the search coil.This semiconductor device is somewhat similar to well known magneto-electric converting devices, except that the sensitivity of this device is several hundred times greater than that of them.
The most significant feature of the new system is its independency of the sensitivity on the rope speed, which substantiated the inspection virtually at any speed including motionless state.
Several units of the device, whose number is consequential to its physical dimensions and also to the inherent directional sensitivity, are laid on a pair of split bobbin to encircle the rope simultaneously at a close two sections to form a twin annular detector assembly.
Serial or cummulative connection of all the units in one section covers the effect of lateral vibration of the rope, and the differential connection between the both halves of the twin results in a satisfactory enhancement of overall noise immunity.
The output voltage ranges approximately ten times greater than the e.m.f.on the conventional search coils at a pertinent magnetization, and may be fed into an appropriate differential amplifier for following signal processing.
For general inspection, the number of the units in each half should not be consistent with the number of strands in the rope in order to reduce the periodical noise caused by the inevitable periodic change in radial clearance between the relief of rope surface and the annular detector assembly while the rope passes.
This system with another version of the detector assembly may also be applied to measuring the let out length of a rope, determining the elongation and examining the uniformity of rope strand, in which assembly the number of the units in each half should be consistent with the number of strands.

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A method to estimate the remaining strength of locally corroded P. W. S. ropes was developed. In this method, the degree of corrosion first evaluated in terms of the loss of cross-sectional area by magnetic inspection. Second, the remaining strength is estimated from the area loss by a numerical simulation of the load-elongation behaviour of the corroded P.W.S. With this method the remaining strength was considerably lower than expected from the area loss, because the P. W. S. consists of wires corroded to various degrees. To verify the validity of this method, bundles of partially thinned wireswere examined as a model of locally corroded P.W.S. The area loss and the strength for these specimens were in good agreement with the actual values. The method was then used to evaluate the degree ofdeterioration of P.W.S. 75 ropes that had been seriously corroded during 15 years' exposure to weather as suspension members of roofing. Two P.W.S. 75's were removed from the roofing for replacementand then subjected to tensile test. The remaining strength of those ropes was successfully predictedbythis method.

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According to the remarkable advances in electromagnetic detecting technique for steel wire rope, it becomes possible to estimate with higher accuracy the static strength of wire rope being used. In addition to this, it is very important to know the dynamic tension loaded on the wire rope during winding.
From these considerations, the authors tried to prepare a tension meter of right-angled triangle type. The reliability and accuracy of this equipment was examined in the laboratory. And afterwards, it was also tested to measure the dynamic tension of the wire rope being used in the inclined and vertical shafts in a coal mine.
From these results, it was confirmed that this equipment is suitable for the practical use: the dynamic tension of vibrating wire rope can be measured accurately.

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The annular detector, through which the wire rope passes in the velocity independent inspection, consists of several units of magnetic sensitive semiconductor device, giving a relatively even spatial sensitivity around the rope. A series ofinvestigation was carried out on the uniformity of the spatial sensitivity.
To flatten out the peak of the rather sharp directional sensitivity curve which individual unit of the device manifests, a length of high permeability metal piece was attached onto each unit as a magnetic flux collector, rectifying the flux in the vicinity of the unit. As the next attempt, to obtain a smooth superposition of the adjoining curves, the declination at the skirt of the flattened curve for various length of the collector was examined, from which relevant physical dimensions of the collector and optimum interval between the adjacent units were determined. The length of the collector, together with the number of units of the device involved, dominate the circumferential length of the annular detector to be assembled; consequently its effective diameter; and eventually the diameter range of the wire rope which leaves an expedient clearance against the detector. This is a significant difference from the detecting coil systems in which the diameter of the detector is not critical.
Fluctuation in the totaled output at the annular detector assembly caused by either lateral vibration or off centering of the rope was examined for several selections of the number of units of device, detector diameters and rope diameters; all under the circumstances that the nominal clearance would be practical. The stabilization is achieved by the complementary interaction over a wide range of the above selections, and the fluctuation stays tolerably small in so far as the amplitude of the rope vibration does not exceed one half the way to come into contact with the detector.

