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Case study analysis of risk from using excavators as ‘cranes’
Abstract
Excavators are frequently used as ‘cranes’ for object handling on construction sites, but this situation brings with it significant health and safety hazards that often, are not fully appreciated by stakeholders. These hazards are identified; their risks explained and studied; and appropriate advice for stakeholders explicated. A developmental approach is employed that embraces accrual of evidence; case studies; theoretical examination; and derivation of guidance. It is found that excavators are often used as cranes employing both ‘formal’ or less satisfactory ‘informal’ methods of load connection. Hazards from using excavators as cranes (found principally among load connection points and associated lifting accessories), are often ‘hidden’ and can lead to catastrophic failure during lifting operations. Stakeholders need to be aware of the hazards and implement suggested risk controls to remove or mitigate them.
... Manufacturers also play a crucial role in safety by ensuring lifting points on equipment like quick hitches are of the "closed eye" type and rated for safe working load (SWL). This helps prevent accidents by guiding operators on how much weight can be safely lifted [111]. ...
Earthmoving operations in the construction process are complex environments that involve interactions between equipment, the workforce, and materials within an overarching construction plan. Over the past two decades, researchers in construction have focused on improving the safety of construction earthmoving equipment due to their omnipresence in the construction environment. Although previous studies have explored safety risks and the causes of accidents involving construction earthmoving equipment, their approaches were common and lacked a comprehensive perspective. Hence, this systematic literature review applies Rasmussen’s (1997) risk management framework using a systems thinking approach to identify and classify the risk factors influencing earthmoving equipment operation safety in construction sites. Utilizing a multistep methodology, this research first identifies 38 risk factors pertinent to earthmoving equipment operations and then classifies them based on systems thinking. Social network analysis (SNA) is employed to analyze the data. The results show that most research on earthmoving equipment safety focuses on monitoring construction sites, but very little on government and regulatory roles. When considering the interdependencies of risk factors, safety training is the most important factor, followed by the largely overlooked earthmoving machinery characteristics and manufacturer’s performance. The results of this review inform both the research community and industry practitioners regarding the less-understood aspects of earthmoving equipment operation safety and future research directions.
... This allowed the nomenclature of the used machines to be shortened, but the practical use of the excavators as cranes on the mining and construction sites continues to be accompanied by some problems due to their design features. One major problem is that the operators and support staff are not trained to handle swinging payloads, which is a premise for accidents and incidents [1]. This circumstance together with the fact that in the most cases the hydraulic excavators are unequipped with the necessary overload protection devices as the cranes -load and load moment limiters, limit switches, operation radius indicators, etc. leads to a large number of incidents with people. ...
The paper presents the development of a Web-based virtual reality (VR) environment for planning and simulation of lifting operations performed by a hydraulic excavator. The excavator is represented as a mechanical system with four degrees of freedom (DOF) consisting of a fixed base body, three-link digging manipulator, and a swinging payload. An inverse kinematic model and a dynamic model of the excavator during performing lifting operations with bucket following prescribed vertical straight-line trajectory are developed. Workspace characteristics of the digging manipulator are determined, and the subset of the workspace corresponding to the cutting-edge positions for constant orientation of the bucket is identified. Using modern Web-based technologies, a VR environment for planning, simulation, and 3D animation of the excavator motion is developed. It consists of an HTML5 Web page with an X3D model of the scene, open-source framework X3DOM, and JavaScript functions. The developed VR environment considerably facilitates the design, investigation, planning, and e-learning of the lifting operations, performed by the excavator.
... Failure in lifting accessories/ equipment (including lifting chains or synthetic slings, hooks and eyebolts) -these can become damaged, or fail, due to factors such as: the safe working load (SWL) being exceeded; natural wear and tear (where the rate of deterioration can increase in adverse prevailing operational conditions); and/ or damage caused by incorrect usage, for example repeated physical contact with the machine can cause 'fraying' of synthetic slings, or a load that is not freely suspended can result in mechanical failure of the master link due to additional stresses occurring within the steel (for a more detailed explanation refer to Edwards and Holt, 2010). For this reason, daily prechecks and periodic thorough inspection (normally every six months) are critical (refer to: HSE, 2008). ...
