Crane Slew Bearing Rocking Test: Importance and Procedure

If you are in the marine industry, you are likely familiar with the importance of maintaining lifting appliances on board your vessel. One essential aspect of this maintenance is conducting regular rocking tests on the crane slew bearing rocking test. These tests are crucial for ensuring the safety and reliability of your lifting equipment.

A rocking test involves measuring the deflection of the crane’s slewing ring bearings to determine if they are becoming worn. The test should be included in your vessel’s planned maintenance system, and each crane should be tested every six months. It is essential to keep a record of these tests and enter them into the Registry of Lifting Appliances. If the amount of wear in the bearing races is within permitted limits, the crane passes the test. If the wear exceeds the allowable limit, you will need to take corrective action to ensure the safety of your lifting equipment.

Crane Slew Bearing Fundamentals

Design and Function

Crane slew bearings are critical components of the crane’s rotating system. They are designed to support the weight of the crane’s superstructure and the loads it carries. The slew bearing is a large circular bearing that allows the crane to rotate 360 degrees. The bearing is mounted on top of the crane’s pedestal, and the superstructure is mounted on top of the bearing.

The bearing has two main components: the outer ring and the inner ring. The outer ring is fixed to the pedestal, while the inner ring is attached to the superstructure. The two rings are separated by a series of rolling elements, which allow the superstructure to rotate smoothly on the pedestal.

Importance in Crane Operations

The condition of the crane’s slew bearings is critical to the safe and efficient operation of the crane. A worn or damaged bearing can cause the crane to become unstable, which can result in accidents and injuries. Therefore, it is essential to perform regular maintenance on the bearings.

One critical maintenance task is the rocking test. The rocking test is used to determine the condition of the bearing by measuring its deflection. The test involves applying a load to the superstructure and measuring the amount of deflection of the bearing. If the deflection is within acceptable limits, the bearing is considered to be in good condition. If the deflection is too high, the bearing may need to be replaced.

Regularly performing the rocking test as part of the crane’s planned maintenance system can help prevent accidents and extend the life of the crane. It is recommended to conduct the test every six months and record the results in the Registry of Lifting Appliances as required by ABS/API procedures [1].

In summary, the crane’s slew bearings are critical components that must be maintained regularly to ensure safe and efficient crane operations. The rocking test is a crucial maintenance task that can help prevent accidents and extend the life of the crane.

Preparation for Rocking Test

Before conducting the rocking test on a crane’s slew bearing, you need to take some necessary steps to ensure safety and accuracy. This section will cover the safety measures and equipment and tools required for the preparation of the rocking test.

Safety Measures

The following safety measures should be taken before conducting the rocking test:

• Ensure that the crane is not carrying any load and is securely parked.
• Make sure that the crane is on a level surface.
• Turn off the crane’s power supply to prevent any accidental movement.
• Place warning signs and barricades around the crane to prevent unauthorized access.
• Use personal protective equipment (PPE) such as gloves, safety shoes, hard hats, and safety glasses to avoid any physical injury.

Equipment and Tools Required

The following equipment and tools are required for the preparation of the rocking test:

Equipment/Tool	Purpose
Spirit Level	To check the level of the crane
Dial Gauge	To measure the deflection of the slew bearing
Spanners	To loosen and tighten bolts
Lubricant	To lubricate the slew bearing
Torque Wrench	To apply the correct torque to bolts
Grease Gun	To apply grease to the slew bearing

It is essential to ensure that all equipment and tools used are in good condition and calibrated correctly. Any damaged or defective equipment should not be used, and it is recommended to get them repaired or replaced before conducting the rocking test.

By following the safety measures and using the appropriate equipment and tools, you can ensure that the preparation for the rocking test is done correctly and safely.

Rocking Test Procedure

Performing a rocking test on crane slew bearings is crucial for ensuring the safety and proper functioning of the crane. This test helps to detect the presence of any wear and tear in the bearing races and prevents catastrophic failure. Here is a step-by-step procedure for conducting a rocking test on crane slew bearings.

Initial Setup

Before conducting the test, ensure that the ship is adjusted to have the least possible trim, preferably on an even keel. Cranes fitted with this type of slew bearing must have rocking tests carried out following the manufacturer’s instructions to determine that the amount of wear in the bearing races is within permitted limits. Here are the steps to follow:

1. Turn off the crane’s power supply to prevent any accidental movement during the test.
2. Remove the load from the crane and ensure that the crane is in its unloaded state.
3. Position the crane in its center position and lock it in place.
4. Set up the measuring equipment, including a dial gauge and a protractor, to measure the deflection angle and the amount of rocking.

