Pressure Reducing Valves Research Articles

Improved Design of Branched Networks by Using Pressure-Reducing Valves

PRV size is determined based on the maximum and minimum flows. Oversizing of PRV may cause operational problems; unstable regulation, chattering, breakage, wire drawing of seats, and excessive wear in the nearly closed position. Undersizing of PRV, on the other hand, may damage the distribution system. Why is the size of PRY computed in an indirect manner in the optimization technique? For a given network, PRY optimization may result in different valve sizes, causing procurement problems from the manufacturer. While optimizing the size of PRV, practical aspects such as partial and intermittent flows and rapid filling of pipelines need special consideration from a pipeline safety point of view.

Improved Design of Branched Networks by Using Pressure‐Reducing Valves

Economical design of hydraulic networks has been a subject of research for some time. Piping has been the main focus of this research because it represents the greatest percentage of the investment in a network. Pipe cost increases with size, but in addition, depends on the material chosen and the pipe class (thickness). However, optimization methods currently available usually take into account only the pipe diameter, as the variable that relates pipe cost to hydraulic capacity. In this paper a method for optimal design achieving greater savings in the investment in irrigation systems by considering factors other than pipe size alone is proposed. The method identifies optimal strategies for use of pressure-reducing valves (PRVs) in order to reduce pressure in the downstream pipes, thereby reducing wall thickness and investment cost in those pipes. PRVs are common elements in irrigation networks so optimal strategies for location represents an opportunity to achieve considerable savings in investment cost. The method is based on a dynamic programming formulation and is demonstrated by application to an example network.

The Influence of Semi-Empirical Control Valve Model Parameter Accuracy on Simulated Hydraulic System Responses

A parameter sensitivity analysis method is applied to an investigation of the importance of the identification accuracy of the parameter values describing the steady-state and dynamic behavior of three commonly used fluid power circuit components, i.e., single-stage pressure relief, reducing, and two-way flow control valves. The component models are verified; these semi-empirical models take into account the most important continuous and discontinuous nonlinearities.

Theoretical and practical design of pulsation damping systems

To ensure error-free measurement of fluid flow it is desirable to reduce pulsation in the measurement system piping. The adverse effects of pulsation on flow measurement have long been established and a more specific definition is being made available as work in this area is continuing. There are several adverse phenomena which cause measurement problems associated with pulsation and these have been previously defined. The most practical method for reducing pulsation in measurement systems is the application of acoustical filtering. In order to design an effective acoustical filter, several theoretical and practical considerations must be taken into account. The design of acoustical filter systems should contain both the lumped and distributed properties of the filter elements. As has been shown, damping, impedance ratios and junction theory all have significant contribution to the overall effectiveness of a filter. The origin and nature of the pulsation helps to define the aspects of the design considerations which must be included to ensure success. Low-frequency narrow-band pulsations such as those produced by reciprocating compressors will require a slightly different approach when compared with pressure reduction valve pulsation, which is characterized by broad-band high-frequency components. It is necessary in high-frequency pulsation problems also to be aware of the various forms of acoustical amplification (responses) which the filter may not be effective in reducing.

Pressure control for leakage minimization in water supply networks Part 1: Single period models

The issue of minimizing leakage in water supply networks by appropriate control of the settings of pressure-reducing valves is addressed. The problem is first formulated as a non-linear, non-convex optimization problem. The limitations of iterative linearization are then discussed. Alternative linearized models based on separable programming are presented. Results of case studies to assess the efficacy and computational efficiency of the proposed models are presented and discussed.

The Utilization of Experimental Data in Modelling Hydraulic Single Stage Pressure Control Valves

Low-order nonlinear models for single stage pressure relief and pressure reducing valves are developed and subjected to experimental verification. The form of both models is postulated by an appeal to physical principles, but the parameter values are identified with the help of simple numerical methods using measured characteristic curves.

Numerical modeling of pressure-reducing valves in water distribution network systems

Computer models are no longer viewed as exotic luxuries, rather they are being increasingly accepted as necessities for effective planning and operation of water distribution systems. In large networks, pressure-reducing valves (PRVs) are common water appurtenances. However, through the use of the Hazen–Williams friction factor, there are difficulties in representing PRVs in network-analysis models. This paper focuses on these difficulties and suggests a procedure for resolving them through the use of modified Hazen–Williams friction factor. The effectiveness of the proposed modification in representing PRVs in the WATER model is demonstrated. Key words: network analysis, numerical modeling, hydraulics, municipal, water distribution, PRV representation, friction coefficient, Hazen–Williams, flow rate, simulations.

