Divided into two power plant groups, the turbine, generator and pump each operate as required. The problem of employees being affected by operating noise is similar at all sites. As the youngest of the Schluchsee Group's power plants, the Waldshut power plant was chosen as the location for a pilot project to improve the working environment. Its maximum flow rate in pumping mode is 40 cubic meters of water per second. The Waldshut power plant generates around 170 million kilowatt hours of electricity every year.

Vibration-insulating panels of the types SLAB 170 to SLAB 720 can be manufactured in many shapes. They have natural frequencies between 12 and 50 Hertz and can be used in load ranges between 0.002 and 0.5 Newton per square millimeter. © ACE

Containment of operating noise
The screw pumps installed there play a large part in this. Weighing 300 kilograms each, they are also at the heart of the noise problem. This is because the direct transmission of the forces generated during the pumping process to the water tank causes the entire structure to vibrate. This is mainly due to the high air content of the oil pumped in the tank. The resulting background noise is so loud that almost all employees at the power plant feel disturbed. To change this, the Schluchsee plant turned to ACE. "We have already worked with ACE shock absorbers on several occasions in recent years," says Gerhard Bockstaller, Production Specialist at the Waldshut power plant.

Udo Fischer, who works for ACE as an engineer and customer consultant in south-west Germany, noticed that it was not just the pumps themselves that could be the problem, but also the way they were bolted to the foundation. He contacted the ACE development team for vibration technology at the company headquarters in Langenfeld in order to fulfill Schluchseewerk's request for structure-borne sound insulation by six decibels in the best possible way. As a result of the assessment, the customer was suggested an elastic screw connection using vibration-insulating panels from the SLAB family to reduce the operating noise measured at 86 decibels. "Udo Fischer and his team took care of the design, test phase and installation of their products for us," says Gerhard Bockstaller.

The consideration of all factors quickly led to the vibration isolation panels from ACE. These are available in three different product families and qualities in the company's vibration technology range. An initial indication of which of ACE's three different panel types would be most suitable in Waldshut was provided by the design using the company's own software. The program can be used to find the correct material type depending on the load by determining the desired insulation in relation to the excitation frequency.

Measurement afterwards with sensor attached to the receiver side: The use of ACE SLAB leads to an isolation of the vibrations by 6.6 decibels. © ACE

The decision was made to use SLAB panels of type SL. These universally applicable vibration insulation panels made of elastic PUR materials can be used in a variety of ways. They are available ex works in Langenfeld with different damping properties, various permissible surface pressures and in variable standard densities and can be ordered, cut to size and delivered directly from there in any desired shape using the online configurator.

Isolating the vibrations
In Waldshut, the first task was to isolate the actual source of the noise. To this end, the ACE team fitted SLAB plates between the tank and pump and between the screw head and pump. This was done in the form of a so-called elastic mounting. With the help of the illustrated screw connection, it was possible to completely separate the structure-borne noise transmission from the transmitter, namely the pump, to the receiving tank. The theoretical calculations carried out in advance predicted a reduction of 6.6 decibels as a result of this measure. Vibration measurements carried out by the team at the customer's request during installation confirmed the theoretical assumption that the special type of elastic screw connection could prevent the residual transmission of vibrations through ACE.

At the end of the day, the customer and ACE were delighted with a value of 6.6 decibels and the fact that the theoretically determined value could be precisely achieved in practice on site and even reduced by ten percent compared to the six decibels targeted by the customer. Depending on the application, ACE offers the measurement service included. If you also consider that a level reduction of three decibels already corresponds to a reduction in sound energy of 50 percent and a reduction of ten decibels is accompanied by a halving of the volume, this result can be seen as a major step forward.

Thanks to the elastic screw connection using SLAB vibration isolation plates, it was possible to completely isolate the structure-borne sound transmission from the transmitter, in this case the pump, to the tank below. © ACE

The fact that ACE's SLAB products can be cut to size and are easy to fit by gluing proved helpful in this solution. This makes them ideal for many damping requirements. The high-tech material made of microcellular polyurethane elastomers is foamed with water in an environmentally friendly way. Thanks to the foaming option, it can also be applied to other materials such as self-adhesive carrier films or wear layers. This increases the range of applications for these products.

To further increase working comfort by further reducing noise, the solution described is supplemented by sound insulation of the drive motor. However, the range of applications for the vibration-insulating SLAB panels from ACE presented here goes far beyond this case. Other areas of application include the reduction of vibrations in the foundations of plant and machinery, pipeline insulation or the stabilization of test benches, measuring tables and their foundations. as