Vehicle inspections in restricted areas18 December 2006
The SeaBotix Little Benthic Vehicle has been developed to work on inspection projects with severely restricted access
The Marine Services Group of Ontario, Canada-based ASI Group specialises in the internal inspection of long flooded tunnels and pipelines. Even though ASI has several remotely operated vehicles (ROVs) that are dedicated to this type of work, there are a number of inspection projects with severely restricted access requiring a more compact and portable system. After a thorough industry search, ASI selected the SeaBotix LBV300XL to be the most recent addition to its fleet.
The selection was based on a number of criteria: the complete system had to be compact and require only 1-2 people to operate, yet large enough to support integration of auxiliary equipment including optional and aftermarket sensors and tools. Clean color and monochrome video was an obvious necessity and, as all SeaBotix systems rated 300m and deeper employ fiber optic telemetry, these requirements were met. Finally, the system had to have a proven track record with performance characteristics allowing deployment in extreme environments for extended periods. The LBV met these criteria.
All LBVs employ an extremely small diameter (7.6mm nominal) umbilical with both copper and fiber optic conductors. If the umbilical was just 2mm wider in diameter, about 24% more drag would be generated. When factoring in the power-to-mass of any ROV, this is the single most important component affecting vehicle performance. The LBV300XL includes 750m of this proprietary umbilical standard allowing ASI to execute longer excursions into intake and discharge pipes, as well as tunnels. ASI has performed pipe inspections in excess of 700m by taking advantage of these performance characteristics. Low drag with an ideal power-to-mass ratio also allows deep deployments to the rated depth in currents while utilising all of the umbilical. ASI also selected a shorter 250m umbilical to increase portability for more routine work including open water applications.
In the case of the LBV300XL, the two conductors carry power to the ROV and the fiber optic conductors handle all of the vehicle telemetry, including ROV thruster and auxiliary control functions, video, and sonar information. The use of fiber optics eliminates electrical noise interference, providing clean video images and sensor data over very long transmission lengths. This meets ASI's requirements for a long umbilical needed for its specialised services.
The LBV300XL is a 6-Thruster, 4-Axis flight ROV. The addition of a Lateral Thruster makes sideways flight possible. This critical feature allows ASI to keep either camera on target without having to turn away from the area of inspection to relocate. The additional two Horizontal Thrusters gives ASI the power to pull the long 750m umbilical with surface speeds in the 4 knot range. SeaBotix 4-Thruster systems have a maximum 350m umbilical with a maximum surface speed of just over 3 knots.
All but one LBV package includes both a color and a low-light monochrome video camera with 90-degree field of view each. The enclosure rotates 180-degrees, providing a 270-degree total field of view. Having both cameras integrated allows the Operator to switch to the more light sensitive monochrome camera when excessive light reflecting off suspended sediments back to the color camera washes out the video image. The LBV300XL includes a standard LED array tracking the primary (color) camera providing 480 lumens of brilliant white light over a 140-degree field of view. External LED and Halogen lighting options are also available.
The entire system is packaged in shock mount and padded cases, which are easily transported in a pick-up truck. It takes up very little room, is powered by a small generator or standard outlet and can be launched and recovered by one person. With very few connections to be made between the power supply, vehicle and control console, the system can be ready including pre-dive checks in less than 15 minutes, according to SeaBotix. For most of the inspection work that ASI conducts, the systems have to be taken off line; the faster the work can be conducted, the sooner the system can be brought back on line and revenues generated.
Another benefit of the compact LBV300XL is that it can be lowered by hand using only its umbilical. ASI has deployed the vehicle by hand over 25m from the surface to the water line. In addition, the umbilical has a 45kg working strength with a 315kg breaking strength. When used with the optional Grabber Arm, it is possible to lift objects as heavy as 45kg to just below the surface, or manipulate large grates, retrieve tools, perform light duties with a team of divers, or other tasks not typically associated with Mini-Class ROVs. A powered, portable line hauler has been designed to make these easier for the Operators.
Video images are generally the main scope of the inspection, but quite often the client requires more quantitative information. ASI has devised its own modified tooling and sensors for the modular LBV. For example, a quick modification to the Grabber Arm made it suitable for a small rotary wire brush to be used. An ultrasonic thickness gauge has also been fitted to the ROV and used to measure the residual metal thickness of an intake pipe. Where marine growth, rust or coatings had to be removed, a pneumatic needle gun was fixed to the frame and the air line taped to the umbilical. Recently, another SeaBotix customer was able to attach a carabineer with a heavy lift line to a sunken speed boat four times in a successful bid to lift the boat from 122m down in Lake Powell, California.
Several of ASI's clients are power generation utilities. Hydro, fossil fuel and nuclear installations all require a reliable supply of water to operate. The intake and outfall or discharge lines are commonly inspected to verify their structural integrity and determine if there is any debris or sediment accumulation in the lines or covering the intake. Where determining the amount of sediment accumulation in the pipe, tunnel, or forebay is required, ASI uses a high resolution Mesotech profile sonar to take cross-sectional images for further processing. This has been accommodated by integration of auxiliary equipment to the LBV300XL, including an optional tool skid mounted underneath the main vehicle used to carry 3rd party sensors and tools.
ASI uses the LBV300XL in a wide range of weather conditions, from outdoor work during the Canadian winter (launched through the ice for a snow mobile salvage) to inspections in Arizona during the middle of the summer (temperatures in excess of 40oC, or 1100F). Here again, the small robust nature of the LBV and the minimal support equipment it requires helps make this work more efficient, says SeaBotix.
For example, a hydro facility recently requested that ASI inspect one of four shafts located a half mile by vehicle inside a mountain. Once there, the LBV was lowered down about 15m to the water line. Being able to rapidly mobilize the system meant that it inspected all four shafts of the facility.
The SeaBotix LBV is available in depths from 150m to 1500m, with umbilical lengths ranging from 100m to 750m. Depending on the system selected, the LBV can employ an all copper transmission of video and data (LBV150), the addition of fiber optic video (for the LBV200L), and a complete fiber optic solution (LBV300 and deeper). Each system includes a reel with slip ring, 15” LCD monitor built into the Integrated Control Console, a Basic Spares Kit and a Spare Thruster. The intuitive Hand Controller includes Auto-Depth, Auto-Heading, and Auto-Trim (speed) standard. All current systems offer a standard 24-Month Warranty. Factory and Onsite training is available, as well as a host of standard options and custom solutions.
For more information about ASI Group Ltd and their services, please contact Bob Clarke at +1 (905) 641-1825 or visit www.asi-group.com. To learn more about the SeaBotix LBV visit www.SeaBotix.com, email [email protected], or tel: +1 619-239-5959