Subsystems In Series Research Articles

Process design for a crystallization system in the urea fertilizer industry

The urea crystallization system in the urea fertilizer industry, which consists of five subsystems in series is discussed. The failure rates for all subsystems are constant and the repair rates are arbitrary. A mathematical formulation is carried out using the ‘supplementary variable technique’. The equations are solved by the direct integration method. Expressions for steady-state availability are given followed by a discussion.

Bayesian Reliability Analysis of Complex Series/Parallel Systems of Binomial Subsystems and Components

A Bayesian procedure is presented for estimating the reliability (or availability) of a complex system of independent binomial series or parallel subsystems and components. Repeated identical components or subsystems are also permitted. The method uses either test or prior data (perhaps both or neither) at the system, subsystem, and component levels. Beta prior distributions are assumed throughout. The method is motivated and illustrated by the following problem. It is required to estimate the unavailability on demand of the low-pressure coolant injection system in a certain U.S. commercial nuclear-power boiling-water reactor. Three data sources are used to calculate the posterior distribution of the overall system demand unavailability from which the required estimates are obtained. The sensitivity of the results to the three data sources is examined. A FORTRAN computer program for implementing the procedure is available.

MTSF and availability analysis of a complex system composed of two subsystems in series subjected to random shocks with single repair facility

The present paper deals with a complex system consisting of two subsystems connected in series with a single repair facility. Subsystem S 1 consists of two units connected in standby redundancy while the other subsystem S 2 has a single unit. The method of the regenerative point technique with Markov-renewal process differing by the failure and repair discipline is used to obtain the various characteristics of the system.

Optimal allocation for a repairable system

A system is composed of n series subsystems. Each subsystem consists of some same type of parallel or cold stand-by components. These components are repairable. We discuss the optimal allocation of this system under various constraints, and give some procedures for solution of this problem.

Availability of a washing system in the paper industry

This paper presents the availability and MTTF of a system with three states—good, reduced and failed—consisting of three subsystems in series having one standby unit in subsystem D. Failure and repair rates are taken to be constant. Formulation of the problem is carried out using simple probability considerations. Tables for various parameters are given which are useful to management for predictions about the behaviour of various equipment.

Reliability bounds for dependent failures

Upper and lower bounds are obtained for the reliability of a series system with statistically dependent component failures. The method can be applied to series subsystems when these are obtained by decomposing a complex system. Numerical examples illustrate the use of the method.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Analysis of 2 Models of Standby Redundant Systems

Two models of standby redundant systems are considered. Failure time distributions are exponential whereas repair time distributions are arbitrary. Model 1 is a 2-unit standby redundant system with failure analysis time and two types of repair. Model 2 has two series subsystems; one is a 2-unit parallel system with s-dependent units; the other has one unit and is given priority in repair. Semi-Markov process technique is used to obtain mean time to system failure, steady-state availability, absorption probabilities, s-expected number of visits to a state, second moment of time in an up state, and s-expected profit.

Availability of a Parallel Redundant Complex System

This paper considers a complex system consisting of three subsystems (A, B, C) in series with a single repair facility. Subsystem A consists of N non s-identical units in series. Subsystem B has two s-identical units in parallel. Subsystem C consists of M non s-identical units in such a way that the failure of one unit causes the whole system to degrade, but not fail. Laplace transform and supplementary variable techniques are used to solve the model under several repair disciplines.

Analyses of Two Different 1-Server Systems

In this paper, the availability and the reliability of two 1-server systems with redundancy have been obtained. System 1 consists of n subsystems in series; each subsystem consists of two redundant i.i.d. components in `parallel' (cold standby) and one server. The times to failure of the components are exponentially distributed; their repair time distributions are arbitrary and different. System 2 consists of n dissimilar units and one server. The times to failure of the units are arbitrarily distributed; the repair rates are constant but all different. Explicit expressions for the Laplace transform of the mean down-time of the system in (0, t) and for the mean time to system failure have been obtained. A few particular cases are discussed.

Availability Models of Maintained Systems

The concept of availability includes reliability as well as preventive and corrective maintenance. An availability model which includes both aspects of this problem is proposed in this paper. The model includes the following decision variables: 1. failure rates and repair rates of individual units 2. the time period for perfect-preventive maintenance for a given mission time 3. the optimal failure and repair rates as a function of design costs, corrective and preventive maintenance costs. The objective is to minimize the design and operating costs where the availability requirements are satisfied. An example is solved for a system with n subsystems in series where two units in parallel comprise each subsystem. The general approach is applicable to solving other complex availability problems.

MACSYMA - the fifth year

MACSYMA is a large symbolic and algebraic manipulation system which has been under development at Project MAC, M.I.T. since 1969. We first discuss some of the design decisions, such as multiple representations, that led to the current system. We then give a brief description of the facilities of MACSYMA by dividing the system into seven packages: language and interactive facilities, general representation, rational function representation and related algorithms, the integration subsystem, the power series subsystem, the MACLISP system, and miscellaneous facilities.

Use of Stochastic Networks in Reliability Analysis

Abstract The application of stochastic networks to reliability analysis is discussed. The article illustrates how the conventional “reliability block diagram” can be replaced by a stochastic network. Once the stochastic network is developed the analyst is able to determine the mean and variance of the reliability of complex systems with relative ease by using the computer program presented. The program is coded in FORTRAN IV and will evaluate the reliability of any mixture of series and parallel subsystems. An example problem is presented in order to illustrate the technique and the use of the program.

Reliability of a Repairable Multicomponent System with Redundancy in Parallel

Consider a multicomponent system consisting of two series subsystems. One contains identical components connected in parallel, while the other has nonalike components connected in series. Each component has constant hazard rate, while the subsequent repairs follow some general distributions. The supplementary variable technique developed by Kielson and Kooharian [1] and the phase technique are used to obtain the various time-dependent and steady-state solutions for the system. A numerical illustration compares the effect of two repair policies on the behavior of the system. The optimum number of components connected in parallel is obtained.

Optimization by Integer Programming of Constrained Reliability Problems with Several Modes of Failure

Reliability optimization problems with N stages or subsystems in series, utilizing parallel or series redundant units, can be formulated and solved as integer programming problems. The systems considered have subsystems with components which can fail in several modes and are subject to linear and nonlinear constraints. Two situations are considered in which components within the subsystem 1) all fail in the same mode, or 2) all may fail in different modes. Expressions are developed for the probability of failure in each case. Two examples are solved.