Modern tracked hydraulic and wheeled excavators (both 180° and 360° models) are widely used throughout the construction and civil engineering industries internationally to undertake earthmoving and site clearance operations for buildings and infrastructure development to support national socio-economic development. Without these versatile machines, the modern digitised ‘smart city’ economies that proliferate throughout the developed (and increasingly) developing worlds would not be possible. Against this backdrop of inhabiting and working within an increasingly digitised world, it seems ironic that a notable lack of simple hand signals for excavators when operating as a crane continues to cause incidents, accidents and fatalities amongst construction workers and members of the public. This issue is perhaps caused in part by the machine’s versatility – made possible by rapid and highly innovative engineering developments that often outstrip the tacit knowledge and formal education/ training of both operators and supervisors of excavators on site. Perhaps some responsibility lies at the door of training providers and accreditation schemes that fail to train operators on basic hand signals – but then again, which signals do they train operators with given a number of international and national standards available? Or perhaps Universities are at fault for not working more closely with industry practitioners to solve real-world problems vis-à-vis blue skies research or fictitious academic pursuits designed purely to publish papers not generate impact? These questions are not intended to be invidious but rather challenge current thinking and encourage wider research and collaboration between industrialist and academics that solve the basic questions regards problems that prevail within the construction and civil engineering industry.
This voluntary code of practice aims to address the issue of poor communication between operator and banksman by providing a set of unequivocal (and in many cases long established) hand signals. Even where other communication devices may be used (such as two-way radio), the basic requirement to communicate using hand signals is essential as technology can, and often does, fail for a variety of reasons.
Readers of this guidance can do so free of charge and all images within are also provided copyright free – we believe at OPERC (as a non-profit making professional body) in sharing good practice to improve the life’s of workers. So please distribute this guidance widely and perhaps together we can engender changes to international standards or at least create a common set of banksman signals for when excavators are used as cranes.
Mr Mick Norton, BEM.
... The reduced ability of the excavators to perform lifting operations increases the risk of accidents with the staff near the excavator, and especially in the vicinity of the freely suspended payload. The statistical reports show a considerable risk of injuries caused by the strike by the bucket or swinging boom. 2 Edwards and Holt 3 have studied the hazards associated with using construction excavators as cranes and have investigated the catastrophic failure of a link. The same authors have studied excavator overturn accidents. ...
This article presents a numerical study of the stability of a hydraulic excavator during performing lifting operations. A planar dynamic model is developed with six degrees of freedom, which considers the base body elastic connection with the terrain, the front digging manipulator links, and the presence of the freely suspended payload. Differential equations describing the excavator dynamic behavior are obtained by using the Lagrange formalism. Numerical experiments are carried out to study the excavator dynamic stability under different operating conditions during the motion along a vertical straight-line trajectory. It is shown that the arising inertial loads during the movement of the links along the vertical trajectory, combined with the payload swinging and the motion of the base body, decreases the excavator stability. It was found that the excavator stability during following vertical straight-line trajectory decreases considerably in the lower part of the vertical trajectory. If the stability coefficient is close to 1, the payload swinging can cause the separation of a support from the terrain; nevertheless, the excavator stability can be restored. A method for tire stiffness and damping coefficients estimation is presented. The validation of the dynamical model is performed by the use of a small-scale elastically mounted manipulator.
... The resistance and crushing force increased gradually when Bucket cylinder cut in the rsesoil and they decreased as the Bucket rod is divorced from the soil.The maximum crushing force relates to the system pressure, the measure of Bucket cylinder diameter, arm force of c, d, e, r. Mostly,there is little difference of the system pressure and the diameter of the oil cylinder [3,[7][8],so the position of the Hinge point should be optimized to get a good change curve of crushing force. ...
According to the working characteristics of working device of WDJ25 multi-functional undercover excavator, the study had calculated and analyzed the mining force of bucket rod oil cylinder and crushing force of bucket oil cylinder of full schedule theory .The force change curve accurately described full schedule working ability of bucket rod and the bucket.
... With the requirements of machine safety increasing around the world [5], nowadays safety performance of these potentially hazardous systems becomes extremely important because it can start a chain reaction of catastrophic failure once one mistake is made accidently. For hydraulic lifting actuators, overspeed dropping caused by pipeline ruptures or other failures could be a serious accident, which would damage the equipment and environment, even injury or kill the operators [6][7]. ...
