2014年5月15日星期四

Properties and Choice Wire Rope

To choose wire rope,it should be according to the core requirement dependent on the opetation conditions of wire rope,at same time consider the basic features of the wire rope and then confirm the specification. 

1. Strenth

the breaking force given in the standard is the minimum one,onle 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 beused approriately, 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 IWRC 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 poossess a better permance
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 abetter 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 6x36WS wire rope is better than 6x19 class ones, while 6x19 class is better than 6x7 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 6x36WS class wire rope is better than 6x19 class ones,while 6x19 class is better than 6x7 class; performance of anti-abrasion of the compacted wire rope is better 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-tesistance 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 manenverability 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 not 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 trands 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 IWRC 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 ratation-resistance When ratation of the clog is forbidden during the lifting operation with wire rope,then rotation-resistant wire rope should bu chosen. The rotation-resistance of 35Wx7 wire rope is better that of 18x7 class ones, 18x7 wire rope is better than compacted 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 imprenated plastic best corrosion-resistance.




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