Best installation

25 April 2008

Regardless of which type of wire rope is used on your crane, proper installation of the rope on the drum is the first step towards successful operation. Correct wire rope installation, maintenance and operation will extend its service life.

Normal spooling and handling can cause twists in a rope. If a twist remains in an installed rope, it can create spooling problems, or a kink, resulting in permanent damage and operational problems with spooling or block rotation. Therefore, it is essential to remove any twists during the rope installation process.

One way to insure proper installation is to remove the rope from the reel and pull it straight out on the ground. Mount the reel on a shaft supported by two jacks, a roller payoff, or unreeling stand. Remove the rope from the spool by taking the end and walking the rope away, keeping it straight. This will allow any trapped twist to come out of the free end when the rope is installed onto the drum.

When in the field or on a jobsite, space for complete unwinding and laying out of the rope is not always an option. If space is limited it can be necessary to install directly from the shipping reel to the drum. This may result in a twist being trapped in the rope on the crane.

Mounting the reel on a shaft supported by two jacks on the ground will allow a direct transfer from the shipping reel to the crane. Prevent over-rotation of the reel by applying a brake, for example, a length of timber, to the flange of the shipping reel while spooling rope onto the crane's winch drum. Never apply a brake against the spooled rope itself or pass the rope between a pair of blocks used as a caliper brake. This can damage the rope and could make it unusable. Install the rope on the drum, focusing on keeping the twist out of it and on thread laying the rope on the drum.

All wire ropes work better on grooved drums (as recent research carried out by the Institute for Materials Handling at Stuttgart University in Germany indicates). The grooves guide the rope for proper spacing of the wraps.

Smooth-faced drums can present problems. Small variation in rope diameter from one reel to another affects the position of the last wrap on the base layer and results in varying space between the last wrap and the flange. This allows the bottom layer to slide on the smooth drum face when the second layer spools over it. It also causes spooling problems at the change of layer point. It is essential to establish proper spooling and greater tension on the lower layers of rope on smooth-faced drums to prevent their displacement as upper layers are spooled over them.

Before proceeding with breaking in the rope, make a final check for twists that might still be trapped in the rope (this is particularly important when a direct-from-spool installation is used). Pull enough rope off the drum to allow it to hang slack from a horizontal position. If it hangs in a 'U' shape, there is no twist. The wrapping together of the rope indicates that twist is trapped in it.

Any twist in the rope must be removed. With a single part line, this may be achieved by extending the crane boom to its maximum length and raising it to its highest point. Then pay out the rope with only the overhaul ball attached, and let it hang, just off the ground, fully extended until the twist works itself out. Twist may also be removed by pulling the rope straight off the drum onto the ground. If this method is used, the end of the rope must be completely straight. Cut off any dogleg present from an end termination and allow the end of the rope to rotate as twist comes out when the rope is spooled back onto the crane's drum.

To train the rope, a brief but thorough breaking-in period is required. The training or breaking-in period has important benefits for length of service and proper spooling. Firstly, breaking-in a rope removes constructional stretch. This slightly reduces the rope's diameter and makes it denser, increasing its resistance to crushing in multiple layer spooling. This is especially important for the lower layers on a drum that may not bear a significant load during normal operations. A proper break-in period also assures that the rope is spooled on the drum under tension. Again, it is very important for lower layers to be spooled under tension to reduce “pull-down” or “suck-in” of tensioned upper wraps. If pull-in of upper wraps occurs, re-install the lower layers of rope on the drum under greater tension.

To break-in a rope, reeve the crane so that, with the boom fully raised and the load ready to be picked up, there are three dead wraps on the drum. Initially, lift a light load – approximately 2 to 3% of the rope's minimum breaking force – off the ground and hold for a few minutes. Slowly lift and lower the load several times and monitor the drum winding and rope travel for any potential problems.

Increase the weight to 20 to 50% of the maximum working load and perform several repetitions of full cycle lifts. The rope will seat itself, removing constructional stretch and increasing its resistance to crushing.

These basic procedures for proper installation will help prevent damage to the wire rope and result in better rope spooling and extend the working life of the rope. Attention to these installation guidelines will pay dividends by eliminating many spooling problems, increasing rope life and reducing downtime. •

Latest News
CSCEC-built spiral tunnel officially recognised as world’s longest
A spiral tunnel in China, built by Chinese construction giant China State Construction (CSCEC), has been recognised as the world’s longest
Consortium wins €302m deal to build Swiss railway plant
A consortium led by Swiss construction company CSC Costruzioni has won a contract worth €302 million (US$327 million) to build a new railway plant in Switzerland
Epiroc to acquire French attachments manufacturer
Swedish OEM continues massive attachments expansion following Stanley acquisition