Problem solving

Modular, high-performance extraction unit

Extracting fine dusts during the manufacture of rotor blades for wind power generating equipment

Without glass fibre reinforced plastic (GRP) wind power technology would not have reached its present state of development.
Only GRP is light enough and strong enough for the construction of pods and rotors. These components have to be light enough to rotate in the wind and strong enough to resist storm-force gales.

Enercon GmbH is Germany's largest manufacturer of wind power plant and uses a lot of GRP components. Some plant components, such as the pods designed by top architect Sir Norman Foster, are manufactured by external suppliers. The development and manufacture of rotor blades are part of the company's core skills and these components are produced in-house.

Rotor blades are laminated and then hardened. In the final stage of the production process, the rotor blades are finished using high-speed hand sanding tools. This stage of the process produces a large amount of fine GRP dust and requires a high-efficiency dust extraction system to prevent the large amounts of dust being projected into the working environment at high speed. The dusts produced during sanding contain the plastic resin styrene, a hazardous substance which irritates the mucous membranes.

Not surprisingly, the fine sanding of small GRP parts takes place in special booths fitted with high-efficiency extraction equipment. This is of course not possible with large components such as rotor blades. Single rotor blades can reach lengths of 30 metres or more. The world's largest wind power station built by Enercon at Magdeburg in Germany has blades which are 52 metres long. That's the same length as 14 Volkswagen Polos parked nose-to-tail alongside the rotor blade.

Enercon takes the health and safety of its workforce very seriously and has invested greatly in dust extraction solutions at source, at the hand sanders.

Ruwac Industriesauger GmbH has developed a central extraction plant for Enercon which meets all the company's health and safety specifications and cost-effectiveness requirements. The two rotor blade production workshops in the company's Aurich production facility have a ducting system with connectors for the hand-operated sanding tools. This means that the sanders can be used almost anywhere. A controller measures the amount of suction power required and switches the three central suction units on and off accordingly. The suction units generate a negative pressure of 2,800 mmWS and operate with air flow rates up to 704 m³/h.

The dusty air extracted at the workstations first goes to a high-speed cyclone where the larger GRP particles are separated out and collected in a silo. When the dust in the silo reaches a preset level, a pipe butterfly valve opens and the dust is fed into a big bag. 95% of the extracted dust is dealt with cost-effectively in this way.

A large, Class C filter is mounted downstream. This filter holds back the fine GRP dust that constitutes a health hazard.
Sensors control the filter status. When the filter requires dedusting the PLC displays a message to this effect for the operator. Dedusting is done with compressed air. If the operator ignores the dedusting message, the PLC will shutdown the extraction plant automatically.

This method provides a safe, reliable method for extracting GRP dusts from extracted air during sanding of the rotor blades. The extraction plant is very efficient and extremely cost-effective. Most of the dust is separated out inside the low-maintenance, high-speed cyclone. All the individual plant components such as the cyclone, the vacuum units and the filter come from Ruwac's modular range. Modularity guarantees that Enercon has a tried-and-tested extraction system tailored to its exact needs.