Saturday, September 14, 2013

Safeties In Engine Room Crane (with pics)

marine engineering success
Safeties In E/R Crane

crane safety marine engineering
An Engine Room Crane is a very important tool for the Crew, working day and night for the maintenance and overhaul of the marine equipment. This is because the marine equipment has weight which is too heavy and beyond the scope of human strength to lift it.
The cranes come in various configuration and capacity. Generally, a E/R crane has SWL of 0.5-15 tonnes.

SWL: Safe Working Load (it is the maximum working load a lift is designed to handle, it is always less than the test load of the crane, but this should never be challenged in working period of the crane)

marine crane merchant navy
Pic Courtesy: Marine Insight
The picture on the right is a typical modern day crane that is installed on the marine vessels.It can move in 4 directions,viz., Fwd, Aft, Port, Stbd.
It uses motors connected with wire drum, this arrangement is mounted on the guide rails.

 Safety Features of Engine Room Crane

  • The most important safety feature of the crane is the electromagnetic fail safe brakes which do not allow the crane to fall with the load even when there is failure of power. For this:

  1. Normally centrifugal brakes are used which are fitted inside the rotating drum.
    centrifugal, brakes, crane
  2. The brake pads are always in applied state and pushed by magnetic springs when not in operation or when there is a power failure.
  3. As the crane is operated or the power is supplied, the spring gets pulled inward or compressed due to the electromagnetic effect of the current. This allows the crane to be operated normally.

  • Emergency stop is provided in the remote so that the operator can stop the crane at any time.

  • The motor is fitted with distance limit switch in both transverse and longitudinal direction so that the travel of the trolley and hence crane should not overshoot the rack’s end.
  • Mechanical stoppers are provided for both directions in case the electrical distance limit trips fail.

  • The up and down travel of the hook is also attaches with automatic stopper to avoid overloading of the motor.

  • The motor is fitted with thermal protection trip. When the motor windings get overheated, trip will activate saving the winding from burning.

crane remote control
  • Load limit switch is also fitted which will trip the motor if the load to be lifted is above the crane capacity.

  • The controls switches of the crane are push button type, while pressing only the power is supplied, this is also one of the safety for crane operation.

  •  Additional tools like i-bolts, shackle, wire sling, belts etc. used for lifting must be checked for fatigue, deformation and SWL (if it suits the load to be picked) before use.
  • It should be noted that no one walks or stand below the crane when it is in the loaded condition.

Thats All Folks :)

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