MONITORING CONDITION OF A ROPE

Abstract

The condition of a rope (20) is monitored according to the following steps: 1) providing a rope (20) with plastic material (22) inside the rope (20) and strength members (24, 28) present at least at the radially outer surface of the rope (20); 2) monitoring the rope (20) during its lifetime until parts of the plastic material (25) move to the radially outer surface until they become detectable at the outer surface of the rope (20).

Claims

1. A method of monitoring the condition of a rope comprising load bearing members that are twisted or braided together, said method comprising the following steps: providing a rope with non-load bearing solid plastic material inside said rope and strength members twisted or braided at least at the radially outer surface of the rope; monitoring the rope during its lifetime until parts of said plastic material move to the radially outer surface until said parts become detectable at the outer surface of the rope.

2. The method according to claim 1, wherein said monitoring is done visually by human eyes.

3. The method according to claim 1, wherein said monitoring is done optically by a measuring device.

4. The method according to claim 1, wherein said monitoring is done mechanically by a measuring device.

5. The method according to claim 1, wherein said load bearing members are steel wires, synthetic fibres, synthetic tapes, synthetic rods, or a combination thereof.

6. The method according to claim 1, wherein said plastic material is a homopolymer, a copolymer, a thermoplastic plastomer, an elastomer, a thermoplastic elastomer, or a combination thereof.

7. The method according to claim 1, wherein said plastic material has a colour different from the colour of said load bearing members.

8. The method according to claim 1, wherein different types of said plastic material are present inside said rope.

9. The method according to claim 8, wherein said different types of said plastic material have different viscosities or different wear rates.

10. The method according to claim 9, wherein said different types of said plastic material are present at different locations inside said rope.

11. The method according to claim 9, wherein plastic material with a lower viscosity or with a higher wear rate is present radially externally to plastic material with a higher viscosity.

12. The method according to claim 1, wherein said rope is a multi-strand rope and wherein said plastic material is present inside at least one of the radially outer strands.

Description

BRIEF DESCRIPTION OF FIGURES IN THE DRAWINGS

[0048] FIG. 1 shows a cross-section of a first rope before putting in use;

[0049] FIG. 2 shows a cross-section of a first rope after some use;

[0050] FIG. 3 shows a cross-section of a second rope after some use.

MODE(S) FOR CARRYING OUT THE INVENTION

[0051] FIG. 1 is a schematic presentation of a cross-section of a steel wire rope 10 before this rope is subjected to loading. The rope 10 comprises a plastic core 12 and a layer of steel strands 14 surrounding the plastic rope core 12. Each of the steel strands 14 comprises a plastic strand core 16 and several steel wires 18 surrounding the plastic strand core 16.

[0052] Still referring to FIG. 1, there may be small openings or interstices between the various steel strands 14, but this does not mean that plastic material becomes detectable or physically present at the outer surface of the rope in the meaning of the present invention. The same is valid for any openings or interstices between the various steel wires 18 of the strands 14.

[0053] FIG. 2 is a schematic presentation of cross-section of a steel wire rope 20, similar to steel wire rope 10, however, after being put in practice and after having been subjected to loading or bending or both so that plastic material becomes detectable at the outer surface of the rope 20.

[0054] The rope 20 comprises a plastic rope core 22 and strands 24 surrounding the plastic rope core 22. During use of the rope 20, the plastic rope core 22 has started moving and flowing until a part 25 protrudes from the rope and becomes detectable at the outer surface of the rope 20.

[0055] At least one steel strand 24 comprises a plastic strand core 26 and steel wires 28 twisted around the plastic strand core 26.

[0056] In addition to the protruding part 25 or alternatively to the protruding part 25, plastic may have moved or flowed so that a part 29 protrudes from strand 24 and becomes detectable at the outer surface of the rope 20.

[0057] FIG. 3 is a schematic presentation of a cross-section of another rope 30 after having been subjected to loading or bending or both.

[0058] Rope 30 comprises a core steel wire 31 extruded with an inner plastic layer 32 that started to move radially externally to form a part 33 that protrudes outside the intermediate layer of steel wires 34. The rope 30 further comprises an outer plastic layer 35 that was extruded around the intermediate layer of steel wires 34 and moved to the outer surface of the rope 30 and formed a part 36 protruding outside the outer layer of steel filaments 37.

[0059] Preferably the plastic material 35 has a lower viscosity or higher wear rate than the plastic material 32 so that is starts to move or flow earlier.

