We all use water – Earth’s most precious resource
Industries, municipalities, and all power generation facilities other than wind and solar utilize water in the manufacture of goods, power generation or as a consumable item either directly for potable use or as a component in a manufactured product. The design and maintenance of the infrastructure for the collection and distribution of water is driven by greater environmental awareness, worker safety requirements and stricter health and safety protocols. These driving forces have improved today’s working environment often by leveraging modern robotic or remote systems.
Material accumulation in conveyance structures
Raw water drawn from lakes, rivers and some wells generally brings along particulate matter as suspended material at a minimum up to logs and other debris. Larger items are typically prevented from entering a system by using screens, trash racks or other barriers, but the smaller particulate matter and aquatic life generally passed through these larger barriers and enters the water conveyance system. Pipes, tunnels, aqueducts and open flow channels are designed to have a certain cross-section to provide an adequate flow and water supply to the end user. As particulate matter settles out or otherwise accumulates in these conveyance structures, the cross-section diminishes and restricts the delivery of water. Also, some aquatic species, in particular, zebra and quagga mussels, will attach to the walls and linings, growing into a mat of shells with flowing water bringing them their food. The layers of mussels can decrease the cross-sectional area but do tend to slough off after a few layers have built up and the bottom ones die off. This leads to another problem in that the remaining shells do not degrade and can accumulate to significant levels in a system that is not maintained, eventually blocking it off.
Apart from reduced cross-sectional area, some sediments and even the mussels can create a micro-environment at the surface of the structure that is detrimental, specifically to the integrity of metal pipe. Anaerobic corrosion, or corrosion that occurs where there is a lack of oxygen, is a common problem where certain bacteria and mussels create an acidic environment that leads to corrosion of the base metal. Even concrete structures are not immune to deterioration. Unless the concrete has been specifically designed to resist sulphate attack, H2S deterioration of concrete can lead to premature failures, delamination from the reinforcing steel and loss of the reinforcement strength.
Maintenance of integrity and restoration of capacity
Regular inspection of water conveyance structures helps determine their condition for their intended use and remaining lifespan. Using the condition of an asset as part of a maintenance regime is called Condition Based Asset Management. This is replacing the former practice of stipulating certain actions at prescribed intervals, regardless of the condition of the asset.
Cleaning the asset in order to inspect it not only restores the original cross-section for design capacity water flow, it also allows the owners to see the condition of the substrate to verify if it is in good condition and can continue to function without intervention. Where anomalies are found, budgets can be prepared in advance of a failure so that pro-active measures can be taken to prevent an expensive unplanned outage.
Accessing the system
Many components of a water conveyance system limit access by personnel primarily by the nature of the system – they are filled with water. De-watering means that either an alternate supply is needed for the downstream activity or that it needs to be put on hold while the system is taken out of service. If the system remains watered up, then divers may be able to enter the system, taking into account the special precautions needed for conducting a “penetration dive” into a confined space and the appropriate isolation of risks using a formal lock-out:tag-out (LOTO) procedure. Other situations arise where the problem area is inaccessible to personnel; it is too far from an access point, too deep (submerged intakes and pipelines) or in an isolated area that is too small for personnel to safely access.
The costs of creating access or mitigating the risks for manned entry may cancel or delay the inspection and maintenance operation. If that happens, risk is now transferred to the asset since its condition remains unknown or essential maintenance is not performed, both of which would lead to unexpected failure or compromise of the system. However, by utilizing a means of doing this work remotely using robotic equipment, risk to personnel is eliminated and the activities of critical inspection, repair and maintenance can be performed.
ASI developed ROSEbud™ as a bespoke solution for a nuclear power client that required cleaning of a fully submerged water supply duct. Divers could not be used since this duct supplied a set of service water pumps had to remain operational and could not be isolated nor did they have an alternative water source for these pumps. They could not simply flush the conduit out because the downstream processes would not tolerate water laden with sediment; in fact, the client stipulated that no extra turbidity could be generated in the cleaning process.
ASI reviewed the types of remotely controlled vehicles (ROV) already available on the market, with the consideration of modifying one specific to this project. When no piece of equipment was identified that met all of the requirements, ASI’s team of engineers designed and fabricated a new system from the ground up.
The design criteria was that it would fit through a standard access hole, would be modular in configuration and not a one-off, project specific design, and that it would have additional capabilities to accommodate different project needs. This award-winning design is hydraulically powered to provide high torque capabilities to its skid steer configuration and operates using fibre optic telemetry. Even though the system presently operates with 500 ft (150 metres) of umbilical, fibre optic systems allow for high capacity and high speed data transfer for remote control and relay of sensor information. It is also immune to electrical noise so that the camera and other sensor images are clear and undistorted. ASI also built in expansion capabilities to the hydraulic system for expansion of the mechanical capabilities.
A 2-inch trash pump is an integral part of the machine. Suction at the vehicle is through an auger arrangement on the front of the machine. This auger can be raised and lowered to help remove larger pile of material rather than simply dig underneath the deposit. Cameras and lights are standard on the machine to assist the operator with the cleaning process. A small sonar is normally mounted on top of the machine to help the operator with positioning the vehicle with respect to its surroundings that may be outside the camera’s field of view.
The modular nature of the vehicle has allowed ASI to integrate a larger 4-inch trash pump directly onto the vehicle for basic sand removal from an intake pipe. Where higher production rates were required, ROSEbudTM was used to simply transport the suction head of 6-inch and a 10-inch pump around a pump well to remove stones and larger debris.
The vehicle has also been used as a heavy inspection vehicle in very high flow areas. Additional sonar systems were added, the spare hydraulic ports were used for additional actuators and the addition of an HD camera were modifications that were easily completed a few days. In addition to cleaning and inspection work, ROSEbudTM has also been used as part of a program that required the installation of a plug to isolate one of several pumps. Apart from the one pump that had to be replaced, the other pumps had to remain online, and since the pumps had a common water supply line, a means of isolating the one pump was needed. ROSEbudTM was used to insert and monitor a pipe plug at the intake of the one pump, allowing that pump to be removed, serviced and reinstalled while all of the other pumps remained on line. ASI’s technicians then used ROSEbudTM to remove the plug so the pump could be put back into service.
ROSEbudTM has proven to be a key asset for ASI and its client base. It is used for regular maintenance cleaning of the same water duct that it was initially designed for, as well cleaning projects for many other clients. Removal of sediment, debris and contaminated waste from pump wells, small containment ponds and reservoirs are the growing list of applications for ROSEbudTM.
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