An IBM-PC and commodore 64 microcomputer-based system for elicitation and recording of eyeblink reflexes

The eyeblink reflex is well suited for the study of habituation, sensitization, reflex modification and classical conditioning in humans. A microcomputer-based system for elicitation and recording of the eyeblink reflex is described. The system consists of three functional units: (1) an air-pressure bottle and pressure-reducing valves for delivery of air puffs to the eye in order to elicit the eyeblink reflex, and a CBM 64 computer for presentations of auditory stimuli in conjunction with air puffs; (2) a pair of light-emitting diodes and photocells placed in a pair of goggles placed on the subject for detection of eyeblinks; (3) an IBM-compatible personal computer, equipped with the ASYSTANT + software for eyeblink data acquisition and overall control of experiment and parameters. The system is presently in use in our laboratory, and technical details about the system can be obtained by writing to the first author.

A methodology for optimal design of pipe distribution networks

A series of computer programs has been developed to assist in the optimal design of pipe distribution networks. These programs are capable of handling nonstandard network components such as booster pumps, minor-loss devices, reservoirs, check valves, and pressure-reducing valves. All three stages of network problem, namely analysis, design, and optimization, can be solved using the same solution procedure. A known technique for layout design has been adapted to help in the selection of redundant links.The problem is formulated as a nonlinear program using as design variables the diameter, discharge, and shutoff head (where appropriate) for each link. Pump lift is assumed to be described by a parabolic Q–hp curve, the coefficients of which may be defined by the user. A powerful, large-scale, nonlinear, sparse-oriented package (MINOS) is used to solve the problem. The continuous solution obtained by MINOS is modified by a discretization procedure to arrive at the optimal discrete solution. The constraint matrix including the loop, nodal head, and continuity constraints is automatically generated.The user is required to supply a simple and concise data file that will be interfaced by a preprocessor to generate the large and complicated data file required by MINOS. The latter data file includes the nonzero elements of the constraint matrix, ordered and stored in a column-by-column fashion. A postprocessor is also used to convert the mathematical output of the package into easily understood engineering data. Three different network examples are used to demonstrate the different aspects of the model (i.e. nonstandard components, discretization procedure, and layout design). Key words: networks, optimization, design, distribution, water supply, nonlinear.

Efficient energy utilization in single purpose desalination plants

Thermodynamic analyses and case studies were carried out on hybridized systems designed to improve single purpose desalination (SPD) plants. The first system considered is a conventional SPD connected to a steam generator by a pressure reducing valve (PRV). In the second system, this is replaced by a mechanical vapour compression MVC/MED unit, and in the third system by a thermovapour compression TVC/MED unit. In the fourth system, a reverse osmosis (RO) unit replaced the PRV, thus using the supplied steam to produce more fresh water. Results of the analysis emphasize the extra water produced and the overall performance ratio increase of the plant. The included case study showed that the plant performance of the SPD was significantly improved by using any of the above systems. The extra water produced amounted to 96, 84 and 46% of the initial plant production in the second, third and fourth system respectively.

Catheter Jet Ventilation, a Favorable Technique during Resection of the Central Tracheobronchial System

Experience with catheter jet ventilation as an optimal ventilation technique during the critical phase of resection in the region of the central tracheobronchial system (bifurcational resections, extended resections in the bifurcational region) in 9 patients is described. For this technique we use a simple and cheap system consisting of a pressure-reduction valve, an interruption valve manually worked with a pistol handle, 2 manometers and a thin plastic catheter as a jet. In 8 cases the anesthesiologic management during the jet ventilation phase, ranging between 35 and 150 minutes, was without any problem; the one complication and the possible way of solving similar accidents are discussed. In comparison with the conventional technique, catheter jet ventilation gives the surgeon the possibility of complete freedom of action during suturing of the airway anastomosis.

