Water Intake Maintenance 101 | Using an Underwater Drone
What is Hydroelectric Power?Hydroelectric power is one of the oldest sources of energy for producing mechanical and electrical energy and up until 2019, it was the largest source of total annual U.S. renewable electricity generation.
A typical hydroelectric plant is a system with three parts: a power plant where the electricity is produced, a dam that can be opened or closed to control water flow, and a reservoir where water is stored. The water behind the dam flows through an intake and pushes against blades in a turbine, causing them to turn. The turbine spins a generator to produce electricity. The electricity can be transported through long-distance electric lines to homes, factories, and businesses.
Consistent inspection and subsequent maintenance of hydroelectric plants is imperative for safe, efficient and effective operation, however there are risks involved in inspection - particularly for underwater components.
What is an Underwater Dam Intake?
Humans have a long history of using the force and power of water running in streams and rivers to produce mechanical energy. Hydroelectric dams allow people to take advantage and harness all of this power. These complicated structures contain various components and structures that may vary to suit the water source. Despite their differences the primary goal of hydroelectric dams is to collect water, run that water through a turbine to turn the turbine and generate energy, then deliver that water out the other side. To actually move water through the turbine it first goes through a pipe, or penstock, which then drives the water through the turbine blades to actually spin those blades to produce electricity.
A water intake is an integral part of power generation and is directly responsible for the water flow efficiency coming into the dam from a stream, river, lake or reservoir. The water intake is right at the front of the penstock where water enters the dam. Water intake gates and screens protect vital components within the dam such as the turbines, pumps, and pipes from damage which can be caused by debris, sediment, invasive species, fish, and ice. In order for hydro-electric dams to generate power at the highest capacity, each aspect of the system requires periodic inspection and maintenance
Why is Water Intake Maintenance Dangerous for Divers?While water intake maintenance is absolutely necessary for safe and efficient dam operation, inspection poses great risk for divers. The only way for commercial divers to inspect water intakes safely is to completely shut down operations with intakes totally turned off and secured. Without these crucial safety steps, the risk of severe injury and death is simply too high to justify putting divers in the water.
One of the most common causes for diver deaths is differential pressure, more commonly known as Delta P. Delta P refers to pressure drops in the water, particularly across a piping component such as a valve or filter. Water moving from an area of high pressure to one of low pressure, such as when an opening is created on one side of a hydroelectric dam, can create enough force to trap divers against intakes. Delta P is a major problem for divers - particularly when it comes to underwater intakes. The pressure created can be in the tonnes, trapping divers, often with tragic results. Furthermore, these vacuums can be difficult to detect until it’s too late. While Delta P is a risk for divers in all circumstances, from underwater construction to inspection, it is especially prevalent near water intakes due to the pressure changes.
There are many other dangers associated with coming too close to hydroelectric dams and stations, which are applicable not just for commercial divers but for swimmers, recreational divers and boats as well. Hydroelectric dams are well marked and monitored for a reason! Risks associated with being in the water near a dam include;
Eddies, visible or invisible, which can drag you under.
- Eddies, or swirling sections of water, can be especially dangerous. A spot that looks calm in one moment can change rapidly and without warning as operators open and close dams or start and stop generating units to suit electricity demands.
- The waters in the head ponds above hydroelectric dams and the waters below them are particularly susceptible to strong currents. As water rushes into and out of the station, strong undercurrents can be created in formerly calm waters.
Sudden changes in water level
- Similar to
Thinner ice in the winter
- The rapidly changing and moving water can result in thinner or less stable ice in the winter, making the area unsuitable for skating, ice fishing or walking.
Why is Water Intake Maintenance Important?In order for hydro-electric dams to generate power at the highest capacity, each aspect of the system requires periodic inspection and maintenance. A water intake is an integral part of power generation and is directly responsible for the water flow efficiency coming into the dam from a stream, river, lake or reservoir. Water intake gates and screens protect vital components within the dam such as the turbines, pumps, and pipes from damage which can be caused by debris, sediment, invasive species, fish, and ice.
Due to their popularity and the historical use of hydroelectric power, many dams are rapidly aging. As years pass, the underwater structures in these dams face several integrity issues.
