The use and scrap standard of wire rope

The use and scrap standard of wire rope

1. The wire rope is mechanically damaged due to the load running on the sharp protrusion.

2. Local wear caused by friction of the supporting structure. The wire rope vibrates between the sky wheel and the drum.

3. Narrow abrasion can cause fatigue fracture. Wire ropes working in too large rope grooves or working in too small support grooves casserole can cause this problem.

4. The steel wire rope is severely worn and the main fiber core is protruding. Should stop using, replace with a new wire rope

5. Severe wear of the steel wire rope twisted in the same direction is caused by the friction between the intersection points of the multi-layer winding steel wire rope.

6. The steel rope will be damaged due to severe corrosion caused by immersion in chemically treated water, so the steel rope should be stored in a moisture-proof and dry place.

7. There is almost no sign of damage on the outside, but the inside is rusted, and the gap between the thighs disappears completely. The surface is damaged.

8. Typical broken wire caused by bending fatigue of steel wire rope. This type occurs mostly in point contact wire rope types, so it is recommended to use wire contact wire rope.

9. Hungry broken wires between strands or rope cores, caused by lack of rope core support, are obviously different from broken wires at the "top" of strands.

10. When the (independent structure steel wire rope main core) is disconnected under high stress, pay attention to the biting of the outer strand steel wire.

11. The strand core is protruding, and the wire rope should be replaced with a larger wire rope because of the unbalanced twist caused by the sudden load.

12. A typical situation of local wear and deformation in previously knotted parts.

13. The multi-strand steel wire rope appears "birdcage" shape, which is caused by unbalanced twisting, which is typically seen at the anchor end of a multi-rope crane.

14. The protruding (main core of independent structure steel wire rope) caused by sudden load.

15. Obvious wear and serious internal corrosion. In this case, high tension, friction and corrosive environments coexist.

The "Safety Regulations for Lifting Machinery" stipulates the scrapping of wire ropes:

Whether the wire rope is scrapped is mainly based on the degree of wire breakage and some other conditions:

1. The number of broken wires in a hoisting machine wire rope within a twist pitch reaches 10% of the total wire rope.

For example, the rope 6×19=114 wire should be scrapped and updated when the number of broken wires reaches 12 wires. For example, the rope 6×37=222 wire should be scrapped and updated when the number of broken wires reaches 22 wires. For steel wire ropes composed of thick and thin wires, the number of broken wires is calculated as one thin wire and 1.7 thick wires.

2. If the radial wear or corrosion of the steel wire exceeds 40% of the original diameter, it should be scrapped. When it is less than 40%, the number of broken wires can be scrapped as required.

3. The number of scrap wires of wire ropes used by hoisting machinery for lifting hot metal or dangerous goods shall be half of the scrap standard of general crane wire ropes

4. For structural steel wire ropes that meet the requirements of the ISO2408 (General Purpose Wire Rope Characteristics" standard, the number of broken wires scrapped should be the number specified in GB5972-86.

5. The whole strand should be scrapped if it breaks.

6. When the diameter of the wire rope is reduced by 7% or more relative to the nominal diameter, the wire rope should be scrapped even if no broken wires are found.

7. The exposed hemp core should be scrapped.

8. The steel wire rope has obvious corrosion and should be scrapped.

9. Part of the outer steel wire elongated in a cage-like state should be scrapped

10. Compare with the typical examples of steel wire ropes in GB5972-86, the ones with the same damage as in the picture should be scrapped.

The overall design of the crane does not allow the wire rope to have an infinite life. For 6-strand and 8-strand wire ropes, wire breakage mainly occurs on the outside. However, it is different for the multi-strand steel wire rope (typical multi-strand structure). Most of the wire breakage of this kind of steel wire rope occurs inside, so it is "invisible" fracture.

The following combined consideration of these factors to illustrate the scrap situation, which is generally applicable to steel wire ropes of various structures.

1. Rope end broken wire

When there is a broken wire at or near the end of the rope, even a small amount indicates that the stress in this part is very high, which may be caused by incorrect installation of the rope end. The cause of the damage should be investigated. If the rope length allows, cut off the broken wire and reinstall it reasonably.

2. Local gathering of broken wires

If the broken wires are close together to form a local aggregation, the wire rope should be scrapped. If such broken wires are gathered in the rope length range of less than 6d, or concentrated in any strand, then even if the number of broken wires is less than the value listed in the table, the wire rope should be scrapped.

