This method statement shall provide minimum guidelines to carry out the Installation and Testing of Grounding System underground & above ground. Main keywords for this article are Grounding Installation and Testing, Grounding Cable Installation, Underground Grounding Cable Installation, Grounding Connection Termination,Pit Installation.
GROUNDING INSTALLATION AND TESTING
(UNDERGROUND & ABOVEGROUND)
Grounding International Standard
NFPA 70 : National Electrical Code (NEC)
ANSI C2 : American National Standards Institute
NESC : National Electrical Safety Code
API RP 2003 : Protection against Ignition Arising out of Static, Lighting, and Stray Currents.
TOOLS AND EQUIPMENT
Tools and equipment needed should be in good condition and must be checked by competent person and respective supervisor prior to use in the plant. Third Party vehicle and equipment inspections and vehicle stickers required. Saudi Aramco certified where required. These Includes but not limited to :
- Welding Machine
- Common Hand Tools
- Chipping Tools (Hydraulic)
- Multi-meters
- Ground Resistance Tester
- Ladder
- Electric Powered Tools (Drill, Grinder)
- Thermite Welding Tools ( Carbon Blocks, charges & flint guns )
- Crimping Tools
- Boom Truck
- Heat Gun
- Cable cutter (ratchet or manual)
- Swivel
- Digging Bar
- Wheelbarrow
- Bulk Hammer
- Hand Held Radio
- Hack Saw
- Insulation Tape
Grounding Cable Installation
- Prior to installation works, above ground & underground grounding materials shall be inspected for possible factory defect or handling damages as per Typical Inspection Plan for Grounding and Bonding, SATIP, and recorded as per appropriate forms stipulated in the standards.
- Ensure that the materials to be used shall conform to SAES-P-111.
- Obtain As Built drawing of the concerned area (if necessary) and study the relationship with the new grounding requirements.
- Transfer sheet/release notice shall be duly accomplished per preceding activity from discipline to another to maintain the quality of work with respect to the required standard (refer to SAES-P-104 and SAES-P-111).
- Verify the layout of the equipment and/or devices that has to be connected to the grounding grid with respect to layout drawings following the detail drawings specified in the Approved for Construction drawings.
- Aboveground or underground grounding cable shall be bare copper conductor and/or insulated PVC sheathed copper conductor, colored green/yellow, depending on the design, installation requirements, grounding details, and in accordance with SAES-P-111, Sect. 5.
- Conductor used as grid conductors, equipment ground conductors, or bonding conductor in grounding systems shall be soft or annealed Copper.
- If larger than 35mm² (#2 AWG), it shall be stranded. Stranding of ground conductor shall comply with the stranding requirements of SAES-P-104. If used for connection of equipment to ground rods and ground grid, it shall be minimum of 25mm² (#4 AWG). Refer to SAES-P-111 section 5 sub section 5.1.
- Ground grid cables shall be connected to standard bus bar aboveground to where the aboveground cable continuations are connected. If an aboveground bus or loop is used for extending the supplementary electrode, this bus or loop shall have two connections to the supplementary electrode.
- Except otherwise noted, conduit, cable tray, or cable armor, shall not be relied on as the equipment grounding conductor and a bare or insulated copper conductor shall be installed in the same conduit, cable tray, cable or cord or shall otherwise accompany the power conductors. Regardless of whether this standard permits conduit, cable tray, or cable armor installation, it must meet NEC bonding and grounding requirement for such use. In hazardous locations, equipment grounding conductors that run in conduit or cable tray shall be insulated or enclosed within the jacket of a multi-conductor cable. Refer to SAES-P-111 section 9.
- Pull the grounding required for aboveground grounding cable through cable tray, PVC conduit or by approved grounding clip as per requirements up to where the cable is intentionally connected.
- For aboveground grounding cabling, PVC conduit and support with U-bolt shall be used for bonding to elevated equipment and piping.
- Provide proper bonding to metallic wire ways as approved and shall be connected to grounding bus bar that is to be continuously connected to grounding grid. Metallic cable trays shall be continuously electrically connected. Aluminum cable trays containing only circuits operated at, or below 50V to ground may be used as equipment grounding conductors provided that NEC requirements for such use are met. On other aluminum cable trays, a common equipment grounding conductor external to the cables in the tray may be used under the following conditions:
- This common conductor shall be sized in accordance with NEC table 250.122 for the largest power conductor in the tray, with a minimum size of 25mm² (#4 AWG).
- Connections shall be made between this common grounding conductor and other grounding conductors for intersecting or brand trays, and to extend the equipment grounding conductor beyond the tray.
- This common conductor (or the largest individual grounding conductor if more than one is installed) shall be bonded to each section of the cable tray system with a connector approved for a copper to aluminum connection.
- Cable tray shall be bonded to main grounding grid at each tray end.
- Bonding jumpers shall be installed on tray at each expansion connection plate and hinged fitting.
- RGS conduit for power cables shall also be bonded to grounded structure at each end.
- All metallic pipes on pipe racks shall be bonded to main grounding grid at each unit battery line. Grounding lug on pipes will be installed at fabrication shop by fabrication contractor.