Safety is the most important issue for mobile and industrial machinery, and overspeed dropping of lifting actuators is extremely hazardous to the equipment, environment and operators. In this paper, to evaluate and improve the safety brake performance of hydraulic lifting systems in this emergent case, a multi-objective optimization model was proposed. Considering the load impacts in the braking process, a novel indicator named remaining vibration energy was defined to simply quantify the cushion performance. A mathematical and simulation model was established, and then the simulation model was verified by experimental tests. Minimization of the remaining vibration energy, the brake distance and the pressure loss of the hydraulic fuse on normal working conditions were considered as optimization objectives after analysis of the system dynamic behavior. The optimization model using a genetic algorithm was applied to a heavy hydraulic elevator system. The results indicated that the pressure impact was reduced, and the plunger stopped more smoothly in the optimized system. Also the brake distance and the pressure loss of the fuse are limited by the design criterion. Therefore, this paper presents an optimization method of hydraulic fuses to design safer hydraulic lifting systems.
Prefabricated construction, known for its efficiency and eco-friendliness, presents new safety management challenges due to its unique characteristics, such as the use of large components and frequent lifting operations. The presence of safety vulnerability in this construction method is influenced by various factors, and Internet of Things (IoT) technologies hold substantial promise in mitigating this vulnerability. This study adopted partial least squares structural equation modeling (PLS-SEM) to comprehensively scrutinize the relationships among various factors and their impacts on the formation of safety vulnerability. Furthermore, a two-mode social network analysis was conducted to quantitatively analyze the mitigation effects of IoT technologies on safety vulnerability. The results revealed that workers' unsafe behaviors, high work pressure, and inadequate construction supervision significantly contribute to the formation of safety vulnerability in prefabricated construction. The study further found that IoT technologies play a crucial role in mitigating safety vulnerability by improving compliance with safety regulations and fostering safety commitment among managers. Notably, sensors and Auto-ID technologies emerged as prominent IoT technologies with substantial reduction effects on safety vulnerability. These findings strongly advocate for the widespread adoption of IoT in prefabricated construction to enhance safety performance.
Purpose
This paper aims to consider opposing influences on workplace plant and machinery health and safety (PMH&S) innovations, highlight examples of these to model PMH&S innovations’ effectiveness at the workplace, develop guidance for improvement of same and for construction of health and safety (H&S) performance.
Design/methodology/approach
This study is a qualitative meta-analysis of data distributed among a sample of published research in the field, and it uses inductive reasoning based on informal, qualitative and interpretative analysis.
Findings
Nearly all PMH&S innovations (positive influences) originate from original equipment manufacturers and specialist companies throughout the supply chain. Negative influences that can counter these potential H&S benefits result mainly from human (in) action(s) at the workplace. These are classified (and analysed) in terms of “error”, “indifference” and “lack of training”. “Tolerant” H&S management is another negative influence found among these classifications.
Originality/value
The study draws from a targeted meta-sample of research in the field, a model of positive and negative influences on PMH&S innovations that emphasises workers’ (in) action(s).
Purpose
In striving to minimise downtime and optimise the productivity of construction excavators, very often, they employ a “quick‐hitch” (Qh) as a means of changing attachments (like buckets) more quickly. Health and safety issues can relate to Qh use. The purpose of this paper is to observe these health and safety issues and consider their implications for stakeholders.
Design/methodology/approach
Triangulation, embracing a literature review; case studies; and the researchers' experiential knowledge, is employed to examine the nature and prevalence of Qh health and safety incidents.
Findings
It is confirmed that significant risks are associated with (inappropriate) Qh use, especially relating to “manual” and “semi‐automatic” types. The main causes of Qh incidents are observed to be due to workers' acts or omissions, particularly, failure to properly implement safety mechanisms.
Practical implications
An identified emphasis on “people” and their actions, suggest a need for changes in construction working methods and management practice, as ways to help remove Qh risks. Accordingly, proffered solutions relate predominantly to improved worker training, combined with stricter site management. Mechanical solutions may involve possible changes to Qh design.
Originality/value
This specific area of academic plant management study is novel.
Purpose
A literature review is presented in the subject of construction plant and equipment management (CPeM) to: delineate the subject; consider its development over recent years; and identify principal themes within it. The paper aims to close the gap in knowledge, by using these objectives as a mechanism to observe how research themes relate to primary CPeM functions, and to suggest future research direction.
Design/methodology/approach
A thematic review of CPeM academic literature (in the main, refereed journal papers published in English‐speaking countries over the last decade) is undertaken; the nature of identified themes is discussed, for instance, regarding why they might have evolved as they have; and based on the foregone, themes for future research in the field are proffered.
