Maximum Permissible Pressure Research Articles

Residual Strength Calculation & Residual Life Prediction of General Corrosion Pipeline

General corrosion is of the primary reason that causes the pipeline to failure. Researching the residual strength and residual life of general corrosion pipeline is the main measure to conduct the pipeline integrity management, and has great significance to ensure the safety of pipeline transportation. The calculation of the residual strength of even corrosion pipeline under the combined effects of internal pressure and axial force was discussed according to the Tresca yield criterion in elasto-plastic fault mechanics, when the defected size is given, the maximum permissible operating pressure under the defect and the calculation formula for the residual strength of corrosion pipeline are given. On this basis, reliability-based residual life prediction of the corrosion pipeline was developed.

The Performance of Turning Diffusers at Various Inlet Conditions

A turning diffuser is often introduced in the flow line to recover the energy losses by converting the kinetic energy to pressure energy. There are two types of turning diffusers, i.e. a 2-D and 3-D diffuser that are commonly defined by their expansion direction. This study aims to investigate the performance of a 2-D and a 3-D turning diffuser with 90o angle of turn and an area ratio, AR=2.16 by means of varying operating conditions. The geometry configurations applied for a 2-D turning diffuser are outlet-inlet configurations, W2/W12-D=2.160, X2/X12-D =1.000 and an inner wall length to an inlet throat width ratio, Lin/W12-D=4.370, whereas for a 3-D turning diffuser, they are W2/W13-D=1.440, X2/X13-D =1.500 and Lin/W13-D=3.970. The operating conditions represented by inflow Reynolds numbers, Rein are varied from 5.786E+04 to 1.775E+05. Particle image velocimetry (PIV) is used to examine the flow quality, and a digital manometer provides the average static pressure at the inlet and outlet of the turning diffuser. A compromise between the maximum permissible pressure recovery and flow uniformity is determined based upon the need. Whenever the flow uniformity being the need it is promising to apply a 3-D turning diffuser for Rein=1.027E+05 - 1.775E+05 and a 2-D turning diffuser for Rein=5.786E+04-6.382E+04. On the other hand, it is viable to opt for a 3-D turning diffuser for Rein=5.786E+04-6.382E+04 and a 2-D turning diffuser for Rein=1.027E+05-1.775E+05 in the case of the outlet pressure recovery being the need. The secondary flow separation takes place prior at 1/2Lin/W1 for a 2-D turning diffuser, whereas approximately at 3/4Lin/W1 for a 3-D turning diffuser.

Pressure generation in coking furnaces: A review

The pressure field in loading coking chambers with coal batch will be affected by the specific temperature field during the release of volatiles at the stages of softening and swelling of the coal grains, the appearance of a plastic layer, and the formation of semicoke and coke. In monitoring the process, the maximum pressure in the middle of the furnace (coking pressure) and at the charge-wall contact (the swelling pressure) are recorded. These characteristics depend on the properties of the coal’s organic mass (petrographic composition, metamorphic stage, degree of reduction), the batch preparation (reduction in grain size, moisture content, density of the charge), the structural characteristics of the working chambers, the temperature conditions, and the duration of carbonization. The maximum permissible pressure values are established specifically for each coke battery, in the light of the batch and technology employed. Usually, a wall pressure of around 7 kPa (∼1 psi) is adopted as the critical value at which unhindered coke discharge is possible. This value determines the limiting attainable quality of blast-furnace coke (within the framework of the given technology).

Recent Innovations in Turbulent Mixing with Static Elements

A lot of static mixers are now available, e.g. Sulzer SMV and SMI, Chemineer KM, the Kenics HEV. These products differ quite considerably and the construction have effects on the manufacturing costs and also on the costs for the inbuilt the mixers in a plant. These well known motionless mixers allow to obtain good performances but usually the mixing length necessary for obtaining the homogeneity is longer than 5-10 pipe diameters. Another important constrain is the maximum permissible pressure loss in the operation.