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The ropes in rope guided winding shafts are generally very long elements, so that at descending or ascending of the cages, ropes show not only forced lateral vibrations but also natural lateral vibrations.
When periodic disturbing force is applied onto the cage, the lateral motion of the cage becomes to be significant and complicated one compared with that in the rigid guide system.
This report discusses the dynamic properties of rope guided winding systems.
Some results obtained are as follows:(1) When a periodic horizontal disturbing force is applied onto the cage, the lateral vibration of the cage has a combined frequency of the distubing force and the 2nd mode of natural frequency of the rope guided winding system.
(2) Rope guided winding systems are not regarded as easily fall into resonance because the frequencies of the natural lateral vibrations of the ropes are low enough and the loading points vary with ascending cage.
(3) Lateral displacement of the cage is proportional to the amplitude of periodic disturbing force.
(4) Relation between equivarent spring ratio of rope guided winding system and the frequency of disturbing force gives two straight lines, on a logarithmic graph.

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The guide rope system in vertical shaft is expected to contribute much to smoother winding of the cage; while, the lateral motion of the cage usually becomes larger and complicated in comparison with rigid guide system.
This report deals to analyze the natural lateral vibrations of the wire ropes in the shaft haulage system. The results can be summarized as follows:(1) The natural frequency of the lateral vibrations of guide ropes, winding rope and tail rope can be calculated by using the average values of the tensions applied to them.
(2) To make a difference between the length of guide ropes is more effective than to make a change of the bottom weight of each guide rope.
(3) It seems to be probable that the both vibrations of winding rope (2nd mode) and guide ropes (1st mode) fall in to resonate.
(4) The resultant natural frequency of winding rope, tail rope, guide ropes and cage is less affected by the change of load on cage.

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Expected and unexpected distributions of defect along the rope length were observed on the electromagnetic inspection chart for several inclined shaft winding ropes, resulting in the discussion about dispersion or concentration of defect settled after the upside-down re-installation, the defect derived from tandem deflection sheaves, and the defect in multilayer rope in which a particular layer tends to be coiled up irregularly on the drum; each of those appeared on the chart.
chart. The amplitude of the background, noise train on the electromagnetic inspection chart had been assumed to be related to the degree of deterioration of the rope, since it represents the magnitude and density of a series of minute imprints on wires as an accumulated effect of bending or change of tension through the time of service, and this was subsequently verified by breaking tests with a number of rope specimens, which were of different noise levels on the chart obtained prior to the breaking test.
The relation confirmed after the breaking test is in an exponential one between the remaining rope strength and the background noise level at the point of attention, if the actual portion where the breakage of wire occurs is not included. The loss of strength resulting from the breakage of wire, which can also be calculated from the height of the impulse on the chart, is then added in order to determine the remaining rope strength.
This relation, which may be called a deterioration index, is so clear and characteristic for each winding system that the remaining strength as well as the rope renewal time can be reasonably predicted with rigid security retained, by studying this index together with the increment of the background noise level on the successive records of the electromagnetic inspection.

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Although a series of comprehensive tests including visual inspection has been conducted according to reg ulations, we consider that the security of a rope haulage system can be confirmed only by comparing the actual dyna mic load with the present strength of the rope.
This paper describes both the tension measurements, using newly developed equipment, of several inclined shaft ropes, and the results of periodic electromagnetic rope inspections.
The highest tension on the rope which would be expected to appear during downward braking, is rather encountered following an upward halt when the tram is pulled downward by gravity after this halt, and particularly when the cars are near the bottom of the inclined shaft.
The background noise level on the electromagnetic inspection chart corresponds to the remaining strength of the rope, so that periodic examinations of record charts enable us to predict reasonably when the rope should be replaced.

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In this paper, to contribute to the development and practice of the electromagnetic inspection of a wire rope, we introduce our method and state the result of some fundamental experiments.
Next, the result of field inspections of a Cable Belt Conveyor which were carriedout with trial equipment and the procedure of estimation of the present strength of a wire rope by the electromagnetic inspection record are stated.

