THE PROCESS OF ERECTING AND DISMANTLING
RESTRICTED HEIGHT MOBILE SCAFFOLDING
READ
21.
ERECTING A MOBILE SCAFFOLD
This unit deals with mobile scaffolds. You should read through the unit materials
before attempting the activity under the direct supervision of your instructor.
The second activity has two options. Your instructor will brief you according to
which of the activities either 2A or 2B you will complete.
This unit has eight topics, each of which deals with a component/part of a mobile
scaffold. The topics are:
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Aluminium Mobile Scaffold
General Information
Access
Access Platforms
Castor Wheels
Working Platforms
Bracing
Colour Coding
Spacing of Members
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Aluminium Mobile Scaffold
Aluminium mobile scaffolds are used by most trades in the building and construction
industry. They are designed, so most people will be able to erect them with ease.
However, it must be pointed out that only a certificate holder in scaffolding can erect
or dismantle scaffolding over the height of 4 metres.
All mobile scaffolds must be constructed, assembled and maintained in accordance
with the manufacturers specification.
Manufacturers have an obligation as
stated in Section 32 Workplace
Health and Safety Act 1995.
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General Information
The height of a mobile scaffold shall
not exceed three (3) times the length
of its least base dimension. The
freestanding height of a light duty
aluminium tower-frame scaffold
with a base width of less than 1.2m
should not exceed twice the base
width.
The height of a light-duty aluminium
tower-frame scaffold must not
exceed 9m (unless specifically stated
in the suppliers documented
information).
A mobile scaffold shall not be used
except on a solid level surface
adequate in strength to support
safely the total load imposed on the
surface by the weight of the scaffold,
the person using the scaffold and the
material to be placed on it.
Figure 42
MOBILE SCAFFOLD
A mobile scaffold must not be
moved:
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whilst any person is upon such scaffold or
by a person upon such scaffold.
A working platform must not be erected between adjacent mobile scaffolds.
A mobile scaffold must not be located any closer to powerlines than the minimum
required distance for a static (i.e. non mobile) scaffold.
Plan braces shall be secured diagonally immediately above the lowest ledger and
transoms, and shall be secured to the corner standards with approved methods.
Wheels are to be locked and checked before use.
It is recommended mobile scaffolds are not erected, over stairs, ramps, walkways or
gantries.
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a guardrail and midrail shall be erected, to the exposed edge of a working
platform, or any other place where a person can fall 2 metres or more
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where the nature of the work makes it difficult for the person to be fully aware
of the proximity of the platform edge (eg overhead work or welding), edge
protection should be provided, regardless of the height of the platform.
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where a person could fall onto or into any substance likely to cause injury or
be harmful to that person
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a toeboard shall be erected to the exposed edges of a working platform or any
other place where tools or material can fall 2 metres or more
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a guardrail shall be positioned no less than 900mm or more than 1100mm
above the edge being protected
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a midrail shall be positioned no less than 450mm or more than 600mm above
the edge being protected.
Damaged or defective equipment should be tagged so others are aware of the damage.
The damaged or defective equipment must be stacked to one side, away from all other
scaffold equipment and removed from the workplace as soon as possible.
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Access
Access to and from the mobile scaffold is to be internal by ladders through and from
approved landing with hinged hatches as specified by the manufacturers.
Mobile scaffolds with working platform heights greater than six metres shall
incorporate a mid-height or intermediate access platform with ladder.
Ladders shall be positioned and fixed at an angle of approximately four vertical to one
horizontal
Access Platforms
Single deck platforms that do not cover the full width of the scaffold may be used as
access platforms provided guardrails and midrails are fixed directly to the perimeter
of the platform. Guardrail and midrails must be secured by using approved couplers
to ensure rails do not move away from the edge being protected. Hinged trapdoor
platforms for ladder must be used with single deck access platform.
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Castor Wheels
Castor wheels used on a mobile scaffold shall comply with Australian Standard
specification for couplers and accessories AS1576.2 - 1991.
