Whether you use commercial or homemade lifting devices, stringent rules apply.
By Evan Gurley, technical services engineer with NPCA.
Lifting apparatuses are said to be some of the more neglected pieces of equipment in the construction industry, many times getting attention only after they fail, are damaged, or are no longer functioning.
Two categories of lifting apparatuses are used in the precast concrete industry: commercial and homemade. Commercial lifting apparatuses include cranes, chains, hoists and forklifts that can be purchased from a manufacturer. Homemade lifting apparatuses can include anything created in-house, ranging from a standard spreader bar to something much more elaborate. Whether commercial or homemade, lifting apparatuses must adhere to industry standards and safety regulations to ensure a safe working environment.
Notes on homemade lifting apparatuses
Each precast concrete plant has its own unique lifting requirements, and shop wizards often fabricate apparatuses in-house to solve plant-specific issues, usually to avoid damage from transporting product. While homemade lifting apparatuses can be extremely beneficial and save the precaster time and money, those that are inadequately designed and maintained can cause more trouble than benefit.
Although homemade devices may offer significant cost advantages, they must adhere to industry requirements. These codes and regulations are set in place to ensure lifting apparatuses used in the plant are able to withstand the working loads imposed on them and that they are inspected and maintained regularly.
Commercial and homemade lifting apparatuses used in the precast concrete industry are required to adhere to industry-recognized and enforced standards, including OSHA, ANSI and NPCA.
OSHA Requirements. OSHA Standards for the Construction Industry are covered in the OSHA “Code of Federal Regulations” Title 29 Part 1926. OSHA regulation 29 CFR 1926.704, “Requirements for Precast Concrete,” states the requirements outlined for precast concrete manufacturing and, more importantly in this case, requirements for lifting apparatuses. OSHA 1926.704 states the following:
• Lifting hardware shall be capable of supporting at least five (5) times the maximum intended load applied or transmitted to the lifting hardware.
• Lifting hardware (lifting apparatuses) shall be designed to withstand the maximum intended load by five (5) times.
ANSI Requirements. The ANSI standard establishes safety requirements pertaining to concrete construction and masonry work, including design, erection, operation and maintenance of aggregate processing plants, concrete mixing plants and conveyances. It also contains safety requirements pertinent to the specialty concrete operations of prestressing by pretensioning or post-tensioning, lift-slab construction, tilt-up construction and slipforms.
Along with OSHA, ANSI is a recognized standard that defines the regulation of practices within the construction industry. Just like OSHA 1926.704(d), ANSI A10.9 outlines the requirements and recommendations for lifting apparatuses. An important highlight of ANSI A10.9 includes Section 9.3.3, which states, “Lifting hardware shall be designed to provide sufficient strength to withstand the imposed loads with a factor of safety of at least five.” Section 9.3.3 in ANSI 10.9 and OSHA 1926.704(d) requirements are equivalent and many times used interchangeably.
NPCA QC Manual. In addition to the industry standards, NPCA sets forth requirements for precast plants that are a part of the NPCA Plant Certification Program to help ensure that added safety and quality control measures are in place. The NPCA Quality Control Manual for Precast and Prestressed Plants includes the following:
• Section 2.3.1 – Lifting Devices and Lifting Apparatuses. Lifting devices used in precast concrete products shall be verified for capacity and shall have an adequate factor of safety for lifting and handling products, taking into account the various forces acting on the device, including release suction and impact, and the various positions of the product during handling. The capacity of commercial lifting devices shall be marked on the devices or posted in production areas. Lifting apparatuses such as slings, lift bars, chains and hooks shall be verified for capacity and shall have an adequate factor of safety for lifting and handling products.
• Section 2.3.1 – Comment. All lifting devices and apparatuses should meet OSHA requirements documented in “Code of Federal Regulations” Title 29 Part 1926. Other applicable codes and standards are ANSI A10.9 and ASTM C857, C890 and C913.
The NPCA requirements add that all non-commercial lifting devices and apparatuses shall be proof-tested by a certified testing lab for the rated working load limit (WLL). A factor of safety meeting the requirements of the OSHA regulation 29 CFR 1926.704 shall be met.
