SAFE WORK METHOD STATEMENT OVERHEAD AND UNDERGROUND ELECTRICAL CABLES

Transcription

1 SAFE WORK METHOD STATEMENT OVERHEAD AND UNDERGROUND ELECTRICAL CABLES NOTE: = Risk Rating befe controls implemented - = Risk Rating after controls are implemented Task - Contact will not be made with underground utilities (contact dial befe you dig) and use suitable utility locating devices OVERHEAD ELECTRIC LINES 1. Ensure wk is not conducted in close proximity to electrical power lines. Check f: - Overhead power lines (including high and low voltage distribution conducts - Single wire earth return (SWER) - Service cables to premises - Communications cables - Electrical transfmers (mounted - lower than cables) 2. Identify: - Befe wk commences in the vicinity of an energised electrical part, no go zones should be established. - Maximum range of equipment and how close equipment load can come to asset (known as design envelope) - Clearance distances f type of asset (***) - Type of asset/cabling (if in doubt contact electrical supplier) - Voltage level - Height of conduct at lowest point - Minimum distance between wires and ground - Degree of sag and sway *** Minimum Clearance zones: - High voltage electrical conducts = 2,000mm - Un-insulated low voltage conducts = 1,000mm - Insulated low voltage (between50v and 1,000 V) = 500mm - Communications cabling = 300mm WARNING: DO NOT ATTEMPT TO DIRECTLY MEASURE THE HEIGHT OF OVERHEAD ELECTRIC LINES. DO NOT USE CONDUCTIVE METALLIC OBJECTS OR MEASURING DEVICES SUCH AS METAL TAPE MEASURES FOR ESTIMATING THE HEIGHT OF OVERHEAD ELECTRIC LINES

2 No Go Zone Approval of the electricity supply authity A no go zone extends in all directions, not just sideways; it is all around the electrical part. A person should not enter a no go zone. The areas of a no go zone may vary, but it will always exist. A no go zone is the area around overhead electric lines electric parts that fms a safety envelope. A safety envelope is the space encapsulating an item of plant, including attachments such as rotating/flashing lights radio aerials, categised as: a design envelope - the space encapsulating all possible movements of the plant and any load attached under maximum reach, a transit envelope - the area encompassing the nmal height and width of a vehicle plant when travelling to from a wksite. No part of a person, hand tools, equipment any other materials held by a person, cranes, vehicles items of mobile operating plant including the load, controlling ropes and any other accessies may cross into the no go zone while the electrical part is energised without the written approval of the electricity supply authity. This approval should be made available at the wksite.

3 Possible Safety Personal Injury: - Electric shock No go zones apply whenever carrying out wk operating plant (f example tip truck, crane, elevating wk platfm, concrete pumping truck), around an energised electrical part and the risk cannot be eliminated. Figure 1: Distance that should be assessed f each wksite In general: - 3m above, either side and below power lines is No Go Zone. - Between 3-6.4m of power lines a Spotter is required. - Further than 6.4m of power lines is open area - No wk to be conducted within 10m radius of SWER transfmer No wk to be conducted within Minimum Clearance Zones without written permission from power supplier and Spotter Wk outside Minimum Clearance Zone, but still in No Go Zones, site-specific SWMS to be developed and Spotter required. Note: Spotter is not required where wk is 6.4m from power line, but design envelope reaches into No Go Zone if: - Wk is designed so no part of machinery load enters within 6.4m - Documented site-specific SWMS is developed and responsible persons assigned to oversee the SWMS

4 3. Implement suitable controls. Examples: - Relocation of cables - Disconnection of power supply (evidence must be obtained from power supplier) WARNING: EVEN IF IT IS BELIEVED THAT THE SUPPLY HAS BEEN ISOLATED, IT MUST BE ASSUMED THAT ALL CONDUCTORS AND COMPONENTS ARE ENERGISED UNTIL AN ACCESS AUTHORITY OR OTHER FORM OF WRITTEN DOCUMENTATION HAS BEEN RECEIVED FROM THE ELECTRICITY SUPPLY COMPANY - Use equipment with smaller design envelope Tempary physical height barriers to limit loads - Longitudinal fencing height markers to indicate extent of allowed movement - Signage - Use of Spotter - establish effective communication system with operat. Note: A Spotter should: be used whenever the wk activity is likely to be perfmed in the authised person zone be positioned at a suitable location to effectively observe both the overhead electric lines and plant be able to immediately and effectively communicate with the operat of the crane mobile plant, other persons if required ensure that all persons stay outside the specified approach distance (unless perfming a rescue in accdance with approved procedures carrying out a specific task that is described in the safe wk method statement, f example a crane dogman holding a non-conductive tag line attached to a load suspended from a mobile crane) not carry out any other wk while acting as a safety observer, which includes the passing of tools, equipment materials directly to the personnel perfming the wk not observe me than one wk activity at a time monit the wk activity being carried out and have the authity to suspend the wk at any time.

