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(1) The wire rope is twisted or bent during the first installation, and the wire rope is unevenly arranged on the reel or no measures are taken when the rope is first climbed.
(2) Improper measures when the end of the wire rope is fixed; the direction of the main rope is incorrect when the wire rope is connected with the wedge; the rope head is too short and not tied with the pressure plate, the bolts are too tight or too loose; At the same place, the number of screw buckles is small, the spacing is unreasonable, or the selection does not match the wire rope.
(3) Reversing pulleys, rope-receiving devices, etc. due to routine maintenance and lubrication are not timely, resulting in stuck.
(4) The lubricant is not properly selected or improperly lubricated daily.
(5) When the amount of wear such as the groove diameter, wrap angle and groove wall at the bottom of the pulley groove approaches or exceeds the specified requirements, the corresponding bending stress and the pressing force of the wire rope will increase.
(6) The position of the pulley or the hoisting drum is improper, causing the yaw angle of the wire rope to wrap around or around the pulley and the drum, that is, the center line of the wire rope and the plane clamp perpendicular to the axis of the pulley or the drum are greater than 4 degrees.
(7) Defects in the manufacture of pulleys or hoisting drums, such as cracks, stomata, sand inclusions and excessive surface roughness.
(8) The performance of the material of the pulley or the hoisting drum can not meet the specified use requirements, and the force of the wire rope is too large, so that the crushing stress is too large.
(9) There is no anti-jumping device on the pulley device or the gap between the anti-jump device and the pulley is too large, exceeding 20% ​​of the diameter of the wire rope or the rigidity of the anti-rope device can not meet the requirements of use, and the wire rope is skipped, causing damage to the wire rope.
The damage of the hoisting wire rope is in addition to the external reasons mentioned above, as well as the internal factors of the wire rope causing its damage.
Damage to the wire rope occurs first on the outer wire of the wire rope. When the outer wire bypasses the pulley or the drum, it is repeatedly bent and pressed under the strong tensile stress, causing metal fatigue. When the limit is reached, the wire rope will break and the strands will be loose, thereby causing the bearing capacity to decrease. The initial point of the break is often at the location of the extrusion or at the rust, crack. Since the wire rope inevitably has frequent starting and braking during operation, vibration stress is generated, which will intensify the damage of the wire rope.
The number of windings of the wire rope is small, the rigidity is large, the winding property is poor, and it is easy to loose; on the contrary, the number of windings is large, the outer layer wire is thin, easy to wear and break, and not durable. The double winding is good in winding, simple in manufacture and low in cost; the twisting tendency of the strands and ropes of the interactive reins can play a certain offsetting effect, and it is not easy to loose during work, but the rigidity is large and the service life is low. At present, the construction machinery mostly adopts the wire contact type steel wire rope, because the wire gap contact stress is small, the wear is small, the service life is long, the filling rate is high, the winding capacity is large, and the bearing capacity is large. The secondary bending stress of the point contact is eliminated, the total bending stress during work can be reduced, and the fatigue resistance is good. The structure is compact, the metal section has high utilization factor and long service life, which is 1-2 times better than ordinary steel wire rope. However, the strength of the wire rope is too large, and the greater the stiffness, the worse the winding. Another type of stranded strand has a large wear point on the drum, high wear resistance, is not easy to break, and has a high structural density. Under the same rope diameter and strength, the total breaking force is large. The service life is about 3 times higher than that of ordinary round wire ropes and is being widely used.
When the steel wire rope is selected, in addition to considering the structural form and performance of the wire rope, the wire rope phenomenon is also generated to prevent the frictional force and the pressing force between the wire ropes. The rope diameter should adopt a steel wire rope smaller than the pitch of the rope groove and the diameter of the rope groove to increase the contact area between the steel wire rope and the reel, and reduce the frictional force of the adjacent steel wire rope, thereby improving the life of the steel wire rope.
Under the same diameter, the more the number of steel strands, the thinner the diameter, the thinner the single steel wire is, the better the winding of the steel wire rope can overcome the reverse bending force of the steel wire rope when entering and exiting the drum multiple times, and the rope is worn. It is also easy. The thicker outer strands, which have thicker steel wires, are better able to withstand abrasion, mechanical damage, corrosion and squeezing forces. Therefore, only the combination of the two advantages can be truly high-performance high-quality steel wire rope.
The maximum breaking force and minimum diameter to be determined in the selection of the wire rope can be calculated by the following formula.
The maximum breaking force of the wire rope can be based on the formula:
F≥P*N/Q
Among them: F - the sum of the breaking force in the wire rope standard; P - the maximum force to be subjected to work; N - safety factor; Q - the conversion factor of the breaking force of the wire rope.
The minimum diameter of the wire rope can be determined by the maximum working static tension of the wire rope;
D=[N/(0.785*K*W*δt)]1/2*S1/2
Among them: D—the minimum diameter of steel wire rope, mm; N—safety factor; Kâ€”æ» folding coefficient; W—wire rope fullness coefficient; δt—nominal tensile strength of steel wire rope, MPa; S—maximum working static tension.
During the long-term use of the equipment, the performance of the wire rope changes at any time, and the performance of the wire will gradually deteriorate and decrease. As a result, it affects the normal use of the entire equipment. By mastering the changing rules of steel wire ropes and organizing technical maintenance at any time, it is possible to eliminate faults in time, extend their service life, increase equipment productivity, and reduce failure rate and operating cost.
Maintenance and selection of bucket lifting rope hoisting rope
The mechanical failure of the bucket-type lifting mixer is more common in the hoisting lifting system, and accidents caused by the damage or breakage of the wire rope of the system also occur from time to time. In order to ensure the safe operation of the wire rope, better grasp the damage law and preventive method of the wire rope, for the structure of such equipment, the following reasons for the damage of the wire rope are analyzed: