Bolt Tensioning Device at Power Station Improves Safety and Usability

By Doug Green, Publisher, Asia Manufacturing News

Two major power stations in South Korea have installed Technofast’s hydraulic CamNut EziJac bolting system, reducing production downtime and improving safety levels for their maintenance engineers.

Park Jong Geun, general manager of the Technical Solutions Team at Korea’s East-West Power (EWP) Company based in Seoul, said the system had been successfully utilized on the steam turbine casings at both the company’s Dangjin and Donghae power stations.

In a letter to Technofast, Mr. Park explained that by installing the CamNut EziJac system, his maintenance team had been able to dramatically shorten the maintenance and upgrade times, reduce downtime, as well as increase production at both locations. He went on to say that by changing from the previous, outdated heating method of loosening and tightening the bolting on the turbine casings, they have also improved the safety of their maintenance engineers.

With the old heating method, the company couldn’t carry out simultaneous operations and needed many hours to heat up and cool down the bolts, as well as for measurement of the elongation. Mr. Park explained that this method could also cause serious damage to the components due to their exposure to excessive heat. But, by adopting the CamNut EziJac system, the maintenance engineers were able to loosen and tighten the nuts simultaneously and avoid thermal stress and heat deterioration of the bolts.

He said that by installing the Technofast system, the power company has drastically reduced the number of downtime days lost, plus increased the reliability, production, safety, and usability of the power plants. At the number-one unit at the Dangjin steam turbine power station, Mr. Park said the company was able to reduce downtime by two days, equating to 840 million Won (US $700,000 approx.) per year. On top of that, the company was able to save 100 million Won (US $85,000 approx.) due to the lifetime extension of other material, due to no thermal stress.

Mr. Park said the company was able to reduce downtime by two days at the Donghae thermal power station, saving 440 million Won (US $374,000 approx.) per year. Again, the company was able to save another 100 million Won (US $85,000 approx.) due to no thermal stress on other material.

Based upon these results, Mr. Park said management will continue to install the systems on the company’s other turbines, valves, and other applications, and recommends the same hydraulic bolting system to other steam plant operators.

The Dangjin coal-fired power complex (4,000 MW) is a core operating site and one of the most eco-friendly plants built in Korea. Eight units are currently being operated in the complex to provide sustainable energy to the metropolitan area, while the Donghae coal-fired power plant (400 MW) is said to be the world’s largest anthracite/CFBC (Circulating Fluidized Bed Combustion) power plant.

Technofast’s Founder and CEO, John Bucknell, said he has had similar glowing endorsements from other industrial users of the company’s hydraulic bolting system. He describes the system as a compact, affordable, and efficient bolting system, which is simple, safe, and easy to use, and 8 to 10 times faster than conventional bolt heating.

Mr. Bucknell explained that a bolt-tensioning tool normally pulls on the bolt threads protruding above the regular hex nut and then screwed down to retain the loads induced by hydraulic operation of the tool. “However, with no available thread, the CamNut system performs as the connection to the bolt for the operation. Its integral collar expands to take up the bolt’s elongation under force and retains the load when the hydraulic charging pressure is released.”

He said the company used 32 3.1/2 CamNuts with four EziJac tensioners on the LP turbines at the larger Dangjin power station, while at the Donghae power station, Technofast installed 68 CamNuts on the horizontal flange bolts, ranging from 6″to 4″.

Mr. Bucknell went on to explain that overhaul and maintenance schedules at power stations accommodate many different operations being performed concurrently or sequentially, with bolting a major operation requiring clear access, which often excludes other activities taking place. “It is one of the first and one of the last procedures in maintenance scheduling, and so it is important to reduce the time taken to unbolt and bolt the turbines as much as possible.”

He said the operators of the turbine, EWP (Korea), were delighted with the installation, with the turbines bolted up in only a few hours. “Normally this would take over two days to complete, as they would have to allow for heating, cooling, re-measuring, and some repeating of this process for adjustment of bolts, which were not to the specified elongation.”

He added, “They were especially pleased with the accuracy of the hydraulic bolt tensioning and how quickly adjustments could be made.”

Mr. Bucknell said bolting applications, such as gas and steam turbine main joints, valve bonnets, and steam supply flanges, rarely have bolts that have sufficient stud length or available room around the nut area to allow engagement of any type of hydraulic bolt tensioner.

“Instead, Technofast’s system replaces standard hex or round nuts with a CamNut, which provides connection to the bolt, attachment for a hydraulic bolt tensioner, and a rigid platform to accept the reaction from the tool.”

According to Mr. Bucknell, the user-friendly CamNuts are fast to install and remove, and require little physical effort. “They are ideal for situations with short bolt grip length and where space for tooling is restricted.” He said by installing the CamNut system, there is no longer any need to replace expensive studs to provide sufficient grip length to be able to use hydraulic tensioning methods.

Designed for extreme situations and adverse conditions, the system can achieve reliable, precise tensioning the first time, all at a minimal cost. They are designed to operate in temperatures from -40°C up to over 650°C, and where simultaneous tightening of bolts and even joint/gasket compression is required. By removing the risk of strike and punch point injuries caused by other tightening methods, the CamNut system is ideal for regular maintenance requiring repeated adjustment or removal of nuts, especially where speed of operation is essential and where bolts are of a large diameter.

“We see ourselves as the providers of the ultimate solution for many of these age-old bolting problems, where we can install systems that safely deliver efficient and accurate outcomes,” said Bucknell. “This is especially relevant for power generation equipment, where reduced outage time means that the plant can be producing and earning much sooner.”

This article is reprinted with permission from Asia Manufacturing News. Across Asia, the Pacific, and around the world, Asia Manufacturing News keeps readers in touch with the latest in manufacturing trends and developments through case studies, as well as product and business news. The publication is a division of JEZ Media and can be found online at www.asiamanufacturingnewstoday.com.

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