捞油作业钢丝绳断裂原因

在捞油施工作业过程中,某采油厂捞油车钢丝绳突然断裂。采用宏观观察、化学成分分析、金相检验、拉伸试验、整绳破断拉力试验、扫描电镜分析等方法研究了钢丝绳断裂原因。结果表明：钢丝绳钢丝表面存在大量磨损挤压损伤,断裂面呈剪切破坏和扭转-拉伸疲劳破坏形貌特征,断裂面裂纹与轴向夹角呈45°;在使用过程中,钢丝表面磨损挤压处萌生初始裂纹,在扭转-拉伸载荷的作用下,钢丝绳松捻结构被破坏,产生了应力集中,最终导致钢丝绳断裂。     

起重用钢丝绳断裂原因

某起重用钢丝绳仅使用1个月就发生了早期断裂,采用宏观分析、微观分析、能谱分析、金相检验、力学性能试验等方法,对钢丝绳的断裂原因进行了分析.结果表明:钢丝绳受到严重的磨损和剪切挤压变形,并引起了温度升高造成组织变化,导致钢丝绳承载能力降低而失效;部分钢丝断裂后造成剩余的钢丝不足以支撑全部的承载力,最终导致钢丝绳断裂失效.     

浅谈起重机钢丝绳损伤及检验

起重机使用的钢丝绳工作环境和条件相对较为恶劣,钢丝绳不仅要经受风晒雨淋的侵蚀,还要承受起吊货物时可能出现的粗暴操作和碰撞以及卷筒缠绕和导向轮弯曲作用。由于上述因素影响,使钢丝绳产生了磨损、疲劳和断丝以及锈蚀和变形。从而降低了钢丝绳的强度,缩短了钢丝绳的寿命。为了保证起重机钢丝绳的安全使用,预防钢丝绳断裂。加强起重机钢丝绳的日常检查和定期保养是非常必要的。     

小问题大危害——小议起重机械钢丝绳安全

通过对起重机械钢丝绳断绳案例的研究,分析起重机械钢丝绳断裂事故的原因,同时提出安全对策措施。     

电梯曳引钢丝绳失效案例分析及预防措施

针对一起电梯曳引钢丝绳断丝、断股事故,全面了解事故发生的内外原因,通过现场勘查、事故调查等手段确定了事故发生的主要原因,通过查阅文献资料对电梯曳引钢丝绳容易出现的磨料磨损、腐蚀磨损、疲劳断丝等失效机理做了详细分析,为检验人员和维护保养人员正确判断缺陷钢丝绳提供了有力依据,并在定期检验和维护保养方面给出了针对性的应对措施,对延长钢丝绳使用寿命与减少电梯安全事故有一定的参考作用。     

水平井中S135钻杆断裂原因分析

某水平井在泥浆循环过程中发生一起S135钻杆断裂事故,为查明钻杆断裂原因,对事故进行了调查研究,并取样进行了包括断口分析、化学成分分析、力学性能测试、金相检验等一系列失效分析。结果表明:该钻杆所处井段井眼全角变化率较大,钻杆外壁受到严重磨损划伤并形成疲劳裂纹,在较大扭矩和拉伸载荷作用下,钻杆最终发生了断裂。     

海上拖缆断裂分析

采用化学成分分析、金相检验、显微硬度测试及断口宏观和微观形貌观察等方法对前后两天断裂的两根海上拖缆的断裂原因进行了分析。结果表明:断裂的两根拖缆都是由于拖力波动较大,使得拖缆内股钢丝绳瞬间负载过大,超过其抗拉强度首先发生断裂,继而导致外股钢丝绳发生过载断裂,从而瞬间形成整绳断裂。     

轻合金自冲铆微动磨损及疲劳性能研究

选择4组轻合金自冲铆进行疲劳实验,用扫描电子显微镜和能谱仪对其断口进行微动磨损机理分析,并系统地研究了接头疲劳寿命和失效形式的影响因素。结果表明,下板与钉腿区的微动磨损是导致下板沿纽扣断裂和铆钉断裂的主要原因,两板间的微动磨损是导致上板靠钉头断裂的主要原因;微动磨屑主要成分为金属板材氧化物,并对微动磨损起缓冲作用。增加板厚可提高接头疲劳寿命,且疲劳载荷较大时寿命提高更为显著;增加板强可提高接头疲劳寿命,且寿命提高程度受疲劳载荷影响较小。增加板厚使失效形式从上板断裂变为下板断裂,增加板强使失效形式从板材断裂变为铆钉断裂。     

