Method Statement for Installation of Earthing and Lightning Protection Systems Including Testing
Location of Work: Primary Substation Building Basement.
1 Method of Installation for Earthing and Lightning Protection Systems
1.1 Prior to installation, materials will be carefully delivered to the correct location. Suitable lifting equipment as applicable i.e. crane or forklift shall be used to shift the materials to the installation site.
1.2 Separate Earthing Systems will be provided for Low Voltage, Extra Low Voltage, and Lightning Protection.
1.3 Copper bonded rod of sizes 16mm/19 mm dia, shall be used as per project specifications. Necessary couplers shall be utilized to extend the length.
1.4 Buried earthing conductors are connected with approved accessories /exothermic Welded (Cu to Earth rod) to be laid at a depth as required and as per approved shop drawing details.
1.5 Earth pits using earth rod electrodes shall be installed with the latest approved drawings.
1.6 Soil resistivity test to be conducted on-site and report to be submitted for consultant approval.
1.7 Earth rod electrodes shall be installed where soil resistivity is low. Provision shall be made for connecting all incoming cables by welding/ earth connectors to the top of the rod.
1.8 No drilling of earth bar shall be permitted except in the main termination points.
1.9 Primary substation main earth mat shall be in the soil level directly beneath the substation.
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2 Method of Installation for Static Grounding
2.1 Separate static Earthing Systems will be provided as per Shop drawings approvals.
2.2 Buried Bare Copper conductor Sizes shall be used as per Approved Drawings and Necessary Exothermic Welding accessories shall be utilized to extend the length / Joints.
2.3 Buried earthing conductors are connected with approved accessories /exothermic welding. The grounding conductor shall be buried below the finished floor level. Finishing grade unless otherwise specified in drawings.
2.4 Exothermic Welding joints as per manufacturer recommendation. Buried bonded conductor shall be connected with earth rods down contactors / Aircraft static Grounding Receptacle.
2.5 All Earthing Interconnections to the main grid shall be achieved by Exothermic welding.
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3 Exothermic welding procedures as per manufacturer recommendations
3.1 An exothermic welding system is a fusion of high conductivity, high copper content alloys which produces a molecular weld. This weld has at least twice the cross-sectional areas of the conductors being joined and a current-carrying capacity equal to or greater than that of the conductor, enabling it to withstand repeated fault current. The weld will not loosen or corrode and is an integral part of the conductor.
3.2 Position cleaned conductor in mould after ensuring mould is dry by pre-heating or making joints.
3.3 Lock mould with handle clamp and place metal retaining disc in bottom of mould crucible.
3.4 Pour weld power into mould and of starting power on edge of mould for easy ignition.
3.5 Close mould lid securely.
3.6 Ignite starting powder using a flint gun.
3.7 Reaction takes place and waits for approx. 3 mins. to allow the metal to solidify before opening mould.
3.8 Remove weld and clean mould carefully before making the next connection.
Exothermic welding according to Wikipedia.org,
Exothermic welding, also known as exothermic bonding, thermite welding (TW), and thermit welding, is a welding process that employs molten metal to permanently join the conductors. The process employs an exothermic reaction of a thermite composition to heat the metal, and requires no external source of heat or current. The chemical reaction that produces the heat is an aluminothermic reaction between aluminium powder and a metal oxide.
4. Testing of Earth Resistance Value
4.1 Earth resistivity test to be conducted on-site and report to be submitted for consultant approval.
4.2 Grounds value separate earth electrode as per specification unless otherwise indicated in drawings.
4.3 Earth rod electrodes shall be installed as per approved shop drawings locations.
4.4 Minimum of 3600mm depth copper bond earth rod (each road 1200mm length x 3 Nose of rod) shall be provided with each down conductor and separately earth pits as indicated in drawings.
4.5 Check the connection(s) of earthing wire to earthing spike rod electrode.
4.6 On completion of the installation, the following measurement and / checks have to be made and the end result recorded in a checklist.
4.7 Each earth electrode and the earth have to be measured.
4.8 Two no’s of spike rod to be fixed for testing near-earth pit as follows the First rod to be fixed minimum distance 5000mm away from earth pit, second rod to be fixed minimum 10000mm away from earth pit.
4.9 3. No’s of testing wires to be connected to earth tester from earth pit and spike rods.
4.10 After connecting the testing wires measurement is to be observed.
4.11 Measure the resistance of the complete installation for earthing and lightning protection system and submit it for review to the Main contractor/consultant/client.
Exothermic welding & Accessories
6 Equipment & Tools
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7 Proposed Control Measures to Reduce the Risks
7.1 Material transportation will be done by 1.5/ 3 ton pickup at the site. Loading and offloading material (only limited quantity of material allowed to be used at site.). All materials will be stored in a covered storage area and ensured 24 hrs security arrangements. All lifting will be conducted by (Main con) in accordance with (Main con’s) lifting requirements.
7.2 All operatives involved in handling material will be undergone a manual handling training program prior to start along with DSTI.
7.3 All machinery involved for loading and unloading of material will ensure safety compliance prior to use i.e. competency, certifications, fitness, inspections, etc.
7.4 All necessary permits shall be obtained from (Main con) HSE Dept for Exothermic welding operation. All the safety measures to be followed as per the method statement such as competent welder, adequate welding equipment, prescribed PPEs, fire fighting equipment, fire watcher, access restriction, warning signage, bucket with sand, area barricading, etc. Copies of all certificates available on site.
7.5 Ensure authorized person(s) to store handle and issue the chemicals and hazardous substances at the site. Applications will be strictly in line with MSDS and COSHH Assessment. (dry flash point temperature 950 C°).
7.6 Appropriate personnel protective equipment such as welding apron, fire-resistant gloves, welding shield, chemical resistant gloves, eye protection, will be provided.
7.7 Hand tools and power tools: All hand tools and power tools (110 V) to be inspected prior to start.PAT tested and mark with current color code.
7.8 General safety precautions
7.8.1 Ensure close monitoring and supervision by competent personnel, continuous monitoring by HSE professionals.
7.8.2 Task briefing and regular toolbox talk to be conducted to all employees by the concerned supervisor prior to start.
7.8.3 Emergency response procedure to be communicated in the pre-task briefing.
7.8.4 Safe access and egress for a worksite to be maintained and housekeeping ensured.
7.8.5 User, storage, content to include checking and eliminating the potential of moisture contaminations.
7.8.6 Exclusion zone will be ensured.
7.8.6 Ensure the first aid, fire fighting, drinking water, restroom, eye washing, and other welfare facilities at the site.
7.8.7 Appropriate signage’s to be posted and housekeeping and frequent cleaning at all times.
7.8.8 Adequate lighting, supervision, and safety cover will be ensured if any task is on the extended hours.
7.8.9 Ensure the welfare arrangements at the site.