[0060] Preferably the plastic material 35 has another colour than the plastic material 32.

[0061] In case one decides that the rope 30 can still function properly despite appearance of plastic parts 36 at the outer surface, one may wait until plastic material 32, 34 becomes detectable at the outer surface. In this way the appearance of plastic parts 36 only serves as a first stage warning.

[0062] The above examples all relate to steel wire ropes. However, the invention is also applicable to synthetic ropes or to hybrid ropes, where synthetic fibres function as load bearing members.

[0063] Synthetic Fibre

[0064] In case synthetic fibres are present in the rope as load bearing members, the invention is not limited to certain types of synthetic fibres but is applicable for all types of synthetic fibres. Examples of fibres are polyamide fibres, polyester fibres, polyolefin fibres such as polypropylene and polyethylene fibres, and particularly high strength synthetic fibres such as high strength polypropylene (HSSP), high modulus polyethylene (HMPE), ultra high molecular weight polyethylene (UHMwPE), para-aramid fibres such as poly(P-phenylene terephthalamide) (PPTA) fibres, liquid crystal polyester (LCP/LCAP), poly(P-phenylene-2,6-benzobisoxazole) (PBO), meta-aramid fibres such as poly (m-phenylene isophthalamide fibres, copolyamide fibres of (terephthaloyl chloride, P-phenylenediamine, 3,4-diaminodiphenyl ether), normally referred to as copolymer aramid).

[0065] The polymer materials may be present not only in fibre format but also in other longitudinal format such as a tape, filament and rods.

[0066] Various different fibres may also be combined in one strand and/or in one rope.

[0067] Steel Wire

[0068] In case of steel wires, the wires of the rope may be made of high-carbon steel. A high-carbon steel has a steel composition as follows: a carbon content ranging from 0.5% to 1.15%, a manganese content ranging from 0.10% to 1.10%, a silicon content ranging from 0.10% to 1.30%, sulfur and phosphorous contents being limited to 0.15%, preferably to 0.10% or even lower; additional micro-alloying elements such as chromium (up to 0.20%-0.40%), copper (up to 0.20%) and vanadium (up to 0.30%) may be added. All percentages are percentages by weight.

[0069] Preferably, the steel wires and/or steel wire strands of at least one metallic layer are coated individually with zinc and/or zinc alloy. More preferably, the coating is formed on the surface of the steel wire by galvanizing process. A zinc aluminum coating has a better overall corrosion resistance than zinc. In contrast with zinc, the zinc aluminum coating is more temperature resistant. Still in contrast with zinc, there is no flaking with the zinc aluminum alloy when exposed to high temperatures. A zinc aluminum coating may have an aluminum content ranging from 2 wt % to 12 wt %, e.g. ranging from 5% to 10%. A preferable composition lies around the eutectoid position: aluminum about 5 wt %. The zinc alloy coating may further have a wetting agent such as lanthanum or cerium in an amount less than 0.1 wt % of the zinc alloy. The remainder of the coating is zinc and unavoidable impurities. Another preferable composition contains about 10% aluminum. This increased amount of aluminum provides a better corrosion protection than the eutectoid composition with about 5 wt % of aluminum. Other elements such as silicon and magnesium may be added to the zinc aluminum coating. More preferably, with a view to optimizing the corrosion resistance, a particular good alloy comprises 2% to 10% aluminum and 0.2% to 3.0% magnesium, the remainder being zinc.

[0070] Preferably, the steel wires and/or steel wire strands are end galvanized. In other words, there is no further drawing carried out for the coated wires or wire stands. Thus, a higher coating weight and a better corrosion resistance are obtained together with a high yield strength.

LIST OF REFERENCE NUMBERS

[0071] 10 rope with polymer material inside before use [0072] 12 plastic core of rope [0073] 14 layer strand [0074] 16 plastic core of strand [0075] 18 steel wire of strand [0076] 20 rope with plastic material inside after some use [0077] 22 plastic core of rope [0078] 24 strand [0079] 25 protruding part of plastic core of rope [0080] 26 plastic core of strand [0081] 28 steel wire of strand [0082] 29 protruding part of plastic core of strand [0083] 30 rope with two types of plastic material inside after some use [0084] 31 core steel wire [0085] 32 inner plastic around core steel wire [0086] 33 protruding part of inner plastic [0087] 34 steel wire of intermediate layer [0088] 35 outer plastic around intermediate layer [0089] 36 protruding part of outer plastic [0090] 37 steel wire of outer layer