INDICATOR YARN CONSTRUCTION

Abstract

The present invention is related to a yarn construction comprising fibres A and at least one indicator fibre, wherein the indicator fibre comprises fibre B and an elemental metal at least partially coating the surface of the fibre B, wherein fibre A and fibre B are dissimilar ultra high molecular weight polyethylene (UHMWPE) fibres. The yarn constructions may be available in different forms, amongst others in ropes, straps, slings, fabrics and synthetic chains.

Claims

1. A yarn construction comprising fibres A and at least one indicator fibre, wherein the indicator fibre comprises fibre B and an elemental metal at least partially coating the surface of fibre B, wherein fibre A and fibre B are different ultra high molecular weight polyethylene (UHMWPE) fibres.

2. A yarn construction according to claim 1 comprising at least one yarn A and at least one indicator yarn, wherein the yarn A comprises fibres A and the indicator yarn comprises the indicator fibre.

3. The yarn construction of claim 1 wherein the fibres A and fibre B differ by at least one property, the property being selected from the group consisting of filament titer, fibre tenacity, fibre elongation at break, fibre tensile modulus and intrinsic viscosity of the UHMWPE.

4. The yarn construction of claim 3 wherein at least one ratio of a property of fibre B to the corresponding property of fibre A is at most 0.95, preferably at most 0.9, even more preferably 0.80.

5. The yarn construction of claim 1 wherein at least fibre B comprises a filler and wherein fibre B comprises at least 2 wt % more filler than fibre A wherein wt % is the weight ratio of filler present in a fibre to the total weight of said fibre including the filler.

6. The yarn construction of claim 5 wherein the fibre B comprises filler with a hardness higher than the hardness of the fibre measured in the absence of the filler.

7. The yarn construction of claim 1 wherein the fibre B is inferior to the fibre A in terms of withstanding a stress.

8. The yarn construction of claim 7 wherein the inferiority is expressed either in that the flexural fatigue strength of the fibres B is inferior to the flexural fatigue strength of the fibres A, in that the elongation at break of the fibres B is inferior to the elongation at break of the fibres A, in that the resistance to abrasion of the fibres B is inferior to the resistance to abrasion of the fibres A, or in that the creep rupture of the fibres B is inferior to the creep rupture of the fibres A.

9. The yarn construction of claim 1 wherein the weight ratio of indicator fibres to fibres A is less than 0.1, preferably less than 0.05, more preferably less than 0.02 and most preferably less than 0.01.

10. The yarn construction of claim 1 wherein the indicator fibre or indicator yarn is twisted, laid or braided with fibre A, with fibre B or with fibre A and fibre B to form an assembled yarn.

11. The yarn construction of claim 1 wherein fibre B is a continuous filament.

12. The yarn construction according to claim 1 being a rope, a sling, a fabric or a synthetic chain link.

13. The yarn construction according to claim 12 comprising a load carrying core comprising at least one indicator fibre or indicator yarn.

14. The yarn construction of claim 1 comprising at least 2 indicator fibres or yarns asymmetrically positioned within the yarn construction.

15. The yarn construction of claim 1 comprising at least 2 distinct indicator fibres or indicator yarns.

Description

EXAMPLES AND COMPARATIVE EXPERIMENT

[0052] Preparation of silver coated fibres and indicator yarns

[0053] Two types of silver coated fibres have been prepared according to the method described in example 3 of EP 2499291. Silver coated fibres have been prepared starting respectively from the commercial UHMWPE yarn grades 3G12 1760 dtex and SK78 1760 dtex sourced from DSM Dyneema. The silver treatment was performed on a 220 dtex filament bundle resulting in silver coated filament bundle 1 (3G12) and 2 (SK78).

[0054] With these 2 silver coated filament bundles, 3 indicator yarns were assembled:

Indicator yarn 1: the silver coated filament bundle 1 was assembled with 20 tz from 8220 dtex 3G12 80 tz to form a 1760 dtex silver coated indicator yarn.
Indicator yarn 2: the indicator yarn 1 was further assembled (4 st/cm, braided) with 3 3G12 1760 dtex yarns.
Indicator yarn 3: the silver coated filament bundle 2 was assembled with 20 tz from 8220 dtex SK78 80 tz to form a 1760 dtex silver coated indicator yarn which was further assembled (4 st/cm, braided) with 3 3G12 1760 dtex yarns.

Preparation of Yarn Constructions

[0055] A rope with a diameter of 21 mm has been prepared comprising the above three indicator yarns. The rope construction was 1217151760 dtex SK78. To avoid the three indicator yarns contacting each other, the indicator yarns were inserted in the S-strands, with an indicator free S-strand between every indicator comprising S-strand. At the ends of the evaluated rope section, the indicator yarns have been exited from the rope construction and connected through copper wires to an adjustable power supply and LED indicator lights.

CBOS Testing

[0056] The rope with a maximum break load of 400 kN was subjected to a cyclic bending over sheave test until complete rupture with a stainless steel sheave of with a D/d of 20, a cycle frequency of 12 seconds and a bend zone of 420 mm under dry conditions. Cyclic Bending Over Sheave test machine sourced from Lucassen Metaalbewerking b.v., NL.

[0057] During the test, the load applied to the rope was ramped up (100 cycles at 10% MBL, 25 cycles at 15% MBL, 25 cycles at 20% MBL) to 25% of its MBL. The rope failed after a total of 1907 cycles.

[0058] The degradation of the rope was monitored by the 3 LED connected to the 3 indicator yarns. After 925 cycles the conductivity of indicator yarn 1 dropped, indicating failure of said indicator yarn at 49% of rope lifetime. Indicator yarns 2 and 3 failed after 1876 and 1899 cycles, i.e. 98 and 99% of the rope lifetime respectively, unacceptably late as an indicator for premature replacement of the rope in a real life application.