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4. Multi-Point Suspended Scaffolds (MPSS)Overview: Guidelines for Multi-Point Suspended Scaffolds (MPSS)

  • ISBN: 0-7794-9927-1
  • Issued: April 2006
  • Content last reviewed: June 2009

These guidelines are being updated to reflect amendments to O. Reg. 213/91 (Construction Projects) that came into force on January 1, 2017.

4.1 Use of MPSS

Multi-point suspended scaffolds are suspended from a permanent building or structure and are used as a work platform for a variety of tasks on construction projects and industrial workplaces. Multi-point suspended scaffolds vary in size and capacity depending on their application.They range from large area MPSS commonly used for bridge repair and restoration work to small scaffolds used for access and inspection applications. MPSS are also used for masonry work particularly in high-rise building construction.

Multi-point suspended scaffold may be designed and constructed to move or traverse horizontally, or move vertically along the structure from which they are suspended, or to remain stationary.

4.2 Description of Major Components of an MPSS

A Multi-Point Suspended Scaffold (MPSS)generally consists of the following major components: (refer to sketch 1 in Appendix A):

  • Platform assembly: the platform surface and structure, which may be one level or multiple levels.
  • Suspension system: the suspension system includes wire ropes, chains and cables, and the anchorage system. It also includes a hoisting mechanism: an assembly that will allow the platform to be moved by mechanical means.

4.2.1 Platform Assembly

The platform consists of three main components:

  1. The main supporting beams or trusses
  2. The joists
  3. The deck surface

The platform may be constructed of wood, steel or aluminium.

4.2.2 Suspension System

The suspension system contains the following:

  1. Suspension assembly includes wire ropes, chains or cables and rigging hardware to connect the platform to the overhead structure, which is normally a permanent structure;
  2. Hoisting mechanism, where the scaffold is to be raised or lowered; and
  3. Anchorage system, which includes outrigger beams, beam clamps, cross tubes, trolley mechanism and other related hardware. Suspension assembly

The suspension assemblies are the primary support system for Multi-Point Suspended Scaffolds. The suspension system assembly connects the platform structure to the overhead structure. The suspension assembly consists of wire ropes, chains or cables.

Wire Ropes and Chains

The most common type of suspension system assembly is steel wire rope or chains to support or suspend the platform from a permanent or temporary structure. Threaded steel rods and steel tubes are also commonly used. This type of assembly normally includes the wire rope or chain, the appropriate rigging hardware, the stirrups or clamps used to attach the wire rope or chain to the main support beams of the platform, and the beam clamps or outrigger beams. The beam clamps and outrigger beams are part of the anchorage system and are attached directly to the permanent structure. Hoisting Mechanism

A hoisting mechanism is connected to the suspension system when the MPSS is designed to move vertically. The two main categories of hoists are manually operated and power operated hoists.

Manually Operated Hoists

The most common hoists are traction type, which are used with a wire ropes suspension system.

Power Operated Hoists

Power Hoists are operated by electric, hydraulic, or pneumatic power. Most of these units use a motor driven sheave or drum assembly. Anchorage System

The anchorage system for the MPSS includes the following:

Trolley and Rollers

Trolley and rollers are used when the platform is designed to traverse or move horizontally. When the trolley mechanisms are attached to the permanent structure, they are considered part of the anchorage system. Trolley mechanisms are sometimes used at the platform level and as such are considered part of the suspension assembly. The use of movement-limiting devices would ensure that trolley movement is controlled.

Outrigger Beams

Outrigger beams may be used as anchorage for an MPSS and are part of the suspension system. They are generally supported on the permanent structure and over hang the edge to provide an attachment for the wire rope or chains of the suspension assembly.

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