Good Engineering Practice in Suspended Elevating Platforms
In designing and constructing suspended elevating platforms and supporting structures, good engineering practice and the following Regulations and Standards and Codes must adhered to:
The Occupational Health and Safety Act and Regulations for construction projects 213/91as amended.
CSA Z271-98 “Safety Code for Suspended Elevating Platforms”
CSA W59.2-M1991 “Welded Aluminum Construction”
CSA W59.1 “Welded Steel Construction”
CSA S16-01 “Limit States Design of Steel Structures”
CAN3- CSA S157-M83 “Strength Design in Aluminum”
Ontario Building Code
The designer must consider the capacity of the powered hoists as well as the rated load and dead load of the platform and components, supporting structure components and rigging components and hardware.
Accidents have occurred when the platform is “snagged” in a projection on the building façade and the hoists operated until their overload protection switch was triggered.
There is a range of hoist capacities. The common hoists used on suspended stages has a rated load of 1000 Lbs. (455 Kgs.) and hoists must be supplied with overload protection switches designed to Kick in” when the tension in the wire rope exceeds
125% of the rated load of the platform.
Suspended elevating platforms and rigging equipment are mobile transportable structures, assembled and rigged on site and thus additional factors of safety are inherent in the design of these members. The CSA Z271 includes additional load factors to supplement those in the Ontario Building Code to account for lack of
redundancy and the dynamic nature of the applied load.
Different lengths of stages are sometimes required to access a building facade that makes modular staging a practical solution. The knocked down modular stages utilize different length sections that connect together to provide the required
length. Corner and circular sections are also available.
When designing the support structure, ergonomics must be considered. Designing and supplying a heavy davit arm (over 150 lbs.) that is difficult to handle by two workers is to be avoided. Davit arms and other heavy transportable members may be designed in sections that are connected on situ.
Rigging equipment that are assembled or moved within 2 meters of a fall hazard must be tied back during erection and transport.
Suspended elevating platforms used to access a façade that is more than 45 meters ((150’) must be stabilized to the building to avoid excessive sway. This is accomplished in a variety of ways by designing vertical tracks or individual “buttons” in the building façade.
When in service, suspended elevating platforms, their rigging and supporting structure must be inspected by a qualified person daily and tested as frequently as is necessary to provide proper maintenance. Special attention must be given to wire ropes, as they are the cause of a variety of accidents and mishaps on sites.
It is important for an employer to ensure that all workers operating or using a suspended elevating platform be fully trained in its use. Training is to include controls, winches, proper rigging and rigging component safety, wire rope inspection, tieback and fall arrest equipment and use, among other.
It is required of the employer to prepare a rescue plan that is put in effect when an accident occurs. All workers on the project must be trained to implement that plan in the event of a mishap.
— Ralph Balbaa M.Eng., P.Eng., is a health and safety expert with more than 40 years of engineering experience and a former Ministry of Labour consultant. He is the President of HITE Engineering, a Mississauga-based consulting firm specializing in industrial and construction safety.