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A periodic inspection of a vertical shaft winding rope with the concentric construction equipped in a Koepe system was carried out by the electromagnetic method throughout its lifetime.
Various features of degrade of the rope resulted from repeated haulage, which may also be a characteristic of particular portion of the rope owing to the winding system, were explained.
Applying appropriate curing at every incident recognized on the inspection chart, approximately 250, 000 windings at the ultimate, which was far beyond the life expectancy, was attained consisting with the thorough safety, while the last three ropes in the same shaft had been renewed conventionally at 170, 000 windings or less
The rope tension, recorded in the vicinity of the head sheave through the rope travel, including various sequence such as an emergency braking, was also discussed standing on the intrinsic safety, referring to the electromagnetic inspection chart.

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An electromagnetic inspection instrument for stationary wire ropes up to 95 mm in diameter has been developed. This instrument utilizes two solenoidal coils coaxial with the rope for magnetizing it longitudinally close to saturation.
Because of the inconvenience of coiling up the conductor around the rope for each test, the solenoid type method of magnetization has not been adopted so widely. However, for large-diameter stationary ropes this method has been recognized to be better than yoke type method, as indicated in the facts which follow:
1) The instrument without iron core weighs 70 kgf and is lighter than that of yoke type.
2) Solenoidal magnetizing coils induce longitudinal magnetic field in the rope more effectively than yoke type electromagnet.
3) The distribution of flux density in the rope due to the coaxial solenoid is relatively uniform, and consequently the difference between the inspection sensitivity of a defect in the surface and that of an inner one is relatively small.
4) Inspection signal is satisfactorily stable with the solenoid type instrument, while the magnetic field in the rope is affected by the motion of the rope with the yoke type instrument, which results in a fluctuation on the inspection signal.
The instrument was applied in the field for inspecting the P.W.S.217 cables installed in a suspension roofing, and localized corrosion in these cables was successfully detected.

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Parallel Wire Strand (P. W. S.) ropes are used as major elements in suspension roofings and bridges. Long-term exposure to weather conditions deteriorate them by corrosion internally rather than on the surface. There has been a great need to evaluate this deterioration to decide whether or not they require replacement.
Some electromagnetic inspection instruments are available mainly for wire strand ropes which move, such as mine hoisting ropes. However, for stationary ropes, such as suspension cables and mooring cables, there is no equipment available for inspection work, and no prior experience in this area outside of visual examination.
A new electromagnetic inspection device for P. W. S. ropes up to 50mm in diameter was developed. This device consists of a exciting coil with two annular poles which magnetizes the rope longitudinally to saturation, and a detector unit which has twin annular arrays of Hall effect elements to sense the radial leakage flux produced by defects. This detector unit has two new features which follow:(1) The inspection sensitivity is independent of the relative rope speed, as required for inspecting stationary ropes.(2) The annular arrays are divided into 6 segments, and each segment can deliver the individual output, enabling us to detect the cross sectional location of defects.
This newly implemented instrument was used to inspect P. W. S. 75 suspension ropes. Evaluated degradation of those ropes in terms of loss in the cross sectional area was proved accurate by results of disassembling inspection.

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The impact test has practiced to investigate the decreasing trend of impact value and the maximum elongation rate, on deteriorated wire ropes which have damages such as corrosion, abrasion and wire breakage individually.
From the test, it has become clear that both the impact value and the maximum elongation rate decrease as deterioration of wire rope progresses, and that there is a certain relation between the decreasing trends of them. The relation is realized on both the deteriorated wire rope caused only by one type of damage defected artificially and the retired wire rope which has various types of damage.
The impact value is one of the characteristics that estimate the safety of wire rope, therefore, it seems possible to estimate the safety of wire rope based on the remaining ratio of the maximum elongation rate i. e. the remaining length against the allowable maximum elongation.
But, in case that tht sharp flaws and deteriorations which decrease cross-sectional area of the wire rope partially are recognized on the surface, it may be necessary to practice the manual inspection or some nondestructive testing methods, because the elongation of wire rope is not clearly realized in spite of sharp reduction of the cross-sectional area.

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