Saturday, 15 February 2014

Safe Erecting and Dismantling Procedures

Safe Erecting and Dismantling Procedures

Erection Procedure
The foundation for system scaffolds should be prepared in the same way as other types of scaffolding, ensuring a firm level base, and using mudsills, base plates, and adjustable screw jacks. The base plates should be laid out in what you estimate is the correct location (LOOK UP). We recommend starter collars since they allow scaffolds to be laid out level and square. The first level of transoms and ledgers should be placed on the starter collars and be leveled using the screw jacks. When the scaffold is square and level you should tighten the connections and nail the base plates to the mudsills. At this point set up an erection platform for installing the standards for the next lift. You now install the second level ledgers and transoms as well as the deck. You must install ledger bracing at the ends of all system scaffolds and at intervals according to the manufacturers’ recommendations. Each brace will be the correct length for the span being braced and should be connected to the attachment point on the standard. You must install face or sway bracing according to Manufacturer instructions. Again, attachment points are set on the standards, and the braces come in specific lengths for the span of the scaffold being constructed. Normally, every third bay is braced for sway.
Guardrails
Generally, guardrails are installed at all working levels. They attach directly to the connection points on the standards.
TRAINING
Workers must be properly trained or instructed before they use equipment. Only competent workers may construct scaffolds.
INSPECTION
Inspect all equipment before using. Never use any equipment that is damaged or defective in any way.
SITE EVALUATION
When possible, always survey the job site to identify any potential hazard condition. Complete jobsite hazard evaluation and amend your standard fall protection plan with site-specific requirements.
FOUNDATIONS
Never construct a scaffold on unprepared foundations. Where necessary, provide adequate continuous wood sills and ensure that they are not less than 50mm x 250mm (2” x 10”) and cover two frame legs in length. Footings, sills, or supports must be capable of supporting at least 2 times the maximum load to which they are subjected without settlement. Any part of a building or structure that is used to support the scaffold shall be capable of supporting the maximum intended load to be applied, and must be verified by a professional engineer.
BASE
Always use adjustable bases with system scaffolds and other components that the manufacturer recommends. Level the base by starting at the highest point of ground level and ensure accuracy, so you do not have to level the scaffold after the base has been completed.
STANDARDS
Standards are manufactured in pre-determined lengths and the spacing of standards is dependent upon the loading to be imposed on the scaffold. Always check loading requirements and if necessary, seek approved engineered drawings.
LEDGERS
Connect the ledgers to the standard at the desired lift height by positive connection. Ledgers are manufactured in pre-determined lengths and the bay size is normally determined by loading criteria. The vertical spacing or lift height between ledgers should not exceed 1.98m (6’-6”). Any ledger that is longer than 1.52m (5’-0”) and is supporting a load should be a double ledger or equivalent.
BRACING – Internal (a)
As bracing has a pre-determined length, select the correct size of bracing, and brace standards internally every 6m (20’-0”) in length, and ensure that bracing extends to the full height of the scaffold.
BRACING – Sway (b)
Sway or fa├žade bracing should be installed on the outside face of the scaffold to full height, and can be either in one single bay or extended across multiple bays. If single-bay bracing is selected, it must be in both end bays and at least every 15m (50’-0”) longitudinally. In the multiple-bay configuration, the desired angle is 45 degrees to the horizontal, close to the note point, and this should be continuous to full height, and in many cases will be designed by an engineer.
BRACING – Plan (c)
Plan bracing (horizontal diagonal) is recommended and often required. As a minimum, it should be installed at the base and on the same level as the scaffold ties.
SCAFFOLD TIES
Where the scaffold height exceeds three times the smallest base dimension (3:1 ratio), scaffolds must be tied at least every 4.57m (15’-0”) interval vertically and 6m (20’-0”) horizontally. Where possible, push/pull ties should be used, ensuring that the tie tube is connected to both standards (or to both ledgers near the standard) with right angle clamps. Tie tubes should be installed on the same bay as the internal bracing. If it is not possible to tie the scaffold to a structure, a professional engineer must provide special design considerations.
WORK PLATFORMS
The work platform provides the worker with a safe environment from which to work. The work platform must consist of a fully-planked/-decked surface and shall have guardrails consisting of top rails, mid rails, and toe boards installed on all open sides. Toe boards shall be installed at the edge of all work platforms and shall be a minimum 100mm (4”) high.
GUARDRAILS, MIDRAILS
Guardrails must be installed on all open sides of the scaffold where a person can fall a distance of 2.4m (8’-0”) or more, and shall be not less than 0.92m (3’) nor more than 1.07m (3’-6”) above the platform, and should be positively connected to the standards. Mid rails should be installed equidistant between the guardrail and the platform.