3. Increasing rate of broken wires

In some applications, fatigue is the main cause of wire rope damage. Broken wires only start to appear after a period of use, but the number of broken wires gradually increases and the time interval becomes shorter and shorter. In this case, in order to determine the increase rate of broken wires, carefully inspect and record the increase of broken wires. Identifying this "law" can be used to determine the future date of scrapping the wire rope.

4. The strand breaks

If the whole strand is broken, the wire rope should be scrapped.

5. Reduced rope diameter due to damage to the rope core

When the fiber core of the steel wire rope is damaged or the steel core (or internal strands in a multi-layer structure) is broken and the rope diameter is significantly reduced, the steel wire rope should be scrapped.

Minor damage, especially when the stresses in all the strands are in good balance, may not be obvious with the usual inspection methods. However, this situation will cause the strength of the wire rope to be greatly reduced. Therefore, when there are any signs of minor internal damage, the inside of the wire rope should be inspected to find out. Once the damage is confirmed, the wire rope should be scrapped.

6. Reduced flexibility

In some cases (usually related to the working environment), the elasticity of the wire rope will be significantly reduced, and it is unsafe to continue to use it.

It is more difficult to detect the decrease in the elasticity of the wire rope. If the inspector has any doubt, the opinion of the wire rope expert should be consulted. However, the decrease in elasticity is usually accompanied by the following phenomena:

a. Reduced rope diameter

b. Wire rope lay length extension

c. Since the parts are pressed against each other, there is a lack of gaps between the steel wires and the strands

d. Fine brown powder appears in the recesses of the rope strands

e. Although no broken wires have been found, the steel wire rope is obviously not easy to bend and the diameter reduction is much faster than simply caused by the wear of the steel wire. This situation will cause a sudden fracture under dynamic load, so it should be scrapped immediately.

7. External and internal wear

Two situations of wear:

a. Internal wear and pressure pits

This situation is caused by the friction between the individual strands and the steel wire in the rope, especially when the wire rope is subjected to bending.

b. External wear

The abrasion of the steel wire surface of the outer strands of the steel wire rope is caused by the friction between it and the rope groove of the pulley and drum under pressure. This phenomenon is particularly obvious when the hoisting load accelerates and decelerates, and the contact part of the wire rope and the pulley is particularly obvious, and the external wire is ground into a plane.

Insufficient lubrication, or incorrect lubrication, and the presence of dust and grit will increase wear.

The wear reduces the cross-sectional area of the wire rope and therefore the strength. When the outer steel wire wear reaches 40% of its diameter, the steel wire rope should be scrapped.

When the diameter of the wire rope is reduced by 7% or more relative to the nominal diameter, the wire rope shall be scrapped even if no broken wires are found.

8. External and internal corrosion

Corrosion is particularly prone to occur in marine or industrially polluted atmospheres. It not only reduces the metal area of the wire rope to reduce the breaking strength, but also causes the surface roughness and the development of cracks and accelerated fatigue. Severe corrosion can also cause a decrease in the elasticity of the wire rope.

External corrosion: The corrosion of external steel wire can be observed with the naked eye. When there is a deep hole on the surface and the steel wire is quite loose, it should be scrapped.

Internal corrosion: Internal corrosion is more difficult to detect than external corrosion that often accompanies it. However, the following phenomena can be identified:

a. The change of wire rope diameter. The diameter of the wire rope at the bending part around the pulley usually becomes smaller. But for the steel wire rope in the static section, the diameter of the steel wire rope is often increased due to the appearance of rust on the outer strands.

b. The gap between the outer strands of the steel wire rope is reduced, and it is often accompanied by broken wires between the outer strands.

If there are any signs of internal corrosion, the wire rope should be inspected internally by a competent person. If serious internal corrosion is confirmed, the wire rope should be scrapped immediately.

Deformation: The wire rope loses its normal shape and produces a visible deformity called "deformation". This deformed part (or deformed part) may cause changes, which will lead to uneven stress distribution in the wire rope. The deformation of the steel wire rope is distinguished from the appearance, which can be divided into the following types:

The wavy deformation is: the longitudinal axis of the wire rope becomes a spiral shape. This kind of deformation does not necessarily lead to any loss of strength, but if the deformation is severe, it will cause beating and cause irregular transmission. A long time will cause wear and wire breakage.

When there is a wave shape, if the length of the wire rope does not exceed 25d, if d1≥4d/3, the wire rope should be scrapped.

