NDT.net • June 2006 • Vol. 11 No.6

Periodic Non-destructive Evaluation of Steel Wire Ropes: Its Importance and Practical Relevance

Debasish Basak (deba65@yahoo.com)
Scientist, Central Mining Research Institute,
Barwa Road, Dhanbad-826001, Jharkhand, INDIA


ABSTRACT

The most effective way in which non-destructive evaluation of rope is currently used is as a means of improving the reliability of the initial identification of the location of significant degradation along a rope. Magnetic flaw detectors are used to determine rope wearing. The detectors can measure loss of metallic area (LMA) and detect the local faults (LF) like broken wires and other faults of the rope. Deterioration of a rope during its lifetime leads to a reduction of the rope safety and to its possible destruction. Magnetic non-destructive testing allows an increase in the safe and use of steel ropes due to objective, reliable and documented evaluation of the real rope condition and by ensuring timely rope replacement.

Keywords: Non-destructive evaluation, magnetic method, flaws

INTRODUCTION

Steel winding ropes which are subjected to severe working conditions in hazardous areas such as in mines and on aerial ropeway installations, deteriorate with use. Assessment of rope condition either by visual examination or drawing a specimen rope length and subjecting it to destructive evaluation seldom speaks about integrity of the entire rope length in the installation. Further, ropes which are used on friction winders and aerial ropeway passenger cable car installations, cannot be assessed at any cost, due to non-availability of rope length for destructive investigation. Under these situations, non-destructive investigation is the only means for its evaluation to study the behaviour.

AVAILABLE METHODS AND SCOPES

The most conventional inspection method for wire ropes is the visual inspection in which the experts observe the surface and assess the rope condition empirically. The experts of visual inspection for wire ropes have decreased and cannot evaluate the inner failure such as corrosion. However, the visual method produces a possibility for inadequate inspection due to its subjectivity. Practically, it is hard and nearly impossible to review thoroughly a rope covered by lubricant and grime when a rope length is up to a hundred meters. Additionally, only surface faults of the rope can be detected and this is insufficient to define its condition correctly.

Visual inspection alone is inadequate to provide a real definition of the rope degradation level, even if the inspection is fulfilled conscientiously. Many of the surface defects like broken wires are not detected by inspectors. Using magnetic method, a rope expert has a possibility to estimate the rope condition.

Magnetic non-destructive evaluation of wire ropes has been in regular use in a number of countries for inspection of hoisting ropes in deep mines and inspection of ropeways. Recently used method is based on magnetization of the rope with permanent magnets and detection of the changes of magnetic field around the rope and total magnetic flux.

Equipment recently used for non-destructive testing of steel wire ropes generally uses "permanent magnetic method" to evaluate the rope condition.

OBJECTIVES

Followings are the main objectives for non-destructive evaluation of steel wire ropes:
  • study the behaviour and condition of ropes over a period of time at regular interval of six months
  • assess the suitability of steel winding ropes in installations by non-destructive evaluation
  • develop the model for predicting the safe and economic condition of operating rope life
  • achieve the optimum safety, economy and reliability during operation of the rope in current installation.

PRACTICAL RELEVANCE, ASSESSMENT AND EVALUATION OF ROPE BY NON-DESTRUCTIVE METHOD

Followings are the practical relevance/utility of the study:
  • Output of the study will be useful for continuous monitoring of rope condition of (a) winder ropes in various mining installations, and (b) aerial ropes in aerial ropeway installations.
  • This will locate the faults over the entire length of ropes in a particular installation.
  • With the results and recommendations of the study, the concerned management will be able to take decision either to remove ropes from installation or to extend the life of existing rope.
  • Periodic in-situ measurement of faults in ropes would help to find out effects of various parameters on rope life.
Assessment of rope condition by non-destructive technique enables : (a) detection of localized flaws such as broken wires --- quantitative inspection, and (b) detection of distributed flaws viz. corrosion, abrasion, wear nicking, pitting etc. --- qualitative inspection.

This technique which would provide great insight on the condition of a rope on installation, would alert the operator in respect to hidden problems such as internal corrosion, internal and external broken/defective wires. A complete documentation of gradual rope deterioration throughout its entire service life by periodic inspection, right since the rope installation, would enable the operator to arrive at a decision for preventing premature rope failure under adverse conditions or extensions of rope life in deserving cases.

CONCLUSION

Application of non-destructive evaluation procedures makes it possible to improve the reliability of detecting broken wires over the whole rope length. It also emphasizes the priorities of wire break discard criteria supported theoretically and experimentally. It is of primary importance to come to an agreement on the method of assessing a rope strength by non-destructive evaluation readings and focus on investigations free from uncertainties and ambiguous judgments.

With this in view, Electrical Laboratory of Central Mining Research Institute (CMRI), Dhanbad, India has been engaged over a considerable period of time in performing non-destructive evaluation on winding ropes in coal and metal mines at BCCL, TISCO, HZL, HCL, UCIL, material handling ropeway at NALCO, and aerial ropeway installations at Parwanoo (HP), Jabli (HP), Joshimath (Uttaranchal), Nainital (Uttaranchal), Science City (West Bengal), Gangtok (Sikkim), Manakamana Darshan (NEPAL).

ACKNOWLEDGEMENTS

The author is grateful to Director CMRI for his kind permission to publish the paper. The views expressed in the paper are of the author's and not of the organization he serves.

REFERENCES

  1. Zawada NDT Homepage http://www.zawada.z.pl/
  2. MD 120B WIRE ROPE DEFECTOGRAPH
  3. http://www.msha.gov , Federal Mine Safety and Health Act of 1977; 30 CFR 56/57.19023 and .19024.
  4. Zawada, Kazimierz (1999), " Magnetic NDT of Steel Wire Ropes", NDT.net, Vol. 4, No. 8.
  5. Moriya, Toshiyuki (2000), "A Magnetic Method for Evaluation of Deterioration of Large Diameter Wire Ropes", 15th World Conference on Non-Destructive Testing, Rome (Italy).
  6. Singh, S.D. & Ghara, B (2000), "Steel Wire Rope Condition Monitoring by Non-destructive Investigation and Evaluation While on Installation/Service", 15th World Conference on Non-Destructive Testing, Rome (Italy).
  7. Halkin International, @1996-19999, e-Mail: Halkin International, "Magnetic Wire Rope Inspection-WT"
  8. Weischedel, H.R. & Chaplin, C.R. (1992), "The Inspection of Offshore Wire Ropes: The State of the Art", 24th Annual Offshore Technology Conference (OTC) Houston, Texas, May 4-7, 1992, paper number OTC 6969, 227-239.
  9. University of Reading. Wire rope non-destructive testing - Survey of instrument manufacturers (2000) UK Health & Safety Executive. Offshore Technology Report OTO 2000064. Prepared by The University of Reading.

© NDT.net |Top|