PLANKS – WOOD
Always use select structural wood plank, LVL (laminated veneer lumber), or equivalent approved 50mm x 250mm (2”x10”) lumber, of uniform thickness. Ensure that wood plank extends a minimum 150mm (6”) and no more than 300mm (12”) beyond the centre of supports and has cleats at one end to prevent lateral movement. Wood planks should not span a length greater than 2.13m (7’-0”) unless engineered otherwise.
PLANKS – STEEL
Most steel planks have a supporting hook and wind lock to prevent uplift. Ensure that the steel plank has a non-skid surface and that the load capacity rated by the manufacturer is not exceeded. Always ensure that the wind lock is in the closed position.
MANUFACTURED DECKING
These are normally constructed from aluminum side frames with a plywood or metal decking and are secured to the scaffold by supporting hooks with wind locks that prevent uplift. The load capacity is identified on the deck and must not be exceeded. Always ensure that the wind lock is in the closed position.
LADDERS
Ladders are used to gain access to the working platforms. Ladders, ladder cages, and rest platforms, when installed on scaffolds, must conform to all applicable codes, and must extend approximately 1m (3’-0”) above the landing area and be secured. Always maintain 3-point contact at all times when climbing.
STAIRWAYS
Manufactured modular stairways are used to gain access to working platforms and must be installed in accordance with the manufacturer’s instructions.
SIDEBRACKETS
Side brackets must be installed at right angles to the scaffold and should be installed in accordance with manufacturer’s instructions. They are an extension of the work platform and must accommodate at least 2 planks and must not be used for storage of materials. Always check maximum loading of side brackets.
CANTILEVERS
Cantilever platforms, except fabricated side brackets, must be designed by a professional engineer and shall be installed in accordance with supplier’s/manufacturer’s instructions.
LOADING
The load on a scaffold must never exceed the safe working load that it was designed for. Most scaffolds are required to support at least four times the intended load, however this varies in different jurisdictions and must be checked. When any unusual load conditions apply, or when the load exceeds 3.5 kN/m (75psf), the scaffold must be designed by a professional engineer.
ENCLOSURES
If the scaffold has tarpaulins or any enclosure system attached, this imposes additional wind loading and must be designed accordingly. Double-wrap #9 wire ties will have a safe working load range from 600lb-800lb with a safety factor of 4:1, keeping that in mind Scaffolds should have ties at every leg every level and be constructed of a tube and clamp system or #9 double wire.
POWER LINES
It is dangerous to construct a scaffold close to power lines. Always consult the power company for specific guidelines and conform to all applicable codes.
FALL ARREST
In certain jurisdictions, unless a safety net or travel restraint system is being used, workers shall wear fall arrest systems if the workers may fall a distance of more than 3m (10’-0”).
Dismantling
Dismantling system scaffolds is essentially erection in reverse. Each tier should be completely dismantled and the material lowered to the ground before beginning to dismantle the next tier. If platform sections or planks have been left at each level during erection, as suggested above, it should be relatively easy to lower platform materials from above and deck in the current working platform completely. Extra platform material can be lowered to the ground. Using this procedure, workers will be operating most of the time from a fully decked-in platform. This makes for easier removal of braces and frames. Dismantled materials should be lowered using a gin wheel and hoist arm or by mechanical means. Dropping materials not only causes damage and waste, but also endangers workers below—and is illegal. When scaffolds have been in the same location for a long time, pins and other components frequently rust, braces become bent, and materials such as mortar or paint often build up on the scaffold parts. All of these can prevent components from separating easily. Removing jammed or rusted scaffold components can be very hazardous. Tugging or pulling on stuck components can cause you to lose your balance and fall.
Workers should wear a full body harness and lanyard tied off to a scaffold frame or lifeline before attempting to loosen stuck or jammed parts.
Dismantling tube-and-clamp and systems scaffolding must proceed in reverse order to erection. Each tier should be completely dismantled as far as connections will allow before you begin dismantling the lower tier. You must dismantle them this way because the bracing for tube-and clamp scaffold is not located in each bay as it is for frame scaffolding. The span or spans with front sway bracing should be the last to be dismantled on each tier.

Please refer to the Construction health and safety manual for a more detailed reference.

All scaffolds shall exceed or at least comply with OHSA Acts and Regulations

No comments:

Post a Comment