Recent Innovations in Turbulent Mixing with Static Elements

Static Mixer consists of a number of stationary mixing elements inserted along the direction of flow in a pipe. Each mixing element allows to divide the flow and to recombine it in a geometric sequence. A lot of static mixers are now available, e.g. Sulzer SMV and SMI, Chemineer KM, the Kenics HEV. These products differ quite considerably and the construction have effects on the manufacturing costs and also on the costs for the inbuilt the mixers in a plant. These well known motionless mixers allow to obtain good performances but usually the mixing length necessary for obtaining the homogeneity is longer than 5-10 pipe diameters. Another important constrain is the maximum permissible pressure loss in the operation. In the recent years, new products composed of a minimum number of elements, have been launched. These new products have a short inbuilt device length, they require a short mixing path and they have low pressure drops. This review analyzes the behaviour of these new innovative static mixers. Keywords: Static mixer, Sulzer CompaX, computational modelling, mixing, turbulent flow

Analysis of rupture instability in the hydromechanical deep drawing of cylindrical cups

This paper presents analyses of tensile instability in the hydromechanical deep drawing process of cylindrical cups. Analytical models are developed based on Barlat-Lian and Hill’s non-quadratic yield criteria and the maximum permissible fluid pressure, above which rupture occurs, is achieved, assuming plane strain tensile failure. The influences of process and material variables on this critical fluid pressure are investigated. The theoretical results are compared with results obtained from experiments to verify the validity of the proposed analytical approaches.

Effect of network arrangement on the heat transfer area of cooling networks

This work presents a study of the effect of the configuration of cooling networks upon the total exchanger area. Most industrial installations have cooling systems whose network of exchangers exhibit parallel arrangement. From the operation point of view, in this arrangement cooling water enters every unit at the same temperature. There are cases, however, where not all exchangers require water at the same cold temperature; therefore, it is possible to generate different arrangements with positive results in terms of equipment size and therefore capital investment. In this work, various cooling network design approaches are analysed subject to restrictions such as the maximum permissible water return temperature and pressure drop. Results show that when exchangers are designed for maximum utilisation of the allowable pressure drop or the maximum allowable fluid velocity, the series arrangement results in lower heat transfer area and lower investment. In the case of existing cooling networks, a practical approach for the minimisation of power consumption is implemented by taking advantage of the installed network area. The procedure is demonstrated using a real case study.

On the design of the tubesheet and the tubesheet-to-shell junction of a fixed tubesheet heat exchanger

For the (mechanical) design of an existing fixed tubesheet heat exchanger, a C2-Hydrogenation reactor in a petrochemical plant, various code solutions are compared with each other and with a Finite Element solution based on the Direct Route in Design by Analysis (EN 13445-3, Annex B). The codes and standards used in the investigation are ASME Section VIII, Division 1 and EN 13445-3, Clause 13 and Annex J. The ASME VIII/2 and TEMA codes are not appropriate for this design. The ASME VIII/1 and EN 13445-3 Clause 13 approaches are similar. Differences in maximum permissible pressures result partly from different nominal design stresses. The modern EN 13445-3 Annex J approach, being based on limit analysis theory, leads to very different, much more efficient results. The Direct Route in Design by Analysis confirms the EN 13445-3 Annex J results, but gives, at the same time, clear insight into the behaviour of the whole structure and the various maximum permissible pressure limiting details.

Boron removal from landfill leachate by means of nanofiltration and reverse osmosis

The removal of boron from chemical landfill leachate, of 25.4 ± 0.7 mg/L boron content, by means of nanofiltration and reverse osmosis was investigated. The BW-30, TW-30, NF-90 and NF-45 (Filmtec) membranes, working at maximum permissible operating pressure were applied. Our experimental results indicated that boron rejection mostly depends on membrane type and leachate pH level while it is almost recovery independent. The more detailed analysis of abovementioned results showed that boron can be effectively removed only at a shifted feedwater pH, close to 11, that is the highest value for long term operation of RO membranes. The highest boron rejection (close to 99%), and the low enough permeate boron content (<1 ppm) were observed in the case of the BW-30 membrane up to 50% recovery only. Thus a two stage RO system, operated under alkaline conditions was proposed to efficiently remove the boron from such leachate.

