fluid · 05 2024 13 Spektrum In recent years, most manufacturers of compact and mini diggers have developed a range of machines with electric drive in parallel to their traditional product range. At the outset, these electric diggers were regarded sceptically, but have now captured their market despite their higher procurement prices. There are many reasons for this: Operating these machines produces neither exhaust gases nor noise emissions, and their performance is now almost equal to that of conventionally powered machines. This profile of properties is especially sought after on inner-city construction sites. It is therefore to be expected that electric drives will prevail in ever higher performance ranges, and not just on diggers. Noise reduction by acoustic decoupling is also an issue with other mobile and electrically driven machines – for example with municipal vehicles. In agriculture, the needs of the user are particularly important: it is easier to work with greater focus in an electric tractor with noise-reduced hydraulics. Two sources of hydraulic noise emissions With conventional diggers, the internal combustion engines (specifically: engine and exhaust noise) are the number one sources of noise. This is followed by operating noises that occur, for example, during excavation – for example, when the digger bucket hits stony ground. Generally, the hydraulics are only the third most common emitter of noise. The order is different with construction machinery fitted with electric drives. Their motors operate quietly, and the operating noises occur only occasionally. This places the focus back on the hydraulics as a source of noise. Basically, a distinction is made between two sources of hydraulic noise emissions. The primary source is the operating noise of the pump. In addition to the noise of the drive itself, the movement of the hydraulic fluid, triggered by the pump, including the pressure pulses in the oil circuit, tends to dominate. The influence of this source can be reduced by low-pulsation or low-noise pumps, and further minimised by damping elements, such as rubber-coated metal rails. This addresses another important solution: acoustic decoupling. It concerns reducing the spread of structure-borne sound. Acoustic decoupling This approach addresses a noise source that contributes more to the sound level than the primary emission, especially in hydraulics. The pumps and the hydraulic fluid that moves or pulsates due to the actuators in the system cause surrounding components, such as lines and containers, to vibrate. This can be felt as vibrations and subsequently as sound emissions. These noises are not only propagated in the hydraulic system along the widely branched lines, but are also amplified by causing other system components and, if fixed, adjacent components to vibrate. Converted into airborne sound, they then reach the human ear as an unpleasant roar. Plastic clamps to fasten hydraulic lines were developed by Stauff, the German developer and manufacturer of components for hydraulic line systems, some sixty years ago. Among other things, their aim was to dampen vibrations and noises in the hydraulic system, and they have significantly helped with sound decoupling. The basic version of these plastic clamps reduced In general, plastic clamps can also be used for the protection or routing of electrical cables and cable bundles.
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