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NEBOSH
WEEK 2 – ELEMENT ELEMENT 8
Construction Activities Hazards & Control
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Effective Management
That there is sufficient time allowed for planning, preparation and the work itself
Early appointment of key people, including competent Consultants, Designers, Principal Contractor and if necessary other Contractors
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Effective Management
That there is sufficient time allowed for planning, preparation and the work itself
Early appointment of key people, including competent Consultants, Designers, Principal Contractor and if necessary other Contractors
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Effective Management (con’t)
All the parties involved co-operate and coordinate their activities to ensure effective management of health and safety throughout the project
Risk assessment and risk management processes are integral to the project
All parties involved in the project have clearly defined roles
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Management of significant construction projects The Five key parties are: 1) The Client 2) Consultants 3) Designers 4) The Principal Contractor 5) Other Contractors
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Clients Duties Appoint competent consultants Appoint competent designers Appoint competent principal contractor Ensure those appointed have adequate resources
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Consultants Duties
Advise client on selection of designers, contractors etc.
Collect pre-construction information
Ensure co-operation between different designers
Give advice to clients and contractors
Provide client with relevant documentation
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Designers Duties
Ensure clients kept informed
Structures designed to avoid risks to health and safety while being built and maintained
Ensure to avoid or minimise risks
Provide information about materials
Co-operate with other designers
Provide information to consultant
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Principal Contractor Provide information to the Client and Consultant Consider health & safety when preparing tender Develop safety plan for construction Co-ordinate activities of all contractors Ensure all on site comply with health & safety rules Take steps to ensure only authorised persons on site Provide health and safety information to all necessary
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Other Contractors (sub-contractor) Duties
Must co-operate with Principal Contractor
Provide relevant information to Principal Contractor
Comply with directions given by Principal Contractor
Should provide Principal Contractor with information on accidents
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Other requirements
Pre Construction information
Construction phase of the project
The project file
Site Precautions
Additional precautions for Children
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Site Security Precautions for preventing children to gain access include :
Fencing
Hoardings
Warning Signs
Security Patrols
Visiting Schools
Viewing Panels
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Site Security Precautions to be taken should access be gained by unauthorised trespassers • • • • • • •
Covering or Fencing excavations Removing Ladders Immobilising plant/machinery Locking away chemicals/tools Reducing height of materials Isolating services Clearing away rubbish and debris
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Main Construction Hazards Falls from height
Vehicles
Fragile roofs
Traffic movements
Falling objects, slips, trips Plant and equipment Excavations
Doors and gates
Demolition
Lighting & Weather
Explosives
Stability
Working in or over water
Fire
Working in tunnels
Material storage
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Main Hazards of Roof Work Roof Types Fragile roof materials Roof edges Slippery sloping roof surfaces Materials falling from roof Contact with overhead electricity cables Hot Bitumen Liquified Petroleum Gases Manual handling
pitched roofs extensive works short duration work flat roofs fragile roofs
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Roof Work
Falling Off No edge protection Slippery surfaces Handling materials
Falling Through Fragile materials Skylights covered over No crawling boards
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Pitched roofs precautions (Over 10 degrees) Carry out survey Safe means of access Roof edge barriers Roof ladders/crawling boards Identifying and covering roof lights Facilities to raise and lower materials Protection for persons below Provision of harnesses No work in severe weather Competent workers
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Bitumen Flat Roof Precautions Safe
use of Bitumen boilers
Safe
use of burning gases
Training
in manual handling
NEBOSH
The Working at Heights Regulations 2005 Hierarchy of working at height Reg 6: Avoid work at height if possible Use work equipment or other measures to prevent falls when they cannot avoid working at height Where they cannot eliminate the risk of falls use work equipment or other measures to minimise the distance and consequences of a fall should one occur Risks from fragile surfaces are properly controlled
NEBOSH
Fragile Roofs - Precautions Crawl boards 430mm wide spanning purlins Boarded valleys Running line and safety harness Barriers or covers to roof lights
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Fall Arrest Systems - Lowest level of the hierarchy - Aim to minimise the risk of injury if there is a fall
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Main hazards when using Ladders
Over-reaching from ladder
Unsecured/unstable ladder
Ladder not extended above step off point
Using a damaged/worn ladder
Metal ladder contact with electrical cables
Falling material being carried up ladder
Vehicle collision with base of ladder
Manual handling – carrying and erecting
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Unsuitable use of Ladders
Stand ladder Stand on unsteady ladderbase on unsteady base
Makeshift and too short
Overload
Overreaching © TWI Gulf WLL 2008
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Minimising Hazards of ladder use (1)
Ladder rested on a firm level base
Use of stabilization devices or otherwise footed
Secure ladder by: Correct angle 75% or 1:4 ratio.
