Wire rope is commonly used in mechanical flexible power transmission components, in terms of cable used on the crane, specification variety, the use of more complex, the strength, flexibility and wearability demand is higher, with the steel wire rope for a long time to use often appear the phenomenon such as damage or breakage, in recent years, major hoisting machinery of the resulting accidents have occurred.
Below, cable manufacturing experts according to the practical experience of recent years for the crane with wire rope several damage and its prevention and treatment.
A, wear & have spent
Wear is the most common wire rope damage phenomenon, generally can be divided into external wear and deformation wear and internal wear three kinds of situations.
1, external wear & have spent
Wire rope in use process its peripheral and pulley groove, volumes are compared. in addition, the hook after first contact surface caused by the external wear rope will become fine, fine steel wire of the outer surface is smooth, reduce the load bearing steel wire cross-sectional area, wire rope breaking load is also reduced.
Wear more serious than the week wear in a single week, should as far as possible make wear into the week even wear in a single week, within the scope of the length of the wire rope as possible even wear.
As in the use of middle removable nipple can prolong the service life of the wire rope 30% ~ 40%.
2, deformation wear & have spent
Due to vibration, collision of the surface of the wire rope damage is a kind of partial abrasion phenomenon.
Other objects such as wire rope on the surface of the block strike, hoisting wire rope to play around each other, or the result of the pulley and roll center deflection of bit line phenomenon, will make the steel wire rope produces deformation wear.
3, internal wear & have spent
In use process, due to the bending of wire rope inside the thin wire interact to produce slip, increases the contact stress between stocks and shares, between adjacent strands of steel wire to produce local creasing deep concave, when repeated cyclic stretch bending in deep sunken place produces stress concentration and broken, constitutes the internal wear.
Usually on the surface of the thin steel pressure is proportional to the pressure of wire rope, due to the compression area tension in the same situation is different, have different pressure per unit area.
Compression wear the face of it, using wire rope line contact than the point contact is relatively good, the surface contact more advantageous than by line contact, so choose the line contact or contact type of wire rope is an effective way to reduce internal wear.
In addition wire bending degree, velocity all affect the internal wear on it.
Second, the fatigue & have spent
Wire rope in use process mainly bear bending fatigue and stretch, distort, vibration caused by fatigue.
1, the bending fatigue & have spent
Wire bending, repeat many times to bypass pulley or drum, make steel wire to produce fatigue and toughness drops, eventually lead to broken wires.
Degree of bending fatigue broken wires generally appear in the stock on the best side of the outer steel wire, usually means of broken wire rope fatigue is close to use later.
Stretch, twist and vibration caused by fatigue & have spent
Crane strapping beginning and end of the wire rope in the starting and braking, bear load before and after, the changes of the tensile stress will cause metal fatigue, and wire rope is often distorted and vibration causes of fatigue.
The principle of fatigue damage in varying stress under the action of fine steel wire surface due to a variety of slip form the initial crack, the crack tip in shear stress under the action of repeated plastic deformation and extend until the fracture.
Fatigue caused by broken wires fracture general level, mostly appear on the surface of steel wire, very regular.
To prevent the fatigue damage of the main ways: one is the case where conditions permit as far as possible make the drum and the diameter of the pulley increase;
The second is when arranging pulley layout to avoid the wire rope reverse bend, reverse bending tests showed that the damage is about 2 times of the synthetic bending;
3 it is as far as possible choose the wire rope with good structure, such as the WS, TX line contact wire rope.
Information source: Marine cable manufacturers in jiangsu sweet sichuan cable technology co. , LTD