Naturally, each component of a crane that comes into direct contact with the rope has an effect on the service life. This also includes the grooves of the sheaves and the drum whose quality and dimensional accuracy have a significant influence on the service life of the rope. Here, the grooves should have a diameter that is slightly larger than the effective diameter of the rope. ISO 16625 prescribes that the diameter of the grooves must be a minimum of 5% and a maximum of 10% more than the rope diameter. As an optimum value, the standard specifies a groove diameter of 7.5% more than the rope diameter.

CAUTION
If the diameter of the sheave is too small for the rope (Fig. A), the rope is compromised when winding on the sheave or drum. This can lead to wire breaks in the inside of the rope caused by so-called arch pressure. An additional effect is excessive length of the outer strands in respect of the reduced rope diameter. This excessive strand length is typically shifted to a point and results in strand loosening or even birdcage deformation.

A rope groove that is too large results in a greater surface pressure of the rope in the bottom of the groove as the support at the edges is missing and therefore the contact area is reduced (Fig. C). The increased pressure in the bottom of the groove and the additional tensions due to the intensified rope deformation (ovalisation of the rope) lead to a reduction of the service life. In general, falling below 5% has significantly more serious consequences for the service life of the rope than exceeding 10%.

To determine the diameter of the rope grooves of sheaves and drums, so-called groove gauges are used. These are pressed into the rope groove and should be well positioned over broad sections of the circumference. The rope groove is then OK.