The type of lifting apparatus used depends on the size and type of load being handled and the type of movement to be performed with the load. When designing a homemade lifting apparatus, the individual creating the apparatus – whether or not an engineer – must be able to back up the design of the device with design calculations. If the designer is not an engineer who can perform the necessary calculations, the homemade lifting apparatus will need to be proof-tested by a certified lab to ensure conformance to industry regulations and standards.
When designing a lifting apparatus, the designer must consider the WLL, the Factor of Safety and, if applicable, the angle of cables.
WLL. The maximum working load limit (WLL) of the apparatus defines the maximum allowable weight of a product that can be lifted and transported. This is the designation typically seen posted on the apparatus itself. Other terms commonly used are Rated Load; Rated Capacity; and Safe Working Load.
To determine the total weight of a precast concrete element to be handled by the apparatus, the following steps are required.
1. Measure the height, length and width of the area that will be cast with concrete. If the form is not finished, find these measurements in your blueprints.
2. Multiply the height, length and width to find the volume of the concrete. The unit of measurement for this volume is cubic feet.
3. Multiply the volume by 143.38 lbs/cu ft. The product of the volume times the unit weight of concrete will determine the total weight of the cast piece.
After confirming that the total weight (design load) of the product to be lifted and transported is under the allowable WLL, proceed with safe lifting procedures.
Factor of Safety. The factor of safety (FS) is a term used to describe the structural capacity of a system beyond the expected loads or actual loads acting upon it. You can use the following formula to calculate the FS and/or use it to determine a missing variable in your scenario.
Factor of Safety = Material Strength/Working Load Limit*
* Design load being the maximum load the device should experience in service
FS = Ultimate/WLL
For example, if you know the FS and the material strength (ultimate) of your lifting apparatus, you can determine the allowable working design load (WLL) of the lifting device.
FS = 5
Material Strength (Ultimate) = 100,000 lbs
Working Load Limit (WLL) = ?
Calculation using FS formula Solution = 100,000 lbs/5
Solution = 20,000 lbs
*20,000 lbs (10 tons) would be the maximum load allowed on this lifting apparatus
Lifting apparatuses are purposefully built much stronger than needed for normal usage to allow for emergency situations, unexpected loads, misuse or degradation. The FS is a constant value imposed by law, standard, specification, contract or custom to which a structure must conform or exceed. As outlined by industry regulations such as OSHA and ANSI, a FS of at least 5 is required for all lifting apparatuses. This FS is typically higher for lifting apparatuses, as they are used repetitively to move precast concrete units, and as such will experience wear and tear. The higher FS allows for some wear and tear in the components until an inspection reveals that the system is in need of repair.
Angle of cables. A general rule of thumb for cables/chains that are used in the design of a lifting system is that the tension on a chain/cable increases when the angle between the product and the chain is less than 90 degrees. As the angles get smaller, the tension increases.
A homemade lifting apparatus that is designed to adhere to a FS of 5 does not imply the device is safe. Additional engineering, quality control, manufacturing, installation and end-use factors will also influence the safety of a lifting device.
Other safety considerations – erection of general elements
In addition to design considerations, personnel operating homemade lifting apparatuses must be properly trained. This will include the following:
• Lifting equipment should be attached to the precast elements by a competent person and the immediate area cleared in preparation for lifting.
• Taglines may be required in some circumstances.
• Under no circumstances should personnel pass or stand beneath a suspended element.
• Consideration must be given to the effect of wind upon the safe handling and erection of elements, if applicable.
• Lifting apparatuses shall be identified with the WLL.
• According to OSHA 1926.251(a), rigging equipment for material handling shall be inspected prior to use on each shift and as necessary during its use to ensure that it is safe. Defective rigging equipment shall be removed from service.
• If the equipment does not have the same shape and dimensions as it had when new, it may be considered defective.
• If a beam is bent, holes are elongated or chain links are worn thin, the lifting apparatus should be removed from service and repaired.
Preventive maintenance, frequent inspection and adherence to industry design standards and guidelines can prevent costly downtime and potentially dangerous situations.