Products strapped securely onto pallets

Products strapped securely onto pallets

Lifting Hooks: Lifting hooks must be used when transporting SVC precast concrete pits that have been manufactured with lifting holes (holes are always marked ‘Lift Here Only’). To prevent any damage from incompatible lifting tools, only the SVC-approved 2.0 tonne lifting hooks should be used (these hooks are available for loan or purchase from SVC). Lifting hooks are suitable for carrying pits weighing up to 2.0 tonne, where two hooks are used per pit. The hooks are connected to lifting chains and inserted into the lifting holes within the pit wall; the other ends of the chains are connected to a central lifting point. It is important to note that the internal angle between the two chains must not exceed 60°.

Lifting hooks must always be inserted from the inside of the pit and should be vertically aligned with the pit wall, keeping the corners of the pit hooks free from any loading pressure. Incorrect placement of the pit hooks (i.e. insertion from the outside of the pit, or pushing pit hooks in too far that the corner of the hook gets pushed inside the hole) will result in loads being applied onto the wrong areas, which can cause subsequent damage to the pit.

SVC-approved pit hooks must be used to lift SVC concrete pits that have been manufactured with lifting holes.

SVC-approved pit hooks must be used to lift SVC concrete pits with lifting holes. Hooks must always be inserted from the inside of the pit.

SwiftLift™ Clutches and Anchors: The most common lifting method across SVC’s suite of products involves the use of SwiftLift™ lifting clutches and anchors. SwiftLift™ anchors are cast into concrete products during the production process and allow flexible positioning of lifting points within a product. They are available in different sizes to suit load ratings ranging from 1.3t up to 10.0t, making them a viable lifting tool for almost every product.

During lifting and transport, SwiftLift™ clutches are connected to chains which are either strung up from a central point, with an internal angle between the chains of less than 60°, or distributed across a spreader bar. When attaching the clutches to the corresponding anchors, it is important to position the tabs so that they are pointing to the same direction in which the product is being lifted.

For more information pertaining to the use of SwiftLift™ devices, please refer to the Reid website.

SwiftLift lifting clutch and anchor

SwiftLift™ lifting clutch and anchor components

Clamp Lifting: Certain products such as concrete sleepers and kerb units can be lifted using heavy duty clamping devices. Clamps are padded with rubber to ensure no markings are left on the product. During lifting, the clamp is connected to a crane hook via a chain, and once lifting commences, the clamp’s grip on the product is increased from the pull of gravity.

Vacuum Lifting: Vacuum lifters utilise strong suction forces via vacuum pads to lift heavy products with a mostly flat surface, such as large-format pavers and concrete slabs. Suitable products generally weigh less than 500kg. Vacuum lifters are available in many types and sizes, ranging from smaller handheld formats to large lifting beds that are connected to a crane hook.

The benefit of using vacuum lifters is that they allow ‘invisible’ lifting, and do not require any physical lifting points within the product. When using a vacuum lifter, it is important to place the lifter exactly in the centre of the product to ensure that weight is evenly distributed when the product is lifted. The suction pads should remain in full contact with the surface of the product during lifting, as any loss of adhesion will reduce the strength of the suction which creates more risk of the product being dropped.

Sling Lifting: Lifting slings are made from a durable polyester webbing material and are available with different load ratings ranging from 2.0t to 10t. Depending on product shape, certain products can be lifted with slings without the need to include a specially designated lifting point. Slings can be additionally padded with rubber or carpeted material to reduce the chances of leaving markings or causing damage to products.

During lifting, slings are looped around products in either a choke sling or cradle sling method. In a choke sling formation, the sling is looped back through itself and the product is lifted from a central point. In a cradle sling formation, two or more slings are passed underneath the product and lifted together using even sling lengths to ensure that the product is balanced safely. If using the cradle sling method, a spreader bar should be used.

Lifting via the choke sling or cradle sling method.

Left: Choke sling / Right: Cradle sling with spreader bar

Custom products can be designed to include in-built sling recesses, which greatly reduces the chances of a sling slipping or the product toppling over. It is worth noting that certain sites may prohibit the use of slings on-site. It is the contractor’s responsibility to ensure that their planned lifting method and lifting tools are suitable for each site and each project.

