Hytec recently designed, manufactured and installed 12 large-scale hydraulic cylinders, power packs and linkage systems to replace the hydraulics systems controlling water flow at the Roseires Dam wall in Sudan. Involving up to 275 tons of equipment – and a complete electronic control system with built-in diagnostics – this project on the Blue Nile River is the largest single hydraulic supply and installation project Hytec has undertaken.
“Hytec became involved with the Australian consulting engineering company, SMEC, through Bosch Rexroth in Germany nearly three years ago when one of the dam’s hydraulic cylinder attachment points snapped and caused a catastrophic failure to one of the dam’s radial gates,” said systems sales manager, Klaus Marggraff. “Upon further inspection, it was decided to replace all the hydraulic systems to reduce the risk of any future failures. As Bosch Rexroth’s representative in sub-Saharan Africa, we managed and co-ordinated the design and manufacture of the cylinders by Bosch Rexroth in Holland, as well as the installation of the cylinders and electronic control solution.”
The project formed part of the dam’s planned 10 metre wall heightening project, which has brought the dam’s total capacity to 6 billion cubic metres. Weighing 85 tons, the radial sluice gates were designed to withstand water forces of up to 4400 tons each. This meant the cylinders needed to provide a lifting force of up to 160 tons to lift and control each sluice gate, so they were designed with 400 mm bore, 13 metre stroke and built-in integrated measuring devices. Each cylinder weighed 13 tons and took three days to install.
Hytec installed a new mechanically articulated linkage system and supplied power packs for operating the cylinders. The system featured a high degree of redundancy with the ability for the cylinders to be operated by any of the five installed power packs should a power pack not be available.
The power generation intake gates featured seven cylinders, each with 500 mm bores, 160 mm rod diameters and 7,5 metre strokes – also with integrated positioning systems. Due to the rods’ constant exposure to water, the cylinders were supplied with a stainless steel rod and a chrome layer to reduce the risk of corrosion. Ensuring that no water seeped through the cylinder interface mounting plates, Hytec supplied special interface seals to help the cylinders cope with the additional 10 metre water height.
The dam’s new electronic system controls the actuation of the cylinders in both the hydroelectric power plant and the deep sluice gates. “We made sure it interfaced with the existing operating system from the power station’s own control room,” added Marggraff. “The power plant’s gates needed to be opened in a very precise sequence to protect the vane inlet control mechanism for the turbines from a sudden rush of water. The radial sluice gates also needed to follow a precise opening and closing procedure because erosion and vibrations into the dam wall can become problematic if the gates are opened in an incorrect sequence or kept at incorrect positions.”
Together with Kulula Technologies, Hytec developed and programmed the software using a Siemens S7 PLC to ensure the accurate positioning of the gates and the control of the non-operating areas of the sluice gates, preventing an operator from entering undesirable instructions into the control system. This greatly enhanced the overall safety of the system and improved ease of operation. The system was further tested to shut the gates safely within the required 60 seconds. All alarms and trip conditions were time stamped for traceability to highlight any potential problem areas, additional operator training required or any possible misuse.
When asked about the project’s main challenges, Marggraff explained that daily temperatures of around 44°C, the removal of the original 30-year-old cylinder connections from the intake gates and rigging the equipment over the completed dam wall made the project demanding, not to mention the language barrier. “We also had to co-ordinate the delivery of the cylinders from Bosch Rexroth in Holland with the arrival of the supporting equipment from South Africa via shipping containers, which meant managing the permits and other logistical challenges; but we successfully completed this large-scale project and we are proud of our achievement,” concluded Marggraff.
For more information contact Klaus Marggraff, Hytec, +27 (0)11 975 9700, [email protected], www.hytecgroup.co.za
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| Email: | [email protected] |
| www: | www.boschrexroth.africa |
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