Abstract of Special Research Report (SRR-No.18)
National Institute of Occupational Safety and Health, Japan
Study on New Inspection Techniques for Lifting Apparatus --Focused on failure of crane wire ropes--
Introduction
SRR-No.18-1 |
Masazumi TANAKA |
: While recently the total number of occupational accidents is steadily decreasing in Japan, the number of crane accidents shows a trend of slight increase on the contrary, and the number of casualties to death due to the failure of lifting apparatus for these five years reached about 80.
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Analysis of Fracture Accidents of Crane Wire Ropes and the Problem Included
SRR-No.18-2 |
Masazumi TANAKA |
: Wire ropes are widely used for cranes, for example, on the lifting and derricking work, under the condition of heavy duty in many cases. And recently in Japan, considerable number of serious crane accidents happened, caused by the fracture of wire ropes. |
On the Propeties of Internal Damage of Crane Wire Ropes
SRR-No.18-3 |
Masazumi TANAKA |
: As it was introduced in the previous chapter, the presice investigations on the crane wire rope fracture accidents showed that the remarkable internal damages formed prior to the accident were found in many cases in IWRC (independent wire rope core) wire ropes.
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Analysis of Progression Properties of Wire Breaking Damage
SRR-No.18-4 |
Masazumi TANAKA |
: To decide the reasonable inspection period and to improve the quality of safety management for crane wire ropes, it is inevitable to predict reliable fatigue life under well known working conditions and moreover to grasp the progression properties of wire breaking damage. However, so far the fatigue life of wire ropes has been assessed hi many cases practically by the number of load repetitions until the number of visible wire breaking detectable by external observation reaches a specific number. And the case of the fatigue life assessment which takes the internal damages especially interested in this specific study into consideration or the study on the progression properties of all wire breaking patterns including internal wire breaking have not been found.
This kind of formula axe thought to be very useful, when studying the damaging state of wire rope including the internal ones. |
Fretting Fatigue Behavior of Wire Rope Steel and SNCM439 Steel
SRR-No.18-5 |
Yoshio KITSUNAI, S.Genesh Sundara Raman and Muthuswamy Kamaraj |
: It is known that one of the most important factors in failure cause of wire rope is fretting fatigue, which occurs as a result of relative cyclic slip at the interface between two surfaces in intimate contact. However, study of fretting fatigue in wire rope is limited because fretting phenomenon is very complex and reasonable fretting fatigue test is difficult. In this study, to assess the important variables that can affect fretting fatigue of wire rope, fretting fatigue behavior of a cold drawn eutectoid steel rod, which has been used to make wire rope, was examined by clamping the contact pads with the same material. Fretting fatigue strength is affected various factors. The effects of specimen configuration, fretting test apparatus, contact pressure and pad span on fretting fatigue strength were examined using two types of specimens and contact pads made of SNCM439 steel.
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On the Countermeasures for Preventing Wire Rope Fracture Accidents
SRR-No.18-6 |
Masazumi TANAKA |
:Through many analysis carried out by the author on the wire rope fracture accidents in cranes, remarkable internal damages were found to exist in IWRC wire ropes. And from the results of such analysis and the thorough certification tests on these kinds of wire ropes, it was concluded that the internal damage was one of the general characteristic for these kinds of wire ropes when they were used as travelling ropes. On the basis of the conclusion, an important problem in occupational safety was pointed out that the existing inspection methods in our country mainly by means of naked eye's observation could not detect correctly such kinds of internal damages.
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Concluding Remarks
SRR-No.18-7 |
Yutaka MAEDA |
: This specific research started with the occasion of the Southern Hyogo-prefecture earthquake in 1995, which caused a great deal of damage to many cranes. The dynamic effect of earthquake on jib cranes and tower cranes is not prescribed in the standard for proof against earthquake of crane.
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