TL;DR
Drift after stop means the hoist brake is not holding. Check the brake air gap and pad thickness. A worn spring or glazed disc cannot hold a load safely.
What you might see
- load slowly descends after releasing the up/down button
- hook creeps downward when hoist is stopped
- brake holding test fails
- brake disc visibly worn or glazed
Likely causes
Brake pads worn below minimum thickness, reducing brake torque
Brake disc glazed from infrequent use or oil contamination, reducing the friction coefficient
Brake spring fatigued, reducing clamping force on the disc
Brake air gap too large, requiring more coil stroke than available to fully release and re-engage
Required tools
- Feeler gauge set
- Vernier calipers (pad thickness measurement)
- Torque wrench
- LOTO kit
- Replacement brake pads and spring (Konecranes part)
Safety first
- A drifting hoist is an out-of-service condition. No loads may be lifted until the brake passes a static hold test.
- Lock out the crane before accessing the brake assembly.
- Do not attempt to lap or sand a glazed brake disc. Replace it.
Procedure
- 1
Lock out the crane at the main disconnect.
- 2
Access the hoist brake assembly. Measure the brake pad thickness. Replace pads at or below the Konecranes minimum thickness (check the CXT maintenance schedule).[1]
- 3
Measure the brake air gap with a feeler gauge. The nominal gap is typically 0.2-0.4 mm for Konecranes CXT. Adjust by adding or removing shims at the brake magnet face.[1]
- 4
Inspect the brake disc surface for glazing (mirror-like finish) or contamination. A glazed disc must be replaced, not sanded.
- 5
Inspect the brake spring. A spring that has taken a permanent set (shorter than nominal free length) must be replaced.
- 6
After reassembly, perform a static brake test: lift a test load to 10% of rated capacity and hold for 10 minutes. Zero drift is the acceptance criterion.
Sources
Konecranes CXT Wire Rope Hoist & Crane Maintenance Manual, Konecranes
Konecranes CXT Wire Rope Hoist Maintenance Manual, brake adjustment and inspection procedures (general)
View source
More guides for Konecranes CXT
How to diagnose a Konecranes CXT hoist that won't lift
If the motor runs but the hook does not move, the hoist brake is stuck engaged. If the motor does not run, read the fault code on the crane controller before anything else.
How to fix excessive hook block swing on a Konecranes CXT hoist
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How to diagnose and fix a limit switch failure on a Konecranes CXT hoist
A limit switch that does not stop the hoist is a safety-critical failure. Lock out the crane immediately. Test the switch contacts with a multimeter and replace if contacts do not close at the correct actuator position.
How to fix jerky travel motion on a Konecranes CXT overhead crane
A rhythmic jerk during travel is almost always a flat spot on one travel wheel. Lock out and rotate each wheel by hand to find the flat spot, then replace the wheel.
Stop fixing the same fault twice.
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