5 LOW VOLTAGE OVERHEAD ELECTRIC LINES NEAR BUILDINGS AND STRUCTURES Electric lines are any low voltage overhead service lines, including: electricity supply authity s low voltage overhead lines including service lines low voltage overhead lines fming part of consumers installations insulated low voltage aerial conducts and associated electrical equipment that are connected from the point of supply (either the overhead electric pole located on the street the consumer s boundary) and terminated on the consumer s building, pole structure at the point of attachment insulated low voltage aerial consumers mains and associated electrical equipment fming part of the consumer s electrical installation. 1. Ensure wk is not conducted in close proximity to electrical power lines. Check f: - Overhead power lines (including high and low voltage distribution conducts - Single wire earth return (SWER) - Service cables to premises - Communications cables - Electrical transfmers (mounted - lower than cables) Figure 14: Low Voltage Overhead Service Lines

6 2. Identify Approach Distances Table 4 provides approach distances f unauthised persons: perfming min building wk in the vicinity of low voltage overhead service lines, (including hand tools held by a person) operating cranes (and their loads) and items of mobile plant in the vicinity of low voltage overhead service lines handling metal materials in the vicinity of overhead service lines (f example scaffolding, roofing materials and guttering) handling non-conductive materials in the vicinity of overhead service lines (f example timber, plywood, PVC pipes and guttering) driving operating a vehicle under overhead service lines. The approach distance specified in Table 4 below is based on the fact that the design transit envelope of the vehicle does not allow any part of the vehicle to come closer than the 0.6 metre approach distance specified. Table 4: Approach distances f wk in the vicinity of low voltage overhead service lines. Hand held tools Unauthised Persons (metres) Operation of crane mobile plant Handling of metal materials (e.g. scaffolding, roofing, guttering, pipes, etc) Handling of nonconductive materials (e.g. timber, plywood, PVC pipes and guttering, etc) Driving operating vehicle

7 If the voltage of the line cannot be determined, the line should be deemed as a high voltage line Examine an insulated low voltage overhead line f visible defects to ensure that the insulation is intact with no tears, cracks other physical defects There are no exposed energised parts anywhere on the line If you cannot determine whether the line is effectively insulated, the line should be treated as being bare. 3. Implement suitable controls. Examples: - Relocation of cables - Disconnection of power supply (evidence must be obtained from power supplier) WARNING: EVEN IF IT IS BELIEVED THAT THE SUPPLY HAS BEEN ISOLATED, IT MUST BE ASSUMED THAT ALL CONDUCTORS AND COMPONENTS ARE ENERGISED UNTIL AN ACCESS AUTHORITY OR OTHER FORM OF WRITTEN DOCUMENTATION HAS BEEN RECEIVED FROM THE ELECTRICITY SUPPLY COMPANY - Use equipment with smaller design envelope Tempary physical height barriers to limit loads - Longitudinal fencing height markers to indicate extent of allowed movement - Signage - if wk has to be carried out in close proximity to the point of attachment and the electricity cannot be isolated, arrange f the electricity supply authity to fit insulated matting and tiger tails at the point of attachment and over the overhead service lines befe the wk commences - Use of Spotter - establish effective communication system with operat

8 UNDERGROUND ELECTRIC CABLES - Contact Dial Befe You Dig - If it is not known whether cables, conduits, equipment situations fm an electrical safety risk, you should either assume that the risk exists, have a qualified person investigate and rept. - Use locat - never assume that the plans you receive contain exact location of underground assets - Befe digging water jetting near a high voltage electrical cable, check with SA Power Netwks on ElectraNet on if there are any special conditions that apply - Paint location marks on ground - Pot hole dig carefully by hand to expose underground assets befe using any excavation heavy digging. Sometimes several potholes will need to be dug manually to determine the exact location because of deviations in the cable alignment. - Always use insulated hand tools (eg spades and shovels, preferably with curved edges). Do not throw spike into the ground. Ease in with gentle foot pressure and dig with the blade of the shovel parallel to the cable route - Arrange f water jetting high velocity air jets incpating vacuum removal if necessary

9 - Where possible the electricity supply to the underground cable should be isolated befe digging - If you need to isolate a SA Power Netwks cable you will need to apply f a permit. The permit will ensure the powerlines will be turned off until the permit is returned. To apply, contact the SA Power Netwks line on Private Property - If excavating on private property, contact the owner occupier of the premises about buried cables befe starting wk. - Look around the property look f such things as direction of overhead cables coming into the property, sewer and IP connections and gas meter plans - Use locat Operation Once an asset location has been determined excavation may proceed - Do not commence mechanical excavation without a dedicated spotter - Visual and verbal contact must be maintained between Operat and Spotter at all times during operation. - Use extreme care dig slowly - Excavate alongside the asset rather than directly above it, where possible - If marker tape is found, stop mechanical excavation. - Final exposure of the asset by hizontal hand digging Always use insulated hand tools (eg spades and shovels, preferably with curved edges). Do not throw spike into the ground. Ease in with gentle foot pressure and dig with the blade of the shovel parallel to the cable route

10 Emergency Procedures - Numerous - Develop and implement an emergency response plan f the site if possible. Include: - Assembly points - Communication /Responsible persons - Emergency contacts - First Aid and Rescue procedures Ensure documented/rehearsed procedures implemented f response after contacting live electricity other utilities. Ensure all relevant persons trained in procedures.