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Explosion prevention is a hot issue within the field of systems engineering/Friction, overheating or sparks could lead to a horror show in potentially explosive environments
Beer-Fördertechnik is a renowned manufacturer of custom-made system components for bulk goods technology. They had been searching for a drive-solution using an integrated brake assembly to optimize the safety of their vat drainage equipment that is primarily used in the chemicals industry. The equipment provides vat drainage of toxic powder materials with grains smaller than 100 µm, a bulk weight of 0.86 kg/l and ignition energy of less than 20 mJ.
DEPRAG is known for its individual client oriented solutions. The engineers at DEPRAG have developed an air-motor holding and brake-drive-system that guarantees explosion prevention in potentially explosive environments according to ATEX. The system also ensures practically dust-free drainage of toxic products from the Beer vat draining equipment with a loading volume of up to a maximum of 200 kilograms.
Beer-Fördertechnik is based in Bad König, Germany and since 1976 the company has been involved with batching, conveying and transportation. Their machinery is designed and built to individual client specifications. They have accumulated a large product library after 30 years of working together with many large companies in the most varied fields and technologies, including chemicals, pharmaceuticals, food processing, mining, energy, waste disposal equipment and back plates.
Wilfried Beer, managing partner of Beer Fördertechnik speaks enthusiastically of the immense advantages of this new type of brake motor. "By using this complete system for my vat drainage equipment, I can save myself enormous additional construction and manufacturing expenses because the brakes, which provide the safety for my mechanism, are already integrated."
This is how the innovative air motor with integrated brakes and planetary gear works: A vat is moved using the power of the air motor to begin a tilting and draining procedure. At the highest point, the dead center, the motor switches off and the brakes are applied, holding the current position.
The integrated brake, which acts as a holding brake, is comprised of three brake disks, a pressure spring and a piston. They are controlled separately using an airline. When the pressure in the control line is over 3-bar and the spring load is less than the compression force, then stress is taken off the brake disks and the motor can turn. If the pressure in the control line is below 3-bar and the spring load is greater than the compression force, then the brake disks are forced together and the motor is blocked.
To produce a motor, which could be authorized for use in potentially explosive environments, DEPRAG engineers had to think outside the box. If an air pressure of over 3-bar remained in the lines that control the brakes, then the brake disks could constantly rub against each other and cause excessive temperature increases. This would of course elevate the risk factor in potentially explosive areas. Gerd Zinn, Manager of the Serial Machine Development Department said: "By implementing a safety valve, we have minimized this risk." The valve turns the air feed off automatically when the pressure falls under 5-bar, causing the pressure applied to the brake to become zero. The brakes are then forced together fully and the motor is blocked.
Product Manager Dagmar Hierl is pleased, stating that, "with this entirely new type of drive system we have been successful in launching an attractive complete system on the market according to ATEX guideline 94/9/EG corresponding with: EX II 2GD c IIC T5 (95°). We are further expanding our leading role as a provider of air motors for all technology markets".
Because of the way they are constructed, air motors are ideally suited for use in potentially explosive environments. The principle is simple: The air pressure, which is created by a compressor, starts the motor rotation. Vane motors function in this way: The rotor, which revolves in an eccentrically set cylinder, is set in motion. There are vanes in its slots, which are pushed outwards against the cylinder wall through centrifugal force. Working chambers are created for the expanding air pressure. Through the expansion of this restricted supply-air, the compression energy changes to kinetic energy and the rotary motion is created.
There is also an additional advantage, in that the expanded air cools down and in fact becomes cold around the motor. Therefore, using an air motor in potentially explosive areas vastly reduces the risk of gases sparking under high temperatures.
Further advantages of this new type of complete system are explained by Project Manager Dagmar Hierl: "A compact planetary gear is needed for a brake air motor, so that the torque and necessary number of revolutions can be defined to fit the client's wishes".
Individual client requests often lead to innovative developments such as the ATEX conforming brake motor. The holding brakes developed for Beer-Fördertechnik are suitable for a braking frequency of up to 600 braking operations per hour.
They are now available in various torque ranges in the 1.2 kW stainless steel motor-program from DEPRAG.
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