Four (4) castor wheels shall be provided under the scaffold to support safely the total
load imposed by the weight of the scaffold, and persons using the scaffold and
material to be placed thereon.
A castor shall be provided with an effective wheel brake, which cannot be
accidentally released.
Wheels shall be either plain or fitted with resilient tyres. Tyres shall be of adequate
section and properly fixed on to the wheel centre. Pneumatic tyred wheels must not
be used.
The castor must not fall out of the end of the scaffold tube when the assembly is lifted
off the running surface.
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Working Platforms
A maximum of two working platforms per tower may be used provided the platforms
are totally separated.
The maximum safe working load for a mobile scaffold shall be 450kg, constituted by:
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a single deck platform having a load equivalent to a uniformly distributed load
of 450kg or
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two working platforms each having a load equivalent to a uniformly
distributed load of 225kg.
Single level working platforms with a safe working load of 450kg shall be decked out
for the full width of the scaffold.
Split or stepped levels of working platforms should not be used.
NOTE:
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Safe working load and platform position must be documented and
issued when mobile scaffolds are supplied by the supplier and/or
manufacturers.
Bracing
All bracing must be in accordance to manufacturers diagrams, however plan bracing
may be replaced by a full width deck fixed to the lowest transom of the end frames.
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Colour Coding
All components of mobile scaffolding should be colour coded to an industry standard.
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Horizontal braces
YELLOW
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Diagonal face braces
BLUE
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Plan braces
BLACK or RED
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When guard rail end frames, guard rails and working platform diagonal braces
are of different design or length they are to be colour coded with the standard
colour plus a second colour.
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An example, would be a top brace which covers two horizontal members, the
brace would be coloured blue as standard plus another colour.
Components shall be colour coded at their ends or hooks and the type of paint used
shall be resistant to abrasion, wear and the effects of sunlight.
The colour coding should be maintained at all times, to make it easier to identify the
different parts when erecting.
ERECTION GUIDE for Z 3m SQUARE TOWERS
Figure 1 ERECTON GUIDE (MOBILE SCAFFOLD)
ERECTION GUIDE for 3m SQUARE TOWERS
1.
Attach horizontal brace (yellow
hooks) to vertical tube of base
frame. Ensure castors are locked.
Frame is now self-supporting.
2.
Attach spare end of brace to end of
other base frame. Attach 2nd
horizontal brace (yellow hooks) to
other side of frame. Attach plan
brace(s) (black hooks) diagonally
onto the vertical tube below the
lowest base frame rung, or as low
down as possible.
3.
Attach six diagonal braces to the
base of the unit as shown. Level the
unit using the adjustable legs. The
base is now complete.
4.
Additional 0.8m extensions. Insert
an extension frame, spigots first,
into the top of the base unit and
secure interlock clips, see drawing.
Attach the diagonals to frame as
shown. Diagonal bracing must be
Dog-legged. Also two horizontals
must be attached every 2nd
extension, and one plan brace every
3.2m (or every 4th extension
5.
Guard rail extension: Fit the
four plain platforms first, then the
walk-through platform with the
hinges of the trap-door to the
outside of the tower. Insert the
guard rails, spigots first, into the
top of the last frame and secure the
interlock clips. Attach two
horizontal braces (yellow hooks)
to the top rung of the guard rail
frame and two diagonal braces,
for rigidity, as shown.
6.
To complete the work platform,
first fit the toeboard to allow the
trapdoor on the platform to open
freely. Finally attach the ladder
through the access platform, as shown, and clip on stand-off hooks, at base of
ladder, to the corresponding rung on the frame. Ensure the access door
movement is not impaired.
BEFORE USE, PLEASE READ RULES ON BASE FRAME
Ladder Change-over platforms:
One walk-through platform is required to
enable safe ladder change-over on towers with
more than one ladder. Attach platform before
ladder. Ensure two horizontal braces are also
attached as guard rails and mid rails.