Distribution of water in deep gold mines in South Africa

Gold mines in South Africa use large volumes of water for cooling and other purposes underground. The mines are often at great depths, for example 3600 metres below surface level. Water piped down the shaft can therefore be at high pressures unless a system of pressure reducing dams or valves is installed. Modern practice is to utilize the high water pressures wherever possible. Examples of the use of water pressure include driving turbines for power generation, moving ore by means of high pressure jets and there is the future possibility of driving mining machinery using the water. The operation and analysis of water reticulation systems is complex owing to the complex distribution system and the number of possible operating conditions. Computer programs for the optimum design of such distribution systems and for the hydraulic analysis of such pipe flow systems have been compiled. The high pressures also pose problems in the design of pipework and equipment.

Long-term optimization model of tree water networks

This paper describes an optimization method to design, over a period of time, a radial water network consisting of pipes, pumps and pressure reducing valves. The network structure can be modified during the planning period by the addition or removal of certain nodes and elements. The evolution of the consumption at the nodes is known. The hydraulic constraints of pressure and flow velocity are respected throughout the studied period. The investment decisions are determined in such a manner as to minimize the sum of the present worth values of the investment costs and operation costs over the planning period. The choice of pipe lengths to be invested in each branch as variables allows one to formulate the dynamic investment problem as a multi-stage linear program. Each stage corresponds to the state of the network at a time of the planning period. Such a formulation of a combinatorial problem of investments allows one to design networks of large dimensions in the long term whilst maintaining acceptable times of computation. An application of the model to a real problem is presented.

Extended Set of Components in Pipe Networks

Models for an extended set of components encountered in water-distribution systems are developed based on graph theoretic concepts. It is shown that components such as check valves, pressure-reducing valves, and booster pumps may be included in the system of equations in which junction (nodal) heads are being solved by selecting appropriate admittance values (similar to those associated with simple pipes) indicated by the current operating conditions of the valves. The formulation-solution procedure is based on sparse matrix methods that leads to efficient and economical analysis of water-distribution systems on a digital computer.

A MODEL FOR CALCULATING STEADY-STATE FLOW IN A WATER NETWORK

Calculation of steady-state pressure and flow distributions in a water network is an important requirement for network operators and planners. The SWAN model described in this report is suitable for simulation of networks comprising pipes, non-return and pressure-reducing valves, pumps and storage tanks or reservoirs. Mathematical formulation of the model is based on description of its hydraulic elements by algebraic equations and nodal topological network analysis procedure. The non-linear model equations are solved by application of the NEWTON-RAPHSON method. Used in conjunction with sparse matrix triangularization and convergence acceleration procedures, this method can be used to calculate large networks, whilst maintaining calculation times and the amount of data storage within reasonable limits. An application of the SWAN model to test and real networks is presented as an example.

Closure to “Pressure Reducing Valves in Pipe Network Analysis”

Closure to “Pressure Reducing Valves in Pipe Network Analysis”

Discussion of “Pressure Reducing Valves in Pipe Network Analyses”

Discussion of “Pressure Reducing Valves in Pipe Network Analyses”

A Pressure Reducing Valve to Slow the Flow of Personnel From the Water Utility

The rate of employee turnover in the water‐supply field, though comparing favorably to some industries, is high enough to be very costly. Seven management tools are offered to control the rate of turnover.

Pressure Reducing Valves in Pipe Network Analysis

The three separate systems of equations that are in common use in solving steady flow problems in pipe networks are described and the method for including pressure reducing valves in each of these systems is given. The emphasis is on use of efficient computer oriented methods. In the method presented the pressure reducing valves are permitted to operate normally in maintaining a constant downstream pressure, or are permitted to act as check valves, preventing reverse flow should downstream pressures exceed valve settings. The inclusion of pressure reducing valves as an integral part of the network of pipes, pumps, reservoirs, and minor loss devices causes no appreciable reduction in the performance of computer programs that have been specifically written to carry out the computations for solutions.

Digital Program for Water Network Analysis

The pressures and flows in a water distribution system are solved by a modified Newton-Raphson method. This method removes the problems of pressure initialization and greatly increases convergence particularly in systems containing pumps or pressure reducing valves, or both. The program will automatically amend pipe resistances so that calculated pressures agree with measured pressures. Both the system equations and those for the automatic balancing routine are derived. Examples are shown of the improved rate of convergence and the automatic balancing.