某塔吊钢丝绳断裂失效分析

某工地塔吊起重机钢丝绳在施工过程中突然发生断裂失效,采用宏观检测、化学成分分析、金相检验、硬度测试、扫描电镜断口分析等方法,对钢丝绳断裂原因进行了分析。结果表明:由于内层钢丝表面润滑剂和锌系磷化膜遭到破坏,在微动磨损和腐蚀的作用下钢丝绳的力学性能严重下降,在拉力的作用下钢丝绳发生了一次性断裂。     

连铸70Y电铲钢丝绳断裂分析

对断裂的连铸７０Ｙ电铲钢丝绳进行了检验分析，结果表明：钢绳表面机械划伤和磨损是造成断裂的重要原因。     

Studies on failure behaviour of wire rope used in underground coal mines

Wire ropes operate at high stress levels and are almost invariably subject to fluctuating loads. The continuous degradation of wire rope affected with operative services will ultimately lead to failure. Study of the causes of failure of two wire ropes from two different Indian coal mines have been carried out and discussed here. The investigating parameters comprises of physical examination, wear & corrosion, lubrication, macro & micro-examination and chemical composition. The investigation revealed that the major cause of failure was due to excessive wear and corrosion resulted in high reduction in diameter ranging from 50%–90% and poor lubrication condition of wire rope. Micro-examination also revealed intergranular corrosion with cracks and pittings, uniform corrosion with pitting along the grain. Further elongated grain which was indicative of stress due to excessive corrosion with sudden impact resulted in its failure.     

Theoretical and experimental investigation of effects of failures on the tensile endurance of elevator ropes

Elevators have an important place in human life just after uprising demands in high rise buildings, skyscraper and luxury residence concepts have surged. Steel wire ropes provide permanent working safety and reliability in the elevator installations. Due to this reason steel wire ropes are one of the vital components of elevators. In this study, effects of discard criteria such as wire breaks, abrasive wear and corrosion where extents of those failures are defined by ISO 4344 standard on the tensile endurance of 6×19 Seale and 8×19 Warrington elevator ropes have been investigated theoretically and experimentally. Tensile endurances of rope samples that have different extents of failure have been determined by using tensile testing machine and comparison is made by undamaged samples for each rope separately. In addition, stress and strain values occurred on the elevator ropes investigated have also been presented. The most critical failure type has been found to be 24 wire breaks for 6×19 Seale rope with fiber core where lifting capacity reduced by 25.99 %. The most critical failure type has been found to be abrasive wear which is 0.1 mm in depth along 100 mm length for 8×19 Warrington rope with independent wire rope core where lifting capacity reduced by 7.93 %.     

Effect of abrasive wear on the tensile strength of steel wire rope

Known amounts of external abrasive wear were introduced into a new 6-strand steel wire rope and the effects of this wear on the tensile strength of the rope examined against the rope discard criteria for wear stated in ISO 4309: 1990 and other selected international standards. The variations of strength with degree of wear in the test rope were compared with continuous observations on two haulage ropes which were in service under abrasive wear conditions up to the stage of failure. The results point to a need for greater caution in applying available discard criteria for wear. The results also indicate the existence of two different rapid strength deterioration regimes in strand wire rope under increasing amounts of external abrasive wear and they direct towards test parameter levels which signal the onset of these regimes.     

Failure Analysis of Failed Wire Rope

Failure of an old rope from a stringing lattice transmission towers occurred in winter while the rope was being removed to make way for a new rope. Fracture took place around mid-span. At that time, ambient temperature was −22 °C. Wire rope was in service for nearly 50 years. We were given the mandate to determine the reasons for the fracture of the wire rope and also to suggest measures to prevent such failures from occurring. The study involved laboratory testing (mechanical and metallographic) of representative wire rope samples. The effect of low temperature (from room temperature to −40 °C) on the tensile behavior of wires and wire rope samples was evaluated. In addition, we designed an instrumented impact test to assess the effect of notches, low temperatures and dynamic loading on the fracture behavior; however, no standards were available for direct comparison. Optical metallography was used to judge the extent of corrosion and the nature of microstructure and the cleanliness of the steel. The fracture morphology of broken tensile and impact specimens was carried out using scanning electron microscopy to establish relations between test parameters and fracture modes. Results indicate that considerations have to be given to the occurrence of corrosion, notches, low temperatures, and dynamic loading conditions when replacing wire ropes and this may necessitate the replacement of wire rope earlier than the time dictated by the criterion of 10% loss in breaking strength. Results also indicate that impact testing is a better evaluator of the susceptibility of wire ropes to brittle fracture than tensile tests.     

