1 year ago

MDA Technologies 5/2015

MDA Technologies 5/2015

earings. Rodriguez

earings. Rodriguez custom manufactured twelve of these components for a well known manufacturer of telescoping offshore gangways. “The required size was determined through intensive discussions and extensive calculations and tailored exactly to the customer’s requirements”, explains Michael Koprek, Product Manager. The result: externally toothed ball bearing slewing rings of high-strength CrMo - alloyed tempered steel (42CrMO4V) with an outer diameter of 3,600 mm, an inner diameter of 3,180 mm and an overall height of 185 mm (outer race height: 138 mm, inner race height: 178 mm). By way of comparison: ball bearing slewing rings for standard applications such as rotary tables for welding robots have a maximum outer diameter of 1,600 mm. Due to the double-row design, each of the special ball slewing rings can bear axial 01 Rodriguez has ball bearing slewing ring with an outer diameter of ten centimetersor almost four meters About Company name: Rodriguez GmbH Headquarters: Eschweiler, Germany Products: Shafts, precision bearings, linear technology. loads of up to 17,500 kN and overturning torques of up to 12,000 kNm. In order for the bolts to withstand these torques the races of the double row slewing bearings were manufactured with a non-standard hole pattern. Long maintenance intervals were an important requirement for reliable use on the high seas. This is ensured in the case of the gangway bearings by central lubrication, which makes the ball bearing slewing rings virtually maintenance-free. Only the threaded joints and the bearing clearance have to be checked at regular intervals. For the seal material Rodriguez chose a special nitrile butadiene rubber (NBR) that features temperature resistance down to -40°C. Due to the completely encapsulated design of the bearings they are not in direct contact with saltwater. Nevertheless, the bearings must pass special tests. “Our double row slewing bearings were subjected to special tests to prove that they can withstand the harsh offshore conditions,” says Michael Koprek. Ultrasonic and surface crack tests were used, for example, to test the forged rings for internal and external defects. Tensile and Charpy impact tests were used to determine the mechanical and technical properties. All test results were carefully documented. The bearing of choice Ball bearing slewing rings are the best choice for supporting high overturning torques or if the construction requires large bearing diameters. The bearing technology must be robust and durable, yet precise. In addition to double-row ball bearing slewing rings for higher loads such as use in gangways or crane systems, Rodriguez also offers single-row four-point ball bearings for standard applications and cross roller slewing rings for heavyduty applications. The construction of the four-point ball bearings allows reliable support of radial and axial loads as well as overturning torques. By combining the bearings and connecting elements in a single component, it is possible to reduce the costs for the design of the connection construction. Therefore, they not only fulfil the requirements for overturning stability and the size of the bearing diameter, but also for cost effectiveness. The product spectrum of the Eschweiler-based drive 02 The company’s product portfolio comprises outer-, inner- and non-toothed ball bearing slewing rings specialist offers two single-row four-point bearing series, which are equipped with double-sealed systems: the light KDL or KDLH (H = high)series and the medium KDM/KDMH series. KDL/KDLH slewing rings are suitable for light applications with average requirements for precision, such as the positioning of tool magazines in machining centers. The compact KDM/ KDMH bearings are designed to fulfil higher requirements for precision and loadbearing capacity. All ball bearing slewing rings are available in the versions nontoothed, externally and internally toothed. The operating temperature of the slewing rings of both series is from -25 to + 80 °C. Individual solutions Rodriguez can deliver all single- and double-row ball bearing slewing rings with outer diameters from 100 to 5,000 mm. The sizes up to 1,600 mm are manufactured by Rodriguez at it’s production facilities in Eschweiler, Germany. Larger dimensions or custom modifications of the standard ball bearing and cross roller slewing rings, such as the double row axial bearings for offshore use, can also be implemented. Examples of such customizations include limiting the bearing clearance, centering or heat resistance up to 150 °C.Customers can likewise request bearing rings with a special hole pattern, special seal materials or a protective finish. Stainless steel versions can also be implemented easily. Photographs: teaser fotolia, 01+02 Rodriguez MDA Technologies 5/2015 23

RUBRIZIERUNGSEBENE I RUBRIZIERUNGSEBEBE 2 SKF replaces 6-tonne slewing ring bearing in just 4 days In the port of Narvik (Norway), Swedish mining company LKAB employs a gigantic shiploading station to load bulk carriers with iron ore In the Norwegian port of Narvik, Swedish mining company LKAB employs a huge loading station to load bulk carriers with iron ore. Any shutdown of the station is enormously costly. Because, in this instance, time really is money, experts from the SKF Solution Factory had to work hard against the clock when replacing a slewing ring bearing. Weighing a total of 2,500 tonnes, the gigantic loader in the port of Narvik (Norway) ensures that iron ore from the mines, finds its way into the entrails of the ships. Max Andersson of the SKF Solution Factory explains: “This port sees a vast number of bulk ore carriers riding at anchor – lining up like a string of pearls. They‘re all ‘on standby’, waiting to be loaded.” He goes on to explain the implications: “If the ship-loading does not run like clockwork and suddenly comes to a standstill, things get seriously expensive. Every hour beyond the agreed loading times that the carriers have to hang about out there consumes huge sums of money.” So, in this case, time really is money. “That makes it all the more advantageous for the companies involved if the maintenance work can be done within the shortest possible time,” says Andersson, emphasising the point. The resulting time pressures then present considerable challenges in terms of planning and personnel. The shiploader‘s range of movement is based, among other things, on two huge slewing ring bearings. The Narvik giant has one at the front and one at the back; both were last replaced almost 20 years ago. “So it was time for a replacement if smooth operation was to be maintained into the future as well. With this in mind, we were first commissioned to replace the rear slewing ring bearing, weighing 6 tonnes, with a new one,”says Andersson. At the start of the project it was agreed that the SKF team was to perform the changeover within 10 days. However, no sooner had the relevant studies been commenced than it became clear that the output of the mines would require leaner ship logistics. So as not to slow down the mining operations and hamper logistics, the mining company LKAB and SKF finally 24 MDA Technologies 5/2015


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