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7 Reasons for conducting regular inspections of underwater infrastructure such as hydro dams, intakes and outfalls, and headrace and tailrace tunnels.

Written by: Bill Sherwood

  1. No One Dies: Divers die in pipeline and confined space penetrations. Divers are from 30 to 40 times more likely than average to be killed or be seriously injured in the workplace. They can become entangled in debris, their breathing equipment can malfunction or, due to the stress of working in this dangerous environment, simply exhaust themselves and run out of air. When inspecting upstream of dam structures they are often sucked into gaps in stop logs or through open vent conduits that were thought to be closed. Upstream vs downstream pressure differential is enormous.
  2. Vital Underwater Infrastructure Has Failed. This necessitates an urgent response to a) determine the location and severity of the problem and b) formulate an appropriate remediation plan. This is a reactive response and is not recommended as it is generally more operationally disruptive and, in particular, expensive than planned outages. Global tunnel infrastructure is under enormous stress. Most of our international ROV projects are in response to catastrophic failure or possible imminent failure. Proactive surveys are preferred but much less common.
  3. Trending of A Known Condition. Sometimes a problem is known to exist but it is either not serious enough to warrant interruption of service or there is no immediate opportunity to shut down the facility to fix it.  Regular surveys are recommended to help predict when and where future interventions may be needed. A combination of sensor technologies (sonar, high resolution video, photogrammetry and laser) can provide a comprehensive, integrated picture of structural conditions. Pressure sensors and dye tests can be combined to determine leak zones. Inertial navigation systems (INS) allow repeat excursions to be location-exact, thereby enabling accurate trending of changing conditions such as sediment accumulation, delamination, geological heave etc.
  4. Pre Commissioning Baseline Surveys. Undertaken post construction or during subsequent de-watering, these provide an excellent basis for trending.
  5. Specialized equipment and sensors exists for almost every remote inspection scenario. This allows for client participation on an unprecedented level, as client can direct pilot to specific areas of interest in the field during the course of the inspection.
  6. Comprehensive Reporting. For ROV’s, underwater time is unlimited so massive amounts of data can be gathered in various formats for post processing. Data is ‘true’ metrology, meaning that distances and orientation between any two points can be measured.
  7. Specialized Equipment Can Be Built or Adapted to Purpose. Where no equipment exists that can solve the problem it can be designed and built to purpose. This includes both inspection and repair.

 

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