ERECT A MOBILE SCAFFOLD
MOBILE SCAFFOLD - ONE BAY WIDE AND TWO BAYS LONG (Figure 39)
The bottom standards, puncheons, ledgers, transoms and struts shall be of steel tubing.
Check all the ledgers and transoms to ensure they are the same length. This is done
by laying the ledgers on a level surface and making all the tubes level at one end. The
other ends are marked with a piece of chalk. A right angle coupler can then be fixed
to each end of each tube. This will ensure that the couplers are the same distance
apart and will assist greatly when squaring the scaffold.
Check the ends of the standards to ensure that the pintle of the castor can be inserted.
Fix the bottom ledger to the bottom of the two corner standards for each side then
stand the four corner standards vertical. (The ledgers to be on the inside of the
standards).
NOTE:
It is important that the right angle coupler securing the ledger to
the standard is fixed at the bottom of the standard.
The end transoms are then fixed inside the end standards and hard down on top of the
ledgers.
NOTE:
Whether the scaffold is erected in the following sequence will
depend on the size of the scaffold.
Lift the frame (consisting of four corner standards, two transoms and two ledgers) and
insert the castor wheels. Check the frame for squareness by measuring the diagonals.
Do not alter the positions of the right angle couplers on the ledger transoms.
Fix a short tube in the centre of each bottom ledger to prevent sag while the rest of the
scaffold is being erected. Ensure there is a slight camber upwards in the bottom
ledgers.
As the scaffold is to be two (2) bays long, puncheons will be required to be fixed to
the ledgers mid-way between the corner standards.
Remaining ledgers and transoms can now be fixed.
Four (4) struts are required to support the centre puncheon. The lower end of each
strut is fixed on top of the bottom transom and hard against the corner standard. The
upper end of the strut is secured to the underside of a transom fixed to the 2 centre
standards. Safety fittings are provided immediately below the right angle couplers at
the top of the strut above and immediately above the right angle couplers at the
bottom of the strut. The angle of the struts should be approximately 45.
After securing of the struts and safety fittings, the short centre tube support can then
be removed.
Diagonal plan bracing is fixed as near as possible to the bottom of the corner
standards. This bracing is commonly known as a Spider brace. Where the braces
cross in the centre a swivel coupler is used to secure the braces together.
Putlogs are placed either side of the centre standard at the required distance. At each
end of the scaffold, it is permitted for the end transoms to act as putlogs.
Right angle couplers are used throughout the scaffold except for putlog couplers
securing the putlogs to the ledgers, a swivel coupler in the spider brace and swivel
couplers on the face bracing.
Figure 45
MOBILE SCAFFOLD ACTIVITY 2 OPTION 1
SELF-CHECK
EXERCISE 5:
1.
SITE PREPARATION AND SET UP
Do castors for mobile scaffolds need wheel locks?
Yes
2.
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or
No
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No
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What is the minimum width of a medium duty scaffold?
Yes
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or
3.
Why is plan bracing needed in a mobile scaffold?
4.
Without supplier’s information or engineer’s approval, how high would you build
a light duty aluminium tower frame scaffold.
5.
Would you fix the ladder access to tower frame scaffold internally or externally?
6.
How is the ladder opening in a tower frame scaffolds working platform usually
protected?
7.
Without supplier’s information or engineer’s approval, how many working
platforms would you place on a light duty aluminium tower frame.
8.
Is it acceptable to use personnel hoists as the only means of access to a
scaffold working platforms?
9.
Does the supplier of prefabricated scaffolding need to provide written
information about the system?
10.
When a scaffold is built on soil, what would you place under the baseplate to
distribute the load?
11.
What minimum width of timber would you use as a soleplate/soleboard?
12.
Are gaps allowed between the planks of a working platform?
13.
Can planks with different thicknesses be used to deck out a working platform?
14.
Would you mix components of two prefabricated systems in one scaffold
without a supplier’s or engineer’s consent?