A new debate is gaining momentum in the underwater inspection world. Should dam owners use divers or remotely operated vehicles to inspect their dams? Suzanne Moxon reports
Dam owners, perhaps more than anyone in the hydro industry, understand the crucial importance of regular dam inspections. ‘There is increasing concern for dam safety around the world,’ said Michel Gariepy, vice president of Canadian monitoring company Geophysics GPR International. ‘Fewer new dams are being built and, especially in the US, many existing ones which were constructed at the beginning of the century are ageing and beginning to show signs of wear and tear. Consequently, many dam owners are concerned and are taking dam inspections very seriously.’
Dam inspections can cover many areas but perhaps the most difficult ones to conduct are those which need to focus on the submerged dam surface. Underwater inspections are not only crucial for checking existing dam faces for cracks and signs of ageing, but they are also required during the construction of a new dam.
According to WJM Vriens from vriens-diving Company in the Netherlands, the world of underwater inspections is progressing at a great pace. One thing, however, is clear: the use of divers as the traditional means of carrying out underwater inspections is being questioned by a relative newcomer to the hydro industry — the remotely operated vehicle (ROV). ‘There is definitely competition between ROVs and divers,’ Vriens admits.
When compared to divers, ROVs are generally defined as unmanned vehicles which are designed to work underwater and are operated or ‘flown’ by a pilot from a control station on the surface. US-based company Perry Tritech describes them in more detail: ‘You can almost compare these vehicles to a robotic diver with a body made of corrosion resistant materials, strong titanium arms fully capable of the most tedious tasks, an advanced computerised brain, eyes (cameras), ears (sonar) and the ability to stay underwater for hours and days at a time.’
Traditionally the ROV has been more popular for offshore work at oil rigs but slowly the hydro power industry is becoming more aware of its usefulness. Perry Tritech was one of the first companies to produce an ROV specifically designed for dam inspections. Manufactured six years ago, the Scout dam inspection system was requested by Canadian utility Hydro-Québec. Capable of working at depths of 250m the ROV could carry out various tasks such as video and photographic documentation, site surveys, mapping and light intervention tasks. As Peter MacInnes from Perry Tritech explains, at the time the ROV market for dam inspections was not an active one and only one model of the Scout was manufactured, for Hydro-Québec. The Scout never became part of a standard product line and, apart from Hydro-Québec, no more have been requested by the hydro and dams industry.
Following on from the Scout, one of the most important developments in the dam inspection/ROV world took place last October. Hydro-Québec granted Geophysics GPR an exclusive licence to market its latest non-destructive inspection technology, developed at IREQ, Hydro-Québec’s research centre. Eight years of research has produced the See All, an ROV for the dam inspection industry.
Capable of descending to depths of 300m, See All is described as being exceptionally manoeuvrable and stable, even in turbulent water. It has a positioning and control system that allows precise changes in all directions of travel, a system for transmitting images and collecting data through fibre optics and sensors, a virtual reality mode and ancillary equipment such as sonar, a stereoscopic camera, a laser camera, an altimeter and a depth meter.
The See All has already proven itself in dam inspections at Daniel Johnson, La Grande 2, Manic 3 and Carillon dams in Québec.
Hydro-Québec developed the See All primarily for its own purposes to inspect its dams. The utility recognised that the visual inspection of dams plays a key role in dam safety. As Jean Lavallée, a researcher at IREQ points out, most of the dam structures such as the upstream face and the inside of tunnels are not very accessible and so the need to ‘see’ requires well-adapted vision systems. Hydro-Québec did not have the necessary equipment for such purposes and, unable to find it on the market, decided to develop a machine based on the Scout.
‘The See All is quite a breakthrough,’ Lavallée said. ‘We reached first base with Perry Tritech and the development of the Scout but since then Hydro-Québec has continued to develop this first vehicle which was more or less a prototype. The See All is quite a different machine.’
A key feature of the See All is its virtual reality component, which has been developed as a navigational and orientation aid. Lavallée describes it as being similar to a Nintendo computer game. It gives a graphic view of the dam so that the operator in the control room can see clearly. ‘Murky water is no longer a problem with See All as it used to be with the old ROVs,’ Lavallée said. Peter MacInnes from Perry Tritech agrees: ‘One problem with ROVs at dam sites is that it is difficult for the pilot to observe the structure underwater.’
Lavallée went on to explain that navigating an ROV in murky waters gives the impression of being in a snowstorm, which makes it difficult for the pilot to interpret instrumentation. This is why IREQ thought it would be sensible to use an interface which provides a view of the dam with the ROV controlled according to the pilot’s instructions. With See All’s accurate positioning system, Michel Gariepy from GPR says that when ‘flying’ this ROV it is ‘just like being underwater at the dam but without getting wet’.
Indeed Gariepy is confident that the See All will have a long and successful future in the dam industry. The See All has been used by Hydro-Québec and the US Bureau of Reclamation to inspect their own dams. Now, as the Canadian utility is confident about See All’s capabilities, it is very enthusiastic about marketing its latest development worldwide.
Gariepy explained that the partnership between Geophysics GPR and Hydro-Québec was a ‘natural progression’. ‘Hydro-Québec was looking for someone to market the See All,’ he explained, ‘and it knew that Geophysics GPR had been involved with dam safety and the use of high technology for over 20 years. Indeed as our company has a lot of contact with utilities and dam owners it was only natural that our two organisations should work together. Geophysics GPR also has company bases in the US, France, Africa and India so it will be very easy for us to market the See All worldwide.
