Work method statement for grounding and lightning arrestor

Srinivasan

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Sep 7, 2017
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work method statement for grounding and lightning arrestor

Activities (Work Scope)

Installation:
  • Install the approved material (Copper Rod, Copper Strip etc.) as shown on the approved working drawings in a manner as defined in the relevant documentation.
  • Copper rod / Copper strip used as grid & riser will be installed as per the drawings to form & complete the Earthing & lighting Protection System joined by means of brazing joints. Contour and wetting of filler will be visually inspected and will be as per the requirement to maintain the strength.
  • Earth electrodes will be installed by means of augers of suitable size.
  • Risers will be brought up. The top arrangement of the risers would be as per the drawings.
  • The entire arrangement of the test links connections would be encased in an inspection chamber formed in the screed concrete with GI Frames Cover.
  • All the Earth electrode will be directly welded with the required place. After the completion of the above activities the earth filling will be done.
Construction Equipment:
The following plant & machinery are envisaged for the construction activity: -

Fitter Tool Box
Welder Tool Box
Electrician Tool Box
Oxy-acetylene torch and gas cylinder
Earth tester

Material:
All materials used at site should confirm to requirements of environmental policy of the project. The following major material will be used for the installation of Earthing Grid

FOR CLEAN EARTH:
Copper Rod:
Copper rods of 20mm diameter will be used for grid as shown in the drawings. The copper will be of electrolytic grade as per specifications the material will be of electrolytic grade as per the specifications laid in IS 191 (Part V)-1980.

Copper Flat:
Flat sections of dimensions 30mm X 10mm will be used for runners and earth Bus as shown in the drawings. The material will be of electrolytic grade as per the specifications. The material will be of electrolytic grade as per the specifications as laid in IS919 (Part V)-1980.

Sub-Stations
Copper Rod:
Copper rods of 20mm diameter will be used as down rods as shown in the drawings. The copper will be of electrolytic grade as per specifications. The material will be of Electrolytic grade as per the specifications a laid in IS 191 (Part V)-1980.

Copper Flat:
Flat sections of dimensions 50mm X 8mm will be used for grid / risers as shown in the drawings. The material will be of electrolytic grade as per the specifications the material will be of electrolytic grads as per the specifications as laid in IS 191(Part V)-1980

Brazing Material (For both Clean Earth and SS):
The filler metal used for Brazing material will comply with IS-2927, clause 3.1, Table-3 (Classification – BACuP3). Filler metal rod will be of 3.5mm diameter.


Construction Procedure and Construction Method
  • Receiving of Material: materials will be unloaded and stored in a proper manner in the receiving store.
  • Material Conformance with Specifications: The materials used for the Earthing work will be as per the required specifications and the material shall confirm with the relevant standard.
  • Visual checks for damage: A preliminary checking prior to the starting of work will be done to assure that the material is free from all kinds of flaw/defects. In case of any defects/damages in material, the same would be replaced.
  • Storage Facilities: Stacking and storing of Copper Conductor at construction site will be done as per the requirement.
  • Temporary Storage: the sub conductor will set up a temporary store at/near the working site where the tools and accessories required for the Earthing work will be kept until the work gets completed. This will be done for the safety of tools and a solution to serve the purpose that the all tools are available as and when required. The temporary store would be set such that no hindrance is created for the other progress.
  • Corrective action: If any flaws/defects in copper material/workmanship are found, the same would be replaced redone.
  • Demarcation of Working area and layout: Area to be demarcated where earthing work and preparation prior to Earthing will be carried out.
  • Approvals Material/Site personnel: The material proposal will be submitted for the approval. Certificates for site Personnel such as welder, fitter etc. will be submitted for review.
  • House Keeping: the subcontractor will take care that no debris remains after completing the daily work related to earthing work. Care would be taken that the scrap/debris is disposed off to a proper place and tools are placed in the temporary store.
  • All necessary information available: The site personnel/subcontractor would be instructed so that the work is carried out according to the design /drawings. Information regarding changes in design/plan or schedule would be provide.
  • Correct tools available: Only appropriate tools to suit work undertaken would be used.


Installation method of plant/materials:

Fabrication of Earths Mats for Clean earth: Earth mats sections of 20mm diameter Cu rods will be fabricated in suitable size with provisions for jointing the same to next section. All the rod-to-rod laps will be joined by brazing.

Fabrication of earth Mats for SS: earth mat section of 50 X 8mm Cu strip will be fabricated in suitable size with provision for jointing the same to next section. All the strip to strip laps will be jointed by brazing.

Shifting and placement of Earth Mat Sections For Clean Earth: The above Earth Mat sections will be shifted from the fabrication yard to the actual locations and will be placed one by one as per lap provision for the next sections the earth mat will be placed 160mm below the bottom of base slab. Plain working area duly excavated 160mm below the bottom of the base slab will be provided by civil section before starting this activity. The location of pits/mat in respect of the grid would be marked with the help of the civil construction section. After the completion of earth mat PCC shall be done by civil section.

Shifting and placement of Earth Mat sections for Sub-Stations: The above Earth Mat sections will be shifted from the fabrication yard to the actual locations and will be placed one by one a per lap provision for the next sections the earth mat will be placed 340mm below the bottom of base slab. Plain working area duly excavated 340mm below the bottom of the base slab will be provided by civil section before starting this activity. The location of pits/mat in respect of the grid would be marked with the help of the civil construction section. After the completion of earth mat PCC shall be done by civil section.

Connection of Earth Mat Sections: The Earth Mat sections will be connected by means of brazing joints to from the required mat of size as per the approved drawings.

Installation of Earth Electrodes (Clean Earth): For installation of Earth Electrode (20mm diameter solid copper rods of 3000mm length) required bore-holes will be made by using augers of suitable size.

Installation of Earth Electrodes (SS): For Installation of Earth Electrodes (20mm diameter solid copper rods of 3000mm length) required bore-holes will be made by using augers of suitable size.

Installation of Risers: Risers from Earth Mat shall be of Copper tape with provision for link arrangement on top as shown in the drawing. From four locations of the mat four risers arrangement as shown in the drawing for connection with the links. These would be joined with grid by brazing and on the top with the earth buses through test links. The entire arrangement of the test link connection would be encased in an junction box.

EARTH PIT AND EARTH MAT CONNECTION:
For Clean Earth:
The entire earth electrode shall be directly welded/brazed with the earth mat.
For Sub Stations: The entire earth electrode shall be directly welded/brazed with the earth mat.

Commissioning:
  • All the installed Earthing material will be reconfirmed as per the drawing.
  • The Earth measurement test will be carried out on the site with the help of a Earth tester (Earth Megger) .
  • Resistance of individuals pits and total grid will be measured separately before connections of grids to pits.
  • Visual inspection shall be carried out for brazed joints may be reheated or redone.
  • Contour and wetting of filler will be visually inspected and will be as per the requirement to maintain the strength.
  • Balance Material: Balance Material to be kept at site the record to be kept in track of the quantity used daily and the quantity as whole.
  • Clearing of Site: After the full completion of laying of earth mat and testing, the scrap/debris/solid waste shall be collected and disposed of to an approved dumping site or pits.
Same is attached below in document format.
 

Attachments

Likes: Velavan. R