Catheads and Catlines
To improve safety on drilling rigs, manual catheads with catlines are being replaced with hydraulic and air type winches, but manual catheads with catlines are still in use on some rigs.
Drilling operators agree that catheads are extremely hazardous unless they are handled correctly and with respect. The cathead should be keyed with the key being covered with a counter-sunk cap screw. No projection whatsoever should be present to catch the loose clothing of any employee unwise enough to wear such apparel. Badly worn, grooved or otherwise dangerous catheads, found at many drilling operations, should be replaced immediately by catheads in good condition.
As would be expected, accidents involving catheads usually occur when employees’ hands are jerked into the cathead and caught beneath the catline because the line fouled by kinking or overlapping. A grooved cathead can cause overlapping of the catline as can frayed or worn lines. In the latter case, a loose strand of rope, caught beneath the adjoining turn of rope, is likely to overlap the two turns and pull the free end of the line into the cathead. If the unwary employee has a firm grip on the line while his attention is fixed elsewhere, one can well understand how his hand becomes caught before he realizes what has happened.
Since the condition of catlines also plays a part in causing accidents, these lines should be closely examined for accident-producing defects. The heavier the load, the greater the number of turns required to gain the friction necessary to raise the load. Exceptionally heavy loads, necessitating several wraps of the line around the cathead, subject the first turn of the line to severe heating. This heat is capable of destroying rope fiber at one or more spots where the rope can unravel later or break altogether when it is expected to hold just an average load.
The catline should be used only on a slowly revolving cathead. Loads requiring more than six turns around the cathead should not be lifted by this means. Wire rope should not be used on the cathead. Wire kinks much more easily than rope and when this happens, some of the metal strands are almost certain to be weakened or broken, thereby making the line hazardous to use. Wire rope is also undesirable as a catline since it will cause undue grooving of the cathead. This does not apply, of course, to a spliced catline, part of which is rope fiber joined to a length of wire rope. In this case that part of the line made of rope fiber would be used on the cathead.
When catlines are not in use, they should receive the care given to any type of rope equipment. They should be neatly coiled and placed aside where they will not constitute a tripping hazard. Every effort should be made to keep them free of oil and grease. Oily and greasy catlines, which are subjected to the weight of every passing foot, deteriorate quickly.