The Drainage Services Department (DSD) has always endeavoured to apply innovative technologies in its daily operation and maintenance work, so as to enhance work efficiency and site safety. For example, in the undergoing "Rehabilitation of Trunk Sewers in Tuen Mun", three robots – "Lung Mun Three Brothers" – are used to assist in desilting and rehabilitation of sewers. This time, I have invited a colleague from the DSD to talk about the details.

Early rehabilitation of pipes as a precaution

The DSD manages over 4 700 km of underground stormwater drains and sewers, some of which have been in use for decades, suffering from a certain degree of damage and depreciation. As a precaution, early rehabilitation is required to reduce the risk of collapse and ensure smooth operation.

The Rehabilitation of Trunk Sewers in Tuen Mun commenced in December 2018, which includes the rehabilitation of about 4.2 km of sewage box culverts at Tin Hau Road and Lung Mun Road. During the construction period, the entire section of the trunk sewers remains in normal operation 24 hours a day. The DSD's Engineer (Project Management), Mr KONG Hiu-lam, Raymond, says that to meet the unique working environment and challenges of the project and to enhance work efficiency, the department and the contractor have collaborated to develop three robots, nicknamed the "Lung Mun Three Brothers", to help desilt and rehabilitate the sewers.

Lung Mun I

In desilting a box culvert, the project team will first lift the Lung Mun I robot safely into the culvert, then shovel the silt built-up at the bottom, and use the lifting device on the shaft to carry the silt to the ground level for disposal.

Lung Mun II

However, when there are many obstructions such as stones, spalled concrete, rebar, etc., in the silt at the bottom of the culvert, or when desilting work has to be carried out deeper than 150 metres into the trunk sewer, the project team will have to use the Lung Mun II robot, whose bucket can pick up the silt and place it in a hydraulic lift bucket at the top for transport to the ground level. Lung Mun II can reach up to 250 metres into the box culvert, making it suitable for situations where only one shaft entrance is allowed at ground level, which is more flexible than the previous practice of having to dig a pair of shaft entrance and exit for desilting.

Lung Mun III

Lung Mun III’s function is pipe installation, particularly in situations where the curved and irregular drainage pipes make it infeasible to use pipe jacking, which is the traditional way of pushing in a pipe by pushing with another pipe. Before designing the length and curvature of each Glassfibre reinforced plastic (GRP) liner with BIM technology to fit the actual situation in the box culvert, the project team will first identify the curvature changes of the existing box culvert using 3D laser scanning technology. When the specially made GRP liner is ready, Lung Mun III can directly push it into the box culvert for assembly.

Real-time cameras for monitoring and control

One of the challenges of the project, as Mr Raymond KONG tells us, is that the work has to be conducted in sewers that are in use 24 hours a day, with very strong current and very high water level during the day. Various types of obstructions in the silt built-up at the bottom of the box culvert also make the works more difficult. However, technicians can grasp the situation inside the box culverts using real-time surveillance monitors at the ground level and control the three robots to conduct desilting and pipe installation.

Reducing the number of shafts necessary

Most of the box culverts in need of repairs were located under a very busy road – Lung Mun Road, which is the main road for Tuen Mun residents to travel to and from the urban area. In order to reduce the impact on the traffic on Lung Mun Road, the project team tried its best to reduce the number of shafts on the busy sections. The distance between the shafts was extended to nearly 300 metres from the original interval of about 100 to 150 metres. As the robots can go into the culvert for as far as 250 metres, the project team can work remotely, resulting in improved work efficiency and lowered safety risks during construction.

Extending the application to other projects

Looking ahead, the DSD will extend the use of Lung Mun Three Brothers to other rehabilitation works of trunk sewers and stormwater drains, as well as desilting of box culverts. I am delighted that works departments have always kept an innovative mind and made constant improvement. Their proactive application of innovative technologies to enhance productivity and performance will give all of us a better living environment.

Fighting the virus together

Meanwhile, under the onslaught of the fifth wave of the epidemic, there is a continuous increase in the number of cases involving mutant strains that carry higher transmissibility. I appeal to you to continue to comply with social distancing measures to protect yourselves and others, go out as little as possible and maintain better personal and environmental hygiene to lower your risk of getting infected with Covid-19. The Development Bureau and the departments under its purview will, as always, keep up our commitment and provide professional services to comply with and support all the anti-epidemic measures. We will do our part for the well-being of the public. I have no doubt that as long as we stay united and work together, we can definitely win the fight against the epidemic.