Tied off at top
Extend suitable distance above step off point (1.00 metres min)
The top of the ladder against a solid surface
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Minimising Hazards of ladder use (2)
Use wooden ladders near overhead cables/erect ‘goal posts’ and signs
Provide equipment to raise materials
Provide holsters to carry tools
Only one person at a time on a ladder
Rungs should be clear of grease, oil or other slippery substance.
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Minimising Hazards of ladder use (3)
Barrier off base and display warning signs
Use of ladder by only trained users
Assistance when moving/erecting ladder
Inspection and maintenance of ladders
Ladder register
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Step Ladder precautions • Inspected for defects before use • Correctly positioned on even ground • Suitable for task • Footed if necessary • Avoid over-reaching • Not overloaded • Positioned on even ground • No work carried off top step • Worker maintains three point contact • Properly erected and legs fully extended
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Scaffolding
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HAND RAIL/ HAND GUARD
Toe board TOE BOARD
Couplers
Transome
COUPLERS
TRANSOM
Standard STANDARD
Boards
DECKING
Bracing BRACING
Base plate BASE PLATE
SOLE PLATE
Sole plate
Ledger LEDGER
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Independent Tied Scaffold
NEBOSH
Through Tied Scaffold Page: 266 Guard Rail (Approx 1.0 m high) Brick Guard END OF
Intermediate guard rail (Max gap of 470 mm) Toe Board (Min 150 mm high)
SCAFFOLD
Scaffolding Planks (Deck area min of 600 mm wide) Transom Facade Brace Through Tie
Large Eye Bolt
Ledger Brace
Reveal Tie Couplers at joints Ledger Standard Eye Bolt and Strap Base Plates Sole Plates
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Through Tie
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Reveal Tie
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Box and Eyebolt Tie
Box Tie
Eye Bolts
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Maximum span of scaffold boards Nominal thickness of boards
Maximum span between transoms
Minimum overhang
Maximum overhang
38mm
1.5m
50mm
150mm
50mm
2.6m
50mm
200mm
63mm
3.25m
50mm
250mm
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Scaffold Types and Spacings Duty
Use of Platform
Max. bay
very light duty
Inspection, Painting, stone cleaning, and access
2.7 m (3 bds)
Light duty
Plastering, painting, stone cleaning, glazing, pointing
2.4m (4 bds)
General purpose
General Building e.g. brickwork, window fixing.
