The three most obvious signs of failure
Product
| Symptoms | Manifestations | Causes |
| Braking force is significantly insufficient | The spring has been adjusted to the tightest position but still fails to hold. The lifting mechanism has a slack hook / the running mechanism slides for too long. | Spring fatigue has occurred, and the elasticity is lower than the designed value. |
| Exceeding the free length limit | Remove the measuring device. If the measured free length is greater than 3% to 5% compared to the label's nominal length (or if the visible gap becomes too large to be compressed), then proceed. | Metal fatigue permanent deformation |
| Appearance defect | The spring has fractures, cracks, severe rust and pitting, and deformation in the inter-ring contact area. | Due to aging or environmental corrosion, replacement is necessary. |
If the locknut is tightened to its limit (spring compressed to minimum allowable length or pull rod thread end), and the braking torque still fails to reach 80% of the rated value, it indicates that the spring has become fatigued and cannot be compensated by further tightening; replacement is required.
During the tightening process, lateral bending of the spring, uneven alignment of coils, and noticeable twisting are precursors to spring failure.
Auxiliary Assessment (Supporting Examination)
If the hinge point is not sticking, the bearing lining is not excessively worn, and the release clearance is normal, but the system still slips or creeps when the actuator is released separately and the spring is fully engaged, this indicates insufficient spring tension.
Comparison of multiple springs of the same model from the same batch: if a spring is noticeably softer or significantly different in length under the same compression, it indicates degradation and should be replaced.
Replacement Precautions
Purchase a main spring that exactly matches the original model (wire diameter, mean diameter, free length, and stiffness); do not use a standard tension spring as a substitute.
After replacement, readjust the spring compression length according to the nameplate and re-equalize the clearance on both sides.
If old spring fragments fall into the actuator or brake wheel, they must be thoroughly removed.
