Routine Care and Maintenance for Crane I

1． Lubrication of Mechanism

The lubrication condition of crane equipment directly affects the normal operation of crane mechanisms and is closely related to extending the service life of the mechanics and promoting safety in production. Therefore, the use and maintenance personnel must carry out regular checks on all lubrication points and fuel on time with oil gun through oil cups of the lubrication points

1.1．      Distribution of lubrication points of hoisting equipment

Hook pulley spindle

Fixed pulley spindle (on the dolly frame)

Steel rope

Reducers

Gear coupling

Bearing boxes (including group wheel and group reel)

Motor bearing

Nodes and axle bolts of brake

Pulley bearing of electric cable

Shafts of grab hinge joints

1.2．      Lubricating condition and materials

Appropriate lubricant grease must be used for hoisting equipment, which should be regularly lubricated and timely replaced; lubrication equipment and the lubrication points must be kept clean. The following table lists the general regulation on lubrication interval time of major components of various mechanisms and lubricating materials recommended to use.

2.       Care and Maintenance of Mechanical Equipment

2.1. Steel rope

Discard standard: according to the relevant provisions in GB6067-85 ''Hoisting Machinery Safety Regulations"

The security level of steel rope is determined by the following items (refer to 2.5.1-2.5.10)

a、 Nature and number of filament breakage

b、 Rope-end filament breakage

c、 Partial aggregation of filament breakage

d、 Increasing rate of filament breakage

e、 Strand breakage

f、 Reduction of rope diameter caused by the damage of rope core

g、 Reduction of elasticity

h、 External and internal wear and tear

1、 External and internal corrosion

J、 Deformation

k、 Damages caused by heat or electric arc

All the above factors should be considered and follow their respective standard. However, the damage of steel rope is often caused by the accumulation of various factors, which requires the superintendent to judge and decide to discard or continue to use the rope.

In all cases, inspectors should ascertain whether the rope damage is caused by mechanism defects; if so, it should be recommended to eliminate the defect before replacing the rope.

2.5.1 Rope-end filament breakage

When filament breakage occurs at the rope end or nearby, even if there is only a small number, it also indicates that the stress of that part is very high, which may be because of the incorrect installation of rope end; the cause of damage should be identified. If the rope length allows, cut out the site where filament breakage occurs and conduct a reasonable re-installation.

2.5.2 Partial aggregation of filament breakage

If for years the filaments gather forming partial aggregation, the rope should be scrapped. If the filament breakage aggregates within the scope of rope length less than 6d, or concentrates in any one strand, even if the number of broken w匹s is less than the value listed in the table, the steel rope should also be scrapped.

2.5.3 Increasing rate of filament breakage

In some use occasions, fatigue is the main reason causing the damage of steel wire rope; filament breakage begins to occur after a period, but the number of broken wires gradually increases and its interval time becomes shorter and shorter. In this case, in order to determine the increasing rate of broken wires, carefully inspect and record the increase of broken wires. Identifying this "law" can be used to determine the future scrapping date of steel rope.

2.5.4 Strand breakage

If the breakage occurs to a whole strand, the steel rope should be scrapped.

2.5.5 Reduction of rope diameter caused by the damage of rope core

When the fiber core of steel rope is damaged or steel core (or the internal strand in multi-layer structure) fractures and it causes significant reduction of rope diameter, the rope should be scrapped.

Minor damage, especially when the stress of all the strands is in good balance, may be unobvious with the usual test method. However, this may greatly reduce the strength of steel wire rope. Therefore, when there are any signs of internal slight damage, the interior of steel rope should be inspected to make clear the signs. Once the damage is proven, the rope should be discarded.

2.5.6 Reduction of elasticity

In some cases, the elasticity of steel rope will be significantly reduced and continued use would be unsafe.

It is rather difficult to find the reduction of the wire rope elasticity; if inspectors have any doubts, they should consult the rope expert. However, the reduction of elasticity is usually accompanied by the following phenomenon.

a、 Reduction of rope diameter

b、 Prolonged lay length of steel rope

c、 As various parts are compressed against each other, there is lack of gap among wires and strands.

d、 Fine brown powder appears in the place of strand cavity.

e、 Although broken w订es are not found, the elasticity reduction caused by obvious difficulty of bending and diameter reduction is quicker than that simply caused by wear and tear of wires. This situation will result in a sudden fracture under dynamic load, so the rope should be immediately scrapped.

2.5.7 External and internal wear and tear

The two-situation causing wear and tear:

a、   Internal wear and indentation

This situation is due to the friction among strands and wires in the rope, especially when the wire rope is subject to bending

b、  External wear

The wear on the wire surface of the outer strands in the rope is caused by the friction in the contact with the rope groove of pulley and reel under its pressure. When the suspended load is acceleration and deceleration movements, this phenomenon is particularly evident at the contact area of wire rope and pulley and it is shown that the external wires are worn into a planar.

