クレーンのワイヤーロープの交換と設置：長期耐久性のための重要な考慮事項とヒント
目次
The proper installation of crane wire rope is critical to the safe and efficient operation of the crane. Wire ropes play an important role in lifting and lowering heavy loads, and any installation problems can lead to operational failures and even safety hazards. This article will cover best practices for installing wire rope on crane.
Preparation Before Installing Wire Rope on Crane
- Before installing the wire rope, preferably when receiving the wire rope, it is advisable to check the wire rope and its certificate of conformity to ensure that the wire rope meets the ordering requirements.
- The minimum breaking tension of the installed wire rope shall not be less than the minimum breaking tension specified by the crane manufacturer.
- The diameter of the new wire rope should be measured in a straight part, under tension-free conditions, and its value (dref) recorded.
- If the wire rope may have corroded after storage for a period of time, the wire rope should be visually inspected for inspection and MRT (wire rope electromagnetic testing).
- Check the condition of all pulleys and reel rope grooves to ensure that they meet the specifications for new wire rope, are free of defects such as corrugations, and have sufficient wall thickness to safely support the rope.
- The diameter of the sheave grooves should be 5 to 10 per cent larger than the nominal diameter of the wire rope and at least 1 per cent larger than the measured diameter of the new wire rope.
Wire Rope Diameter in Relation to Sheave and Reel Rope Grooves
It is important to use pulleys, sheaves and reels with proper rope grooves, and they must be thoroughly picked up before installing new rope. Sheave grooves and wire rope must be empty Chan, and the rope has a wrap angle of 60 degrees of ring support to ensure the normal operation of the strand and allow bending. When the wheel groove is worn, the wire rope is jammed, the movement of the strand and wire is blocked, and the wire rope bending capacity is reduced.
In accordance with national standards, the actual diameter of the wire rope are positive tolerance (general diameter of 0 ~ +6%). And the use of the expiry of the scrapped wire rope diameter are less than the nominal diameter, when the old rope groove is ground deep and the diameter is small.
When the new rope replacement, and the old rope groove diameter has a very obvious difference, the new rope may not be able to fit the old rope abrasion marks, will produce unnecessary wear and tear on the wire rope. Therefore, the rope groove must be picked up every time the rope is replaced. If the new rope is thought to be too worn when replaced, the groove can be machined to correct it.
Installing Wire Rope on Crane
Handling of Wire Rope
When loading and unloading the wire rope disc, it must be loaded and unloaded by crane, so as not to cause damage to the disc and the phenomenon of chaotic rolls; when handling on the ground, the disc of the wire rope is not permitted to roll on the uneven ground, so as to cause the surface of the wire rope to be pressed and injured; when handling the wire rope without the outer packaging, the surface of the wire rope must not be adhered to the rocks, clay, etc., which affects the use of the wire rope.
Unwinding of Wire Rope
- When unrolling or installing wire rope, all measures should be taken to avoid rotation of the wire rope. Failure to do so may cause the wire rope to loop, kink or bend, rendering it unusable.
- To avoid these undesirable trends, it is advisable to unwind the rope in a straight line with the minimum permissible slack.
- Ropes supplied in coils should be released in a straight line on a rotating device, but when the length of the coils is short, the outer rope end can be left free and the rest of the rope can be rolled forward along the ground.
- Rope shall not be released by pulling the rope from a coil or reel lying flat on the ground or by rolling the reel along the ground.
- Wire ropes supplied in reel condition shall be placed with their supports as far away from the crane or hoist as possible in order to minimise the effect of rope deflection and thus avoid unfavourable rotation.
- In order to avoid sand or other dirt getting into the wire rope, the wire rope should be placed on a suitable mat (e.g. an old conveyor belt) during operation, not directly on the ground.
Wire Rope Reel Operation
- A rotating wire rope reel may have a great deal of inertia and needs to be controlled in order to release the wire rope slowly. For smaller reels, a brake is usually sufficient for control. Large reels have a great deal of inertia and may require a large braking torque to control once they are turning.
- During installation, wherever conditions permit, it is important to ensure that the rope is always bent in one direction, i.e. the rope released from the upper part of the supply reel enters the upper part of the crane or lifting hoist reel (known as ‘top-to-top’) and the rope released from the lower part of the supply reel enters the lower part of the crane or lifting hoist reel (known as ‘top-to-bottom’). The rope from the lower part of the supply reel enters the lower part of the crane or hoist drum (called ‘bottom to bottom’).
- Regulate the way of rope loading to avoid making the wire rope loose twisted or tightly twisted, or even knotted.
- For multi-layer wrapped ropes, a tensioning force of approximately 2.5-5 per cent of the minimum breaking tension of the rope is applied to the rope during the installation process. This helps to ensure that the bottom layer of wire rope is firmly wound and provides a solid foundation for subsequent ropes.
- Fix the wire rope ends on the reel and external fixing points in accordance with the crane manufacturer’s instructions.
- Avoid friction between the wire rope and any part of the crane or hoist during installation.
Wire Rope Hauling Operations
It is important to maintain the wire rope in its factory condition. Hauling should not be assisted by using old rope, the best way to do this is to use a wire rope rope sheath with a fibre rope eye coupling.
1. Use the old rope as the new rope hauling rope, can not use the new and old rope end to end welding coupling method, because this way will seriously damage the structure of the new wire rope.
The correct way of coupling is: using wire rope strands braided into the towing cage to connect the rope end, or the end of the new rope welded rings, pressure head, twisted head.
2. Use fine steel wire rope or three-strand fibre rope with the same twist direction as the new wire rope as the tow rope.
Wire rope cutting head tying method, tying hand length of at least 2 times the rope diameter.
The Use of Wire Rope Clips
The Winding Direction of The Wire Rope on The Rope Drum
The direction of the left and right twisted wire rope on the reel must be wound according to the direction that makes the wire rope tightly twisted rather than loosely twisted. Right twist (Z) of the wire rope, such as the drum from the top downward rotation, the wire rope should be arranged from left to right (as shown in Figure a), such as the drum from the bottom upward rotation, the wire rope should be arranged from right to left (as shown in Figure b); on the contrary, the left twist (S) wire rope, the arrangement of the direction of the wire rope on the drum should be according to the Figure c and Figure d shown.
Rope Winding Method
(1) Single layer winding
1 – the section where the load is wrapped around the drum when the load is lifted and other sections where the most serious interference occurs (usually at the same time as the maximum deflection of the rope);
2 – the section where the rope enters the pulley block when the load is lifted;
3 – the section which is in direct contact with the balancing sheave, in particular at the point of entry.
(2) Multi-layer winding
1 – a cross overlap zone and the zone where the most serious interference occurs (usually at the same time as the maximum deflection angle of the wire rope);
2 – a zone where the wire rope enters the top pulley when the load is lifted;
3 – a zone where the wire rope enters the lower pulley set when the load is lifted.
Trial Operation of New Wire Rope
Before the wire rope is put into use on the crane, the user should ensure that the limiting and indicating devices related to crane operation work properly.
In order to enable the wire rope assembly to be adjusted to the normal working condition to a greater extent, the user shall operate the crane at low speed and light load [10% of the ultimate working load (WLL)] for a number of working cycles.
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