Chain-Only Lifting: Crane operators have been using chains to lift and transport products for many decades. Like slings, chains are used in a choke or cradle hold to lift products. Many chain types and sizes with different load ratings are available.

SVC recommends the use of lifting slings rather than chains, especially when transporting products that are designed for an architectural or aesthetic purpose. This is because the chain-only lifting method has a higher likelihood of causing damage to product, particularly if utilised by less experienced operators.

Spreader Bar: In certain lifting applications, a spreader bar will be required in addition to the lifting equipment listed above. This is typically the case when the internal angle between the lifting chains exceeds 60°. When using a spreader bar, chains must be vertically aligned with the lifting points and set at a minimum length of 600mm. The overhang of the spreader bar over the chains must be equal on both sides to avoid any weight imbalances.

Concealment of lifting points after installation

Products that are installed above ground in a landscape or architectural application may have in-built lifting points, such as SwiftLift™ anchors, in a visibly noticeable area. As these are no longer required post-install, some customers use a variety of methods to conceal the lifting points.

Concrete infill: An option is to ‘patch up’ the lifting point by infilling it with concrete. This is generally not advised as the best option, as it is always quite apparent that there has been some patchwork done. Often, the colour of the infilled concrete does not exactly match the rest of the product.

Stainless steel caps: There are certain products that can be inserted over lifting anchors, such as small stainless steel caps. These provide a subtle additional feature that is still noticeable when looking at the product, but manages to hide the actual lifting anchor.

Separate design elements: Most commonly, lifting points can be concealed by other material components of the product design which are installed later, after the concrete product has been placed on-site. An example of this is a concrete bench with lifting points on the top, which become hidden from view by the installation of a timber seating frame above the concrete.\

Patching of SwiftLift lifting points using stainless steel inserts.

Patching of SwiftLift lifting points using stainless steel inserts.

When should I start thinking about lifting?

Lifting considerations should not be treated as an afterthought. Product handling and transport should be considered early in the process, especially for custom or non-conventional products. During the process of creating workshop drawings for the approval of custom products, SVC’s drafting team will include lifting points in areas of the product we deem most logical and practical for delivery. If customers wish to use a certain lifting technique or would like to make specific requests regarding lifting points, it is during the design development stage that this must be communicated.

As a rule of thumb, it is the customer’s responsibility to be aware of any lifting restrictions, issues regarding site access or any other considerations that may affect the delivery of products.

Key considerations when selecting a lifting technique

Generally, the weight of a product indicates what methodology will be used to transport it. However, weight is not the only influencing factor. Various other factors such as product shape, site conditions, access points and the type of lifting gear available all contribute to the decision of which lifting methods and devices will be most appropriate.

For example, objects that are oddly shaped or unevenly weighted may not be transportable via forklift. Certain products may need to be loaded onto the delivery truck a certain way or into a certain position. Customers should also consider whether there is suitable access and stable ground conditions on-site to allow for the heavy machinery and equipment required for delivery.

Maintain best practice lifting procedures

To achieve best results and maintain safety precautions when lifting heavy products, all lifting equipment and machinery should be tested and tagged on a regular basis, at least once a year.

Staff who are operating cranes or other lifting equipment must always remain aware of safe operating procedures. For example, no individual nor object should ever be directly underneath a product that is being lifted. If a staff member acting as a crane chaser/dogman needs to guide a product, this can be done by attaching a rope to the product, allowing the crane chaser/dogman to keep a safe distance away. The crane chaser/dogman should always be accompanied by a spotter who is able to see everything that is going on.

The key to ensuring a safe and smooth process during product handling and transport is for all stakeholders to be aware of their responsibilities during a project. Designers should consider lifting points, site access and restrictions and how the final product will look on site before deciding on their final design. Installers should also be aware of site conditions and are responsible for making sure that their machinery and equipment are safe for operation. All staff involved in the operation of cranes and other heavy machinery should be well-versed with compliance regulations and the safe operating procedures.

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