Execution Steps

Once the initial setup is complete, follow these steps to conduct the rocking test:

1. Apply a load of 10% of the crane’s safe working load to the jib head.
2. Measure the deflection angle and the amount of rocking by reading the dial gauge and protractor.
3. Repeat the test with a load of 50% of the crane’s safe working load and record the readings.
4. Repeat the test with a load of 100% of the crane’s safe working load and record the readings.
5. Compare the readings with the manufacturer’s specifications to determine if the bearing races’ wear is within permitted limits.

If the readings are beyond the permitted limits, the crane’s slew bearing should be replaced. It is crucial to perform the rocking test regularly to ensure that the crane’s slew bearing is functioning correctly and to prevent any accidents.

Interpreting Test Results

After performing the rocking test on your crane’s slewing gear, it’s important to interpret the results accurately to ensure the safety and reliability of the crane’s operation. In this section, we’ll discuss the acceptance criteria for the test results and common findings and solutions.

Acceptance Criteria

The acceptance criteria for the rocking test results are determined by the crane manufacturer and/or the regulatory bodies such as the American Bureau of Shipping (ABS) and the International Association of Classification Societies (IACS). The test results must be compared against the acceptance criteria to determine whether the crane’s slewing gear is within the permissible wear limits.

The permissible wear limits are usually expressed in terms of the maximum allowable deflection between the crane pedestal and the rotating crane housing in the way of the slewing ring. The permissible wear limits can vary depending on the crane manufacturer, the crane type, and the regulatory requirements. For example, ABS requires that the maximum deflection should not exceed 1/600th of the distance between the crane centerline and the slewing ring centerline.

Common Findings and Solutions

If the rocking test results show that the crane’s slewing gear is outside the permissible wear limits, there are several common findings and solutions that can be considered. Some of the common findings and solutions are:

• Excessive wear on the slewing ring bearings: If the rocking test results show that there is excessive wear on the slewing ring bearings, the bearings may need to be replaced. The replacement of the bearings should be done according to the manufacturer’s recommendations and the regulatory requirements.
• Misalignment between the crane pedestal and the rotating crane housing: If the rocking test results show that there is misalignment between the crane pedestal and the rotating crane housing, the alignment may need to be adjusted. The adjustment of the alignment should be done according to the manufacturer’s recommendations and the regulatory requirements.
• Loose bolts or fasteners: If the rocking test results show that there are loose bolts or fasteners, the bolts or fasteners may need to be tightened. The tightening of the bolts or fasteners should be done according to the manufacturer’s recommendations and the regulatory requirements.

In conclusion, interpreting the rocking test results accurately is crucial for ensuring the safety and reliability of the crane’s operation. The acceptance criteria and common findings and solutions discussed in this section can help you interpret the test results effectively.

Maintenance and Follow-Up

Post-Test Maintenance

After conducting the rocking test on the crane slew bearing, it is essential to carry out post-test maintenance. This maintenance ensures that the crane is in good working condition and is safe to use. You should check the following components:

• Slewing ring bearings: Check for any wear or damage to the bearings. If there is any damage, you should replace the bearings immediately.
• Lubrication system: Ensure that the lubrication system is working correctly. Check the oil levels and look for any leaks in the system.
• Bolts and fasteners: Check that all bolts and fasteners are tight and secure. If any bolts are loose, tighten them immediately.

Regular Inspection Schedule

It is crucial to have a regular inspection schedule for the crane slew bearing to ensure that it is in good working condition. The inspection schedule should include the following:

• Visual inspection: Inspect the crane slew bearing rocking test for any signs of wear or damage. Check the lubrication system and look for any leaks. Inspect the bolts and fasteners and tighten any loose bolts.
• Non-destructive testing: Conduct non-destructive testing to check for any cracks or defects in the crane slew bearing.
• Rocking test: Conduct a rocking test every six months to ensure that the crane slew bearing is not becoming worn. Record the results of the test in the Registry of Lifting Appliances.

By following a regular inspection schedule, you can ensure that the crane slew bearing rocking test is in good working condition and is safe to use. It is essential to conduct regular maintenance and inspections to prevent any accidents or downtime due to equipment failure.