Greetings! The hook of the cargo crane goes up very slowly. There is no accompanying information or prompts from the automation.
In this article, let's figure out what this problem is and how to fix it. First of all, you need to understand that we are only interested in the section of the circuit that is responsible for the “hoist up” hook command (not the jib).
Accordingly, we look at the instructions for troubleshooting the problem associated with the definition of “hoisting”.
The instructions indicate checking the circuit: Joystick - PLC - relay - Proportional drive - Proportional valve. In simple words, the operator, using a joystick, transmits a command to the proportional valves (hook up and down) through the PLC module and proportional driver.
The main visual indicator that the joystick is working are the LEDs on the driver "Output A" and "Output B". They light up when commands are executed on the hook up and down. Also, the 58K circuit preparation relay and PLC module work without any problems.
The first thing to check in this case is the 24V DC that comes to the solenoid valve coils. Voltage comes to both coils. The next task is to check the readings of the currents that go from the driver to the coils of the proportional valves.
To do this, you need to connect a multimeter in milliammeter mode to the open circuit of T0235 and T0239.
We connected two multimeters to the open circuit of the hook up and down. We measure the current when the crane is operating. It can be seen that with maximum position of the joystick, the current reaches 300 mA on both (hook up and down) lines. This suggests that the problem is not with the driver, it is working good. Otherwise, if there was a problem with it, then you can do a calibration using potentiometers or replace the driver.
When replacing, be sure to install the jumpers on the rear panel as they were on the original driver.
It is also necessary to check the currents, although from the factory they should be set to a maximum value of 300mA.
In our case, referring to the instructions, we move on to a proportional valve with two solenoids.
It is necessary to check the coils, the resistance of which should be 41 ohms. This action should be performed at the very beginning of checking the circuit. After testing the coils, we made sure that the resistance values also corresponded to the instructions.
All that remains is to disassemble, clean and check the proportional valve.
Disassembling and cleaning the proportional valve also did not give a positive result. The problem was discovered directly in the operation of the pump itself (it did not produce enough pressure), after which it was disassembled and defects were discovered.
Some worn parts were found in the hydraulic pump for hoisting operation. As a result, the pump had to be replaced.
The problem turned out to be in the hydraulic pump, but to get to this point we had to check many other components of the system and spend a lot of time. Despite this, the article shows all the automation points that may fail when this problem occurs.
When a crane hook goes up slowly, it could be due to several issues. Here's a structured approach to troubleshoot the problem:
1. Mechanical Issues
- Load Bearing Capacity: Ensure the load being lifted is within the crane's capacity. Overloading can cause the crane to lift slowly.
- Wire Rope Condition: Check for wear, damage, or incorrect spooling on the drum.
- Hook Block Condition: Inspect the hook block and sheaves for any signs of wear or damage that could cause resistance.
- Brakes: Verify that the brakes are fully releasing when the hoist is operated.
2. Hydraulic System (For Hydraulic Cranes)
- Hydraulic Fluid Levels: Ensure the hydraulic fluid is at the correct level and check for any leaks in the system.
- Hydraulic Pump: Inspect the pump for proper operation. A weak or failing pump can reduce lifting speed.
- Valves and Hoses: Check for blockages, leaks, or malfunctions in the valves and hoses.
3. Electrical System (For Electric Cranes)
- Power Supply: Ensure the crane is receiving adequate power. Low voltage can cause slow operation.
- Motor Condition: Inspect the hoist motor for signs of wear, overheating, or other issues.
- Control System: Check the control system and wiring for any faults. Loose connections or faulty control circuits can affect performance.
- Drive Mechanism: Examine the drive mechanism, such as gears and couplings, for any damage or misalignment.
4. Operational Factors
- Operator Error: Ensure the crane operator is using the equipment correctly and following the manufacturer's guidelines.
- Environmental Conditions: Consider if environmental factors such as wind, temperature, or ground conditions could be affecting crane performance.
5. Maintenance and Inspection History
- Maintenance Records: Review the crane’s maintenance records to identify any overdue maintenance or previous issues that might have recurred.
- Inspection Schedule: Ensure regular inspections are conducted as per the manufacturer's recommendations and regulatory requirements.
Step-by-Step Troubleshooting
- Visual Inspection: Perform a thorough visual inspection of the crane, looking for any obvious signs of wear, damage, or leaks.
- Operational Test: Conduct a test lift with a light load to observe the crane's behavior.
- Load Test: If the crane operates normally with a light load, gradually increase the load to determine if there is a specific point where the issue occurs.
- Diagnostics Tools: Use diagnostic tools or software if available, to check the crane’s systems.
- Consult the Manual: Refer to the crane’s operation and maintenance manual for specific troubleshooting steps and guidelines.
If the problem persists after following these steps, it may be necessary to consult with a professional technician or the crane manufacturer for further assistance.
Crane model: DMC DDKC-3026-00 (Dongnam Marine Crane)
Also read other articles about DMC cargo cranes:
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