Scrapping standard of steel wire rope

The safety degree of wire rope shall be determined by the following items:;

a. Nature and quantity of broken wires;

b. Broken wire at rope end;

c. Local aggregation of broken wires;

d. Increase rate of broken wire;

e. Strand breaking;

f. Rope diameter reduction due to damage of rope core;

g. The elasticity decreases;

h. External and internal wear;

i. External and internal corrosion;

j. Deformation;

k. Damage due to heat or arc.

i. The rate of increase in permanent elongation.

All inspections shall consider the above factors and follow their respective standards. However, the damage of the wire rope is often caused by the comprehensive accumulation of various factors, so the competent personnel should judge and decide whether the wire rope is scrapped or continued to be used.

For the damage of the wire rope, the inspector shall find out whether the damage of the wire rope is caused by the defect on the mechanism. If so, it is suggested to eliminate the defect before replacing the new wire rope.

1.1 nature and quantity of broken wires

The overall lack of juice of the lifting machinery does not allow the wire rope to have an infinite life.

For 6-strand and 8-strand wire ropes, the broken wire mainly occurs on the surface. However, the steel wire rope with multi-layer strands (typical multi strand structure) is different. Most of the broken wires of this steel wire rope occur inside, so it is "invisible" fracture.

Therefore, these factors are considered in Table 1 and table 2. Therefore, when combined with the factors in GB / t5972-20062.5.2-2.5.11, it is applicable to wire ropes of various structures.

When formulating the scrapping standard of anti torsion steel wire rope, the structure, working time and use mode of the steel wire rope shall be considered. See Table 2 for the control standard of the number of broken wires of the anti torsion wire rope on the steel pulley.

Special attention shall be paid to the local rope sections where the lubricating oil is dry or deteriorated.

Table 1 control standard for number of broken wires of round strand wire rope working on steel pulley

Number of broken wires

Number of steel wires carried by outer strand n typical example of steel wire rope structure (gb1102-74) number of visible broken wires related to fatigue when the steel wire rope in hoisting machinery must be scrapped

Organization work level

M1 and M2 m3, M4, M5, M6, M7, M8

Cross twist, twist, twist, twist

Length range

6d 30d 6d 30d 6d 30d 6d 30d

≤50 6 × 7、7 × 7 2 4 1 2 4 8 2 4

51~75 6 × 12 3 6 2 3 6 12 3 6

76~100 18 × 7 (12 external shares) 4 8 2 4 8 15 4 8

101~120 6 × 19、7 × nineteen

6X（19）、6W（19）

thirty-four × 7 (17 external shares) 5 10 2 5 10 19 5 10

121~140 6 11 3 6 11 22 6 11

141~160 6 × 24、6X（24）、

6W（24）、8 × nineteen

8X（19）、8W（19） 6 13 3 6 13 26 6 13

161~180 6 × 30 7 14 4 7 14 29 7 14

181~200 6X（31）、8T（25） 8 16 4 8 16 32 8 16

201~220 6W（35）、6W（36）、

6XW（36） 8 18 4 9 18 38 9 18

221~240 6 × 37 10 19 5 10 19 38 10 19

241~260 10 21 5 10 21 42 10 24

261~280 11 22 6 11 22 45 11 22

281~300 12 24 6 12 24 48 12 24

＞300 6 × 61 0.04n 0.08n 0.02n 0.04n 0.08n 0.16n 0.04n 0.08n

Note: ① D - diameter of steel wire rope.

② The filling steel wire cannot be regarded as the bearing steel wire, so it shall be deducted from the inspection number. Only visible outer strong strands shall be considered for multi-layer strand wire rope. For steel wire rope with steel core, its core shall be regarded as internal strand and shall not be considered.

When lifting molten or red hot metals, acid solutions, explosives, inflammables and toxic substances, the number of broken wires in the above table shall be reduced by half.

