Installation Instructions For Mobile Cranes
Many crane manufacturers work with special rope diameter tolerances. These must always be observed in order to achieve the best rope performance.
Pulling on the new rope
If you unwind the rope from the supply reel, this must be mounted so that it is free to rotate. Pulling the new rope off a stationary pulley or non-rotating reel will cause twist in the rope and the rope may be destroyed during installation. It must also be ensured that the rope surface remains clean and that no sand or dirt adheres to the rope lubricant. A dirty rope will damage the wires if the rope runs over sheaves.
The following illustrations show the correct and wrong way to unwinding a rope. Special care must be taken to ensure that the rope does not come into contact with parts of the steel structure or other fixed parts. The deflection angle between the supply reel and the first pulley of the crane must not exceed 2°.
Winding the rope onto the drum
The notes on pages 4 to 6 should be followed for pre-tensioned rope installation. In particular, sufficient pre-tensioning of the rope on the drum must be given. Renew the pretension at regular intervals so that all rope layers can work together firmly as a “package”.
This can be done in the field as follows: Extend the boom so far or so high that you can unwind the entire rope length up to the 3 safety coils on the drum. Now lift a sufficient load so that the rope is wound from the first drum layer with sufficient pre-tension of at least 2.5% of the MBL or 10% of the SWL. This procedure is also necessary if the crane has only worked with a part of the total rope length. The start and stop movements of the drum cause the rope layers to shift to the lower layers and become loose. If the pre-tension of the rope on the drum is too low,
the individual layers become loose and the rope strands that run up under tensile stress can pull themselves into the loose drum layer. This causes the rope to be crushed and severely damaged.
Rope Reeving and Rope Twisting
During reeving might the balance of rope falls in the hook block. With an uneven ratio of the falls the hook block gets unequal and it occurs rope twist.
Twisting of the Hook Block
There are several reasons why a hook block can twist:
1. The reeving of an odd number of falls is significantly less stable than the reeving of even falls. A 3-falls reeving is less stable than 4 falls.
2. Während der Installation des Seiles wurde ein Drehmoment oder eine Seilverdrehung in das Seil eingebracht. Oftmals wurde hier der maximal zulässige Ablenkwinkel von 2° überschritten.
3. Der Lastschwerpunkt befindet sich nicht unter dem Haken.
4. Falsches oder ungleiches Anschlagen bei der Verwendung eines Doppelhakens.
5. Schrägstehende oder schlecht ausbalancierte Unterflasche.
7. Poor rope lubrication or re-lubrication
8. Diagonal pull during load pick-up (>2°)
9. Incorrect reeving of the rope with deflection angles >2°.
10. Misalignment of the crane
11. Handling operation (always the same activities with high repetition rates)
Untwisting of Rotation Resistant Ropes
Detach the rope end from the fixed point. Turn the rope end in the opposite direction to the twisting of the hook block. When the hook block turns 1/2 turn, turn the end of the rope 180°. If the hook block rotates 3 full turns, turn the rope end 3 times around itself against the direction of rotation. Reattach the rope end and guide the rope (without load) through the entire reeving by lifting the hook block. The twists are thus distributed over the entire rope length and significantly reduced. If the hook block still twists, this process must be repeated.
Hitting rope falls in the free rope length is always a sign of unbalanced torque in the rope. The friction, generated between the rope, leads to damages on the rope. One method of untwisting the rope length is described on page 26. Occurred damages must be rated with the help of this brochure or according to official standards.
If rotation-resistant ropes such as verotop, verotop S or verotop E are used, a swivel can also be installed between the fixed point and the crane. This swivel absorbs possible twist or eliminates twist that is already in the rope. Once the twist is removed from the rope, the swivel can be blocked, completely removed or permanently installed. After the installation of a new rope, the rope should run several times under low load and at reduced speed with the boom fully extended. Repeat this procedure with increasing load and speed. This will allow the rope to adapt to the working conditions and all strands and wires will sit in a neutral position. Ideally, you should loosen the rope end again after the running-in time to release possible torque and twist that were built up during installation and running-in time.