Insights into successful plunger and piston pump operation

Plunger and piston pumps are positive displacement pumps in the truest sense. Their flow delivery is directly related to their speed and the volume swept, and bead capacity is defined by vertical lines. The strength of the pump components themselves determines the maximum permissible pressure rating, and top running speed is decided by the limitations on the piston speed valve operation and cylinder, fill time. If, for example, the fluid is very viscous, more time will be needed to fill the cylinder, and so the pump must run slower. The capacity of the pump falls correspondingly.

Soil criteria for assessing the maximum permissible ground pressure of agricultural vehicles on Chernozem soils

The maximum permissible ground pressure of agricultural vehicles to permit satisfactory crop production on heavy loamy Chernozem soil was estimated from six criteria: (1) changes in soil water-physical properties; (2) crumbling characteristics; (3) depth of compaction; (4) rut depth; (5) soil strength potential; (6) self-loosening characteristics. Using these criteria it was possible to obtain reliable data for the maximum permissible ground pressure which was found to be correlated with the soil water content at the time of tillage. At a water content equal to or somewhat lower than the water content at optimal soil crumbling (0.16–0.24 kg kg −1), the permissible ground pressure was found to be within the range 80–120 kPa. At soil water contents slightly above the optimum soil crumbling (0.26–0.28 kg kg −1), the permissible ground pressure was within the range 30–60 kPa.

Thermodynamic analysis of a closed-cycle, solar gas-turbine plant

Thermodynamic analysis of a closed-cycle, Brayton gas-turbine plant with a heat exchanger powered by the sun has been studied. A Brayton cycle is simpler than a Rankine cycle and has an advantage in places where water is scarce and expensive. A simple expression is derived for calculating the efficiency of the cycle in terms of the compression pressure ratio, the pressure loss coefficient and the ratio of the lower to higher temperature in the cycle with the efficiency of various components. The maximum permissible pressure loss coefficient has also been calculated.

Variational problem of optimum side wall design for a narrow three-dimensional nozzle

The optimum design of the side walls of the supersonic section of a three-dimensional nozzle with two planes of symmetry is considered in the narrow channel model approximation, which reduces three-dimensional to two-dimensional flow. This nozzle realizes maximum thrust for given sonic or supersonic inlet flow, upper and lower walls, maximum permissible length and pressure outside the nozzle. In general, an approximate solution of the variational problem can be obtained by the indeterminate control contour method [1]. For nozzles with nonexpanding “end” sections of the upper and lower walls this is a rigorous solution. Numerical algorithms, based on the method of characteristics, for constructing the optimum, side walls and calculating the flow in narrow channels are developed in the formulation adopted using the optimality conditions found, which generalize the wellknown conditions for plane and axisymmetric configurations [1]. In addition, the three-dimensional supersonic flow in the nozzles thus designed has been calculated in accordance with a shock-capturing marching scheme [2], which for the uniform grids employed in the calculations gives a second-order approximation. A rather complex relation is established between the thrust of the optimum configurations constructed and the shape of their inlet cross sections.

Empreintes dues à l'implosion de bulles isolées : Etude paramétrique expérimentale

With the aim of gaining a better understanding of the significance of various parameters on the cavitation erosion mechanism, an experimental study has been conducted on the marking of polished materials subjected to the collapse of a vapour bubble engendered by a discharger inside a pressurizable vessel. The parameters studied are: the pressure inside the vessel P, the distance relating to the centre of a (d/R max < 1.5) sample bubble, the material (99.99 % aluminium and 316 L stainless steel). Several conclusions can from now on be drawn: * The implosion of a bubble can engender many holes, which demontrates that the collapse in the form of a torus plays a determining part. * The maximum marking is obtained for a d/R value of less than 1.1. * For a given material, there exists a maximum permissible pressure below which no implosion is marked of about 0.07 MPa for aluminium and 0.15 MPa for steel.

