Overhead Crane Maintenance Manual: Cable Inspection, Brake Testing, Limit Switch Verification and Hook NC

1. Scope and Purpose

This maintenance manual covers key aspects of periodic inspection and maintenance of overhead cranes, including inspection of steel wire ropes, testing of braking systems, verification of limit switch operation and non-destructive testing (NDT) of the load hook. The purpose of this document is to ensure safe and reliable operation of crane equipment, reduce the risk of failure and extend the service life of components. Regular implementation of these procedures is mandatory in accordance with the requirements of DSTU EN 15011:2018 "Cranes. Overhead and gantry cranes" and prevents accidents at work.

2. Precautions

WARNING: Be sure to perform the Lockout and Tagout (LOTO) procedure before starting any maintenance or inspection work on the overhead crane. Disconnect the main power supply to the faucet, lock the main switch and post warning signs. Make sure all moving parts of the crane are completely stopped and locked. Use personal protective equipment (PPE): protective glasses, work gloves, protective shoes with metal toes, protective helmet. Perform work at height only with insurance and in accordance with the rules of safety for work at height.

WARNING: Avoid contact with moving parts. Keep a safe distance from live electrical components.

WARNING: Before using cleaning agents or lubricants, read their Material Safety Data Sheets (MSDS).

3. Necessary Tools and Materials

4. List of Checks before Service

5. Step-by-step Service Procedure

5.1. Inspection and Maintenance of Steel Rope

1. Visual rope inspection:

   • Completely unwind the rope to its full working length, if possible, to inspect all areas.
   • Use a flashlight and an inspection mirror to inspect hard-to-reach areas, especially where the rope passes through the blocks and winds onto the drum.
   • Look for: broken wires, damaged strands, deformations (bends, loops, flattening), signs of corrosion (rust).
   • Typical mistake: Incomplete inspection of the rope. Always inspect the entire length, especially those areas under load or subjected to intense bending.

2. Measuring the diameter of the rope:

   • Using a caliper or micrometer, measure the actual diameter of the rope at several points along its length.
   • Compare the measured values ​​with the nominal diameter specified in the rope's passport.
   • Rejection criterion (DSTU EN 12385-3): If the diameter has decreased by more than 7% of the nominal for round ropes or by 10% for stranded ropes, the rope must be replaced. For example, for a rope with a diameter of 16 mm, a reduction of 7% is 1.12 mm (16 mm * 0.07), that is, with a diameter of 14.88 mm and less, the rope is missing.
   • Typical error: Measurement in only one place or inaccurate measurement. Measure carefully and in several places.

3. Count of broken wires:

   • Count the number of visible broken wires in a coil step (usually 6 rope diameters).
   • Rejection criterion (ISO 4309): For general purpose steel ropes, if the number of broken wires reaches 6 in a coil step or 3 in one strand, the rope should be replaced.
   • Typical mistake: Ignoring wires that are protruding but not completely broken. Even such wires can indicate fatigue of the material.

4. Rope lubrication:

   • After inspection and cleaning, apply a thin layer of special lubricant for ropes.
   • The grease should be adhesive, anti-corrosive and penetrating, providing protection to both the outer and inner parts of the rope.
   • WARNING: Use gloves. Make sure that the rope is completely de-energized if the crane is equipped with a rope current removal system.
   • Typical mistake: Over-lubrication, which leads to dirt build-up, or under-lubrication, which does not provide adequate protection.

5.2. Testing and Adjustment of Lifting Mechanism Brakes

1. Visual inspection of the brake system:

   • Inspect the brake disc/drum, brake pads/pads, springs, levers, and solenoid.
   • Check for cracks, deformations, excessive wear, hydraulic fluid leaks (if the brakes are hydraulic).
   • Typical mistake: Insufficient attention to springs, which can lose their stiffness over time.

2. Measuring Brake Pad Wear:

   • Use a caliper to measure the thickness of each brake pad.
   • Rejection criteria: Brake linings must be replaced if their thickness has decreased by more than 50% from the original, or to the minimum permissible value specified by the manufacturer (for example, 4 mm).
   • Typical mistake: Replacing only one worn pad. Always replace all pads on the same brake mechanism with a uniform braking kit.

3. Brake clearance adjustment:

   • Make sure the faucet is de-energized. Adjust the brake clearance between the pads and the disc/drum according to the crane manufacturer's recommendations (usually 0.2-0.5 mm).
   • Use a set of feelers to accurately set the gap.
   • Tighten the adjusting bolts with a torque wrench to the values ​​specified in the operating instructions. For example, for M12 bolts of strength class 8.8, the recommended tightening torque is 75-80 Nm.
   • Typical mistake: Incorrect clearance causes the brakes to overheat or fail to act properly.

4. Functional testing of the brakes:

   • After completing the adjustment and visual inspection, restore power (after checking that there are no people in the crane movement area).
   • Do a series of test lifts and lowers with different weights (starting light, then rated if possible) checking braking performance.
   • Make sure that the brakes operate smoothly, without jerks, and securely hold the load.
   • Typical mistake: Testing without load or with excessive load. Always follow recommended testing procedures.

