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A powerhouse in the drainpipe - and supplier of green electricity

29 February 2012

Four applications demonstrate powerful versatility of air motors.

Dagmar Dübbelde, from drive specialists DEPRAG SCHULZ GMBH u. CO., described the air motor as a “universal genius”, and gave four impromptu and exciting examples of how such motors are deployed. As a compact power pack, it helps a cutting robot to battle its way through the muck inside the drainpipe. The air motor adds enormous power to a truly amazing transporter device. As an ATEX-compliant brake motor for potentially explosive areas its job here is to optimise a barrel emptying system. As an innovative GET turbine generator its energy recovery credentials are extremely “green”; it even generates power from small amounts of process gas.

Temperatures globally have been rising inexorably for 30 years now. Researchers and industrialists have struggled to counter the effects of climate change with innovative products and processes. At its test laboratory DEPRAG is producing the prototype of Furore, its Green Energy Turbine generator (GET), which is able to convert even small quantities of unused process gas into usable energy. The ambitious project is now sufficiently far advanced that it can be tested in conjunction with appropriate partners. DEPRAG Managing Director Dr. Ing. Rolf Pfeiffer said: “In a small, local energy recovery plant our progressive new turbine generator can convert even tiny amounts of residual energy, of between 5 and 20 kilowatts, into electric power.”

The innovative DEPRAG turbine generator is based on the expansion turbine principle. The GET represents a compact unit consisting of a turbine and a generator that has been developed especially for this application. Excluding its control cabinet, it is not much bigger than a shoe box, and can be used locally on the “plug and earn” principle wherever unused gas either exits from the industrial process or where the pressure level is decreased from high to low.

The gas flows into the turbine, where it is pushed through nozzles and accelerated. As it meets the blades on the turbine and is diverted, it releases its energy. The kinetic energy is converted into electrical energy inside the generator. The turbine and generator represent a compact unit, and share a common shaft. The result is that the turbine rotates, the generator rotor rotates at the same speed - and electricity is produced!

Helmut Pfeifer, applications technician at Bodenbender GmbH, who has worked in drainage repair technology for 30 years, literally swears by the virtues of the air motor - such as its indestructible robustness and its tremendous power density. While previously, work on main drainage systems meant that road surfaces had to be dug up, today’s modern reinstatement concepts mean that excavation work is a thing of the past. The defective drainpipe is not replaced, but is relined instead.

A type EU Robot 150 milling robot by BRM GmbH, based in Biebergmünd, near Frankfurt-am-Main, is inserted through the manhole into the defective pipe. The milling robot removes deposits, smooths out casing cross-overs, cuts away any protruding sockets, and removes encroaching roots. A DEPRAG air vane motor, which never fails even under the most difficult of working conditions, runs tirelessly inside the robot’s cutting head. It is only 118 mm long and 57 mm diameter. With output power of 600 W, rated torque of 0.95 Nm and a speed of 12,000 rpm, this machine is just perfect for use in tight spaces. Systems technician Helmut Pfeifer said: “The performance of this compact drive is second to none.”

Once the milling work is complete the actual repair work begins. An “inliner” tube impregnated with special resin is introduced into the defective pipe. Hot water runs through the tube and this causes the hard resin to react. Ninety minutes later it has hardened sufficiently that the special drain section reinstatement is complete. All that now remains to be done is to carefully open the inlets into the pipe that became sealed during the process.

How is it possible for a person to move huge rolls of paper weighing several tons using just one hand, or effortlessly push railway carriages back and forth - or even manhandle an aircraft into its parking spot inside a hangar. It sounds like magic, but it can be done - with the “Easy Roller”. Its very name explains how it works. Using this inconspicuous roller transporter one person can manoeuvre weights of up to 100 tons without major physical effort.

A cable roll weighing several tons requires careful manoeuvring. To do this, the “Easy Roller” is simply placed in position in front of the cable drum. It travels on two rubber rollers and the device’s rubber drive roller is positioned above these. Springs press the front roller against the drive roller, and to start with there is empty space at the rear one. The worker now actuates the manoeuvring valve handle and an air motor starts up, setting the drive roller in motion by means of a chain.

What is actually happening? The drive roller transfers the movement to the front roller and the Easy Roller now moves towards the cable drum. At the same time, the manoeuvring device is pressed down, and this also creates contact from the drive roller to the rear travelling roller, where the forward rotation torque is transferred. When the contact pressure on the rubber drive roller, which is pushed with increasing pressure against the object, is high enough, the torque transfers to the cable roll - it now moves and rolls along!

In this amazing piece of equipment too an air motor takes care of the power drive. The DEPRAG stainless steel air vane motor produces 1.2 kW of power. 218 mm in length, and with a 100 mm diameter, it weighs a mere 9.1 kilogrammes. It rotates constantly to the right and has an idle speed of 100 rpm, with a rated torque of 500 Nm. Once he had weighed up all the factors, Andreas Hufmann, Managing Director of Easy Roller GmbH in Feucht, Germany could see that there was only one air vane motor candidate for this job.

The air motor also cuts a fine figure in potentially explosive areas. A special brake motor complies with all the explosion-protection regulations imposed by the ATEX Directive 94/9/EC. A complete system consisting of air motor, holding brake and gearbox has been built for Beer Fördertechnik, who for 30 years have been manufacturing bulk goods handling systems. The drive system with its integral brake is used to optimise a Beer low-dust barrel emptying system to empty toxic products at load volumes of up to 200 kg.
An ATEX-compliant brake motor was the result, and today it forms part of DEPRAG’s range of stainless steel motors. The barrel emptying system works as follows: An air motor places the barrel in motion, and the tipping and emptying process begins. At the highest point, the dead point, the air motor switches off, the brake comes into action, and holds the barrel in position.

The integral holding brake consists of three brake discs, a pressure spring and a piston. It is triggered separately via a compressed air line. When the pressure is above 3 bar, the spring tension is less than the pressure force - the brake discs have no load and the air motor can rotate freely. If the pressure falls below 3 bar, the spring tension is greater than the pressure force - the brake discs are pressed together and the air motor is blocked. A safety valve prevents any remaining compressed air in the line from causing any inappropriate friction on the brake discs. A compact planetary gear system, sized to suit the customer’s torque and speed requirements, rounds off the system.

For several decades DEPRAG SCHULZ GMBH u. Co. has been involved with air motors and the wide variety applications for them. Product manager Dagmar Dübbelde summarised her view of the benefits of such motors: “Air motors - they are from a proven technology, on the basis of which we are constantly able to derive pioneering and innovative products, such as the energy recovery turbine generator. Moreover, these robust air motors can be put to use wherever an overload-safe, high performance drive is required and where conventional motors would simply not operate”.

For further information, please contact: Dagmar Dübbelde, DEPRAG SCHULZ GMBH u. CO.
Phone: +49 (0)9621 371 343
FAX:  +49 (0)9621 371 199
E-Mail: d.duebbelde@deprag.de
Internet: www.deprag.com
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