Design and Development of a Low Emission Combustor for a Car Gas Turbine

The limit levels for pollutant emissions of automotive vehicles of 0.41 g/mile HC, 3.4 g/mile CO and 0.4 g/mile NOx which have been set in the USA up to the 80s may be likely achieved or even bettered by an appropriately designed gas turbine. Premixing of the fuel with air and its prevaporization before entering the combustion zone, in conjunction with continuous adjustment of the fuel/air ratio in this zone to the respective operation condition, seems to be the favorable approach for attaining this goal. Losses in output and economy are not to be expected; but as compared to spark-ignition and diesel engines, competitive fuel economy can only be reached at turbine inlet temperatures higher than presently obtainable, which call for ceramic components. The problems which are to be solved are treated and the results of the evaluation of a variable geometry combustor are presented on the basis of projected pollutant concentrations along a steady-state turbine operating line. The methods of water channel and electrical analogies which have been applied for optimizing the flow-contours in the premixing and combustion zones and their results are discussed, and the various principles investigated for mixture preparation are described in brief. In the second part, the results of experiments and measurements which have been performed, and the influences of the various parameters on pollutant emissions are shown in detail. Finally, results of particle and aromatic compound measurements are reported. The aim of the work is a combustor whose pollutant emissions at a specified maximum permissible pressure loss do not exceed the half-limit levels of the Muskie Standards at any steady-state point of operation.

Vacuum and Ultrahigh Vacuum for Particle Accelerators and Storage Rings

Particle accelerators operate at pressures of about 10-7 Torr. Storage rings require 10-9 to 10-11 Torr. The maximum permissible pressure is determined by many perturbing interactions between beam particles and gas molecules. Proton storage rings have additional problems from interactions with layers of gas adsorbed on the chamber walls. Most accelerators and storage rings have a tubular structure with pumps connected in regular intervals. The pressure behaviour in such a system can be calculated from a differential equation, which can be extended to include beam-wall interactions, readsorption and distributed pumps. The systems are pumped by sputter-ion pumps, pre-evacuated by turbopumps and controlled by computers. Radioactivity poses special problems.

An Investigation of Internal Combustion Engine Silencing Using Reflection and Absorption Phenomena

An investigation has been made to determine the most influential parameters for efficient silencer design. These parameters lead to new insights into silencer operation containing both reflection and absorption phenomena, where damping is found to be effective at lower frequencies. Hence, objectionable deep exhaust tones of engines at frequencies of about 80–100 Hz can be significantly reduced. Efficient and economic silencing of engine exhaust noise can be applied to a large number of internal combustion engine installations including 2- and 4-cycle engines—e.g., cars, buses, trucks, locomotives, lawn mowers, chain saws, and motorcycles. Two important factors were considered simultaneously, i.e., the aerodynamic criterion (which specifies the maximum permissible average pressure drop through the silencer at a given temperature and mass flow) and the geometrical criterion, which specifies maximum allowable volume and restrictions on shape. Results of this study are: (1) Identification of parameters influential to silencer design. (2) A better understanding of silencer operation incorporating reflection and absorption phenomena. (3) A more efficient overall silencer system. (4) Lower noise levels associated with internal combustion engine operation.

Process Computer Application in Gas-Pipeline System

The use of a process control computer for supervision and optimal distribution, in a pipeline system for natural gas, will be discussed example: Gewerkschaft Brigitta, Hannover).After a brief description of the theoretical fundamentals of gas transport in high-pressure pipes, it will be explained which methods, in principle, are possible for pipeline supervision. Tracing of local pres sure differences becomes apparent as most suitable. With this method, a pipe leakage can be recognized and localized with a good response sensitivity.The relatively complicated conditions of a moderately branched network will be briefly discussed.In the second part of the paper, it will be shown how optimal control of the feedlocations can be derived from a forecast of the gas consumption and the given delivery conditions of the consumers. The pressure of the gas contained in the pipe must, for this purpose, lie within a certain range which depends on the maximum permissible pressure within the pipe and the delivery pressure, as required by the customer. The best way to achieve this is to minimize the number of adjustments made to the feed-in flow.