The Tubeshor Active Thermal Compensator (ATC) is a patent protected Tubeshor accessory that can reduce thermal loading by up to 90% compared to a mechanically locked off prop, it is claimed.
Tubeshor is Altrad RMD Kwikform’s hybrid hydraulic shoring system for propping waler beams or capping beams of large excavations. It comes in a range of diameters to cater for all duties of shoring requirement. The ATC is an evolution of Tubeshor to compensate for thermal loading.
Prop installation and pre-loading on site is carried out in the same way as for any standard proprietary prop. Because Tubeshor ATC units are assembled directly into the prop makeup, standard prop end-fittings such as swivel units and spherical bearers can be used, and props can be installed into the excavation in the usual manner.
The Tubeshor ATC contains a 450-tonne hydraulic cylinder coupled to a bladder accumulator that is pressurised to suit the individual prop design geo-load before dispatch.
Most of the time, the pressure in the accumulator exceeds that in the hydraulic system and normal prop stiffness results. But when higher temperature forces excessive thermal expansion in the prop, the compressed nitrogen in the accumulator comes into play and results in a phase of reduced prop stiffness. This means that a further increase in prop length resulting from thermal expansion does not result in the usual increase in prop load.
Ian Fryer, global product innovation director at Altrad RMD Kwikform, explained: “Once the props have been installed, their confined nature means that temperature changes bring about changes in the axial prop load with axial loads increasing as temperatures rise and decreasing as they fall.
“Historically, design for thermal loading has not been such an issue in the UK due to the relatively even climate. However, consulting engineers are now interpreting industry standards differently, meaning an increased contribution from solar gain also has to be taken into account, which, when combined with seasonal and daily variations can produce a design thermal range in excess of 35 ̊C.
“Using this temperature range, thermal loading can account for 50% of the axial load capacity of the props, so half of the steel in the excavation is there purely to take account of thermal loading. The resulting need for larger or more props can sap scheme efficiency, push up the equipment cost, and take up valuable excavation space.
“What’s more, installation may require heavier plant and more labour to assemble the equipment, incur greater costs for transportation and result in a larger carbon footprint. Our revolutionary new Tubeshor Active Thermal Compensator helps to mitigate these factors, reducing thermal loading by up to 90% compared to a mechanically locked off prop, while offering a raft of additional benefits.”
