First of all, you need to construct and complete a concrete slab. When that is done, a Mechanical Electrical Plumbing (MEP) clearance needs to be submitted to the subcontractor, to enable them to start fixing the cable tray, ladder, trunking, and other fittings.
The clearance should be sent to the MEP subcontractor or department (for in-house installation) as the case may be by the quality engineer.
Before beginning installation, be sure that the method statement for installation of cable tray, trunking, and accessories is approved by the project and construction manager before the consultant also approves.
Implementation of the method statement for installation of cable trays, ladders, and accessories is required for quality control of MEP.
Method Statement for the Installation of Cable Tray, Trunking, and Accessories
This method statement for the Installation of Cable Tray, Trunking, and Accessories shows and explains the procedure must be followed to install the cable tray and accessories to comply with the specification and scope as well as to achieve the requirements of the project.
The purpose of establishing the method statement and procedures for the Installation of G.I. Cable Tray, Ladder, and Trunking System for building MEP services.
• MEP Specification – Galvanized Steel Tray and Accessories Section 07770
• Material Submittal
• Shop Drawing
• Cable tray
• Cable ladder
• Trunking and accessories
• Galvanizing paint
• Project Manager
• Construction Manager
• Project Engineer
• Site Engineer
6. Equipment and Tools
• Scaffolding/Mobile scaffold
• Spirit Level
• Drilling Machine
• Grinding Machine
• Power tools
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7.1 Installation of Cable Tray, Ladder, and Accessories
7.1.1. To ensure that the materials and documentation necessary are of the quality reviewed by the client, the Construction department should be sure to go through them.
7.1.2. The area and assets must be examined to ensure that they are in good shape and that construction can be safely carried out before any construction activity can start.
7.1.3. Materials needed for the installation of cable tray should be delivered to the site ahead of time. They should be handled with care and the right equipment should be used to lift the materials eg crane. Note that only materials that are needed for the installation should be moved to the site and those not needed at the moment should be kept aside safely and in order, to enable adequate working space.
7.1.4. When bringing down materials, they should be handled with care and lowered carefully to the ground. They should not be dropped.
7.1.5. Make sure that it is the appropriate quality of cable tray, ladder, and accessories that are delivered for installation.
7.1.6. The location of hangers and supports should be carefully marked to fit the original specifications as approved.
7.1.7. Required sizes of holes should be marked and drilled appropriately using a drilling machine.
7.1.8. The threaded rod should be fixed carefully into the anchor using clamping tools for a balance n smooth twist. The threaded rod should be of the required thickness and length. Sizes should be as approved in the drawing. It should be done in such a way as to avoid damage to the threaded rod.
7.1.9. When that is done, a washer should be inserted into it. The washer should also be of the required size and quality. It should be fixed properly and the nut fastened tight to ensure that the threaded rod is strong and able to bear load.
7.1.10. where there is a need for support to be attached to structural metalwork, devices not requiring drilling or welding should be used. Instead, the support should be fixed using beam clamps or other suitable devices.
7.1.11. Next, the hanger, hanging support, cable tray bracket, and ladder should be trimmed to the required size, and galvanizing paint should be applied on the edges.
7.1.12. Ensure that the ladder and tray, dimension and elevation, and other fittings are properly leveled and that they are coordinated to the other services n fixtures.
7.1.13. When sufficient numbers of hangers, support, and brackets are fixed, the ladder/ tray shall be installed in position in accordance with the manufacturer’s standards and specifications.
7.1.14. The tray and ladder size should be as specified in shop drawings and other approved regulations.
7.1.15. At every maximum of 1200 mm horizontally and 1500 vertically supports should be installed.
7.1.16. Ensure that the supports are firm enough and do not deflect when fully loaded pass the specified midspan.
7.1.17. The maximum deflection should be l/100 for length and w/20 for width for cable ladder and trays made to BS EN 61537. This is according to load test measurements
7.1.18. At the safe working load for beams, cantilevers and hangers made to BS EN 61537 the maximum deflection is l/20.
7.1.19. The maximum allowable deflection is L/200 for beams & L/180 for cantilevers made to BS EN 61537.
7.1.20. Any cutting on the cable tray to be done along the solid area and not across the perforation of the cable tray. Burrs need to be removed and cuts need to be protected with anti-rust galvanized paint. Where all cut sections are available, they should be free from sharp edges and jointed using fish-plates with bolts and nuts.
7.1.21. fitting and supports to be used should be in accordance with the manufacturer’s specifications in the installation of trays and trunking.
7.1.22. Accessories for a change of direction /elevation must also fit approved drawings. Where necessary, additional support can be added.
7.1.23. At all joints and fittings, continuity strips should be fixed and the bolts need to be tightly fixed. At each bar, a separate cable tray or ladders should be installed.
7.1.24. If the conductors carried by trays or ladders are of varying systems, the ELV and data processing or different insulation, the cable ladder or trays should be separate. Use insulating barriers where it is necessary. However, approval from the engineer is required.
