Enerpac, an international market leader in high-pressure hydraulics, has supplied Korean based engineering company, KLES, with strand jacks for an innovative tower scaffolding system called SKYFFOLDING (Platform-supported Boiler in-Furnace Scaffolding and Lifting System). The Enerpac HSL1507 strand jacks support and lift the pendant-type, scaffolding system, as it grows, providing a safer working environment than traditional scaffolding during power plant boiler furnace maintenance.
Scaffold platforms supported by the heavy strand at 2m intervals are easily accessed by integral staircases.
Traditional scaffolding is a stacked structure constructed from bottom to top, concentrating the total load on the base. Typically, 70m high, the height varies according to boiler size of thermal power plant. In the event the lower levels of scaffolding are damaged, it may trigger a complete collapse with potentially disastrous consequences. In an effort to reduce the risk of collapse, KLES has developed the SKYFFOLDING system, a new approach that reverses the order of scaffolding construction from top to bottom.
The SKYFOLDING lifting system involves the installation of a network of typically 20 Enerpac strand jacks onto a heavy girder at the top of the boiler. The strand jack wires are lowered and connected to uphold and lift a support platform, the uppermost support frame of the scaffold system. Robust wire ropes connected to the support frame used to support pendant scaffold platforms attached beneath at 2m intervals by with repetitively jacking up the platforms with the SKYFOLDING lifting system. Each pendant platform features an integral staircase allowing easy of movement between each level. This allows the synchronised strand jacks to hold and lift the entire scaffolding as a single unit.
HSL1507 strand jacks have individual capacities of 17 tons but work together as a system of 20 jacks to raise the scaffolding tower.
The synchronized SKYFFOLDING system is able to reliably and safely lift the scaffolds with an even load dispersion, keeping deviations in lateral and vertical directions to a minimum. As an additional safety measure, special fail-proof fasteners on the suspended platform have been designed such that the grip on the wire rope increases in direct proportion to the load applied as the scaffolding structure grows. In consequence, the stability of the entire scaffolding system is maintained even if structural problems occur at the lower levels, unlike a conventional scaffolding tower.
View from above: Strand from strand jack connects to highest level of scaffolding system lifting it up to intended elevation.
The 17 ton capacity Enerpac HSL1507 strand jack acts like a linear winch. A bundle of steel cables or strands are guided through a hydraulic cylinder; above and below the cylinder are anchor systems with wedges that grip the strand bundle. By stroking the cylinder in and out while the grips are engaged in the anchors, a lifting or lowering movement is achieved.
The motion of the cylinders is driven by hydraulic power packs. They can be electric or diesel powered. Enerpac’s SCC software program synchronizes the motion of the strand jacks and adjusts the motion to the loads per lifting point.
The SKYFFOLDING system has been deployed for boiler maintenances in a number of major thermal power plants. including KOSPO Hadong, KOEN Samchenpo, EWP Dangjin, KOMIPO Boryeong and WP Taean coal powered power stations.