intorq articles

Functional safety: TÜV certifies INTORQ BFK458 also as an operating brake

INTORQ 1/30/2018

BFK458 Functional SafetyThe characteristic safety values for the successful INTORQ brake series BFK458 have recently been tested and confirmed by the TÜV. For the brake torque range between 4 Nm and 600 Nm, the customer will now have at his disposal the characteristic safety values for the 9 sizes for his own proof of functional safety. This results in less testing efforts for the customer for both their use as a holding brake and as an operating brake and it simplifies the proof of safety for the entire drive.

"The customer feedback shows us that we can now provide important data with the available and tested characteristic safety values that our competitors cannot provide", says Dr. Matthias Callesen, INTORQ Product Management.

The basis for the verification of suitability is the number of switches determined in a series of tests until the dangerous failure of 10 percent of the brakes is reached during the test. A dangerous failure that may pose risks for people and machines means that the brake will no longer achieve the required minimum torque. The reliable adherence to the brake torque is often to be verified, especially for applications that involves suspended loads (cranes and hoists) or a high drive dynamic (robotics, machine tools, packaging machines) in order to prevent damage.

The rating of the safety function of the modular brake series BFK458 of sizes 06 – 25 for single brakes was carried out for the Performance Levels PL-c as well the Safety Integrity Levels SIL-1. For the double brake, a higher level PL-d and SIL-2 was accepted due to the redundancy.

The requirement for the adherence to the safety function is the intended use and the reliable installation of the spring-applied brake on the motor. During the planning, a noise-reduced rotor with a toothed intermediate ring is to be selected and a fail-safe shaft/hub connection is to be designed by the customer. The wear of the friction lining must be checked under the load of the application. The brakes are also to be planned so that 80 percent of the specified rated torque is sufficient for the vital function.

If safety prompts are integrated into the drive control, the brake might be rated at a higher performance level. Detailed characteristics such as MTTFd or PFHd are provided on request and will support the mathematical proof for the functional safety of the drive system.