Lack of lubrication, improper lubrication, or the existence of dust and grit will accelerate the wear.

The wears reduce the sectional area of steel rope and thus reduce the strength of the rope. When the wear of outer wire reaches 40% of its diameter, the rope should be scrapped.

When the diameter of steel rope decreases by 7% or more compared to the nominal diameter, even if no broken wire is found, the wire rope should also be scrapped

2.5.8 External and internal corrosion

Corrosions will happen very easily in the sea or in the atmosphere subjecting to industrial pollution. It not only reduces the metal area of the wire rope and thus reduces the breaking strength, but also will cause a rough surface which may be developed into cracks accelerating fatigue. Serious corrosion can also reduce the reduction of rope elasticity.

2.5.8.1 External corrosion

The corrosion of external wires can be observed with the naked eye. When there is deep pit on the surface and the wire is quite loose, the rope should be scrapped

2.5.8.2 Internal corrosion

The internal corrosion is difficult to find than the external corrosion often accompanying the internal corrosion. However, the following phenomena can be identified:

a、The change of wire rope diameter: The diameter of the bending part through the pulley usually decreases. But the diameter of steel rope in the still part usually increases due to rust accumulation of the outer strands

b、The gap reduction between the outer wire ropes is also often accompanied by filament breakage in the single strand

If there are any signs of internal corrosion, the inspection of the steel rope interior should be attached great importance to by testing personnel. If serious internal corrosion is identified, the rope should be immediately scrapped.

2.5.9 Deformation

Loss of normal shape and visible malformation of wire rope are known as "deformation". This kind of deformation may cause the uneven distribution of internal stress in the steel rope.

Distinguished from the appearance, the deformation of steel rope can be mainly classified as the following types:

2.5.9.1 Wave-type

Wave-shaped deformation is: the vertical axis of the rope turns into the spiral shape. This deformation does not necessarily lead to any loss of strength, but serious deformation will lead to jumpiness and cause irregular transmission. Such deformation for a long time can cause wear and filament breakage.

When the wave shape occurs and the length of the rope is no more than 25d, if D1≥4d/3

In the formula d is the nominal diameter of steel rope; d1 refers to enveloping diameter after steel wire rope deforms.

2.5.9.2 Cage-type deformation

This deformation appears in the wire rope with steel core. When the outer strands become detached or become longer than the internal strands, the kind of deformation will occur. The rope deformed into cage shape should be血mediately scrapped.

2.5.9.3 Strand extrusion

This situation usually occurs accompanying cage-type deformation. The strand extrusion means the imbalance of steel rope. The rope whose strand is extruded should be immediately scrapped.

2.5.9.4 Wire extrusion

This kind of deformation is because part of the wires or wire tendons hog forming into ring shape on the side against the pulley groove. This distortion is often caused by impact load. lf such deformation is severe; the rope should be scrapped.

2.5.9.5 Partial increase of rope diameter

There is possibly partial increase of rope diameter and can spread to quite a long rope. The increase of rope diameter is usually associated with the distortion of the rope core (for example, in a special environment, the fiber core will inflate due to damp), and it will lead to the imbalance of outer strands and incorrect positioning. The rope whose partial diameter is severely enlarged should be scrapped

2.5.9.6 Kink

Kink occurs when the rope is tensed up in the rotation because the ring-like rope cannot wind around its axis. This will result in the unevenness of lay length and extra wear. When this situation is severe, the rope will be distorted and only a very small part of the rope strength remains.

The steel rope having severe kinks should be immediately scrapped.

2.5.9.7 Partial decrease of rope diameter

The partial decrease of rope diameter is often related to the fracture of rope core. Carry out particularly careful examination to check whether there is such deformation in the rope-end part.

The steel rope whose partial diameter severely decreases should be scrapped.

2.5.10.8 Parts flattened

The parts of steel rope are flattened due to mechanical accident. If it is severe, the rope should be scrapped.

2.4.9.9 Beading

Bending is the angle deformation of steel rope caused under the outside influence.

The steel wire rope having such deformation should be immediately scrapped. 2.4.10 Damages caused by heat or electric arc

If influenced by special heat the steel wire rope shows identifiable color, the rope should be scrapped

Maintenance: wire rope should be regularly checked and special attention should be paid to the fixation situation of the rope end. Jn order to avoid rapid wear of steel wire rope, wire rope should be maintained in good lubrication. Before lubrication, use steel wire brush to rod the dirt on the rope, wash it with kerosene, and then conduct lubrication with hot oil according to the regulation.

Replacement: The new wire rope must be consistent with the original design model, specifications, nominal tensile strength of wire rope and other requirements. It is prohibited to use the connected steel rope. The bolts at pressure pad, rope clamp etc must be firm and solid.