Hired videoscopes reduce cooling tower inspection times

Reported incidents of Legionnaires' Disease have more than doubled over the last 25 years in England and Wales, according to Health Protection Agency figures. Wet cooling systems (cooling towers and evaporative condensers) have been the subject of increased attention and a number of initiatives are underway to improve the situation.

Poor compliance with the requirements of the COSHH regulations and the HSE Approved Code of Practice (L8: 'Legionnaires' disease: The control of legionella bacteria in water systems') have, in conjunction with poor cooling tower control, been found to give rise to the potential conditions in which the growth of Legionella bacteria can occur.

However, since 1997, there has been a programme of action to improve levels of compliance, and the inspections of installations, in conjunction with high levels of enforcement, have become important features of the programme. Cooling tower inspections include a physical examination of the cooling pack to check for scale, slime, algae and physical obstructions, any of which could harbour Legionella bacteria as well as hamper the performance of the cooling system.

Following a series of trials, ABB consultants have demonstrated that rented videoscopes from Ashtead Technology Rentals can save substantial amounts of money and time in the routine inspection of cooling towers.

In the past, it has been common practice to remove the cooling pack for the purposes of the inspection and cleaning (regardless of whether the tower needed to be cleaned or not). However, depending on the size of the unit, this can take anything from a few hours to two days to complete. During this time the cooling system would be shut down resulting, in many applications, in the closure of the entire facility.

However, engineers at ABB, which offers a range of services providing cooling system optimisation under the umbrella of its Engineering Services Division, have demonstrated that effective inspections can take place without having to remove the cooling pack. This has been achieved with the use of hired high-resolution videoscopes from Ashtead Technology Rentals, a company that specialises in high-tech instruments for hire.

Following work at a number of sites, ABB has demonstrated that hired videoscopes can reduce inspection times, and thereby minimise shut-down times from as much as two days down to as little as one hour.

“Cooling tower inspections have always formed a critical component of ABB's Total Cooling System Management; however, removal of the cooling pack has imposed substantial penalties and risk (working at height, in confined spaces) for our customers so we have been looking for alternative effective inspection methods that would not result in lengthy shut downs,” said water technologist Melvin Hall.

“Our work has indicated that the iPLEX videoscope is ideal for such work because it enables us to inspect the internal components of the tower from top to bottom using a small access point. The probe can extend up to almost 10 meters providing clear, 3-dimensional video images that can be stored or transferred to a PC.”

Renting the videoscopes from Ashtead avoids the large capital cost of purchase. The instruments are easy to use, but Ashtead offers technical support both on-site and by telephone so customers are able to start recording images almost immediately, he added.

One of the key features of the iPLEX range is the quality of the images generated. Images with a limited dynamic range tend to lose detail in the brightest and darkest areas. However, the iPLEX instruments have virtually eliminated such whiteout and blackout through a newly developed, proprietary image-processing algorithm that greatly expands the dynamic range. The resulting rich gradations naturally represent the inspection area as seen by the naked eye, allowing much more accurate inspection.