Findings
CPeM is found well established within the broader subject of construction management. Eight principal themes are identified, namely plant maintenance; downtime and productivity; optimisation; robotics and automation; health and safety; operators and competence; machine control; and “miscellaneous”.
Research limitations/implications
It is proffered that based on informational/technological advancements coupled with growing environmental/financial pressures, future CPeM research will strive to facilitate even greater plant reliability and safer modes of working. It is suggested that “optimum production methods” and “minimal resource consumption” will become inherent theme goals.
Originality/value
This is the first time that CPeM research has been consolidated and reviewed for publication in this manner.
Purpose
The extensive use of mini‐excavators in construction presents a significant health and safety risk from their tendency to become unstable, or in the extreme to roll‐over, under certain working conditions. No standard exists to specifically assess excavator stability, so the purpose of this paper is to document the development and trial of a series of practical field tests designed to achieve this.
Design/methodology/approach
Tests were designed in collaboration with a group of plant experts and competent operators. The tests were subsequently trialled by applying them to four mini‐excavators, the aim being to see if these plant items could be reliably assessed in terms of their stability characteristics. Results of the study were presented to H&S experts for comment.
Findings
The tests were able to assess mini‐excavator stability. For each machine, five “stability criteria” were scored thereby producing an overall score, by which mini‐excavator stability could be conveniently represented.
Research implications
No previous field test research has been identified in this area. The results produced here may go some way towards developing an international standard for on‐site stability tests.
Practical implications
The tests are easy to apply at the work site so long as performed by competent persons under appropriately risk‐assessed and risk controlled conditions; and if disseminated to industry, could act as a means of standardising mini‐excavator stability tests until such time an International Standard becomes available.
Originality/value
Research in this area is entirely novel.
Cranes have come to symbolize building construction itself. They perform indispensable services in moving materials and components vertically and horizontally. Used since antiquity, their history is interrelated with the development of new power sources that replaced man and mule, first steam and later internal combustion, diesel, and electric engines. Mobile cranes can be rapidly deployed to lift heavy loads. New models with telescoping booms and all-terrain travel capability, compact urban machines, and even hybrids with tower cranes are beginning to replace the familiar lattice boom truck cranes. Mobile cranes have dominated the North American market, but a cultural change appears to be taking place toward tower cranes for building projects. Tower cranes, common in Europe for decades, are globally gaining in popularity with surging real estate developments. Ideal for dense urban environments and coming with a small footprint, they are available in a growing diversity of sizes and configurations. Sophisticated electronic controls and operator assistance devices are enhancing their safe and productive operation. While cranes occupy a central role on midrise and high-rise building projects, they operate in conjunction with other types of supporting equipment that are an essential part of the overall equipment array on today's industrialized construction sites.
Automation of excavation operations can be realized by an automatically controlled excavator system that is able to perform autonomously a planned digging work and to quickly comply to interacting forces experienced during excavation. The development of such an automated control system is usually based on a dynamic model of the system that describes the motion with time. A dynamic model for an excavator that is needed for the controller design can be derived by applying Newton-Euler equations to each link in succession. The model obtained describes the motion of the excavator. It corrects several shortcomings that appear in previously published excavator model. On the basis of the model derived, a proportional-differential controller is designed that makes the bucket to track a specified trajectory. It can be used to automate the machine operations, for example, for terrestrial and planetary excavations as well as for mining applications.
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Cranes have come to symbolize building construction itself. They perform indispensable services in moving materials and components vertically and horizontally. Used since antiquity, their history is interrelated with the development of new power sources that replaced man and mule, first steam and later internal combustion, diesel, and electric engines. Mobile cranes can be rapidly deployed to lift heavy loads. New models with telescoping booms and all-terrain travel capability, compact urban machines, and even hybrids with tower cranes are beginning to replace the familiar lattice boom truck cranes. Mobile cranes have dominated the North American market, but a cultural change appears to be taking place toward tower cranes for building projects. Tower cranes, common in Europe for decades, are globally gaining in popularity with surging real estate developments. Ideal for dense urban environments and coming with a small footprint, they are available in a growing diversity of sizes and configurations. Sophisticated electronic controls and operator assistance devices are enhancing their safe and productive operation. While cranes occupy a central role on midrise and high-rise building projects, they operate in conjunction with other types of supporting equipment that are an essential part of the overall equipment array on today's industrialized construction sites.
