Critical Human Errors Research Articles

Reliability analysis of a powerloom plant with cold standby for its strategic unit

A powerloom plant consists of two units A and B( n) connected in series. Unit B( n) has n components in parallel redundancy that carry threads of different varieties/colours to unit A. Unit A is the strategic unit that weaves these threads together and produces a long piece of cloth of some standard size. Failure of unit A makes the entire system fail whereas the failure of k components out of n in unit B( n) results in the system working in a degraded state. The present paper deals with the reliability analysis of the powerloom plant with a cold standby for its strategic unit. The common cause failure and critical human errors have also been considered to avoid overestimation of the reliability of the system. Results of Dhillon [ Int. J. cyst. Sci. 23, 1277–1287 (1992)] have been deduced as a particular case of our result.

Two unit redundant system with adjustable failure rate, critical human error (CHE) and inspection

The present paper deals with the analysis of a two unit redundant system with adjusting failure rate of the operative unit and critical human error (CHE). A single repair facility is used and after each repair the unit is sent for inspection to decide whether the repair is perfect or not. Using the regenerative point technique with a Markov renewal process, several reliability characteristics of interest have been obtained.

Availability of a man-machine system with critical and non-critical human error

Abstract This paper presents a newly developed probabilistic model representing two units in parallel and one on standby system with critical and non-critical human error. Repair times of the failed system are arbitrarily distributed while all other transition time distributions are negative exponential. A general formula for the system steady-state availability is developed with the aid of the method of supplementary variables, the Markov approach and Laplace transforms. Specific plots and tables are shown to demonstrate the impact of critical and non-critical human errors on system steady-state availability.

Reliability analysis of a three-state multi-component warm standby redundant complex system with waiting for repair

Investigations have been carried out with the help of Laplace transforms and supplementary variable techniques for the evaluation of reliability analysis of a three-state multi-component warm standby redundant complex system suffering three types of failures, namely minor, major, and human due to critical human errors incorporating the concept of waiting for repair.

Human error analysis of a standby redundant system with arbitrarily distributed repair times

This paper presents human error analysis of a (two units working and one on standby) system with arbitrarily distributed repair times. The supplementary vairables method is used to develop the system availability expressions. A general formula for the system steady-state availability is developed when the failed system repair times are gamma distributed. Time-dependent availability, system reliability with repair, mean time to failure and variance of time to failure formulae are developed for some particular cases. Selective plots are shown to demonstrate the impact of critical human error on system availability and reliability.

Availability, MTTF and cost analysis of a three-state parallel redundant multi-component system under critical human failures

This paper deals with the availability, MTTF and the cost analysis of a single server complex system consisting of two classes A and B with three possible states, viz. good, degraded, failed and suffers two types of failure, viz. unit failure and failure due to critical human errors. Sub-system A has two dissimilar units arranged in parallel whereas sub-system B has three non-identical units arranged in series. Failure and repair times have exponential and general distributions respectively. There is only one repair facility when the system is in failed state due to failure of sub-system B. Several parameters of interest are obtained using the supplementary variable method. A numerical example has been appended. Five graphs have also been given in the end.

Stochastic modelling ofk-out-of-nunits family of systems

Two newly developed stochastic models to perform reliability and availability analyses of (n − 1)-out-of-n units and (n − 2)-out-of-n units systems with common-cause failures and critical human errors are presented. The supplementary variables and Markov methods are used to perform analyses. For both models, generalized expressions for Laplace transforms of state probabilities are developed along with generalized formulae for system steady-state availability and mean time to failure. Some plots are shown to demonstrate the effect of common-cause failures and critical human errors on system steady-state availability and mean time to failure.

Stochastic analysis of a two-unit redundant system with two types of failure

The present paper investigates a stochostic model of a two-unit warm standby system with a single repair facility. Before repair, the failed unit is sent for fault detection to decide whether it failed due to machine defect or critical human error. The probability of having machine defect and C.H.E. has been fixed. Using the regenerative point technique in the Markov renewal process various measures of system effectiveness are obtained.

Cost analysis of a multi-component parallel redundant complex system with overloading effect and waiting under critical human error

The cost analysis of a multi-component parallel redundant complex system is considered, incorporating the concept of overloading effect and waiting time for repair under critical human error. Failure and waiting times follow an exponential time distribution, whereas repair time follows a general distribution. Using the supplementary variable technique, Laplace transforms of the probabilities of the complex system being in various states have been computed. Some graphs have been plotted to highlight the main results.

A 1-out-of- N: G system with common-cause failures and critical human errors

A system which has N operating units and r repair facilities with common-cause failures and critical human errors is presented. The system is of 1-out-of- N: G nature. Failure rates are constant and the repair rate is arbitrary. Mathematical formulation is carried out using the supplementary variable technique. Lagrange's method for partial differential equations is employed to solve the governing equations. Various probabilities, system parameters and special cases are discussed.

