Industrial Heavy-Duty Cardan Shaft (Universal Joint Shaft) Usage Precautions

Core Principle: Focus on installation alignment, bolt tightening, and regular lubrication, combined with daily inspections.

1. Installation & Alignment — The Primary Step

Phase Alignment: For shafts with a splined coupling, align the arrow marks on the splined shaft and sleeve. Ensure the phase difference of the bearing hole axes at both yokes is ≤1°. Incorrect alignment causes severe impact and torsional vibration.

Angle Requirements: Ensure the drive shaft, intermediate shaft, and driven shaft are in the same plane, and the inclination angles between the intermediate shaft and both end shafts are equal. If both eccentricity and angular misalignment exist simultaneously, the allowable values must be reduced by half.

Gap Control: Adjust the axial clearance of the crosshead during installation. For reversible couplings, use a smaller clearance value.

2. Bolt Tightening — The Top Priority

Cleaning & Pre-tightening: Clean anti-rust oil from the flange surfaces and wipe dry before installation. Flange bolts must be tightened with a torque wrench to the specified torque. Bolt performance grade shall be no lower than 10.9.

Repeated Re-torquing (Critical): After one shift (8 hours) of operation under load, immediately check bolts for loosening and re-tighten to the specified torque. Repeat this process for several shifts until torque stabilizes. This is the most effective method to prevent bolt fatigue fracture.

3. Lubrication Maintenance — Determines Service Life

Grease Selection: Typically use NLGI Grade 2 lithium-based grease. Add a small amount of molybdenum disulfide (MoS₂) to the splined coupling area.

Greasing Interval:

1）Initial Period: During the first week of operation, grease bearings once per week.

2）Normal Period: Grease bearings every 3 months; grease the splined coupling every 6 months.

3）Continuous Operation: Grease approximately every 500 hours.

4）High-Temperature Environment: Grease weekly.

5）Application Method: When adding new grease, continue until old grease is completely forced out from the seals.

4. Daily Inspection & Monitoring

Perform checks each shift using visual, auditory, and tactile methods:

Listen: Check for abnormal impact noise or periodic noise.

Observe Running: Check for smooth operation and abnormal radial runout.

Check Axial Movement: Check the spider (cross bearing) for axial play.

Measure Temperature: Check bearing areas for abnormal heating.

5. Periodic Maintenance & Replacement

Maintenance Interval: Perform a complete disassembly and inspection every 6 to 12 months under normal operation.

Critical Wear Limits (Replace immediately if exceeded):

Bearing raceway or crosshead journal wear depth or Brinell marking >0.25 mm (0.010 in).

Spline tooth backlash excessive or wear >0.35 mm (0.014 in).

Cracks found in the crosshead or yoke (using NDT methods).

Reversing Use: During overhaul, the crosshead can be rotated 180° during reassembly to alternate the loaded contact areas, extending service life.

6. Safety Guarding

Guards Mandatory: Install robust guards around the cardan shaft to prevent injury from flying parts in case of bolt fracture or spider failure.