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Mayr10414technical articles

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Brake monitoring currently engaged in the Stage Technology more and more into focus. The built at the stage drives electromagnetic braking systems are put to the test, because they have to save lives in an emergency. Mayr Antriebstechnik can already provide braking systems available that are optimized and equipped for proper braking monitoring.

Brake systems in stage technology are selected by the planners and installed by the system manufacturers. After the initial acceptance by the expert, however, they often fall into oblivion more or less often. The brake systems, for example, have a responsible task in prospect trains: they must save lives in an emergency. In the event of a power failure or emergency stop, it is imperative that the load bar is brought to a standstill as quickly as possible before personal injury or property damage can occur. But can the built-in brake system really do this in an emergency? Is the one-year review by the expert sufficient in this respect, or does more frequent monitoring, targeted brake monitoring, be required?

Enlightenment work is necessary

Contrary to the allegation that brake manufacturers would not care enough about the specific use of the brakes; The drive specialist has been successfully providing information for years to the plant manufacturers and operators, who are often only provided with insufficient data and operating instructions. The company has set itself the task of making winch drives for stage technology safe. To this end, the Allgäu develop industry-specific safety brakes and supply plant manufacturers and operators with the industry-specific data required in a targeted manner. If necessary, the engineers even develop new procedures or create new series of tests to provide missing data and incorporate them into the final test. The recently introduced, newly developed non-contact release monitoring by means of magnetic field-fixed initiator is just one example. It compensates for the known disadvantages of the hitherto commonly used mechanical microswitch in common brake systems of all manufacturers.

The existing brake systems of the manufacturer can be mechanically upgraded for a comprehensive brake monitoring. However, the brakes in stage technology do not receive enough attention from the control side today. The control system still requires a limited number of potential functions to be queried, monitored and documented in order to make the system transparent and even safer.

Release monitoring increases safety

By contrast, in the lifting axles of industrial plants, the company has been using appropriately equipped brake systems for a long time. Here too, similar to stage technology, it is a matter of deliberately and reliably excluding personal injury and property damage. So-called safety systems - a software solution tailored to the braking system - are integrated in the control systems used here. At fixed intervals or before a pending increased safety requirement, these brakes are provided by the so-called Release Monitoring permanently polled for their switching function. In addition, in order to be able to conclude the static braking torque, the motor drives against the closed brake with a motor current value and time window defined by the system manufacturer. If the defined motor current value is reached, then also the static braking torque in order and axis is safe. If, on the other hand, the motor can "pull through" the brake before the motor current value is reached, the axis is blocked. The controller in this case detects an axis that is not safe. So that the system can be released again for further processing, previously defined processes must be carried out.

The motor current therefore makes it possible to determine the braking torque almost exactly as the most important variable when using safety brakes. There is currently no direct reading option on the brake system itself. In addition, there is already the possibility today to equip the brake systems with the aforementioned non-contact, fail-safe release monitoring, temperature monitoring, wear monitoring and the corresponding rectifier components switching time optimized. The brake manufacturer thus also creates the conditions for stage brakes in order to be able to integrate brake monitoring into the control system in the future.

Conditioning of friction linings

Mayr20414Not negligible are the brake pads with the possible friction lining conditions. Because a brake system is only as good as the selected friction system with corresponding friction lining and its actual state. Currently, a safety brake is delivered with a friction lining in "green state". Although this guarantees the minimum nominal torque, the surface is not yet classified as thermally stable.

The term "green state" is used when the friction lining has not yet done any friction work, that is, it has not yet been braked or conditioned. If the friction linings are not braked after the traction drive has been installed, they can be destroyed during the acceptance test by the expert in the worst case scenario. Because of the maximum load can lead to a thermal overload of the friction lining surface. A conditioned friction lining can absorb much higher friction work in the form of thermal loads due to its achieved after braking properties, without being destroyed.

No compromise in terms of safety

A thermally overloaded, destroyed surface must never occur during operation. In this case, it must be assumed that there is no longer a functioning friction pairing - and thus a brake system that no longer functions. The coating is thermally destroyed and the braking torque is in an indefinable value. A secure hold is therefore no longer guaranteed. Therefore, the process of conditioning in the future should be part of the brake monitoring and integrated with the controller. This stabilizes the braking system for its long service life. The conditioning causes braked friction linings with improved reaction and optimum operating characteristics.

However, general information on the required data for the conditioning or for a Auffrischungsvorgang the friction linings are not possible. Improper use can lead to the destruction of the friction lining and consequently to a loss of braking torque. Specific data can be requested from the manufacturer. These are then stored as required in the control as a data record.

In addition, the associated installation and operating instructions are already extensively designed and can be retrieved industry-specific. Special adjustments and additions are possible on request at any time.

A basic requirement for brake monitoring in stage technology is a precise definition by the respective responsibilities and finally the implementation by the plant and control manufacturers. Already today there are optimized and equipped systems for targeted brake monitoring. It is therefore no longer a question of whether the necessary technology is available, but only more, if you want to operate the additional effort for greater safety and reliability. There should be no compromise on security though.
Image above: Magnetic field-proof initiator: Mayr brake systems can be equipped with a non-contact, fail-safe release monitoring and with temperature and wear monitoring.
The author is Peter Lucke, branch manager for stage technology at Chr. Mayr GmbH + Co. KG in Mauerstetten.
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