Tension control system prevents leaks

The RotaBolt 2 provides a large range of tension control on installation, tightening and in-service checking.

RotaBolt's approach to bolted joint integrity has achieved a total leak-free start at Antwerp's Nuclear Generation plant following its annual shut down.

RotaBolt's tension control system allowed the 24-inch steam valve to remain leak-free for the first time in seven years.

The 680kg steam valve had leaked on every start-up since it had been installed.

A technical analysis of the valve and its joints indicated that a complete re-design was necessary if joint integrity was to be achieved.

RotaBolt's technical team, working with James Walker Belgium, recommended the use of RotaBolt 2 to achieve the necessary installed design tension and for the ongoing monitoring in service.

RotaBolt 2 provides a large range of tension control on installation, tightening and in-service checking.

It offers two tension settings in a single sensor and features a dual load indicator cap - the outer cap for high tension setting and inner cap for low tension - giving the choice of an operational tension range for overload or maintenance control.

The design of the new joint incorporated the use of a Metaflex gasket, the fitting of a silver plated C-ring and new housing dimensions of the male/female flange.

Twenty 76mm RotaBolt 2s were used, with an operational tension range set at 125 and 150 tonnes.

Test pressure for the valve was set at 130bar at room temperature, with start-up at 160bar at increasing temperature.

The process pressure was set at 60bar at 260C.

The steam valve with its newly designed joints was fitted during the shutdown in August of this year and remained totally leak-free when the plant was restarted.

James Walker Belgium is now working with Antwerp's plant engineers to see how tension control can achieve joint integrity in other areas of the plant and its processes.

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