1.2 broken wire at rope end

When broken wires occur at or near the rope end, even if the number is small, it indicates that the stress at this part is very high, which may be caused by incorrect installation of the rope end. The damage reason shall be found out. If the rope length allows, the broken wire shall be cut off and re installed reasonably.

1.3 local aggregation of broken wires

If the broken wires are close together to form local aggregation, the wire rope shall be scrapped. If such broken wires are concentrated within the rope length of less than 6D or in any rope strand, the wire rope shall be scrapped even if the number of broken wires is less than the values in Table 1 and table 2.

1.4 increase rate of broken wire

In some applications, fatigue is the main reason for the damage of the wire rope, and the broken wire begins to appear after a period of use. However, 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 check and record the increase of broken wires. This "rule" can be used to determine the future scrapping date of wire rope.

1.5 strand breaking

If the whole strand breaks, the wire rope shall be scrapped.

Table 2 control standard for the number of broken wires of anti torsion steel wire rope working on steel pulley

The number of visible broken wires related to fatigue of the crane wire rope meeting the scrapping standard

Organization work level

Working level of M1, M2, m3 and M4 mechanism

M5、M6、M7、M8

Length range

≤6d ≤30d ≤6d ≤30d

2 4 4 8

A) a broken wire may have two visible ends

BD is the nominal diameter of steel wire rope

1.6 rope diameter reduction due to damage of rope core

When the fiber core of the steel wire rope is damaged or the steel core (or the inner strand in the multi-layer structure) is broken, resulting in a significant reduction in the rope diameter, the steel wire rope shall be scrapped.

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

1.7 external wear

The wear of the steel wire surface of the outer strand of the steel wire rope is caused by its contact and friction with the sheave and the rope groove of the drum under the pressure. This phenomenon is particularly obvious at the part where the wire rope contacts the pulley during the acceleration and deceleration of the lifting load, and the external wire is ground into a plane shape.

Insufficient lubrication, incorrect lubrication, and the presence of dust and sand particles will aggravate wear.

Wear reduces the cross-sectional area of the wire rope and thus the strength. When the wear of the outer wire reaches 40% of its diameter, the wire rope shall 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 wire is found.

1.8 elastic reduction

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 is difficult to detect the decrease of the elasticity of the steel wire rope. If the inspector has any doubt, he shall consult the steel wire rope expert. However, the decrease in elasticity is usually accompanied by the following phenomena:

a. Rope diameter decreases;

b. Elongation of lay length of wire rope;

c. Due to the mutual compression of various parts, there is no gap between the steel wires and the rope strands;

d. Fine brown powder appears in the rope strand recess;

e. Although no broken wire is found, the wire rope is obviously not easy to bend and the diameter decreases much faster than that caused solely by wire wear. This situation will lead to sudden fracture under dynamic load, so it should be scrapped immediately.

1.9 external and internal corrosion

Corrosion is particularly prone to occur in marine or industrial polluted atmospheres. It not only reduces the metal area of the steel wire rope and thus reduces the breaking strength, but also causes the surface roughness and cracks to develop from there to accelerate fatigue. Severe corrosion will also reduce the elasticity of the wire rope.

1.9.1 external corrosion

Corrosion of external steel wire can be observed with naked eyes. When there are deep pits on the surface and the steel wire is quite loose, it shall be scrapped.

1.9.2 internal corrosion

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

a. Change of wire rope diameter. The diameter of the steel wire rope at the bending part around the pulley usually becomes small. However, for the steel wire rope in the static section, the diameter of the steel wire rope is often increased due to the rust accumulation of the outer strand.

b. The gap between the outer strands of the steel wire rope is reduced, and the broken wire between the outer strands often occurs.

If there is any sign of internal corrosion, the wire rope shall be inspected internally by the competent person. If serious internal corrosion is confirmed, the wire rope shall be scrapped immediately.

1.10 deformation

The visible deformation caused by the wire rope losing its normal shape is called "deformation". This deformed part (or deformed part) may cause changes, which may cause uneven stress distribution in the wire rope.

