Overhead crane safety:

  1. The most important safety feature of the crane is the electromagnetic fail safe brake which do not allow the crane to fall with the load when even there is a power failure. For this:Normally centrifugal brakes are used which are fitted inside the rotating drum.The brake pads are always in applied state and pushed by magnetic springs when not in operation or when there is a power failure.As the crane is operated or the power is supplied, the spring gets pulled inwards or compressed due to electromagnetic effect of the current.This allows the crane to be operated normally.
  2. Emergency stop is provided in the remote so that operator can stop the crane at any time.
  3. The motor is fitted with distance limit switch in both transverse and longitudinal direction.
  4. Mechanical stoppers are provided for both directions in ace of electrical distance limit trips fail.
  5. The up and down travel of the hook is also attaches with automatic stopper to avoid overloading of the motor.
  6. The motor is fitted with thermal protection trip. When the motor winding's get overheated, trip will activate saving the motor winding from burning.
  7. Load limit switch is also fitted which will trip the motor if the load to be lifted is above the crane capacity.
  8. Its the responsibility of senior officers to operate the crane and to make sure all the personal involved in any lifting operation are at the safe distance during operation of the crane.
  9. Additional tools like I Bolt, shackle, wire sling, belts etc, used for lifting must be checked before use.
  10. It should be noted that no one walks or stand below the crane when it is in loaded condition.

Electromagnetic brakes:
The main parts of the electromagnetic brakes are:

  • The brakes shoes, which are connected to two levers,
  • The spiral springs which are connected to the levers, and 
  • Electromagnetic solenoid, which is connected to the two levers.
Electromagnetic brakes are usually found on machines like cranes and lifts and they work as backup braking systems. These breaks only work when the electricity supply, how to make sure that for example,the load carried by the crane for lift that moves up and down in a building does not fail the lord that the crane of the leaf was carrying fail it could cause serious damage to the property as well as serious injury or even death to people underneath the load or in the lift. The breaking action of the electromagnetic brake works as follows:

  • When electricity is flowing, electromagnetic solenoid uses magnetic force to pull the two levers in towards it, which keeps the spring attached to the top of the levers open.
  • The open springs keep the brake shoes, which are positioned on each shoes, which are positioned on each side of a shaft, away from the shaft while it is turning.
  • When electricity stops flowing, the electromagnetic solenoid stops working, with the magnetic force gone, the spiral spring closes, which pushes the brake shoe against the shaft to stop it from tuning.

The main parts of the thrust brake systems are:

  • The hydraulic centrifugal pump which is connected to the thruster piston.
  • The thrust piston which are connected to the pump and to the braking springs.
  • The friction pads and the brake disc


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