2.1m (5bds)
Heavy duty
Blockwork, Brickwork, heavy cladding
2.0m (6 bds)
Masonry or special duty
Masonry, Concrete Block, very heavy cladding
1.8m (7 bds) © TWI Gulf WLL 2008
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Scaffold Inspection After Erection Every 7 days Adverse weather After struck by vehicle After modification
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Reasons for Scaffold Collapse
Wrong materials
Unstable foundations
Improperly designed
Improper erection
Overloading
Modified incorrectly
Undermined by excavations
Hit by machinery
Excessive winds/Rain
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Inspection of scaffolds
Base – Firm ground and sole plates
Line of standards and ledgers
Spacing of transoms to support boards
Boards good condition
Guardrails and toe boards
Bracing
Means of access
Ties – number and position
Correct couplers
Joints staggered
NEBOSH
Putlog Scaffold Brick Guard
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Guard Rail (Approx 1.0 m high)
Intermediate guard rail (Max gap of 470 mm) Toe Board (Min 150 mm high) Scaffolding Planks (Deck area min of 600 mm wide) Putlog
Through Tie Facade Brace Couplers at joints Ledger End Brace Standard Putlog Base Plate Sole Plate
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Putlog Scaffold
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Putlog Scaffold – Through Tie
NEBOSH
Scaffold Towers • Main Hazards • Overturning • Collapse • Fall from height • Falling objects • Overhead obstructions
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Scaffold Towers - Ratios
Height/ Width Ratio Static internal
4:1
Static external 3.5:1 Mobile internal 3.5:1 Mobile external 3:1
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Scaffold Towers - Stability Affected by: • sheeted in strong winds • overloaded with equipment or materials • used to hoist heavy materials or support rubbish chutes • used for operations such as grit blasting or water-jetting • climbed from the outside • used to support ladders
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Precautions using of scaffold Towers
Mobile Towers only be used on firm &level ground
Tower only be moved by pulling or pushing at base
Working platform be clear of men and materials when scaffold is being moved
Wheels be turned outwards and locked when tower being used
Correct height to width ratio
Diagonal bracing
Platforms must be fully boarded with guardrails and toe boards
Not overloaded
Access be on the inside of the narrowest side Inspected every 7 days
NEBOSH
MEWPs Hazards • Equipment failure • Unsuitable ground conditions • Defective or unused outriggers • Overloaded carrier • Carrier struck by a slung load • MEWP struck by another vehicle
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Mobile Elevating Work Platforms (MEWPs) Precautions Trained & Competent Guardrails and toeboards Firm/level ground Not overloaded
Clear of overhead obstructions Area cordoned off Outriggers extended Procedures If machine fails Well lit
NEBOSH
Self Propelled AWP Aerial Work Platform
Will pass through standard doorways 1.36m long 0.76m wide Turns 360 degrees in 1.5 m radius Max Height 5.8m SWL 227 kg
NEBOSH
Self Propelle Propelled d AWP AWP Do Not Work close to overhead cables Allow arm to protrude into traffic route Move with platform raised Check limitations
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Suspended Access Equipment M ai ai n p r e c a u t i o n s s h o u l d b e :
Regular inspection Safe working load Competent staff Safety equipment working Platform edge protection Guard rails and toe boards fitted Adverse weather weather rules Protected electricity supplies Communication Emergency procedures
NEBOSH
Excavation Hazards
Collapse Of The Sides Over Running Of Vehicles Vehicles Persons Falling Into The Excavation Materials Falling Into Excavations Underground Services Access And Egress Hazardous Atmospher Atmospheres es Undermining Adjacent Structures Flooding Buried Services
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Excavation Inspection Excavations should be inspected: 1) At the start of every shift before work starts 2) After any event likely to affect the strength 3) Any accidental fall of rock earth or other materials
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Excavations Assessment
Soil types and conditions
Existing structures and roads
Underground services
Flooding
Protection of Public
Depth-support?