Common Water Intake Issues
Cracks and defects in the dam
- Defects such as cracks, dents or cavities in the dam face can seriously impact the structural integrity of the dam itself - creating a potentially serious safety issue.
Issues surrounding emergency gates and seals
- In order to ensure safe operation, emergency gates and seals need to be consistently and thoroughly inspected to prevent any leaks and to confirm operability.
Unsafe operation of lowering gates
- There are several potential issues surrounding lowering gates including grooves, dents, debris or corrosion that could negatively impact the operation of lowering gates.
Deteriorating Penstock lining integrity
- The lining of penstocks plays an important role in preventing water leakage, making regular inspection of the cement lining critical.
How Can You Use an Underwater Drone for Hydroelectric Dam Water Intake Maintenance?The diversity of intake locations can mean that regularly scheduled maintenance can be difficult and costly. In the past, dive teams have needed to be contracted for inspections, sometimes for extended periods of time, or in extreme cases, reservoirs are drained to replace screens, repair intakes or remove debris. This massive cost and disruption of service are felt by not only the power producers but also the municipalities that rely on them.
Using submersible remotely operated vehicles or ROVS for underwater maintenance and inspection on underwater structures allows teams to save significant amounts of both time and money, while keeping human divers safe.
Maintenance teams simply deploy the camera-equipped vehicles to be able to safely inspect all underwater structures. Operated with the handheld controller, ROV pilots get a live view of their submerged infrastructure, as well as the ability to record collected data.
What are the Benefits of Using an Underwater Drone?The benefits of using an underwater drone to perform inspections are numerous. The DTG3, REVOLUTION and PIVOT ROVs are able to be launched from the surface and are utilized to inspect a water intake to verify what is required for maintenance pre-emptive of a diver or dive team. Inspections provide real-time data of debris, sediment removal, repair or replacement requirements. This initial examination greatly reduces the time requirements of divers; allowing them to prepare in advance of going in the water. Additionally, Deep Trekker ROVs work up to 8 hours on a single charge, utilizing onboard batteries. This immediate deployment tool greatly reduces inspection and maintenance time. Comprehensive analysis is conducted without dragging multiple cases, or generators to a site or worrying about dive times.
Once maintenance activities have been ascertained, Deep Trekker ROVs are ideal to launch again in unison with a diver. Here the HD camera can monitor the safety of the diver while they work, in addition to collecting other relevant data from the work site that can be historically cataloged and utilized for future planning activities.
The primary benefits of Deep Trekker ROVs for underwater dam maintenance include;
- Deep Trekker’s ROVs are battery powered, with up to 8 hours of drive time. As there is no need for outside power sources, the vehicles can be easily and quickly transported to a variety of worksites and deployed in minutes. Furthermore, Deep Trekker vehicles arrive in a wheeled Pelican case to ensure ease of transport.
Save Time and Money
- In addition to quick deployment times, ROVs require significantly less time and personnel to conduct inspections in comparison to divers. The vehicle can be launched at a moment’s notice and driven around the intake without completely shutting down operations. Ease of operation means that minimal team members are required onsite to conduct the inspection, with little pre-planning and organization.
Keep Human Divers Safe
- With the use of an ROV, divers can stay completely out of dangerous waters. It has been established that water intakes can be incredibly risky for divers. By using robotics in lieu of people, human beings are not required to risk their lives for underwater inspections.
- Deep Trekker’s module design means that users can add enhancements to their vehicle as needed. Water surrounding dams can be turbid, making sonar especially valuable for accurate inspections. Various sonar options allow teams to create their ideal ROV. Positioning tools such as USBL and DVLs also make navigating in murky waters simple and precise. grabber claws and manipulators of various sizes make underwater work more straightforward. Additional sampling, measuring and sensing tools make inspections thorough and complete.
Simplify Your Underwater Intake Maintenance With a Deep Trekker ROVThe energy that hydroelectric dams produce plays a key role in everyone's day to day lives. Deep Trekker ROVs are helping ensure these structures are properly inspected to provide clean, efficient, cost-effective, and safe power to our communities.
Deep Trekker has embarked on a mission to provide safe, cost-effective and efficient tools for underwater observation. As the pressures to find cost-effective methods to maintain our world's aging infrastructure; Deep Trekker has expanded its product offerings to continue providing innovative and purpose-built inspection robots for your next underwater inspection.
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