New South Wales’ Roads and Traffic Authority has worked in partnership with high force hydraulics specialist Enerpac to devise a way to hoist bridges with maximum safety, simplicity, efficiency and minimum disruption to traffic.
Using ultra-compact but powerful 700 bar CLP 100-ton hydraulic cylinders bracketed in pairs around pillars supporting the structure, the system is powered by a new generation ZU4 pump through twin four-way manifolds that synchronise the lift to replace worn expansion bearings.
The single-acting CLP Pancake cylinders feature low collapsed height (137mm retracted) for use in confined spaces, with a lock nut for positive and safe load holding over extended periods. Safety is further enhanced by V66 manual shutoff valves on each cylinder to complement the safety offered by the cylinders’ own load-holding capacity.
Introduced into service on the main highway bridge at the eastern entrance to Bathurst, the system is housed within a Megashore prefabricated propping system which, in the Bathurst lift, supported the cylinders and pump as they exerted an average of 66 tons force per cylinder to lift the bridge platform so the 36 bearings could be slipped out and replaced.
According to Enerpac, the whole job is really all about health and safety, simplicity and reliability. With clear guidelines from the RTA’s engineering staff, Enerpac has devised a system that can be used time and time again with proven safety procedures. The system can be applied to routine maintenance work throughout the entire Western Bridge Services territory of which this bridge is part, an area which covers hundreds of bridges extending from Broken Hill to Lithgow.
Enerpac applied to the project many of the safety and failsafe procedures applied during its decades of experiences working in infrastructure, civil engineering and mining projects throughout Australasia.
According to Enerpac, as there is no second chance at safety around some of the massive equipment Enerpac has worked with, it becomes second nature to design safety into systems that can be operated simply with totally repeatable procedures.
Starting with the robust Enerpac CLP cylinders, single-acting types from a family of cylinders widely used in mining and civil engineering projects in capacities up to 520 tonnes each, a four-way manifold was devised incorporating the V66 valves for load holding and Enerpac 700 series thermoplastic safety hoses. The Enerpac CLP cylinders feature a 4:1 safety factor for demanding applications (the hose is designed to carry four times the load for which it is specified, exhibiting low volumetric expansion under pressure to enhance overall system efficiency).
The custom-fabricated manifolds, incorporating pressure gauges on each cylinder are linked to a single high efficiency Enerpac ZU4 electric pump, a cool-running and energy-saving design engineered to save time and labour on repetitive tasks while improving operator safety.
Requiring 18 per cent less current draw than comparable pumps, a self-priming first stage of the pump increases its performance by supercharging the second stage piston pump, improving oil flow in both hot and cold weather operations. In addition to being less sensitive to voltage fluctuations in remote areas, the pumps feature a low-voltage (15 vdc) pendant with sealed switches for remote operation and enhanced personnel safety.
Operated by a single person, the pump, manifold and cylinder system is co-ordinated to gently and evenly advance the cylinders millimetres at a time to attain the lift of 30 or 40mm required for the worn bridge bearings to be removed and replaced on the 16 pillars and one abutment involved.
According to Enerpac, because the system is so safety-intensive and robust, it assists the client in achieving maximum use of the road above, while work is in progress. The aim on the Bathurst lift was to keep two lanes open at all times, which is important on a highway used by 10,000 vehicles a lane every day. We also scheduled our lifts on the same day each week, so people became accustomed to any work we had to do over the 20-week duration of the project.
In addition to specifying and providing correct equipment for the job, Enerpac contributed to the development of written safety protocols to be employed on the Bathurst lift and subsequent jobs. Enerpac’s knowledge in this area draws on more than 50 years experience in Australasia and involvement in some of the biggest hydraulic bridge jacking projects worldwide, including the recently completed Eiffage/Millau viaduct in southern France, which, with a total height of 343 metres, soars twice the 141-metre height of the Sydney Harbour Bridge.
According to Enerpac, they worked closely with the RTA to develop ongoing safety procedures. The RTA was strongly focused on maintaining the bridge’s structural integrity during the work, and on providing high levels of protection for people doing the job. Enerpac wanted the ideal and repeatable safety procedures in place, so that safety became second nature to everyone involved. The system Enerpac developed and which has been audited by RTA’s safety experts works well indeed.