‘We believe that this ROV is a very good inspection tool for use at submerged dam surfaces. It is a highly accurate piece of equipment. We are very confident,’ Gariepy added, ‘that the use of ROVs in the dam industry will be an expanding market in the future.’
The way forward
But do those involved with the See All really believe that this newly developed ROV will pose a threat to divers, replacing them at underwater dam inspections?
Opinions on this subject are varied. Lavallée explains that Hydro-Québec did originally use divers to inspect the utility’s 540 dams but this was a time consuming process. It was also difficult for divers to locate cracks again, once they had been found, especially as many dams in the Canadian province of Québec are over 250m high. ‘Quite simply,’ Lavallée says, ‘the ROV is more economic and gives a better view of underwater operations. Before, an engineer also had to be a trained diver to be able to inspect a dam but now the engineer is located above water in the control room and the images underwater are transferred to him.’
But surely See All pilots need extensive training to be able to operate the equipment? Lavallée disagrees. ‘It is not a problem to find pilots for the See All,’ he said. ‘After one hour of training any one can use the See All.’
Not everyone in the dams and hydro industry is convinced that ROVs are the way forward. Mr Domenico from the Great Lakes and Ohio Division of the US Army Corps of Engineers said that they strictly use the ‘human element’ to inspect dams in their care. The reason for this is that many of their projects’ gates and valves which need to be inspected are difficult to access with an ROV. ‘Divers are also much more flexible when inspecting a dam,’ Domenico said. ‘If you find something wrong mechanically and you have a diver in the water you can fix it there and then.’
There are however, disadvantages, as Domenico went on to explain. At present diving safety requirements specify that to make up each dive team there have to be three divers who are qualified, plus attendants and supervisors on the surface. The US Army Corps is trying to reduce this to a two-man dive team, plus attendants and supervisors, in order to reduce costs. ‘It is very expensive to maintain a dive team,’ Domenico said. ‘You have to maintain the equipment and also keep up annual training and fitness requirements for the divers.’
WJM Vriens from Vriens Diving Company believes that ROVs have a place in the dam inspection industry. ‘If you just want to check up on something and affirm your expectations using an ROV this is fine,’ he says, ‘but forget the ROV if you’re uncertain about what you’ll find. An ROV can’t solve problems as well as divers can.’
Chris Roper from US company Stolt Comex Seaway agrees: ‘For specific work the use of ROVs in the US has caught on. If you want a visual indication of the underwater structure, using an ROV is the way to go. But,’ he added, ‘it’s not the same as having a man in the water. You don’t get the same hands-on effect with an ROV. A diver is capable of probing and sometimes this means that inspections with a diver are just that much better.’
Lavallée from Hydro-Québec is quick to point out that in the next few years several million dollars will be spent on improving the See All further, specifically to increase the actual ‘hands-on’ work that the ROV can carry out. ‘The ROV is a threat to divers,’ Lavallée says, ‘but divers still have the edge when carrying out repairs at dam sites. They have much better manipulation, but with the improvements being carried out on the See All these differences are becoming much less marked.’
The introduction of See All does not mean the end for divers. Lavallée explains that they will still be very useful at smaller dams or perhaps at locations where less data and photographic images are required. He believes the ROV will come into its own at larger dams where greater depths may pose problems for divers. As Chris Roper explains, ROVs can work at greater depths than divers. Dams located at high elevations are not usually inspected by divers due to the conversion factors when diving at altitudes and the remote location of high altitude dams. ROVS such as the See All can also work underwater for longer periods — there is no limit to the amount of time the See All can remain under the surface. In this respect the ROV will be more cost-effective. It is also small to transport to sites and does not require a large support team, as divers do.
Furthermore, ROVs can ensure that hydroelectric production loss is minimised during inspections. When divers are inspecting gates and working units they have to be closed down for safety reasons, with an ROV some units can still operate so that the plant does not lose production. ‘There are a lot of economic advantages to using an ROV,’ Lavallée said.
The extent to which ROVs such as See All will penetrate the hydro industry remains to be seen. As industry observers are keen to point out, even though ROVs have their advantages there are still good reasons for using divers for underwater inspections. However, with improvements and new pieces of equipment such as the See All, it would seem that the appeal of the ROV to the hydro industry may improve in the future. Increased education about the ROV’s usefulness is another key.
‘Education of the customer is undoubtedly an important aspect in the sale of an ROV system,’ Howie Doyle from UnderWater magazine comments. ‘A misconception with new buyers is that your company must be composed of rocket scientists and electronics engineers in order to get into ROV operations.’ This, as Lavallée has explained, is not so.
The See All has other misconceptions to correct. Domenico from the US Army Corps of Engineers believes that ROVs would not be suitable for use at their dams as the water is murky. ‘We primarily use divers as the water is so murky that sometimes the divers can only use ‘feel’ to find their way around and do work. Working in such conditions probably wouldn’t be possible with ROVs,’ he believes. In addition Vriens Diving Company’s experience is that ROVs are more suited to working in clear water, which is not always present at dam sites. So perhaps the key to the See All’s success will be its virtual reality feature, which will enable it to be used in murky waters. After all the key to dam safety inspections is the ability to see clearly.
The ultimate question — to ROV or not to ROV? — can only be answered by dam owners themselves. One thing however is clear: although ROV manufacturers have taken great leaps in improving the technology and its application to the hydro industry, there are still good reasons why dive teams need to be deployed at dam sites. As Michel Gariepy says: ‘ROVs will not replace divers but rather focus their work to their best capabilities and limit the risks of their trade. If ROVs allow more inspections, then divers will probably have to intervene more frequently to do what robots cannot do.’
The underwater competition between man and robot is becoming more intense but, as yet, there is no clear victor.