Plain Pipe Research Articles

Prediction of creep failure life of internally pressurised thick walled CrMoV pipes

Creep continuum damage finite element analyses were performed for a typical internally pressurised main steam thick-sectioned plain pipe geometry subjected to a range of axial loading conditions. The creep failure lives, for a range of loading levels, were obtained. The stress distributions showed the presence of a skeletal point or representative rupture stress. Life estimates were made using alternative stress forms and these were compared with the failure lives predicted using continuum damage analyses. For the particular ferritic material properties used in the analyses, the failure life of the pipe can be obtained accurately using the steady-state reference rupture stress or the skeletal point rupture stress.

Assessment of creep behaviour of a narrow gap weld

Finite element creep analyses have been performed using Norton's secondary creep law and continuum damage equations for a thick-walled narrow gap pipe weld. The creep stress and failure life were obtained using combinations of material properties which allowed different strengths for the parent material, heat-affected zone and weld metal for 1/2Cr1/2Mo1/4V: 2 1/4Cr1Mo welds. The stationary-state failure prediction was performed based on a steady-state rupture stress. The failure times obtained from continuum damage modelling were used for assessing the results and the accuracy of the steady-state approach. The results show that the creep stress and failure life of the narrow gap weldments of both materials data options were similar to those of the V-shaped weldments over a range of narrow gap weld widths from 8 to 12 mm. The conservatism of the steady-state analysis method is illustrated, from the life estimates. The data also allow estimation of a possible effect of the presence of a weld in a plain pressurised pipe.

50 QEEG in the study of psychotropic drugs interactions

The present study introduces a method to determine the load interaction behaviour in pressurised structures. A plain pipe was selected, in the first instance, to demonstrate the application of the method. The stress levels from various load categories, which were determined using the finite element method (FEM), were apportioned according to the combining loads and summed. The maximum resultant effective stress gave an indication of first yield of the structure and, for the load combinations, a series of first yield interaction diagrams were drawn. These compared well with theoretical analysis, thus illustrating the value of this method for producing load interaction rules for design purposes.

Estimating Hazen-Williams Coefficient for Polyethylene Pipes

Polyethylene is the predominant pipe material for trickle irrigation laterals and submains because of its flexibility and resistibility to the sun. Laboratory experiments have been conducted to determine the proper values of the Hazen-Williams friction coefficient for commonly used polyethylene plain pipes of different diameters. The commonly recommended values of the Hazen-Williams coefficient range from 130 to 140 regardless of the pipe diameter. Results of this investigation indicate that the average Hazen-Williams coefficients are 129, 136, 144, and 148 for pipe diameters of 13, 16, 19, and 22 mm, respectively. The differences between the measured friction losses and those calculated based on the average Hazen-Williams coefficients are small and vary from 8 to 14% at pipe diameters of 13 and 22 mm, respectively. The differences in calculating friction losses based on the commonly recommended values of the Hazen-Williams coefficient (130 to 140) and those based on the average coefficients reach 27% at a pipe diameter of 22 mm.

Load interaction in pressurised structures using the finite element method

The present study introduces a method to determine the load interaction behaviour in pressurised structures. A plain pipe was selected, in the first instance, to demonstrate the application of the method. The stress levels from various load categories, which were determined using the finite element method (FEM), were apportioned according to the combining loads and summed. The maximum resultant effective stress gave an indication of first yield of the structure and, for the load combinations, a series of first yield interaction diagrams were drawn. These compared well with theoretical analysis, thus illustrating the value of this method for producing load interaction rules for design purposes.

Significance of Energy Losses Due to Emitter Connections in Trickle Irrigation Lines

A study has been made of the effect of on-line emitters on the energy losses in trickle irrigation laterals. The study involved eight types of emitter with various barb areas installed into five commonly used polyethylene pipes of different diameters. Results of the investigation indicate that there are significant energy losses due to the emitter connections. The values of these losses are a function of the area of the emitter barb protrusion and the lateral pipe diameter. An increase in the energy loss of more than 32% compared with plain pipe was observed for laterals of 13 mm diameter. A simple procedure is suggested to incorporate the emitter barb losses in the design of trickle irrigation laterals.

