Measuring Rope Diameter
Rope diameter is specified by the user and is generally given in the equipment manufacturer’s instruction manual accompanying the machine on which the rope is to be used.
Rope diameters are determined by measuring the circle that just touches the extreme outer limits of the strands - that is, the greatest dimension that can be measured with a pair of parallel-jawed calipers or machinist’s caliper square. A mistake could be made by measuring the smaller dimension.
Unreeling & Uncoiling and Kinks
- The Right Way To Unreel. To unreel wire rope from a heavy reel, place a shaft through the center and jack up the reel far enough to clear the floor and revolve easily. One person holds the end of the rope and walks a straight line away from the reel, taking the wire rope off the top of the reel. A second person regulates the speed of the turning reel by holding a wood block against the flange as a brake, taking care to keep slack from developing on the reel, as this can easily cause a kink in the rope. Lightweight reels can be properly unreeled using a vertical shaft; the same care should be taken to keep the rope taut.
- The Wrong Way To Unreel. If a reel of wire rope is laid on its flange with its axis vertical to the floor and the rope unreeled by throwing off the turns, spirals will occur and kinks are likely to form in the rope. Wire rope always should be handled in a way that neither twists nor unlays it. If handled in a careless manner, reverse bends and kinks can easily occur.
- The Right Way To Uncoil. There is only one correct way to uncoil wire rope. One person must hold the end of the rope while a second person rolls the coil along the floor, backing away. The rope is allowed to uncoil naturally with the lay, without spiraling or twisting. Always uncoil wire rope as shown.
- The Wrong Way To Uncoil. If a coil of wire rope is laid flat on the floor and uncoiled by pulling it straight off, spirals will occur and kinking is likely. Torsions are put into the rope by every loop that is pulled off, and the rope becomes twisted and unmanageable. Also, wire rope cannot be uncoiled like hemp rope. Pulling one end through the middle of the coil will only result in kinking.
- Kinks. Great stress has been placed on the care that should be taken to avoid kinks in wire rope. Kinks are places where the rope has been unintentionally bent to a permanent set. This happens where loops are pulled through by tension on the rope until the diameter of the loop is only a few inches. They are also caused by bending a rope around a sheave having too severe a radius. Wires in the strands at the kink are permanently damaged and will not give normal service, even after apparent "restraightening."
When wire rope is wound onto a sheave or drum, it should bend in the manner in which it was originally wound. This will avoid causing a reverse bend in the rope. Always wind wire rope from the top of the one reel onto the top of the other. Also acceptable, but less so, is re-reeling from the bottom of one reel to the bottom of another. Re-reeling may also be done with reels having their shafts vertical, but extreme care must be taken to ensure that the rope always remains taut. It should never be allowed to drop below the lower flange of the reel. A reel resting on the floor with its axis horizontal may also be rolled along the floor to unreel the rope.
Wire rope should be attached at the correct location on a flat or smooth-faced drum, so that the rope will spool evenly, with the turns lying snugly against each other in even layers. If wire rope is wound on a smooth-face drum in the wrong direction, the turns in the first layer of rope will tend to spread apart on the drum. This results in the second layer of rope wedging between the open coils, crushing and flattening the rope as successive layers are spooled.
A simple method of determining how a wire rope should be started on a drum is shown above. The observer stands behind the drum, with the rope coming towards him. Using the right hand for right-lay wire rope, and the left hand for left lay wire rope, the clenched fist denotes the drum, the extended index finger the oncoming rope.
Wire Rope Clips
Clips are usually spaced about six wire rope diameters apart to give adequate holding power. They should be tightened before the rope is placed under tension. After the load is placed on the rope, tighten the clips again to take care of any lessening in rope diameter caused by tension of the load. A wire rope thimble should be used in the eye of the loop to prevent kinking.
U-bolt Clips. There is only one correct method for attaching U-bolt clips to wire rope ends, as shown in the "Correct Way". The base of the clip bears on the live end of the rope; the "U" of the bolt bears on the dead end.
Compare this with the incorrect methods. Five of the six clips shown are incorrectly attached - only the center clip in the top view is correct. When the "U" of the clip bears on the live end of the rope, there is a possibility of the rope’s being cut or kinked, with subsequent failure.
Correct Twin-Base Clips
Seizing Wire Rope
Proper seizing and cutting operations are not difficult to perform, and they ensure that the wire rope will meet the user’s performance expectations. Proper seizings must be applied on both sides of the place where the cut is to be made. In a wire rope, carelessly or inadequately seized ends may become distorted and flattened, and the strands may loosen. Subsequently, when the rope is operated, there may be an uneven distribution of loads to the strands; a condition that will significantly shorten the life of the rope.
Either of the following seizing methods is acceptable. Method No. 1 is usually used on wire ropes over one inch in diameter. Method No. 2 applies to ropes one inch and under.
Method No. 1
Place one end of the seizing wire in the valley between two strands. Then turn its long end at right angles to the rope and closely and tightly wind the wire back over itself and the rope until the proper length of seizing has been applied. Twist the two ends of the wire together, and by alternately pulling and twisting, draw the seizing tight.
Method No. 2
Twist the two ends of the seizing wire together, alternately twisting and pulling until the proper tightness is achieved.
The Seizing Wire
The seizing wire should be soft or annealed wire or strand. Seizing wire diameter and the length of the seize will depend on the diameter of the wire rope. The length of the seizing should never be less than the diameter of the rope being seized.
Proper end seizing while cutting and installing, particularly on rotation-resistant ropes, is critical. Failure to adhere to simple precautionary measures may cause core slippage and loose strands, resulting in serious rope damage. Refer to the table for established guidelines. If core protrusion occurs beyond the outer strands, or core retraction within the outer strands, cut the rope flush to allow for proper seizing of both the core and outer strands.
In the absence of proper seizing wire or tools, the use of sufficiently-sized hose clamps is acceptable.