Microstructural manifestations of fractured Z-profile steel wires on the outer layer of a failed locked coil wire rope

Locked coil wire ropes, by virtue of their unique design and construction, have specialized applications in aerial ropeways, mine hoist installations, suspension bridge cables, and so forth. In such specialty ropes, the outer layer is constructed of Z-profile wires that provide not only effective interlocking but also a continuous working surface for withstanding in-service wear. The compact construction and fill-factor of locked coil wire ropes make them relatively impervious to the ingress of moisture and render them less vulnerable to corrosion. However, such ropes are comparatively more rigid than conventional wire ropes with fiber cores and therefore are more susceptible to the adverse effects of bending stresses. The reasons for premature in-service wire rope failures are rather complex but frequently may be attributed to inappropriate wire quality and/or abusive operating environment. In either case, a systematic investigation to diagnose precisely the genesis of failure is desirable. This article provides a microstructural insight into the causes of wire breakages on the outer layer of a 40 mm diameter locked coil wire rope during service. The study reveals that the breakages of Z-profile wires on the outer rope layer were abrasion induced and accentuated by arrays of fine transverse cracks that developed on a surface martensite layer.     

Effect of degradation and impaired quality on wire rope bending over sheave fatigue endurance

This paper reports the outcome of a series of tests undertaken on six strand and multi-strand ropes to investigate the effects of degradation and impaired quality on the rope’s Bending-over-Sheave (BoS) fatigue endurance. The simulated degradation and quality impairment investigated were: wire breaks (internal and external); plastic wear, abrasive wear, corrosion, slack strands, slack wires and torsional imbalance. Theoretical predictions of rope fatigue endurance have been made to compare with the experimental values, using Feyrer’s equation. The investigation indicates that the bending over sheave fatigue endurance of rope is little influenced by degradation and impaired quality, which is primarily dependent on the rope construction and the diameter ratio of sheave to rope. The study establishes methodologies for assessment of the residual BoS fatigue endurance of degraded or impaired rope, which can inform the practical operation, inspection and discard of wire rope thereby enhancing safety.     

Loss of metallic area in winder ropes subject to external wear

The paper presents investigations related to quantification of wear in head ropes of mine drum winders. The loss of metallic area (LMA) of a worn-out rope is determined based on the geometry of the wear and on loss of wire mass. It is then related to the loss of corresponding breaking strength of the rope (LBS). The relation between the two is used to quantify the reliability of various rope condition assessment methods.     

Failure analysis of a wire rope

Wire ropes, pulleys, counterweights, and connecting systems are used for auto tensioning of contact wires of electric railways. A wire rope in one such auto tensioning system suffered premature failure. Failure investigation revealed fatigue cracks initiating at nonmetallic inclusions near the surface of individual wire strands in the rope. The inclusions were identified as Al-Ca-Ti silicates in a large number of stringers, and some oxide and nitride inclusions were also found. The wire used in the rope did not conform to the composition specified for AISI 316 grade steel, nor did it satisfy the minimum tensile strength requirements. Failure of the wire rope was found to be due to fatigue; however, the ultimate fracture of the rope was the result of overload that occurred after fatigue failure had reduced the number of wire strands supporting the load.     

Metallurgical Investigation of Failed Locked Coil Track Ropes Used in a Mining Conveyor

A locked coil track rope (LCTR) is essentially composed of wires (round and rail-shaped) laid helically in different layers. These wire ropes are sometimes used in conveyors carrying empty and loaded buckets in mining areas. During service, such wire ropes may fail prematurely due to disintegration/failure of individual groups of wires. To understand the genesis of LCTR wire failures, a detailed metallurgical investigation of failed rope wires was made and included visual examination, optical microscopy, scanning electron microscopy (SEM), and electron probe microanalysis (EPMA). Two types of failed wires were investigated; one is from a 40 mm diameter locked coil track rope and the other from a 53 mm locked coil track rope. Optical microscopy of failed round wires in the 53 mm diameter rope clearly revealed fully decarburized layers at the surface and a few grain-boundary cracks. From the location of the failure, it was clear that apart from static tensile loads, the wire ropes had been subjected to bending and unbending loads near the saddle, as fully loaded or empty buckets traveled access the conveyor. The SEM studies confirmed that the fracture had been caused by initiation of fatigue cracks in the decarburized zone under conditions of repeated bending and unbending stresses superimposed on the static tensile load.     

Failure Analysis of Wire Rope Used for Hoisting in Mining: A Case Study

Wire ropes are used in vast range of applications and many of the applications are safety critical. In the mining industry wire ropes are extensively used for hoisting/haulage. Due to the hostile operating load conditions, many wire ropes degrade in service. Fatigue of wires in rope in combination with other detrimental factors is frequently responsible for rope deterioration and premature failure during operation. In this paper the causes of failure of a wire rope used for hoisting in an Indian mine are determined with only a minimum level of information provided by the customer. Samples of the failed rope were obtained and analyzed and potential remedial measures to prevent such degradation are discussed. Reprinted with permission from Proceedings of AIME 2006, held on January 20–21, 2006 organized by Jamia Milia Islamia (a central university) New Delhi-110025, pp. 122–132.