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Installation of OFC Ducts by Trenchless Techniques By HDD

➤ The ducts in the intra-city fibre routes (including such inter-city routes that are common with intra-city routes) shall be installed by Horizontal Directional Drilling method unless approved by the Company in writing for installation by other methods.

 The Contractor shall mobilize equipment suitable to install the ducts up to required / specified depth below ground in all types of soils.

 All concerned authorities (water, oil and gas pipeline operators, telecom operators, power companies etc.) who may have their underground utilities in the area shall be informed well in advance and as built drawings obtained to ensure proper planning of HDD operation and drilling profile.

 Cross pits shall be made across approved duct alignment to verify information about existing underground utilities/facilities as provided by authorities having jurisdiction over the area and also to ascertain type of soil for safe working of HDD equipment.

Duct Installation Specifications

 Unless specified and /or agreed in writing by Company, the duct for intra-city networks shall be installed at a specified depth below ground except at entry and exit areas. The minimum depth at entry and exit pits shall be 1.2m for intra-city networks.

 The installation of ducts by HDD along inter-city routes (except those in common with intra-city routes) shall be at the same depth as specified for inter-city ducts installation by open-cut (i.e. 1.65m) or as per requirements of the authorities(e.g. in case of NH/SH/Railway/canal crossing etc.).

 Entry and exit pits shall be dug at both ends of the segment which shall later on become either a location for man-hole/hand-hole in case of intra-city routes or for installing duct couplers in case of inter-city routes. For inter-city routes MH/HH locations shall be as per issued for construction drawings only.

 The drilled hole profile between entry and exit pits (except transition areas) shall be as straight as possible. The final HDD profile shall become part of as-built documents.
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 The hole made by HDD equipment shall be of adequate diameter to allow pulling all the ducts in one go as a bundle. The ducts in the bundle shall be properly bundled using suitable spacers and tied together during pulling. The capacity of pulling equipment shall be at least 1.5 times of theoretical calculated pull force.

 The Contractor shall submit a detailed HDD procedure for review/approval of Company. The procedure shall include at least following information:

(A)  Proposed locations, size and depth of entry and exit pits.
(B)  Proposed number of holes, hole diameter and hole profile for pulling HDPE duct(s).
(C)  Proposed HDD machine details along with drilling direction control/steering system                details.
(D)  Pulling load calculations and details of pulling equipment (pull head, winch, rope, etc.).
(E)  Method of safe disposal of bentonite slurry.
(F)  Follow the drawing provided the company.

 Upon obtaining approval of procedure, the Contractor shall prepare site by marking route and digging entry/exit pits at predetermined locations and drill the hole of required size for pulling the ducts through. Once the hole is ready, required number of ducts, already de-coiled and spread on the ground, shall be connected to a pulling head and pulled through the hole. Suitable swivel joint shall be used during pulling to prevent twisting of ducts during pulling.

 The drilling machine and pulling equipment shall be removed and moved to new locations. The pits shall be replaced with man-hole/hand-hole for termination of ducts and later blowing of cable and remaining area backfilled and restored to a conditions agreed to with the authorities having jurisdiction over the area. Bentonite slurry, if used, shall be recovered from the pits and disposed-off in a safe and environmental friendly manner and at locations approved by Authorities.

 The Contractor may have to deploy more than one set of HDD equipment to achieve required lay rate demanded by contract schedule.

  HDD shot must be HH to HH or MH/MH. Don't use couplers between the water/rail/culvert etc. crossing.

  HDD shot not considerable less than 100 Mtr. if crossing is upto 150-200mtr.