Problems with cargo cranes. Some problems with cargo cranes that occur on the ship

Cargo cranes on ships are vital for the efficient loading and unloading of cargo. However, they can encounter various issues that impact their functionality and safety. Some problems with DMC cargo cranes that occured on the ship.

Deck crane hoisting limit switches

While checking hoisting limit switches, due to incorrect setting of the hoisting limit switch on deck crane no. 1, noticed that the system differs from the ones on other sister ships. Hoisting up limit switch is no longer activated by means of a small weight that slacks the chain when the hook touches it, thus activating the micro switch, as on the previous sister ships; instead it has been put on the cam limit switch together with lowering limit. This means that the hoisting up limit is no longer fixed, to hook being about 2 meters below the boom head regardless to the boom angle; but that it is activated when the exact amount of wire rope is wound up on the drum. 

Therefore, the limit switch activation depends on the boom angle. This is obviously ineffective due to the fact that for lower angles of the boom the limit is not even functional, increasing the risk for crane damage. On board, it is set to activate the limit switch when hook is 1 meter from the boom head with the boom angle 40 degrees and when the angle is increased the distance between the hook and the boom head is increased as well (for example for 55 degrees the distance is about 5 meters). Below boom angle of 37 degrees the hoisting limit switch can’t be activated at all.

Deck crane air heaters

The heaters inside the deck cranes have low insulation resistance on all 4 cranes (varying between 1 and 10 MΩ when measured cold). When the heaters are switched on the insulation resistance soon drops to 0 MΩ and the 440v low insulation alarm is sounded in ECR. Each crane has 9 heaters in star connection. To determine which heater is causing the low insulation, all connections were removed and insulation resistance of all heaters, one by one, was carried out, but without obvious success. 

The problem is that, while disconnecting the heaters, the heaters cool off a bit and insulation resistance rises, disabling the proper evaluation of their insulation values.  Although a couple of the heaters measured this way had insulation resistance of 0.5 MΩ, it has been noticed that the insulation resistance of each heater drops significantly when hot. Also please note that we don’t have any instruction books or drawings for these heaters.

Common problems associated with cargo cranes on ships

Here are some common problems associated with cargo cranes on ships:

1. Mechanical Failures:

   • Hydraulic System Issues: Leaks or failures in the hydraulic system can cause the crane to lose power or operate erratically.
   • Motor Failures: Problems with the electric or diesel motors can prevent the crane from functioning.
   • Wire Rope Failures: Worn or broken wire ropes can snap, leading to dangerous situations and potential cargo loss.

2. Electrical Problems:

   • Electrical Malfunctions: Faulty wiring, blown fuses, or issues with control panels can disrupt crane operations.
   • Power Supply Issues: Inconsistent or insufficient power supply can hinder crane performance.

3. Structural Issues:

   • Wear and Tear: Regular use can cause wear and tear on crane components, leading to structural weaknesses.
   • Corrosion: Exposure to harsh marine environments can cause corrosion, weakening the crane’s structure.
   • Fatigue Cracks: Repeated loading and unloading can cause fatigue cracks in the crane’s structure.

4. Operational Problems:

   • Operator Errors: Inexperienced or inadequately trained operators can cause accidents or damage to the crane.
   • Improper Maintenance: Lack of regular maintenance can lead to the deterioration of crane components and unexpected failures.
   • Overloading: Exceeding the crane’s maximum load capacity can damage the crane and pose safety risks.

5. Safety Mechanism Failures:

   • Brake Failures: Malfunctioning brakes can lead to uncontrolled movement of the crane or dropped loads.
   • Limit Switch Failures: Defective limit switches can fail to stop the crane at the end of its travel, causing collisions or overloading.

6. Environmental Factors:

   • Weather Conditions: High winds, heavy rain, or icy conditions can make crane operations hazardous and increase the risk of accidents.
   • Saltwater Exposure: Continuous exposure to saltwater can accelerate corrosion and damage electronic components.

7. Communication Issues:

   • Lack of Coordination: Poor communication between the crane operator and the deck crew can lead to mishandling of cargo.
   • Radio Interference: Interference with communication systems can prevent effective coordination during cargo operations.

8. Software/Automation Failures:

   • Control System Errors: Software bugs or glitches in automated cranes can cause operational failures or unsafe movements.
   • Sensor Malfunctions: Faulty sensors can provide incorrect data, leading to improper functioning of the crane.

To mitigate these issues, regular maintenance, thorough inspections, proper training for operators, and adherence to safety protocols are essential. Additionally, investing in high-quality components and staying updated with technological advancements can help improve the reliability and efficiency of cargo cranes on ships.

Crane model: DMC DDKC-3026-00 (Dongnam Marine Crane)

Also read other articles about DMC cargo cranes:

1. The cargo crane does not slew. Troubleshooting
2. The crane hook goes up slowly. The cargo crane is not working. Troubleshooting
3. PLC failure. The cargo crane does not start. Troubleshooting
4. Motor Fault on the crane. Troubleshooting
5. The crane jib is luffing down under its own weight. Troubleshooting