Gear test benches for the wind industry
Wind turbine gearboxes have to withstand high loads during operation and are therefore put through their paces on the gearbox test bench: Here, real operating conditions can be simulated with torques and loads that arise from the dead weight of the system, the rotors and external influences such as wind or gusts. The load can be increased to 10 to 20 times the nominal operating load. Electric motors, flywheels and hydrodynamic brakes are installed in the transmission test bench to simulate the influence of rotor movements and wind. The data is obtained via sensors that measure parameters such as temperature, vibrations, loads and speeds and monitor operation.
The gearbox test bench is used to conduct extensive tests to identify weaknesses in gearbox prototypes and new gearboxes. However, tests are also carried out during series production to ensure quality by means of random sampling. In addition to series tests, overload tests are carried out up to the material limits – extreme loads can occur during normal operation in storms and gusts, when braking or switching off the system. The tests on the wind turbine gearbox provide information about the structural load capacity, quality and service life, energy transmission and heat generation. Noise and vibrations are monitored, as are the behavior of the material and possible deformations, as well as cooling and lubrication.
Gearbox test benches are designed to accommodate gearboxes of different types, sizes and manufacturers. In serial operation, these are tested one after the other. Parallel operation is only possible with several test benches. The occupancy times vary: while function and acceptance tests can take hours to several days, the test bench is occupied for up to several months for load and endurance tests. The same applies to development or prototype tests.
Kind of couplings in the transmission test bench
The shaft of the gearbox under test and the drive, such as a motor or flywheel, must be securely connected in the gearbox test bench. For this, mechanical or hydraulic shrink discs are one kind of coupling.
Hydraulic shrink discs generate high pressure, enabling a frictional connection without play between the parts, making the connection particularly precise and robust. The high torque and loads of the wind power can thus be safely transmitted from the drive shaft to the gearbox. The connection is secured against slippage or even breakage, regardless of temperature, speed or vibration. The critical areas are where component surfaces are joined. If the pressure of the pressing is insufficient, wear and tear will occur. If parts slip, there is a risk of so-called material wastage, which can cause major damage: in the planetary gear, for example, the carrier as the main component is one of the most expensive parts in the system. If it is damaged, it costs a lot of money. This does not happen with hydraulic shrink discs. They are designed to withstand high loads over the long term: not least because they are made of high-strength materials such as steel. The raw material is forged and rolled during production to achieve the greatest possible stability.
With factors such as energy consumption, maintenance, spare parts requirements and service life in mind, various types of couplings can be used in the transmission test bench. None of them stands out with particular advantages. However, another requirement is crucial in the test bench: quick assembly and disassembly, for example in serial tests.
Save time with hydraulic shrink discs
Hydraulic shrink discs make it possible to quickly get up and running and reduce the time the test bench is occupied.
Unlike mechanical shrink discs, which have to be bolted on, hydraulic discs are easy to mount and dismount. If necessary, the entire system can even be pre-assembled outside of the test bench. TAS Schäfer GmbH, a leading manufacturer of friction-locked connections in drive technology, has further simplified the assembly of hydraulic shrink discs with its bayonet system: the system generates the lock and blocks the retaining screws. This means that tools no longer need to be used to tighten screws. Assembly is faster and at the same time the workload for employees is reduced, because the locking process can be completed in seconds. By way of comparison, clamping wind turbine gearboxes on the test bench used to take up to one or two shifts, not least because the dimensions are extreme; a shrink disc here can quickly have a hub diameter of one meter. Today, it can be done in a few minutes. The market recognized: TAS Schäfer has become the market leader, and the bayonet system has established itself on test benches worldwide due to its easy handling and the great time savings.
Advantages are also noticeable in occupational safety. Hydraulic shrink discs from TAS Schäfer, for example, manage with significantly less pressure: They usually require 180 bar of pressure, with a maximum of 200. Others require up to 1000 bar to achieve the necessary compression and thus the frictional connection between the hub and shaft. The easy handling also has an impact on occupational safety, since the bayonet system eliminates the need to tighten screws one after the other.
Adaptability and maintenance
It is advantageous if it is possible to test different hollow shafts on the gearbox with just one hydraulic shrink disc. To do this, it must be adaptable to different diameters; its design requires adapter rings or slotted inner rings. This approach reduces investment costs, as one shrink disc can be used to cover different scenarios. This is also relevant for maintenance: if companies can service their own shrink discs, lubricate them and repair them, they can save a huge amount on investment costs. There is no need to ship the disc to the manufacturer, which would result in the disc being out of action for weeks. There is also no need to have a replacement disc available to keep the operation running during maintenance.
Companies overseas, in China and India, for example, benefit enormously from this. TAS Schäfer’s system makes such on-site maintenance possible by reducing the intensity of maintenance, using standard components such as O-ring seals or screws, and modifying components. This reduces wear and tear on components and makes it easy to replace them. With regular maintenance, shrink discs can last for over 15 years and achieve their maximum lifespan even under high loads.
More versatility
Quelle: https://energie-fachzeitung.com/getriebepruefstand-windindustrie/6869/