5.3. Verification of Limit Switches

1. Visual inspection:

   • Inspect the physical condition of the limit switches on the lifting mechanism and travel mechanism. Inspect the housings for cracks, fasteners for reliability, integrity of electrical cables and contact groups.
   • Make sure the switch levers or pushers are not deformed and move freely.
   • Typical mistake: Insufficient attention to contamination that can prevent correct operation.

2. Electrical Integrity Testing:

   • WARNING: Make sure power is off and locked before testing electrical components.
   • Disconnect the limit switch from the tap network. Using a multimeter in ringing or resistance mode, check the operation of the contacts (normally open and normally closed) when manually pressing the lever.
   • Check the resistance of the contacts - it should be close to 0 ohms in the closed state.
   • Typical mistake: Testing the circuit breaker under live conditions, which could result in electric shock.

3. Crane functional testing:

   • After power is restored (after safety check), slowly move the crane or hoist until each limit switch is activated.
   • Verify that the switches operate in the specified positions (eg, lift up and down, bridge and trolley end positions).
   • The upper and lower lift position limit switches should shut off the engine and activate the brake.
   • Check the operation of the emergency limit switches (if any) - they should stop the movement completely, regardless of the main ones.
   • Typical error: Testing only one limit switch. Be sure to test all limit switches in each direction of travel.

4. Adjusting the position of the limit switches:

   • If the switches do not operate at the required points, adjust their position or the position of the stops.
   • Make sure that the switch fasteners are securely tightened after adjustment.
   • Typical mistake: Insufficiently secure fastening after adjustment, which can lead to confusion of settings.

5.4. Non-destructive testing (ND) of the cargo hook

1. Preparing the hook for inspection:

   • Clean the surface of the hook from dirt, grease, paint and corrosion with a brush and cleaner. The surface must be clean and dry for effective detection of defects.
   • Use brake cleaner to remove stubborn dirt.
   • Typical mistake: Insufficient cleaning that masks cracks.

2. Visual inspection:

   • Carefully inspect the hook for cracks (especially in areas with high stress concentration: the transition from the rod to the jaw, the inner radius of the jaw), deformations (opening of the jaw, twisting), wear (reduction of the cross-section).
   • Measure the jaw opening of the hook with a caliper.
   • Rejection criterion (DSTU EN 13001-3-1): An increase in the opening of the jaw hook by more than 10% from the initial one or a decrease in its height by more than 10% is a reason for rejection.
   • Typical mistake: Ignoring small hairline cracks that can turn into serious defects.

3. Magnetic powder flaw detection (MPD) or Capillary flaw detection (CD):

   • MPD (recommended for ferromagnetic materials):
     1. Magnetize the hook area using a magnetic yoke.
     2. Apply a slurry of magnetic powder (such as black powder for contrast on light surfaces) to the surface.
     3. Powder will collect in areas of magnetic field disturbance, indicating cracks or other defects.
   • KD (for non-ferromagnetic or when MPD is not possible):
     1. Apply the penetrant to the surface and allow it time to penetrate the defects (5-15 minutes, depends on the penetrant).
     2. Remove excess penetrant.
     3. Apply a developer that will pull the penetrant out of the defects, making them visible.
   • WARNING: Use PPE (gloves, glasses) when performing MPD/KD. Ensure proper ventilation of the room. Follow the chemical reagent manufacturer's instructions.
   • Typical error: Incorrect sequence of operations or use of inappropriate reagents, leading to false results.

4. Interpretation of the results:

   • Any detected linear indications (cracks) on the surface of the hook are grounds for its rejection and replacement.
   • Non-linear indications (for example, porosity) should be evaluated according to standards (for example, DSTU ISO 6520-1) and manufacturer's recommendations.
   • Typical mistake: Ignoring defects that seem insignificant. Any defect in load-lifting elements is critical.

6. List of Checks after Maintenance

7. Troubleshooting Guide

8. Recommended Maintenance Schedule

9. Directory of Spare Parts

To order spare parts and receive detailed information, visit our electronic catalog UNITEC-D.

10. Links

• DSTU EN 15011:2018. Cranes. Overhead and gantry cranes. (EN 15011:2011+A1:2014, IDT).
• DSTU EN 12385-3:2018. Steel wire ropes. Security. Part 3. Information for use and maintenance. (EN 12385-3:2004+A1:2008, IDT).
• ISO 4309:2017. Cranes — Wire ropes — Care, maintenance, installation, examination and discard.
• DSTU EN 13001-3-1:2018. Cranes. General design provisions. Part 3-1. Limit states and verification of suitability of steel structures. (EN 13001-3-1:2012+A1:2013, IDT).
• GOST 2688-80. Steel ropes. Cargo, double roll, type LK-R. Construction and main dimensions.
• Crane equipment manufacturer (OEM) recommendations.