The deformation of steel wire rope can be distinguished from the appearance, mainly including the following:

1.10.1 wave shape

The wave shape deformation is that the longitudinal axis of the steel wire rope is in a spiral shape. This kind of deformation does not necessarily lead to any loss of strength, but if the deformation is serious, it will produce runout and cause irregular transmission. Long time will cause wear and broken wire.

In case of wave shape, if D1 ≥, the steel wire rope shall be scrapped within the range of the length of the steel wire rope not exceeding 25d.

Where D is the nominal diameter of the steel wire rope; D1 is the diameter of the envelope after deformation of the wire rope.

1.10.2 cage distortion

This deformation occurs on a wire rope having a steel core. This deformation occurs when the outer strands are disjointed or become longer than the inner strands. The cage shaped deformed wire rope shall be scrapped immediately.

1.10.3 strand extrusion

This condition is usually accompanied by cage distortion. The rope strand is extruded, indicating that the wire rope is unbalanced. The steel wire rope extruded by the strand shall be scrapped immediately.

1.10.4 steel wire extrusion

This kind of deformation is that a part of the steel wire or steel wire bundle is arched at the side of the steel wire rope away from the pulley groove to form a ring. This deformation is often caused by impact load. If such deformation is serious, the wire rope shall be scrapped.

1.10.5 rope diameter increases locally

The diameter of the steel wire rope may be increased locally and can affect a considerable length of steel wire rope. The increase of the rope diameter is usually related to the distortion of the rope core (for example, in a special environment, the fiber core expands due to moisture). The inevitable result is that the outer rope strand is unbalanced, resulting in incorrect positioning.

The wire rope with serious local increase in rope diameter shall be scrapped.

1.10.6 kink

Kink is a kind of deformation caused by the tension of the steel wire rope when it is impossible to rotate around its axis. As a result, the uneven twist pitch will cause extra wear and tear, and in serious cases, the wire rope will be twisted, leaving only a small part of the strength of the wire rope.

The seriously twisted wire rope shall be scrapped immediately.

1.10.7 local reduction of rope diameter

The local reduction of the wire rope diameter is often related to the fracture of the rope core. Special attention shall be paid to check whether there is such deformation at the rope end.

The steel wire rope with severely reduced rope diameter shall be scrapped.

1.10.8 partial flattening

The wire rope was partially flattened due to mechanical accidents. If it is serious, the wire rope shall be scrapped.

1.10.9 bending

Bending is the angular deformation of the wire rope caused by the external influence.

The deformed wire rope shall be scrapped immediately.

1.11 damage caused by heat or arc

The steel wire rope shall be scrapped when it is exposed to special heat and has identifiable color.

(2) use record of wire rope

The correct record of relevant information made by the inspector can be used to predict the effective performance of a given type of wire rope on the lifting machinery. This information is useful in adjusting maintenance procedures and controlling the stock of spare wire ropes. If such prediction is adopted, the inspection shall not be relaxed or the service life shall not be extended beyond the conditions specified in the preceding clauses of this specification.

(3) equipment related to wire rope

The winding drums and pulleys shall be inspected regularly to ensure that these components operate normally on their bearings.

Inflexible or jammed pulley or rotating parts cause sharp and uneven wear, thus causing serious wear to the wire rope. An ineffective balancing wheel can cause unbalanced load on the bypassed wire rope.

The bottom radius of all sheave grooves shall match the nominal diameter of the rope. If the groove bottom radius becomes too large or too small, the rope groove shall be re turned or the pulley shall be replaced.

(4) inspection record of steel wire rope

For each regular inspection, the user shall prepare a record book, which shall record the inspection of the wire rope each time.

(5) storage and identification of steel wire rope

In order to prevent damage to the spare wire rope, it shall be stored in a clean and dry warehouse, and inspection records or methods for clearly identifying the wire rope shall be provided.