Tunnel Cable Installation System

THE MACHINERY

The purpose of the HLSM (Hydraulic Lifting and Snaking Machine) vehicle is to install electric power cables. The machine itself resembles a small train which pulls more than a kilometre of cable into place at a time on hundreds of small trolleys.

The machine was designed to address the following challenges with the current process of tunnel cable laying:

  • Reduce tension and subsequent damage to the cable
  • Increase safety across the complete installation process
  • Reduce project completion time
  • Increase efficiency in staffing levels required for projects
  • Reduce the need for specialised staff

The HLSM has proven itself in meeting the needs and requirements of the tunnel cable laying process whilst also performing within the restrictions that characterise such tasks.

STATISTICS SUMMARY

  • Locomotive is powered by a Perkins 3.152 diesel, 28KW engine
  • Maximimum cable laying speed is 2 kilometres per hour
  • The drawbar pulling capacity of the cable layer is up to 30 KN depending on floor conditions, whilst the maximum tensile load imposed on the cable during handling is only about 1 KN
  • It is estimated the machine reduces the required staff requirements from 35 people to 12 (based on the results of the Auckland project)
  • The cable trolley system involves a series of up to 420 small trolleys fixed at 2.5 metre intervals along a wire rope to support and transport the power cable.

SAFETY

The HLSM system addresses the fundamental safety challenges that occur with the underground cable laying process. It also provides additional advantages in its construction that enhance the safety of workers and equipment.

The machine itself boasts the following safety features:

  • The bi-directional operation means that the machine does not need to be turned 180 degrees once positioned in the tunnel.
  • The Diesel engine features environmental emission filters, tank baffles and marine non-spill fittings.
  • Fire suppression systems, with enclosures for both the engine and the hydraulic pumps, as well as fire extinguishers fitted to the vehicle.
  • Hydraulic braking
  • Guards and on bogey drives and trolley conveyer
  • Enclosures and dead man controls at both operator areas

Whilst the fully integrated system means that there are significant safety concerns addressed across the following areas:

  • Reduced manual handling of cabling for laying and positioning
  • Reduction of workers involved in the process, meaning less staff exposed to risks
  • Reduced tension on the high voltage power cable decreasing potential damage and possible accidents resulting from such damage
  • Intercom system between drivers which can also be interfaced to allow communication with all site workers

PROJECT SPECIFIC/INDIVIDUAL REQUIREMENTS

Tescorp worked effectively with both project partners who have to date successfully used the HLSM system for their respective projects, in addressing the issues and challenges that the specific tasks posed.

Additional specifics for projects would also be addressed in the design, construction and supply of the HLSM, including the toe/shoe unit, trolley system and turntable. Variables that need to be considered and addressed include: cable weight, lengths, conductor type, methods of dealing with thermal expansion, tunnel dimensions, guidance system employed and various other details. Because the HLSM is designed and manufactured for specific projects it is incomparable to other ‘off the shelf' systems that may be available - it is project specific and will produce individualised results.

EFFICENCY

One of the main advantages in adopting the HLSM for projects would be the projected efficiencies in both project completion time and labour requirements.

A) TIMELINESS

  • The HLSM has achieved a 12 hour completion time for a cable ‘pull and shoe' for a 700m length, so the actual job and project time can be completed in a timely fashion with the desired result.
  • The enhanced safety features also provide time saving in injury down time and damage repairs.

B) STAFF REQUIREMENTS

  • Reduced staffing numbers increases efficiencies with project recruitment time, training and of course wage expenses
  • There are also significant reductions in staff training time, as specific qualifications are not a requirement to operate the HLSM

TESTIMONIALS

As indicated 2 of the HLSMs have been developed and supplied thus far. One to Energex, Auckland, New Zealand who used it to assist in rebuilding the power supply system to the city following a dramatic blackout over 12 months prior. After successful installation of the high voltage cabling, Robert Jones of Energex Limited offered this note of thanks to Tescorp,

I would like to acknowledge the contribution your company made to ENERGEX's successful installation of 96 km of high voltage cables in Auckland's three metre diameter 9.2 km long cable tunnel...The quality of the equipment operating and maintenance manuals was commendable and proved invaluable during the project."

Robert Jones - Auckland Tunnel Project Manager and Construction Engineer (ENERGEX Limited)

It should also be noted that Robert, in further discussions with Tescorp Management noted there was not a single lost time injury and he was impressed with the time efficiency of the system in towing and shoeing a cable a day. Considering the demands of the environment they were working in, and the strict deadline they had for completion of the project, Robert was impressed with the machine and the job it did.