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 3 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 at Hytec, Klaus Marggraff. “Upon further inspection, it was decided to replace all of the hydraulic systems to drastically 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, and 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 4 400 tons each. “This meant our 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 weighs 13 tons, and with critical planning, took 3 days to install by carefully lowering the ancillary equipment, and then the cylinders to the bottom of each gate,” says Marggraff.
Hytec installed a new mechanically articulated linkage system and supplied power packs for operating the cylinders. The system features a high degree of redundancy with the ability for the cylinders to be operated by any of the 5 installed power packs, should a power pack not be available.
The power generation intake gates feature 7 cylinders, each with 500 mm bores, 160 mm rod diameters and 7.5 metre’s strokes – also with integrated positioning systems. Due to the rods’ constant exposure to water, the cylinders have been supplied with a stainless steel rod and a chrome layer to reduce the risk of corrosion. Ensuring that no water seeps 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’ve made sure it interfaces with the existing operating system from the power station’s own control room,” adds Marggraff. “The power plant’s gates need 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 need 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 a sluice gate preventing the operator entering undesirable instructions into the control system. This greatly enhances the overall safety of the system and improves ease of operation. The system was further tested to safely shut the gates within the required 60 seconds.
“All alarms and trip conditions are time stamped for traceability. It gives us an idea about potential problem areas and what additional operator training may be required. It also highlights any misuse, which we’ll pick up when we perform site visits,” added Marggraff.
When asked about the project’s main challenges, Marggraff explained that daily temperatures of around 44°C, and removing 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 precisely 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 the project and we are proud of this large-scale project,” concluded Marggraff.
From: CubicICE (Pty) Ltd (011) 705 2545
Submitted: Zelda Onay [email@example.com]
Compiled: Ryan Joubert
PR: PR HYT 3700 Roseires Dam