Risk management of machines in open pit mines

Fenomen rizika treba najpre definisati, a da bi se njime upravljalo, potrebno ga je i meriti. Merenje je neophodno da bi se utvrdili ciljevi koji se žele postići i stepen ostvarenja ciljeva. Merenje može biti kvalitativno i kvantitativno, zasnovano na statistici, merenju fizičkih veličina, ili na procenama datim od stručnih lica. U ovom radu je prikazan model upravljanja rizikom mašina koje rade na površinskom kopu, sa posebnim osvrtom na uticaj ljudskog faktora.The phenomenon of risk should first be defined, and in order to be managed it is necessary to be measured. The measurement is necessary to determine the objectives to be achieved and the degree achievement of the objectives. Measurement can be qualitatively and quantitatively, based on statistics, the measurement of physical quantities, and the estimations given by experts. This paper deals with models of risk management of machinery of open coal mines, with special focus on human resource influence

Basic parameters of the static stability, loads and strength of the vital parts of a bucket wheel excavator's slewing superstructure

Determining a bucket wheel excavator (BWE)'s slewing superstructure weight and its center of gravity (COG) is of extreme importance not only in the design phase, but also after the completion of the erection process and during the operation of the machine. This paper presents a critical comparative analysis of the basic parameters of the static stability of a BWE 1600 superstructure, with the parameters being obtained by both analytical and experimental procedures. The analysis shows that a relatively small difference in superstructure mass, obtained by calculation, leads to a relatively large unfavorable shifting of its COG, necessitating a significant increase in counterweight mass for balancing. A procedure for superstructure 3D model mass correction is presented based on results obtained by weighing after the completion of the erection process. The developed model provides enough accuracy to determine the superstructure's COG in the entire domain of the bucket wheel boom inclination angle, and enables accurate load analysis of the superstructure's vital parts. The importance of this analysis is reinforced by the finding that the procedure prescribed by standard DIN 22261-2 gives results which are not on the side of safety, as shown by an example of strength analysis of a bucket wheel boom stays' end eyes

Basic parameters of the static stability, loads and strength of the vital parts of a bucket wheel excavator's slewing superstructure

Determining a bucket wheel excavator (BWE)'s slewing superstructure weight and its center of gravity (COG) is of extreme importance not only in the design phase, but also after the completion of the erection process and during the operation of the machine. This paper presents a critical comparative analysis of the basic parameters of the static stability of a BWE 1600 superstructure, with the parameters being obtained by both analytical and experimental procedures. The analysis shows that a relatively small difference in superstructure mass, obtained by calculation, leads to a relatively large unfavorable shifting of its COG, necessitating a significant increase in counterweight mass for balancing. A procedure for superstructure 3D model mass correction is presented based on results obtained by weighing after the completion of the erection process. The developed model provides enough accuracy to determine the superstructure's COG in the entire domain of the bucket wheel boom inclination angle, and enables accurate load analysis of the superstructure's vital parts. The importance of this analysis is reinforced by the finding that the procedure prescribed by standard DIN 22261-2 gives results which are not on the side of safety, as shown by an example of strength analysis of a bucket wheel boom stays' end eyes

Bucket wheel excavator Integrity assessment of the bucket wheel boom tie-rod welded joint

The bucket wheel boom tie-rods are vital structural parts of the bucket wheel excavators (BWE) Their failures inevitably cause BWE collapse and are followed among other things by a substantial financial loss (millions of E) Non-destructive testing revealed a flaw in the butt welded Joint of the body and eye-plate of the bucket wheel tie-rod Its size exceeds the level allowed by current technical regulations An integrity assessment of the bucket wheel tie-rod has been carried out i e the remaining fatigue life has been determined based on the stress-state characteristics in the welded Joint and defined by experimental research in real working conditions The calculation results show that despite the excessive size of the internal flaw the welded Joint integrity is not compromised During periodical inspections of the welded joint in the past two years (BWE was put into operation in December 2007) changes that could compromise the structural integrity were not observed In this way by using a fail-safe philosophy design a considerable financial saving (ca 1 600 000 (sic)) was achieved while at the same time there was no threat to the worker s safety and life the safety of the machine and the production process in the open pit min

Failure analysis and reconstruction design of the slewing platform mantle of the bucket wheel excavator O&K SchRs 630

The slewing platform is the fundamental part of the bucket wheel excavator (BWE) structure. The occurrence and propagation of cracks in the zones of the slewing platform mantle holes, may probably lead to BWE collapse. The goals of the study presented in the paper were to: (1) Diagnose the cause of cracks occurrence; (2) Define the reconstruction design of the mantle; (3) Verify the reconstructed structure by numerical-experimental analysis. The identification of the stress-strain state of the mantle is done by applying the finite element method. Experimental stress analysis of the reconstructed mantle's structure is executed two times in the BWE real working conditions, using methods of strain gauges. The maximum measured value of stress is about 10% lower in relation to the calculated value of stress for the studied load case. Speaking from the engineering standpoint, the mentioned deviation is quite acceptable, particularly having in mind the stochastic character of the excavation process. Besides experimental investigations, the validity of the presented reconstruction also unquestionably confirms the mentioned failure-free exploitation, while the BWE excavated more than 2.6 x 10(6) t of coal after the reconstruction

Disaster of the bucket wheel excavator caused by extreme environmental impact: Consequences, rescue and reconstruction