Where d is the nominal diameter of the wire rope; d1 is the diameter of the envelope after the wire rope is deformed.

Cage distortion: This kind of distortion occurs in a steel wire rope with a steel core. This deformation occurs when the outer strands become disjointed or become longer than the inner strands. Wire ropes with cage distortion should be scrapped immediately.

Strand extrusion: This condition is usually accompanied by cage distortion. The strands are squeezed out, indicating that the wire rope is unbalanced. The steel wire rope extruded from the strands should be scrapped immediately.

Wire extrusion: This kind of deformation is a part of the steel wire or wire bundle arched to form a ring on the side of the wire rope backing the pulley groove. This deformation is often caused by impact loads. If such deformation is severe, the wire rope should be scrapped.

Local increase in rope diameter: The diameter of the wire rope may increase locally, and it can affect a relatively long section of wire rope. The increase in rope diameter is usually related to the distortion of the rope core (for example, in a special environment, the fiber core swells due to moisture). The inevitable result is the imbalance of the outer strands, which causes incorrect positioning. Wire ropes with severely increased rope diameters should be scrapped.

Kink: Kink is a kind of deformation caused by the wire rope being tensioned when it is looped and it is impossible to rotate around its axis. As a result, uneven lay length will cause extra wear. In severe cases, the wire rope will be twisted, leaving only a small part of the wire rope strength. Severely kinked wire ropes should be scrapped immediately.

Local reduction in rope diameter: The local reduction in the diameter of a wire rope is often related to the break of the rope core. Special care should be taken to check whether there is such deformation at the end of the rope. Wire ropes with severely reduced rope diameters should be scrapped.

Partially flattened: The partial flattened wire rope is caused by a mechanical accident. In severe cases, the wire rope should be scrapped.

Bending: Bending is the angular deformation of the wire rope caused by external influences. This deformed wire rope should be scrapped immediately.

Damage caused by the action of heat or electric arc: When the steel wire rope has been subjected to special heat, and its appearance has a recognizable color, the wire rope should be scrapped.

(1) There are two ways to connect steel wire ropes: small connection and large connection.

The small connection method is within the range of the joint. The strands of the two ropes are joined together, so the rope head becomes thicker and its joint length is shorter. The large connection method cuts off the strands of the two rope ends in half, and then inserts the two rope ends together. Its joint length is longer. The thickness of the rope connected by this method remains unchanged. The location of the joint is not visible on the surface. When the wire rope is used as a sling, it needs to be manually inserted before it can become a sling, commonly known as the small connection method. Wire rope insertion methods can generally be divided into five types: one-in-one-in-one method, one-in and two-in method, one-in and three-in method, one-in and four-in and one-in and five-in. The most commonly used method is one-in three-insertion method, one-in-five insertion method is mostly used for wire rope summary

(2) When the steel wire rope is fastened by braiding, the length of the braiding shall not be less than 20 times the diameter of the steel wire rope, and not less than 0.3 meters, and the thin steel wires shall be bundled in the braided part.

(3) When the steel wire rope is fixed by a rope clamp, the number shall not be less than 3, and the distance between the last clamp and the rope end shall not be less than 0.14 meters. The rope clamp plate should be on the side where the force is applied. The "U"-shaped bolt should be at the end of the wire rope, and must not cross between the front and back. The clamp should be tightened to make the two ropes squashed about 1/3 of the height. After the rope clamp is fixed, the steel wire rope should be tightened again after being stressed. Rope card matching table:

Wire rope diameter mm 10 10~20 21~26 28~36 36~40 Minimum number of rope cards (piece) 3 4 5 6 7

Rope clamp spacing mm 80 140 160 220 240

When the diameter of the crane wire rope is reduced by less than 20%, the use is allowed to be reduced, provided that there is no broken strand. The scrap standard of the wire rope:

1. Scrap where the diameter of the surface steel wire rope is more than 40% of the original diameter

2. The wire rope is scrapped when the reduction in diameter reaches 7%

3. The steel wire rope has obvious internal corrosion and must be scrapped

4. The local outer steel wire rope elongation shows "cage" distortion and must be scrapped

5. The whole strand of the wire rope must be scrapped

6. The fiber core diameter of the steel wire rope must be scrapped when the increase is serious

7. The wire rope must be scrapped when it is kinked, deformed and deformed, the hemp core is pulled out, and the performance index of the wire rope is affected by the high temperature burn of the electric arc.