- Dry-type lighting or building service transformers in substations, switchgear rooms, or in equipment rooms may be connected to a ground bus that is directly connected to the grid or other grounding electrode.
- Connect all equipment to grounding grid using insulated grounding cable following the indicated detail drawing. Three-phase electrical system shall be grounded at the neutral point of the wye-connected windings of the transformer or generators and connected as directly as possible to the grid or grounding electrode and be routed separately from equipment grounding connections. Refer to SAES-P-111 section 8.
- Above ground grounding installations shall be inspected ensuring that the cables are properly installed and supported as per SAES-P-111.
Underground Grounding Cable Installation
- Before commencing on grounding calbe laying/pulling underground, the following items shall be verified and inspected.
- Trenches and Duct bank shal be inspected and free of any foreign material or sharp edges.
- Sand bedding material to be used shall be as pe SAES-P-104 sec.10.
- Sand bags should be ready and placed before and after duct bank, corner trench and partitions.
- Underground cable shall be identified by the cable number stamped on the band which shall be of non-corrosive metal.
Grounding Connection Termination
- Ensure that the installed cables aboveground were properly installed, accepted and documented by the concerned QC inspector.
- Terminate grounding cables to its terminal using the approved connection as indicated in the detail drawing. Proper tools shall be used for the work. If bolt connection is indicated, ensure that the connection is appropriately tightened as required.
- For connection of aboveground grounding branch wire, approved compression connector shall be used in accordance with SAES-P-111, 5.4.
- Prior to welding connection or crimping, finalize location of joint by cleaning the portion involved together with the approved thermite molding to be used or by brazing as specified in the Approved for Construction drawings. Standard materials and tools shall be permitted as per SAES-P-111.
- Weld all connection including straight run joints, crossed joints, and end connection using cad weld connections and/or crimping type as indicated in the Approved for Construction drawings. Tools and dies to be used shall ensure tightness and continuity of the system. All cad welding connections shall be done using appropriate amounts of powder as per required quantity.
- Terminate grounding conductor inside grounding pit and connect to grounding electrode using cable lug tinned copper. Cable lug shall be coated with denso paste and wrapped with denso tape to prevent corrosion. Connections shall be cleaned to bright metal before make-up.
- Exact location of equipment and piping grounding lugs shall be confirmed at site and the grounding cable length shall be adjusted to suit the exact lug location.
- Install grounding bus neatly and safely. Stamp ground bar to provide identification following the required detailed drawings specified to its location with respect to the given layout as per Approved for Construction drawing.
- In accordance with NEC as supplemented by SAES-P-104.
- By thermite welding sub-contractor.
- To structural steel using compression type connector bolted to bare steel, by thermite welding, or by other approved means.
- Connect ground bonds comprising a flexible connection with compression type cable lugs to bond all steel platforms, operating floor, ladders, handrails, structural steel work, etc., which does not have a solidity welded path to a main structure/or grounding grid. For grounding of steel structure refer to SAES-P-111 section 9, subsection 9.8.
- Termination of armoured cables should be effectively clamped at termination point and bonded to ground. Single core cables, installed in either trefoil or flat formation shall be bonded strictly in accordance with the detailed drawings. Cable shall be terminated and identified in a manner specifically indicated in the drawing. Refer to SAES-P-104, subsection 5.10 and 5.11.
- Equipment Grounding: Check the status of the concrete foundations and embedded steel bars. Turnover report for concrete foundation shall be provided by.
- Expedite steel materials intended for equipment grounding supports utilizing boom truck from lay down yard to job site.
- Excavation works for branch trench shall be based on approved drawings. Thermal sand bedding, clearing, watering, compaction and thickness of sand shall be per standard and approved.
- Equipment grounding shall be installed properly conforming to the approved grounding installation details and in accordance with SAES-P-111 section 9 and section 12.
- If in case equipment grounding medium voltage cable was used, conduct Hi potential test (voltage pressure) to complete the requirements.
- Equipment grounding initial testing are as follows: Resistance test and Insulation test.
Grounding Electrode, Well Assembly and Grounding Pit Installation
- Verify the layout of the required grounding pit/grounding electrode as indicated in the layout drawings as per latest issued drawings. Location shall consider the nearby structure, and/or equipment affected. Ground rod and ground well assembly shall be carefully reviewed. Installation shall conform to the construction plan layout and drawing and to the given grounding installation details as well.
- Install driving stud to ground rod before driving it manually to the ground surface. Ground rods to be driven shall be checked for proper size, depth and position as per latest issued Approved for Construction drawing.
- Driving cap shall be used at all times for safety installation of grounding electrodes and to prevent mechanical damage to the material. Installation of grounding electrodes shall conform to SAES-P-111 section 7.
- Ground rod shall have a minimum length of 2.4 m as per SAES-P-111 Sect. 5 item “c”. Joint rods are permitted but each joint be at least 2.4 m. long. Grounding pit shall be installed.
- Ground wells or electrodes shall not be located under roadways, storage area or any other area where physical damage may occur.
- Verify integrity of the connections and installation of grounding electrode system for plant and equipment safety ground and instrument reference grounds.
Main keywords for this article are Grounding Installation and Testing, Grounding Cable Installation, Underground Grounding Cable Installation, Grounding Connection Termination,Pit Installation.