Robotics for Process Tank Cleaning

We are interested in robotics systems that can clean our water reclamation plant process tanks without requiring human entry. We seek solutions that can potentially eliminate manual labour from the tank cleaning process, thus eliminating any safety risk associated with manual labour.

The robotics system shall be able to perform the following tasks:

1. Dislodge sludge from tank surfaces, including walls, floors, and scrappers. The proposed cleaning method shall match or exceed the cleaning performance of existing water-jetting methods.
   
   
2. Remotely controlled to navigate the process tank, in order to effectively clean the interior surfaces of the tank without damaging the surfaces and tank components.
   
   
3. Dispose sludge via the sludge hopper or other mechanisms that remove the sludge from the process tank.
   
   
4. Document cleaning outcomes as evidence for the completion of works.
   
   
5. With the new robotics system, the maintenance process for the process tanks could be reviewed and redesigned for more frequent but less intensive cleaning, after considering the feasibility and viability of the robotic cleaning process.
   
   

For the pilot project, we will first focus on the cleaning of primary sedimentation tanks. We plan to scale this method for other process tanks such secondary sedimentation tanks and bioreactors basin. There are more than 60 process tanks within one plant that could benefit from the solution.

The proposed solution should be able to accommodate the following developments in the future:

1. Inspect tank to assess structural and mechanical integrity of process tank, in order to support planning of maintenance and repair works
   
   
2. Autonomous navigation and cleaning of the process tank to lower the skill requirement to operate the solution and improve cleaning consistency.
   
   

Besides robotics systems, we are open to hard automation solutions that are cost-effective, easy to maintain and scalable across the process tanks.

A. System Requirements

1. The robot shall be able to transverse wet and uneven terrains, including a sludge layer of up to 0.3m, and overcome large obstacles such as scrappers with a height of 0.3m.
   
   
2. The robot shall minimally be able to travel 15 m from the tank entrance while avoiding any potential entanglement with the components inside the tank.
   
   
3. The sedimentation tanks can be divided to two decks, a top deck and bottom deck. The robot should ideally be not more than 0.8m x 0.8m in size to fit through the tank submarine door to access the bottom deck and/or access hatch to access the top deck.
   
   
4. The robot shall be portable and weigh less than 20kg so that it can be carried by one person.
   
   
5. The robot shall minimally be rated IP67 to withstand the tank condition and be intrinsically safe.
   
   
6. The interior of the process tank is dimly lit. The robot shall be equipped with adequate illumination devices to monitor the cleaning process.
   
   
7. The robot shall include detection systems to prevent falls over the edge of the deck and holes within the deck.
   
   

B. Cleaning and Handling of Sludge

1. Slurry-like substances that could harden over time to form encrustations shall be cleaned.
   
   
2. Stronger cleaning chemicals, e.g.: sodium hypochlorite can be considered for use to improve cleaning effectiveness.
   
   
3. For the cleaning of walls, the cleaning method should ideally be able to reach up to 8m in height. Most of the walls found on the top and bottom deck have a height of 4m.
   
   
4. For water-jetting methods, the robot should be equipped with counterweights to cope with opposing force generated.
   
   
5. The cleaning method shall be suitable for a low oxygen environment.

A. Tank Cleaning Maintenance Work. 

John is responsible for cleaning the Sedimentation Tanks at Changi Water Reclamation Plant on a monthly basis, where each tank is typically cleaned once every 4-6 months. Unfortunately, this task exposes John to hazardous conditions such as confined spaces and working at heights. To address this issue, robotic solutions can be implemented. By using a remotely controlled robot to clean the tank, John can minimize his need to enter the tank himself and human entry into the tanks is only required for the deployment and retrieval of the robot. This approach significantly reduces the risks associated with the hazardous conditions, creating a safer working environment for John and his colleagues.

By the end of the pilot, the project should aim to develop a site-tested prototype that can effectively and safely clean at least one type of process tank found in the water reclamation plant, without requiring human entry into the tank. A redesigned cleaning operation plan as well as a method to properly dispose loose sludge should also be established. After each deployment, a report documenting the cleaned tank is generated.

The  pilot project is to be completed within a period of 18 months. Below are the suggested project scope and timeline:

Below is a guide for the timeline and activities to be included in your proposal. Please note that the timeline and activities may vary depending on the type and maturity of the technology.

1. Identify and validate user and site requirements – 1 month
   
   
2. Build and customise prototype – 1 - 4 months
   
   
3. Solution deployment and iterations to successfully perform cleaning operation for at least one primary sedimentation tank. – 5 – 12 months
   
   
4. Conduct techno-economic analysis and finalise reports – 1 month
   
   

If the pilot is successful, PUB would be interested to deploy the solution through a service model  where the equipment is owned, operated, and maintained by the company.