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EVALUATING DRUMS

Even though both these gauges properly follow groove contours, when used
side-by-side they indicate grooves are too close and that the "Drum Pitch" is less
than the rope diameter. Two gauges which overlap in this manner reveal that
wraps of rope will scrub when spooling on to or off the drum.


Inspection criteria for drums will usually specify the following:

- Minimum number of dead wraps to remain on the drum.
- Condition of drum grooves, if a grooved drum, and the surface of a smooth drum.
- Condition of flanges at the ends of the drum.
- Rope end attachment.
- Spooling characteristics of the rope.
- Rope condition, particularly at pick-up points on the rope.

There is wide acceptance of the following guidelines for checking drums and drum operation:

GROOVES -

Grooves should be of proper contour and checked with a groove gauge if normal tolerances apply. Bottoms of grooves should be smooth. Drums that become imprinted with the rope's tread or excessively roughened should be corrected or replaced. The grooves should also be correctly spaced so one wrap of rope does not scrub the next wrap as it spools onto the drum. This spacing is referred to as the drum groove pitch and is the actual distance between the centre line of one groove and the centre line of an adjacent groove. The drum pitch can be accurately measured by counting 10 grooves and then positioning a tape measure on the outside crown of the 1st and 10th groove. This reading can then be divided by 10 for the individual groove pitch and compared to the actual rope diameter. Most equipment manufacturers machine the drum grooves with an acceptable oversize tolerance, taking into consideration the rope type and design tolerance specified by the wire rope manufacturer.

SPOOLING - Spooling is the characteristic of a rope which affects how it wraps onto and off a drum. Spooling is affected by the care and skill with which the first layer of wraps is applied on drums with two or more layers. Wraps should be tight. It is important to examine a rope for kinks or other damage when loose or irregular spooling has been observed.
DRUM CRUSHING - Drum crushing is a rope condition which indicates deterioration of the rope. Sometimes crushing is inevitable on a given drum winding, as is deformation of the wires in the rope, usually described as peening. Crushing and peening affect rope performance insofar as these conditions impair adjustment of wires in the rope and damage the wires themselves. When observed, either condition should be noted and careful evaluation of the rope made. If this condition continues to appear on each rope as it is installed contact your rope specialist for recommendations on a construction which will reduce this condition.