Service Life of Winch Hoist Wire Rope

[Engineer FPCL 4]

We have a wire rope installed for luffing of a scrapper system of our Portal Reclaimer. The specifications of wire rope are as below:

Wire Rope Name: 24NAT, 6X19+IWRC 1770
Diameter: 24 mm
Length: 200 m
No. of Layers on drum: 04
Construction: Single Layer
Type of Lay: Right sZ
Working grade: M4
Scrapper System Load: 70 Tonne
Sheave Diameter: 560 mm EA

Questions:

1. How do we define the service life of a wire rope. In time or bending cycles?

2. This rope rolls out from a multi-layered drum (4 layers) and then passes over 2 pulleys, one fixed & other moveable (with 3 sheaves on each). With a total of 6 sheaves. There is constant load of 70 Tonnes on the pulleys with 3 rope cycles (load divided into 6 wires). How much life would this wire rope have in terms of cycles or time.

 

[oldestguy]

For a start, have you checked with government agencies that periodically inspect elevators? There may be government codes related to rope condition and acceptable/rejecting rules.

 

[miningman]

How often are you greasing the rope?? What is the diameter of the drum???

 

[Engineer FPCL 4]

1. The wire is used for luffing of scrapper to reclaim coal from a pile, there are no government codes related to this service. The OEM has referred to ISO 4309 for discard criteria of the rope.

2. Diameter of Drum: 482 mm
Greasing & Cleaning Frequency: Twice a week

 

[SlideRuleEra]

The outer strands of wire rope are the most highly stressed. Sections of wire rope should be routinely cleaned for visual inspection to look for breaks:

See: US Department of Labor (OSHA) "Working Safely With Wire Rope".

http://www.SlideRuleEra.net

 

[RolMec]

If one reads M4 to be the Mechanism Group as per FEM II and concludes from the constant loading that load Spectrum class would be the severest (L4), then your rope system is designed for a max. lifecycle of 800 h running.
However, no one would sign that, or do more guesswork based on the data provided.
If you've an issue, get someone experienced and let him/her have a close look at your overall systems and operations settings.
24 NAT doesn't ring a bell as brand, but 6x19 IWRC as such is not a high-performance design but rather a general purpose winch rope. I'd check suppliers recommendations concerning multilayer winding.
However II: There's more, for sure, but esp. one thing makes me feel uneasy:
requ. safety factor at M4 is 4, so with 700kN /6 a SWL (min. breaking load) of appr. 480 kN would be required. I don't see suchlike with a dia. 24 6x19 IWRC @ 1770 wire strength around me here.

Concluding: In the worst case you are looking at rather fast rope wear, don't you? What do you say?

However.. III, please have someone check the setup, lest to be on the safe side. I'd rather be wrong with my opinion in this case, see?!

Regards
R.

Roland Heilmann

 

[miningman]

I tend to agree with these comments. In the mining industry we work with a maximum 80:1 ratio between drum and rope diameter. Granted this is on a more critical life / death usage but your numbers compute to only 20:1. This is really hard usage with excessive wear / breakage on the outer strands to be expected. Suggest you keeps lots of spares in your warehouse.