CHE failure in a two-unit standby system with slow switch, repair and post repair

A mathematical model of a two-unit cold standby system with critical human errors (CHE) and slow switch is investigated. The CHE leads to complete system failure, and repair and post-repair are needed before the system can be put back into operation. Slow switch means that on failure of the operative unit the switch puts the standby unit into operation after a random time. Failure time and switchover time distributions are negative exponential whereas all the repair and post repair time distributions are general. Using a regenerative point technique, we obtain various reliability characteristics which can be used to carry out the cost-benefit analysis. In a particular case, the behaviour of the cost function is also studied graphically.

A reliability analysis of a k-out-of-N:G redundant system with common-cause failures and critical human errors

This paper presents a reliability of a k-out-of-N:G redundant system with common-cause failures, critical human errors and r repair facilities. The system is in a failed state when k units failed, by a common-cause or by critical human errors. Laplace transforms of state probabilities and system reliability are derived. The steady-state availability is also reported.

Common-cause failures and critical human errors in repairable and non-repairable systems

This paper presents a reliability analysis of a k-out-of-N:G redundant system with common-cause failures, critical human errors and r repair facilities. The system is in a failed state when common-cause failures or critical human errors occurred or k units failed. When less than k units failed, the failed units are to be repaired. If the whole system is in a failed state, it cannot be repaired. Laplace transorms of state probabilities and system reliability are derived. Various versions of mean time to failure of a system are also reported.

Stochastic analysis of a parallel system with common-cause failures and critical human errors

This paper presents reliability and availability analysis of a n-unit parallel system with common-cause failures and human errors. Laplace transforms of state probabilities, system availability, and reliability are presented. A formula to estimate system mean time to failure is developed. Special case expressions for steady-state probabilities and system availability are derived.

Critical and non-critical human error modelling in redundant systems: modified block diagram approach

Abstract Three newly developed models are presented for performing reliability analysis of redundant systems with erlangian-distributed critical and non-critical human error times. Parallel, k-out-of-n and parallel-series configurations are analysed. System reliability, mean time to failure, time-to-failure variance, failure density function formulae, and hazard rate function formulae are developed. Selective plots are shown to demonstrate the effect of varying critical and non-critical human errors.

A method to evaluate reliability of systems with critical and non-critical human errors

This paper presents a newly developed method to perform reliability analysis of redundant systems with critical and non-critical human errors. The method is demonstrated using k-out-of-n units, parallel and series-parallel configurations. Time dependent analyses are developed for exponentially and Rayleigh distributed failure times. System reliability and mean time to failure formulas are presented.

Reliability analysis of networks with human errors: A block diagram approach

This paper presents an approach for performing reliability analysis of bridge and parallel-series networks with critical and non-critical human errors. Reliability and mean time to failure formulas are developed for exponential and Rayleigh distributed failure times. Selective plots are shown for demonstrating the effect of human errors on system reliability and mean time to failure. Equations for estimating a number of units in series, parallel, series-parallel and parallel-series networks are presented.

Reliability analysis of a two-unit redundant system with critical human error

A two-unit standby redundant system with the concept of critical human failures is considered. Occurrence of failures due to random causes and critical human errors (CHE) are exponential, whereas all other distributions are arbitrary. CHE leads to complete system failure and needs repair and post-repair before the system is put back into operation. The method of embedded SMP is employed to obtain several reliability parameters, MTSF, steady-state availability, absorption probabilities, etc.

Availability and MTTF analysis of a three state repairable redundant electronic equipment under critical human errors

In this paper investigations have been carried out for the availability and mean time to failure analysis of a three unit repairable electronic equipment having three states; viz; good, degraded and failed under critical human errors. The three states three units repairable electronic equipment suffers two types of failures; viz; unit failure and failure due to critical human errors. Entire system can fail due to critical human errors. The failure and repair times for the system follow exponential and general distributions respectively. Laplace transforms of the probabilities of the complex system being in various states are obtained along with steady state behaviour of the equipment. A numerical example has also been appended to highlight the important results. Three graphs have also been given in the end. There is only one repair facility, which is availed only when the system is in either degraded or failed state due to unit failure.

Cost analysis of an electronic repairable redundant system with critical human errors

In this paper, an electronic system consisting of two subsystems connected in series has been considered. One subsystem consists of two identical units connected in parallel while the other subsystem has only one unit. The system is to be in any of the three states: good, degraded and failed. The system suffers two types of failures, viz; unit failure and failure due to critical human error. The system can be repaired when it fails due to the failure of the units in the subsystems and cannot be repaired when it fails due to critical human errors. The repair for the system in any state follows general distribution. To make the system more applicable to practical life problems, time dependent probabilities have been evaluated so as to forecast the expected profit and the operational availability of the system at any time.