In a general sense, control can be described as a cyclic sequence of observing, planning, and executing new actions. Similar to the human body, robotic devices are being equipped with a wide variety of sensors for the purpose of acquiring the needed information for planning and replanning. Because of the harsh work environment, construction robots, such as autonomous excavators, depend on hardened and reliable sensory systems, thus limiting the choices for selecting sensors. For control purposes, the sensory data need to be evaluated for decisionmaking purposes. The intelligence for this endeavor has to be based on a thorough understanding of the meaning of the sensory data and high confidence in the appropriateness of future actions. In addition, a special obstacle-avoidance concept is needed to prevent collisions and other types of accidents. The present paper discusses methods for both motion control and path planning for backhoe excavation. Experimental laboratory data are used to verify theoretical findings and to discuss the use of pattern recognition for the purpose of intelligent reasoning about the sensed environment. It is shown how patterns found in collected data could be used for automatic control of an autonomous excavator.
The technological advancement of earthmoving equipment during the 20th century includes the introduction of at least seven completely new forms. The purpose of this paper is to analyze the introduction of five new forms (track-type tractor, off-highway truck, wheel tractor scraper, hydraulic excavator, and loader-backhoe) and their subsequent incremental improvement. The description of innovation for each machine includes markets and the state of technology at introduction, differences of the new form, and changes during subsequent development. The major findings from this analysis are the key role of new technology for machine systems in the development of the new forms. the continued importance of each form in earthmoving markets, and the significant continued advancement of the equipment through incremental improvements. These findings are relevant for practice to assist in identifying possible improvements in equipment capability and work procedures. The results will also assist educators in courses concerning equipment capability and technical advancement and researchers in considering new equipment forms and capabilities as a part of developing new tools to model and improve equipment-intensive construction operations.
The rate of innovation in construction equipment is measured by using two variables over a 30-year period, 1962-92: The number of new models introduced every year and the technological life of eight earthmoving equipments are considered in this study. The findings indicate that the rate of innovation in the construction equipment industry increased in the 30-year study period. The findings also suggest that these innovations are incremental in nature, stimulated by technological advances in other industries, but primarily driven by market forces. Technological advances are not confined to the industry that produces innovations. The mapping of the interindustry flow of innovations highlights that while construction companies play a predominant role in generating their own technological innovations, they are also heavily dependent on other industries, such as the construction equipment industry for the flow of technical system innovations. As such, the continuous and incremental innovations in the construction equipment industry are bound to act as a catalyst for the generation of technological advances in the construction industry.
Automation of excavation work calls for a robotic system able to perform the planned digging work that is responsive to interaction forces experienced during excavation. The development of automated excavation control methods requires a dynamic model to describe the evolution of the excavator motion with time. The joint torques of the boom mechanism are generated by hydraulic rams that also affect the torques at other joints. Analyzing each link in succession as a free body and applying the Newton-Euler formulation in the local coordinate frame, a dynamic model for an excavator can be derived in a straightforward manner. The model presented in this paper is intended for further development of an automated excavation control system for terrestrial, lunar, and planetary excavation.
In robotic excavation, hybrid position/force control has been proposed for bucket digging trajectory following. In hybrid position/force control, the control mode is required to switch between position- and force-control depending on whether the bucket is in free space or in contact with the soil during the process. Alternatively, impedance control can be applied such that one control mode is employed in both free and constrained motion. This paper presents a robust sliding controller that implements impedance control for a backhoe excavator. The control law consists of three components: an equivalent control, a switching control and a tuning control. Given an excavation task in world space, inverse kinematic and dynamic models are used to convert the task into a desired digging trajectory in joint space. The proposed controller is applied to provide good tracking performance with attenuated vibration at bucket–soil contact points. From the control signals and the joint angles of the excavator, the piston position and ram force of each hydraulic cylinder for the axis control of the boom, arm, and bucket can be determined. The problem is then how to find the control voltage applied to each servovalve to achieve force and position tracking of each electrohydraulic system for the axis motion of the boom, arm, and bucket. With an observer-based compensation for disturbance force including hydraulic friction, tracking of the piston ram force and position is guaranteed using robust sliding control. High performance and strong robustness can be obtained as demonstrated by simulation and experiments performed on a hydraulically actuated robotic excavator. The results obtained suggest that the proposed control technique can provide robust performance when employed in autonomous excavation with soil contact considerations.
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