In North America, ensuring worker safety during rigging operations in the construction sector is of paramount importance. This involves adherence to a set of regulations and best practices that govern the safe use of rigging equipment. The factor of safety, also known as design factor, must be incorporated into the design capacity of all rigging components, while the sling-angle reduction factor is another impacting element for rigging capacity.
This article provides a brief overview of these two factors as outlined in Canadian and United States regulations and explains how MTC Solutions applies these standards to recommend safe capacities for all its rigging products.
Approximately 6-minute read.
The factor of safety, or design factor in Canada, is a fundamental principle that underpins the safe operation of rigging equipment. It represents the ratio of the breaking strength of the rigging equipment over the working load limit (WLL) to provide a margin of safety for situations of unintended overloading. As long as the WLL is respected, the workers can trust the equipment used in the hitch.
Similarly, the sling-angle reduction factor is another essential consideration in rigging safety. This factor adjusts the WLL based on the sling angle, that is, the acute angle between the sling and the construction element. As this angle deviates from vertical (90°), the tension on the sling increases due to a horizontal load component, thereby reducing the overall capacity of the system.
Canadian Regulations
In Canada, construction rigging safety is primarily regulated at the provincial level, as there is no federal governing body overseeing the standards. Each province establishes its own regulations through legislation and safety codes that construction must comply with. For example, Ontario, Quebec, British Columbia, and Alberta—the four most populous provinces—mandate compliance with specific safety codes:
Additionally, the Infrastructure Health & Safety Association (IHSA), an organization providing safety training and materials in Ontario, publishes a Hoisting and Rigging Safety Manual, which is recognized as compliance material in Quebec’s Safety Code.
These guidelines uniformly set the factor of safety at 5:1 for most rigging components, including anchors and their attachment system (e.g., the sling and the D-ring). The sling-angle reduction factor remains largely consistent across jurisdictions due to its mathematically derivative nature.
For example, British Columbia’s regulations specify that the WLL of a rigging system is reduced to 90%, 70%, and 50% of its maximum value at vertical when the sling angle falls within the ranges of [60°, 90°), [45°, 60°), and [30°, 45°), respectively. Sling angles less than 30° are prohibited unless part of an engineered lift. This advisory is echoed in IHSA guidelines, which deem sling angles less than 30° as highly dangerous and recommend maintaining sling angles greater than 45°.
Figure 1. Relationship between Sling Angle and WLL
United States Regulations
In the United States, the Occupational Safety and Health Administration (OSHA) is the federal agency responsible for establishing rigging regulations, which are aligned with the ASME B30 standard. Similar to Canadian regulations, OSHA sets the factor of safety for all rigging components to 5:1. While there are no clear stipulations for the sling-angle reduction factor in OSHA’s guidelines, its universal applicability remains relevant.
MTC Solutions Rigging Systems
In our Rigging Design Guide, we determine the safe capacities for our various rigging systems based on thorough mechanical testing and fastener strengths detailed in ICC-ESR 3178 and 3179. We follow the specific methodology described in Section 12.3 of NDS. These design values incorporate a factor of safety of 5:1, along with other adjustment factors, and are recommended for rigging scenarios where the sling angle is 60° or greater.
It is crucial to strictly follow safety rules specific to your location when rigging construction materials, including those made with mass timber. Licensed rigging professionals and site supervisors must ensure that the rigging equipment used has a factor of safety of at least 5:1. It is important to make sure that this factor of safety is included in the design capacity of the anchoring devices. If not, the design capacities must be adjusted accordingly. Other factors, like the sling-angle reduction factor, may also need consideration to ensure safety. Adhering to proper rigging practices is essential for a safe working environment and to minimize the risk of on-site injuries.
If you have any questions about our rigging systems or need help with rigging planning, contact our Technical Support Team. 😉
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