A slope failure was the cause of a severe accident of bucket wheel excavator (BWE) Takraf SRs 1200. This paper is dedicated to the engineering challenges that accompanied the process of returning the BWE from its after accident state to the state of full exploitation readiness. After the accident, temporary stabilization of the superstructure was carried out as well as cutting off of severely damaged parts of the bucket wheel boom (BWB) with excavating device. Successful completion of the very delicate BWE rescue and balancing operation was followed by the reconstruction of the heavily damaged slewing platform. The integrity of the slewing platform structure was preserved by removing structural parts which were seriously damaged during long-term exploitation and breakdown, and installing the newly designed elements in critical zones. The redesign of the slewing platform structure produced favorable loads and stiffness distribution while eliminating geometrical stress concentrators. Comparative analyses of the stress states pointed out that the redesigned slewing platform structure meets the strength criterion, unlike the original structure. The redesign solution enabled reconstruction in field conditions. This way the time of the reconstruction realization was drastically cut and losses due to the downtime of the machine were reduced several times over. After completing the slewing platform reconstruction, the newly manufactured BWB structural elements as well as the newly manufactured bucket wheel with drive were installed i.e. a partial revitalization of the BWE was done and by that the BWE's life was essentially prolonged

Bucket wheel excavator Integrity assessment of the bucket wheel boom tie-rod welded joint

The bucket wheel boom tie-rods are vital structural parts of the bucket wheel excavators (BWE) Their failures inevitably cause BWE collapse and are followed among other things by a substantial financial loss (millions of E) Non-destructive testing revealed a flaw in the butt welded Joint of the body and eye-plate of the bucket wheel tie-rod Its size exceeds the level allowed by current technical regulations An integrity assessment of the bucket wheel tie-rod has been carried out i e the remaining fatigue life has been determined based on the stress-state characteristics in the welded Joint and defined by experimental research in real working conditions The calculation results show that despite the excessive size of the internal flaw the welded Joint integrity is not compromised During periodical inspections of the welded joint in the past two years (BWE was put into operation in December 2007) changes that could compromise the structural integrity were not observed In this way by using a fail-safe philosophy design a considerable financial saving (ca 1 600 000 (sic)) was achieved while at the same time there was no threat to the worker s safety and life the safety of the machine and the production process in the open pit min

Service FMECA of a bucket wheel excavator

Surface mining systems (SMSs) are among the most significant 20th century achievements in mining industry, whose significance to miners is comparable to the invention of dynamite in the 19th century. However, problems of SMS risk assessment are very scarce in relevant literature. For this reason, this paper aims to establish a consistent risk quantification approach for bucket wheel excavators (BWEs), the backbones of these systems. Based on the original structural scheme of a BWE, the risk parameters assessing criteria stemming from multidecadal experience and the database of recorded standstills (in the considered case, one hour of SMS downtime generates indirect financial losses of approximate to 15000(sic)), a study was conducted applying the Service FMECA technique to the BWE SRs2000 (one of the best-selling models from "Takraf"), with the following conclusions: (a) the material conveying subsystem is the highest contributor in the total number of mechanical and electrical failures, as well as in total downtime; (b) during the monitoring period, there were no extreme risk level failures. Besides, corrective actions for reducing risk levels of the most critical mechanical and electrical failure modes are given in the paper. The presented approach for risk quantification for a BWE can be successfully applied to other SMS subsystems, notably spreaders

Service FMECA of a bucket wheel excavator

Surface mining systems (SMSs) are among the most significant 20th century achievements in mining industry, whose significance to miners is comparable to the invention of dynamite in the 19th century. However, problems of SMS risk assessment are very scarce in relevant literature. For this reason, this paper aims to establish a consistent risk quantification approach for bucket wheel excavators (BWEs), the backbones of these systems. Based on the original structural scheme of a BWE, the risk parameters assessing criteria stemming from multidecadal experience and the database of recorded standstills (in the considered case, one hour of SMS downtime generates indirect financial losses of approximate to 15000(sic)), a study was conducted applying the Service FMECA technique to the BWE SRs2000 (one of the best-selling models from "Takraf"), with the following conclusions: (a) the material conveying subsystem is the highest contributor in the total number of mechanical and electrical failures, as well as in total downtime; (b) during the monitoring period, there were no extreme risk level failures. Besides, corrective actions for reducing risk levels of the most critical mechanical and electrical failure modes are given in the paper. The presented approach for risk quantification for a BWE can be successfully applied to other SMS subsystems, notably spreaders

Failure analysis and redesign of the bucket wheel excavator two-wheel bogie

This paper discusses the cause of the failure in the vital part of the crawler travel gear of the bucket wheel excavator (BWE) - two-wheel bogie (TWB). The results of the finite element analysis (FEA) point out that the main reason of the TWB failure is its insufficient strength under lateral forces acting during curve travel. The weak points in the TWB structure are removed by suitable redesign while keeping in mind all restrictions ensuing from installation conditions and functionality of the existing crawler travel gear. In addition to the numerical analysis (FEA), a parallel experimental analysis of the original as well as the redesigned TWB is conducted on a test board especially designed for this purpose. The experimental results have confirmed the considerably improved response on lateral loads of the redesigned TWB. The exploitation of the redesigned TWB with no failures has confirmed the validity of the reconstruction design