As temporary structures and proprietary designs for access scaffolding systems become more and more advanced, the practice of mixing components of different original equipment manufacturers (OEM) has become more common but is raising safety concerns in the scaffold industry. When we use the term “mixing OEM components,” we refer to the connecting of different OEM modular components into one structural system whereby the components must structurally interact with each other. There are many aspects to be considered when assessing the mixing or substituting of OEM components in a scaffold system. However, by far the most important issue is safety — the risk of structural component failures or even complete collapse of the structure. This article provides an independent perspective of potential risks associated with mixing different OEM components in scaffolding structures.
The connections between structural components are probably the most critical element of any structure and are often the most misunderstood. Design engineers require accurate quantitative data regarding connection performance to properly analyze and design the overall structure. Since connection characteristics will vary from one OEM to another, mixing OEM components in the structure could result in inadvertent overstress or failure of individual components.
The overall structural response of a scaffold system may change significantly when substitutions are made with components having different material properties, dimensions and specifications. Even if different OEM components are dimensionally compatible and may fit together, variations in physical and material properties will often result in unpredictable load paths within the structure, resulting in some components becoming overstressed. Unknown or differential material properties of any one component in a structural system can create an unpredicted structural response to the applied loads, resulting in increased deflections, overstress or failure even under normal loading conditions.
During the erection and dismantling of a scaffold, workers often use the components of the scaffold as an attachment point for their personal fall arrest systems. For this reason, it is absolutely critical that the anchor or attachment point on the scaffold have adequate structural integrity to safely resist the potential fall arrest forces while not compromising the structural stability of the scaffold. Fall arrest anchor points should always be tested and verified by the OEM and should be incorporated into the fall protection procedures developed by the user for the particular type of scaffold system.
Recommendations:
- Based on the assessment of risks associated with mixing OEM scaffold components, it is recommended that only components of the same OEM be used in the same structure. Components of different OEMs should not be connected together to form one structural system.
- Users of proprietary scaffold systems should ensure that technical data and user manuals are provided by the OEM.
- Where OEMs advertise their products or components to be compatible with other products or brands, the components should be tested in all the possible configurations to ensure the structural characteristics and behavior of the overall structure are acceptable to each of the OEMs involved.
- If designers accept components advertised as compatible from different OEM manufacturers, appropriate test information and certifications should be provided by each of the manufacturers. An independent structural analysis should be carried out to ensure the compatibility of the components that may have different structural characteristics.
James Wilkinson, P.Eng., is president of Wilkinson Technical Services Inc. and specializes in risk assessments and forensic engineering services for the construction industry. He is a director of the Scaffold Industry Association of Canada.
For more information, visit www.industrial.peri-usa.com or call (773) 517-2237, or contact Wilkinson at (905) 434-4501 or jim@wilkinsontechnical.com