Surcharge loads
Access and egress
Lighting
Experienced Operatives
PPE
NEBOSH
Precautions To Prevent Trench Collapse Slope or bench the sides of the excavation, Support the sides of the excavation, or Place a shield between the side of the excavation and the work area
NEBOSH
Methods of Demolition By Hand By machine Pusher arm Wire rope pulling Demolition ball Impact hammer Power grabs
By Chemical agent Demolition by explosives Gas expansion bursters Hydraulic bursters Expanding demolition agents Hot cutting High pressure water jetting
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Main Hazards of Demolition
Falling debris, masonry
Premature collapse of building
Falls from height or on the same level
Services (electricity, gas and water)
Explosion and fire
Chemical contamination - Lead dust, silica dust, asbestos, gases vapours and fumes
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Main Hazards of Demolition
Asbestos
Biological - Weils disease, hepatitis (syringes) sewage contamination
Manual handling e.g. Strains, fractures
The use of explosives
Collisions with heavy plant, plant toppling over
Noise e.g. Heavy plant, pneumatic drills, power tools
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Demolition Protection of Public Restricted areas Safe distances Airborne contamination Protection of Workforce Sequence of demolition Permit systems Existing/temporary services Flammables Segregation PPE
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Safety precautions for Demolition
Identification and isolation of services Barriers, Fences, Restricted access Means of preventing falls Use of “Elephant Trunks” to remove debris Means of suppressing dust Identification/Removal of hazardous substances Competent Staff – Clear responsibilities Preventing premature collapse Sequence of demolition followed Properly maintained equipment
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Construction Health Hazards Noise
Dusts
Vibration
Saw dust
Solvent and cleaners
Lead dust
Fumes and radiation Biological hazards
Silica dust Asbestos fibres
Cement Irritant dermatitis Allergic dermatitis Skin burns and ulcers
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Storage of materials Sand and aggregate
Bricks, Blocks, Roof tiles Roof trusses Various pipes
Main hazards
Precautions
Falling from lorries
Minimum quantities
Tripping hazards
Effective storing
Obstructing traffic/walkways
Low as possible
Materials falling from piles
Clearly marked areas
Causing dust hazards
Ensure good housekeeping
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Storage of Flammable Materials
Keep quantities to a minimum
Secure storage areas
Storage area properly ventilated
Containers and cylinders returned to storage at end of day
Prohibit smoking and other ignition sources from storage area
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Storage of Flammable Materials
Suitable and properly labelled containers for decanted materials
Protection of storage area from vehicle impact
Inspection of gas cylinders to ensure valves fully closed
Correct and right number of fire extinguishers
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Safe Practices for the use, collection and removal of skips from site Suitable skip from reputable supplier/ contractor Hazardous waste stored separately Skip in good condition
Skip not overloaded Located on firm level ground Adequate room for delivery/removal Chutes for filling Netting or sheeting for removal PPE for staff
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Safe use of portable tools on site
Ensuring suitable equipment
Reduced voltage 110V supply system
Extra low voltage for wet locations
Use of Residual Current Devices (RCDs)
Double insulated tools
Battery operated tools
Suitable connections
Pre-use inspections
Inspection, testing and maintenance
Competence of workers
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Precautions for Electricity on Construction Sites
Underground CAT Scanner
Crossing points
Goal Posts
Underground Cable Detector CAT up to 3meters
NEBOSH
Overhead power cables The MINIMUM recommended safe working distance is 6 METRES from the nearest part of the crane (usually the jib) even when the crane is working in the opposite direction Overhead high electrical cable
voltage
6 metres
If the minimum distance cannot be maintained the electricity supply should be disconnected
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Overhead Electrical Services
Isolation of power if possible
Safe path marked (Use of barriers, fencing)
Height restrictions marked by goalposts
Warning notices
Ban equipment capable of reaching overhead lines
Limiters fitted to cranes
Supervision
NEBOSH
Underground Services Service
Hazards
Electricity cables
Explosive effects of arcing current & consequential fires electric shock
Gas pipes
Noxious or flammable atmospheres
Water pipes
High pressure jets Flooding - drowning or undermining the excavation
Sewerage
Risk of contamination
Other pipelines
Flammable liquids and gases Toxic liquids and gases Inert gases that may displace oxygen and asphyxiate Liquids under pressure
Telecoms
Business interruption Gases from other sources may accumulate in cable ducts
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Underground Services Controls Planning the work Locating the services Identifying the services Safe Digging practices PLID All services should be assumed live unless proven otherwise
