The role of robotics in the trenchless industry

The official definition of a robot is “a machine or device that operates automatically or by remote control,” yet this does not really define the information and functions that the robots in the Trenchless Technology industry provide to engineers from local water authorities, municipalities and other utility owners.

It can be argued that the first step towards what we know today as “˜robots’ was the use of tube cameras to inspect mainline sewers – CCTV inspection. This system of cleaning and winching the camera through the sewer was very labour intensive and, due to these manpower requirements, quite expensive. Despite this, the information gathered was invaluable in the asset management project.

The problem with the winch system was that it required an entry and exit manhole; to operate this system two access points were required. For example, laterals that connect from the property directly into the main sewer lack the appropriate access. The advent of the cable and drain rods pushing system facilitated these inspections. This was further developed by Pearpoint Limited of the UK (now part of SPX) when the conductors that transferred the camera image to the control screen were incorporated inside a semi rigid rod, removing the need for a separate cable and rod. Finally the advance in technology of CCDs that produce the image surpassed the use of tube cameras and monochrome pictures were replaced by colour.

The first camera-mounted robots – crawlers/tractors – provided completely new scope of possibilities. These robots enabled increased inspection distances, single entry point inspection and eventually “˜pan and tilt’, which allowed the inspection of laterals from the main sewer to the building. It was a major step for the industry. Whether they were “˜shaft driven’ or “˜chain driven’, the only limitation became the loss of picture quality over greater distances.

The risk of explosion created in sewers or confined spaces produced the next generation of robots. The advance in this particular industry gave rise to explosion proof systems, either by means of “˜flame paths’ or “˜inert gas-filled,’ the robots can now travel and inspect pipes that, 20 years ago, were uncharted territory.

All of this advancement had to be co-ordinated and the results assessed using a single system of examination.

In 1974, the Water Research Centre in Swindon, UK provided such a method of evaluation. The system of fault classification and fault severity is used worldwide in both normal sewer (OX20) and brick sewer (OX21). The classification of grading, 1 (good) to 5 (collapsed or near collapse), allows local water authority engineers, municipalities or other utility owners to set priorities in the next step of sewer robotics – sewer rehabilitation. So were CCTV inspection cameras the original robots? According to the definition, cameras with remote functions such as focus, iris and rotate functions, and crawler/tractors obviously qualify. They were and still are an extension of the human eye.

Robots in sewer rehabilitation

If CCTV inspection is an extension of the human eye, repair robots are an extension of the human hand. These types of robots are performing tasks remotely and the benefits they provide, either financially or solution wise, are incalculable. The introduction of Trenchless Technology gave local engineers a more cost effective and cost efficient method to maintain the sewer systems within their control. Especially pertinent in today’s financial situation, using trenchless solutions makes the sewer infrastructure rehabilitation budget stretch that little bit further. The old idea of “˜dig it and fill it’ is expensive and intrusive; in comparison non-disruptive, remote repair by robot is unobtrusive and inexpensive.

There are two main classes of rehabilitation robot, those that grind or cut and those that repair leaking joints or laterals.

Grinding or cutting robots are the teeth of the sewer rehabilitation industry, removing intruding laterals or re-opening the laterals of relined pipes can be done with ease. The fundamental question that arises is how the grinding/cutting can be achieved quickly and cost effectively. There are two main methods:

1. Air driven systems: air driven motors that are used in the grinding produce a good result in some materials, but not in all. The torque produced at the point of grinding/cutting can be considerably less than the alternative, hydraulic driven. The other problem, as most people are aware, is reliability and maintenance. The amount of debris and vibrations created during the process can cause slow and expensive repairs.
2. Hydraulic driven systems: the use of hydraulic methods has shown that the vibrations and debris have no effect on the reliability of the system. The torque produced at the point of grinding/cutting easily and quickly deals with any material. This makes the system more cost effective and efficient. Although the amount of investment required in owning such a system can be higher than air driven systems, the difference is soon recovered with the increase of productivity.

KATE-PMO AG of Freienbach, Switzerland, a leading manufacturer of hydraulic driven grinding/cutting robots for over 20 years, pioneered the use of this type of robot system and still has originally manufactured systems working in Germany today.

Lateral repairs

In 2004, an independent German organisation IKT (Institut für Unteridische Infrastruktur), together with 26 sewage network operators from different cities, assessed the different methods available for the repair of sewer pipe lateral connections. In order to assess the products capability of sealing internally and externally, the repairs ranged from standard damage to strong damage. A system of measurement was introduced:

  • Very good – 1.0 to 1.5
  • Deficient – 5.6 to 6.

Seven robotic systems were tested and comparatively evaluated. In these tests it was shown that the system of repair from KATE-PMO AG was the highest rated product. Using the lateral shield, more than one repair can be carried out in the sewer length at any one time. The shield can be adjusted to suit the angle of entry into the sewer making a perfect mould for the resin to bond to the pipe material.

Alternative robots in the sewer

The use of sewers to deploy cables is not a new idea; it was first pioneered by the French in Paris at the turn of the 1900s. Robots have been developed by companies, including KATE-PMO AG, to deploy fibre optic cables in sewers with diameters from 200 mm up to and including 700 mm. What is special about this system is the software that creates a map of the sewer line. Each joint, lateral or defect is measured and recorded. The position of the tubes is set by the clamps installed in the sewer length in order to avoid interfering with laterals and the primary use of transportation of waste material. More than 400,000 metres have been installed to date with minimum excavation, making it an environmentally friendly solution for telecommunication companies, disaster recovery situations and local authorities.

The Future

The future for robotics in sewers is vast, and the ever increasing market in Trenchless Technology will no doubt provide new advances in the design, manufacture and materials. Reliability and quality must be maintained in order to consolidate the trenchless industry in today’s market place.

Paul Heenan is the International Sales and Marketing Manager for KA-TE.

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