7.1.25. It is necessary that a dedicated cable tray/trunking for communication cabling should be installed.
7.1.26. A very strong ladder rack should be used for all heating ventilation cables within the building substation.
7.1.27. For shaft cable trays and ladders that are vertical, all supports and fixings should be done as approved.
7.1.28. Where is it necessary, provisions for flexible expansion joints/connectors shall be provided in tray runs.
7.1.29. Frame size wall structure sleeves to be provided in cable tray/ladder and fire stopping sealant to be utilized for shutting the openings at wall space and slabs. Seal penetrations through fire and smoke barriers as stated in the specs.
7.1.30. Do not install Cable trays & ladders in lengths below water/sewage pipes.
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7.2 Procedure for installing GI Trunking
7.2.1. Position for support channels or brackets should be marked in line with shop drawing.
7.2.2. At regular intervals, trunking shall be fixed as specified below.
Trunking Size maximum Distance
• Up to 50 mm x 50 mm – 900 mm
• Up to 75 mm x 75 mm – 1200 mm
• Up to 150 mm x 150 mm – 1500mm
• Larger than 150 mm x 150 mm – 1800 mm
7.2.3. As always, the manufacturer’s instructions and other specifications should be diligently followed in Installations.
7.2.4. Group parallel runs of trunking should be supported together where it is possible.
7.2.5. The support channel should be installed according to the specifications of the shop drawing. There is a need to grind and file all cut sections and galvanizing paint should be applied. This is to remove sharp edges and prevent rust.
7.2.6. Insulated tie-off studs should be used to support the weight of cables for vertical sections of trunking over 900mm long.
7.2.7. The trunking should be treated like the support channels above. However red oxide paint should be used before a final code of the galvanizing paint is used.
7.2.8. There should be a visual inspection of the inside of the trunking after installation. This is to be sure that there are no sharp edges that could cause damage to the cables during installment.
7.2.9. Changes in direction, elevation and connections should be made in accordance with the required specifications.
7.2.10. It is required that where ever the trunking passes through firewall openings, an approved fire-stopping sealant compound shall be used.
7.2.11. When the installation cable tray is completed, covers should be fixed. Where trunking runs underground, Install trunking covers. The area should be open when debris falls.
7.2.12. The cover of trunking should be accessible and removable through the front.
7.2.13. Termination trunking runs shall be mechanically and electrically continuous throughout its length.
7.2.14. Flanges shall be used to make connections to the boards. This is to allow full trunking capacity.
7.2.15. Segregation of the various services should be made by providing different compartments in the trimmings and fittings.
7.2.16. Where necessary, movable expansion joints should be provided for trunking runs. This should be according to specifications.
7.2.17. The width of the Cable Tray/trunking/ladder should have sufficient width to take the cable without crowding and shall allow for future 25% space. The cables should not be stacked together.
7.2.18. Sharp edges or other things in cable trays, trunking, and a ladder that are capable of damaging the insulation or cable sheaths should be avoided. All the accessories shall be factory-made.
7.2.19. For adequate space for cable installation and maintenance, sufficient space shall be provided and maintained above the cable tray, ladder and trunking.
7.2.20. All materials should meet the required specifications. The quality control engineer and site supervisor should ensure that this is strictly adhered to.
7.2.21. Work inspection report (IR) for installation of cable tray and trunking shall be submitted to the consultant after the complete installation.
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8. Safety for Installation of Cable Tray and Trunking
8.1. The GI Cable Tray, Ladder, Trunking, and accessories are to be transported safely by 3-ton Truck to the site. All machinery used should not be more than 10 years old from the manufacturing date. The site speed limit is 20 km/h and all traffic rules should be followed.
8.2. The subcontractor for installation of cable tray and trunking including accessories will monitor all loading and offloading at the site, lifting should be done carefully using the proper required instruments. Safety measures should be carefully followed.
8.3. All loading and offloading will be conducted by the Main contractor in accordance with the approved method statement for loading and off-loading. He should employ the service of other necessary agents the crane operator. He is to provide all the necessary equipment and also that the lift permit is done.
8.4. Materials should be stored according to a specification which is the maximum 1.5m height from the ground. Suitable support should be provided. The storage should be done in a designated area and proper covering should be provided.
8.5. Employees should be properly trained and that they are knowledgeable about safety precautions and other emergency procedures before they are allowed into the site. This is to be done by the subcontractor.
8.6. Job Safety Analysis and PTB are required to be carried out daily by the engineer and supervisor to ensure safety before work begins.
8.7. Health and safety commission officers should train all operatives engaged in the installation on manual handling and should follow the main contractor working at height safety procedures.
8.8. Ensure that all tools and equipment are thoroughly inspected every three months before they are used to ensure they are in proper working conditions. power tools must be 110 V with an industrial socket and double insulated cables. Colour coding should be maintained as are specified.