Characterization of Turbulent Flows by NMR Measurements with Pulsed Gradients

Abstract A theoretical description is given of the dependence of the signal from a turbulent flowing liquid in a pulsed-gradient nuclear magnetic resonance measurement. The relationships between the characteristic time scale of velocity fluctuations of the fluid and the timing parameters of the gradients and NMR pulse sequence are made explicit. An experimental approach has been developed by which the time scale of random changes in the velocity can be determined, and this has been used to show that pipe flow at Reynolds numbers of 0-3000, and grid-generated turbulence, are characterized by correlation times that are relatively long on the scale of the NMR measurement. The turbulent intensity has been measured at different spatial locations distal to meshes of different spatial frequency as well as in a pipe with Reynolds numbers of 0-6500. The onset of turbulence at Re ≍ 2300 in plain pipe flow and the spatial variation of turbulent intensity distal to each mesh are in good agreement,vith measurements made by other techniques. NMR may have unique advantages for spatial mapping and characterization of some turbulent flows.

The behaviour of pressurised plain pipework subjected to simulated seismic loading

AbstractA series of simulated seismic tests have been conducted using mild steel and stainless steel plain pipe specimens. These specimens were pressurised and subjected to fully reversed cyclic bending moments at frequencies of about 5 Hz. The bending moments and surface strains on the pipe wall were monitored and are reported here. Significant ratchetting was observed which, in the case of the mild steel specimens, lead to gross swelling and eventual failure. Although ratchetting was observed in the stainless steel specimens it was not so pronounced and failure appeared to be by low cycle fatigue.

Techniques for the investigation of the ratchetting behaviour of piping components under internal pressure and simulated seismic loading

The ratchetting behaviour of piping components under internal pressure and simulated seismic loading has been investigated using special fixtures and a standard laboratory universal testing machine fitted with a fatigue module. Experimental arrangements are presented for testing plain pipes with or without thinned sections, elbows and tee branch junctions under in‐plane dynamic bending; similar fixtures and arrangements could be used for reducers and flanged connections and other types of loadings. Input accelerations up to 5g have been achieved and the results demonstrate that a great deal can be learnt about piping component behaviour from such simple arrangements and without resorting to sophisticated or expensive experimental techniques. The necessary instrumentation and algorithms for the analysis of results are described. Some sample results are included and discussed in terms of overall piping component behaviour. Two recommendations are suggested to more realistically simulate typical earthquake input spectra.

Evaluation of the Mechanical Behavior of Plain and Spirally Stiffened Polyvinyl Chloride Pipes

Abstract The evaluation of the merits of spirally stiffened polyvinyl chloride pipes over the merits of conventional plain (unstiffened) pipes is achieved experimentally. Various relevant standard tests have been performed on both types of pipes made of the same material. These tests are bursting, impact resistance and short- and long-term stiffness tests. The experimental results are compared favorably with appropriate formulae found in the literature. It is concluded that considerable saving in material could be realized with no significant loss in pipe stiffness or impact resistance by adopting a spirally stiffened pipe design rather than a plain design.

The effect of permeable surrounds on the performance of clay field drainage pipes

The relative performances of a plain clayware drain and ones with a partial and a complete gravel surround were investigated by measuring the drain discharge rate from each during ponded conditions when installed in a sand tank. From the drain discharge the effective radius of each drain installation was calculated and these values used in the hodograph solution of the drainage problem to obtain steady state theoretical relationships between water-table height and drain discharge. Comparison of the values with those observed in experiments in the sand tank revealed reasonable agreement. Using the values of effective drain radius for the various drain installations, the drain spacings for representative Western European conditions were calculated using the hodograph analysis, and the results expressed as a percentage of the spacing calculated for an “ideal” drain. This showed, that for a deep soil a partial surround, either above or below the drain, would allow an increase in spacing of some 100% as compared with the plain pipe. The corresponding figure for a complete surround being 120%.

