Properties and Choice of Wire Rope
To choose wire rope, it should be according to the core requirement dependent on the operation conditions of wire rope, at same time consider the basic features of the wire rope and then confirm the specification.Professional technicians from DAWSON GROUP LTD. Possess abundant experience would like to help customers to do this work.
1.Strength
The breaking force given in the standard is the minimum one, only applicable to the new and unused wire rope.The wire rope should not work in a condition where the required force is equal or approaching to the Min. breaking force. The actual breaking force of a new rope must be large or equal to the minimum breaking force, during the effective service life, due to the abrasion on the surface and metal fatigue, the strength of the wire rope may decrease gradually. If not be used appropriately, the strength of the wire rope may vanish suddenly. For the breaking force of the ropes in same size, the rope with larger tensile strength is bigger than the one with lower tensile strength, rope with lWRC is bigger than the one with FC, linear contact lay rope is bigger than point contact lay rope,compacted wire rope is bigger than linear contact rope, double compacted is the biggest one.
2.Anti -fatigue
Anti-fatigue include the metal fatigue of the steel wire in the wire rope, to possess a better performance of anti-fatigue, the steel wire should possess the capability of bending repeatedly under tension.For the same size wire rope, the one which contains more small size steel wire has a better anti-fatigue performance than that which has relative less small size.To reduce the effect of the fatigue, keep it in mind that don't wound the steel wire on the pulley or spool which has a too small diameter.The anti-fatigue performance of 6×36WS class wire rope is better than 6×19 class ones, while 6×19 class is better than 6×7 class.
3.Anti-abrasion ( resistant to metal loss and deformation)
Metal loss means the actual abrasion of the outer steel wire of the wire rope，this abrasion can decrease the tensile force of the steel wire; metal deformation means the shape change of the outer wire of wire rope, the change may decrease the anti-fatigue performance, then affect the move of steel wire when wire rope bends,also this may cause additional stress. For the same size wire rope, the ones which contains less outer steel wire and bigger size outer wire has a better abrasion-resistance than that which contains more outer steel wire and small size outer wire.
The compacted wire rope has relative more steel wires in one strand; it can improve the anti-fatigue performance and the anti-abrasion performance.
The anti-abrasion performance of 6×36WS class wire rope is better than 6×19 class ones, while 6×19class is better than 6×7 class; performance of anti-abrasion of the compacted wire rope is batter than that of ordinary round wire rope.
4.Anti-extrusion
Extrusion is caused by outside pressure on the wire rope, the pressure can cause deformation of the cross section , strand and the core, also can damage the wire rope when it is serious.If the wire rope is damaged by the pressure , the steel wires, strand , core can't move easily when in operation, thus additional stress is produced. Wire ropes with IWRC core have better anti-extrusion performance than the ropes with fiber core; regular lay wire ropes have better extrusion-resistance than lang lay wire ropes. 6 strand wire ropes have better extrusion-resistance than 8 strand and 19 strand wire ropes, compacted wire rope is better than round wire rope , double compacted wire rope has the best performance of anti-extrusion.
5.Stability
This is to describe the maneuverability and the performance.There is no explicit measure method.For example, the wire rope which can be wound and can be paid off on the smooth spool, or there is no twist when being used in a assembly winding system , should be considered as a stable one.The construction of wire rope and construction is important to the stability of wire rope, regular lay wire rope is more stable than lang lay wire rope, wire rope containing 7 wire strands is more stable than these ropes which strands has more steel wires and has more complex construction.
6.Flexibility
Flexibility means the wire rope 's capability of bending to arc.
Small size wire rope bends easily than big size wire rope, wire ropes with fiber core bend easily than the ones with lWRC core , bright wire rope bend easily than galvanized wire rope,point contacting wire rope bends easily than line contacting wire rope, line contacting wire rope bends easily than compacted wire rope.As a universal criterion, for same size wire rope, wire ropes compose by more small size steel wire than these composed by less big size steel wire.
7.Rotation-resistance
Wire ropes tends to rotate around the axis under the load, rotation-resistance means the capability of rotation-resistance When rotation of the clog is forbidden during the lifting operation with wire rope, the rotation-resistant wire rope should be chosen. The rotation-resistance of 35W×7 class wire rope is better that of 18×7 class ones, 18×7 class wire rope is better than compacted 4 strand wire ropes, 4 strand wire ropes is better than 6 strand wire rope.
8.Corrosion-resistance
Corrosion-resistance of galvanized wire rope is better than that of bright wire rope, galvanized steel wire rope with impregnated plastic has best corrosion-resistance.
Use of Wire Rope
Pay off
For wire rope with reel, place the reel on a stand which allows the reel rotate, control the rotation speed of the reel, pull of the wire rope slowly.
For wire rope without reel, pull of the wire rope in the direction reverse to the end of wire rope.
End treatment
Sizing: Iron wire is recommended to be used to seize the wire rope, at the location where the wire rope will be cut, put one end of the iron wire along the wire rope axis, and leave a length of 4 times diameter of wire rope; begin to wind the iron wire on the wire rope closely from the other side of iron wire at the cutting position, the winding length should be about 3 times of rope diameter, then strain the ends of the iron and screw it closely, the screw length should equals the diameter of the wire rope then the screwed section should be set between the groove of the strands.
