Wear and Maintenance 

Wear to spring-applied brakes

INTORQ spring-applied brakes are wear resistant and designed for long maintenance intervals. The friction lining, the tooth system between the brake rotor and the hub as well as the brake mechanics, however, are all of course subject to function-related wear. For safe and trouble-free operation, the brake must therefore be checked, adjusted or replaced on a recurring basis.

The following table describes the various causes of wear and their effect on the components of the spring-applied brake. For calculating the service life of the rotor and brake and for determining the maintenance interval to be specified, the decisive influencing factors must be quantified. The most important factors here are the dissipated friction energy, the initial speed of the braking and the operating frequency. If several of the causes of wear to the friction lining occur simultaneously in an application, the influencing factors need to be added when calculating the wear.

Component

Cause

Effect

Influencing factors

Friction lining
Braking during operation
Emergency stop
Wear caused by overlapping when the drive is started up or shut down
Active braking via the drive motor with brake support (Quickstop)
Wear during start up in motor mounting position with vertical shaft, inc. with open brake
 Wear to the friction lining
Dissipated friction energy
Number of start-stop cycles
Armature plate and flange Brake pad rubbing Armature plate and flange wearing down Dissipated friction energy
Tooth system on the brake rotor Relative motion and jolts between brake rotor and brake hub Wear to the tooth system (primarily rotor-side) Number of start-stop cycles
Support for the armature plate Load alternation and jolts in the reverse backlash between the armature plate, sleeve bolts and guide pins Armature plate, sleeve bolts and bolts knocked out of position Number of start-stop cycles, level of braking torque
Springs Axial duty cycle and shearing force load of the springs through radial reverse backlash of the armature plate Weakening of the spring pressure or failure due to fatigue Number of brake switching operations



Maintenance and inspection of spring-applied brakes 

For safe and trouble-free operation, spring-applied brakes must be checked and maintained on a recurring basis. In the plant, the expenses associated with service work can be reduced by ensuring that the brakes are easily accessible. This should be taken into consideration when fitting the drives in the plant and during installation.

The necessary maintenance intervals for working brakes are derived initially from the load on the brake in the application. When calculating the maintenance interval, all causes of wear must be taken into consideration. For low-load brakes, e.g. holding brakes with emergency stop, it is recommended that a regular inspection is carried out at fixed time intervals. To reduce costs, the inspection can be performed during other regular maintenance work carried out at the plant.

If the brakes are not maintained, this can result in failures, loss of production or damage to the plant. Therefore, a maintenance concept adapted to the operating conditions and brake loads must be drawn up for each application. The following table lists the maintenance intervals and work required for the INTORQ spring-applied brake series. Maintenance work is to be carried out in line with the detailed descriptions in the INTORQ operating instructions for the respective brakes.


Series

Time interval

Maintenance work

BFK457-xx
BFK460-xx
BFK461-xx
BFK458-xxx
BFK468-xxx
 For service brakes:
  • As shown in service life calculation,
  • Otherwise half-yearly,
  • At the latest after 4000 operating hours

For holding brakes with emergency stop:
  • At least every 2 years
  • At the latest after 1 million cycles
 Inspections for an installed brake:
  • Check release function and control
  • Measure air gap (adjust if necessary)
  • Measure rotor thickness (replace rotor if necessary)
  • Thermal damaging to armature plate or flange (dark blue starting action)

Inspections after brake dismantled:
  • Check backlash of the rotor tooth system (change rejected rotors)
  • Move away torque support on sleeve bolts and armature plate
  • Check springs for damage
  • Check armature plate and flange
    - Evenness of BG06-BG12 > 0.06 mm
    - Evenness of BG14-BG25 > 0.1 mm
    - Max. infeed depth = nominal air gap of the BG
Brakes with defective armature plates, sleeve bolts, springs or flanges must be completely replaced.
BFK458-xxL For service brakes:
  • As shown in service life calculation,
  • Otherwise half-yearly,
  • At the latest after 4000 operating hours
For holding brakes with emergency stop:
  • At least every 2 years
  • At the latest after 10 million cycles
  • Plan shorter intervals for frequent emergency stops
BFK418-xxR Holding brake with emergency stop:
  • At least every 2 years
  • At the latest after 5 million cycles
  • Plan shorter intervals for frequent emergency stops
 Inspection of the brake fitted in the motor:
  • Check release function and control
  • Wear control only possible by measuring the release current (current?)Worn-out BFK418s must be completely replaced - repairs not possible.


As a general rule, during inspection and maintenance work the following must be taken into consideration:

  • Remove any contamination from oils and greases with a brake cleaner, determining the cause of the problem and then, if necessary, replace the brake. Any dirt or particles in the air gap between the stator and armature plate can affect the function and must be removed.
  • After replacing the rotor, the original braking torque is only reached after the friction surface has been broken in. After changing the rotor an increased initial wear occurs on worn-in armature plates and flanges. In this case, adjust the air gap early on if necessary.