Rope clamp: Steel wire ropes are bended to a ring, fixed with wire,and then using double-saddle bolts clamping.
Fuse end of wire rope: using special electric heating equipment of steel wire rope, under half melting state, through the chunk rotating wire rope and then the rope of all steel wire welding together forming conical end of wire rope.
Check pulley groove
Before install the new wire rope,check the pulley groove carefully,the groove must be smooth, the rope groove radius should be large than the wire rope radius by 7.5%. Use the special radius gauge to measure groove radius.
Check angle of fleet
Before install new wire rope,must check and measure the angle of fleet. Angle of fleet means the included angle between the center line of the rope and perpendicular line of pulley axes, which is measured when wind the rope till the edge of the drum.No matter it is groove drum or plain drum，the angle should not be more than 1°30"
Installation
When wind the rope on the drum in multi-layers, must coil the bottom wire rope closely under tension.otherwise the wire ropes in upper layer will wedge into the lower layer and cause damage by extrusion.After the wire rope is installed, it should be run for some time under medium load with a low speed.After the wire rope adapt to the application conditions, then gradually increase the operation speed and increase the loading. Forbid to use the wire rope under heavy load in high speed as soon as it is installed.
Note:the new and unused wire rope is more likely to be extruded than the used wire rope.
Check and Replacement of Wire Rope
Frequency and item of checking
APIRP54 suggest, inspect all the lifting rope being used visually everyday, and perform a thorough examination every month and make a monthly examination record.
Following should be inspected periodically: diameter of wire rope, lay pitch, numbers of broken wires,surface damage of wire rope.
Type of broken wire
Wire breaking is one of the signs of deterioration of wire rope.According to the location of the broken wire in wire rope, it can be classified into 2 types; one is broken wire in the crown of strand and broken wires in the dent location between strands.The broken wires in the running rope is the wires in the crown of strands, locates in the abrasion position of wire rope surface. Broken wires in standing rope often take place in the dent between strands, present at the fixed ends or other location where the rope is restricted,steel wires in such location are damaged by the energy released by damping vibration .
How to find out broken wires
Remove the wire rope from the pulley and put it at plain and steady position, clean the surface of the wire rope,thus can find the breaks in the crown of strands.
Bend the wire rope, can expose the breaks hiding in the dents between strands.Breaks in the wire rope need to be examined more carefully then it can be found.
Location of examination
·Drum
When the wire rope is coiled on the drum, it may rub with the rope of upper lays at the overlap point,thus the edge of the wire rope will be rubbed and damaged.When wire rope fall into the dent between the 2 sections ropes，then frictions happen. Also when there is a fleet between adjacent wire ropes, then friction may take place.when wire rope traverse the upper layer, for there is only one contacting point, so it is easy to be extrude.This extrusion may increase the pressure, and this pressure may deform the cross section of wire ropes,strands and core, thus damage the wire rope.Extrusion may happen at the exchange point of the layer, and the out edge of the drum where the wire rope wedge in.New wire rope is easily to be extruded and dam aged, if the wire rope in former 2 layers or 3 layers is not tensed, then outer wire rope may wedge into the inner layer and can cause serious damage.Compared with grooved drum,when single layer wire rope is coiled in plain drum, the wire rope and drum will be worn more quickly.
·Pulley
Wire rope groove will become less and less during the application, the groove which is too small may hoop and shrink wire rope, increase the abrasion, also it will restrict the slide of the strand and steel wire thus cause additional stress; a groove which is too big may stave the wire rope.Above 2 statuses can decrease the service life of wire rope.
·End accessories
Movement of wire rope near to the end accessories is limited, when the damping vibration happen on one section of the wire rope, then this section will be fatigued.
·Contact point
The contact point is to hoist to in each ascending initial load， steel wire rope and drum or pulley contact area. These areas will soon appear internal and external wear for two reasons: one is the steel wire rope runtime acceleration greater load; The second is rope will load the diameter in transfer to block or on the web. In the point of contact areas that need to be key observation wire diameter decreases,broken wire, steel wire rope wear and deformation.
Replacement of wire rope
·Running rope
For 6 stand and 8 strand wire rope, if find 6 broken steel wires distributed randomly in one lay pitch, or in one strand find 3 broken steel wires, then replace the wire rope.
For rotation-resistant wire rope, find 2 broken steel wires distributed randomly within the length of 6times diameter of wire rope, or find 4 broken steel wires within 30 times of diameter of wire rope,and then replace the wire rope.
Standing rope (guy line,life line, hang line)
In one lay pitch find 3 broken steel wires,or at the end find more than one broken wires, or find broken wire in the dent between strands, then replace the wire rope.
Replace the wire rope in other necessary conditions
·Corrosion cause wire rope sunken
·Find corroded steel wire in the end joints
·End joints was corroded, damaged, bent or worn or be used in wrong manners There is kink , extrusion, cut or wire knot or stretched core
·1/3 the worn location is over than the 1/3 of the original diameter of the wire rope
·The diameter of wire rope decrease greatly ,There is evidence show that the wire rope is stroke
and dam aged
·The lay pitch increase obviously
Wire Rope Breaking Testing Machine:
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