Study on Exhaust Pipes with an Ejector

When two exhaust pipes of an internal combustion engine are connected to a short plain pipe or a diffuser at their open ends, it is possible to promote the scavenging of cylinders by the rarefaction waves in the exhaust pipes which are produced by the blow down from one of cylinders. By measuring the pressure variations in the exhaust pipes of an air model, the effect of the short pipe or the diffuser on the energy of rarefaction waves has been investigated. Further the optimum area-ratio of the short pipe or the diffuser to the exhaust pipe to produce the maximum energy of rarefaction wave has been theoretically calculated on the assumption that the relation of steady flow can be applied to the short pipe or the diffuser. The results obtained agree fairly well with those of the experiment.

Study on Exhaust Pipes with an Ejector

When two exhaust pipes are connected with a short plain pipe or a diffuser at their open ends, it is possible to promote the scavenging of cylinders by the rarefaction waves produced in the exhaust pipes with the blow down in either of them. By measuring the pressure variations in the exhaust pipes of an air model, the effect of the short pipe or the diffuser on the energy of rarefaction waves has been investigated. Further the optimum area-ratio of the short pipe or the diffuser to the exhaust pipe to produce the maximum energy of the rarefaction wave has been theoretically calculated on the assumption that the relation of steady flow can be applied to the short pipe or the diffuser. The results obtained agree fairly well with those of the experiment.

Air Flow in a Naturally Aspirated Two-stroke Engine

The problem of scavenging of naturally aspirated, two-stroke cycle engines by utilization of wave effects in the exhaust and induction system is treated theoretically and investigated experimentally by systematic variation of the exhaust and induction system, as well as engine speed. In the theoretical treatment accuracy is achieved with a minimum of numerical computation by the adoption of the theory of waves of finite amplitude and the use of charts, wherever possible. These two features constitute the most significant departure from List's very thorough analysis (List 1949/50)‡, which is based throughout on the small-wave theory and in which little attention appears to have been paid to the simplification of numerical work. The theoretical section is divided into two parts dealing with (1) the analysis of cyclical pressure fluctuations in the engine cylinder and pipe system, and (2) the treatment of the gas-exchange process in the cylinder on the basis of ‘perfect mixing’ and the derivation of the conditions for dynamic similarity. A novel experimental technique is used, air from an external compressor being admitted to the cylinder of the motored engine through a rotary valve. In this manner release pressures comparable with those obtaining in the firing engine are attained, while the effects of high temperatures, which are of secondary importance in relation to wave phenomena, are eliminated. The experimental work is divided into two parts: (1) tests corroborating the wave theory; and (2) systematic air-consumption trials with variable induction-pipe lengths and exhaust systems, incorporating ( a) plain pipes, ( b) an exhaust ejector similar to that described in the Kadenacy patent specifications, ( c) an expansion chamber, and ( d) a diffuser. The general conclusions are: (1) good agreement between observations and analytical results is obtained, (2) high air-consumption is possible with natural aspiration provided that effective use is made of wave action by correctly designed exhaust and inlet systems; and (3) satisfactory scavenging is only achieved if not only the external pipe system but also the engine speed and geometry conform to certain requirements conveniently expressed in the form of dimensionless groups.

Heat Loss from Gilled Metal Pipes

In a previous paper, on “Heat Transfer between Metal Pipes and a Stream of Air”, presented to the Institution in 1933, an account was given of measurements on the transfer of heat between plain pipes and a stream of air. The present paper is an extension of this investigation to gilled pipes. Observations have been made on the heat loss from four gilled pipes of diameters between 1 and 2½ inches, with gills varying in diameter from 2 to 4⅓ inches. Each pipe was studied as a single unit in the wind tunnel, whilst one size of pipe was also examined when built into a battery of similar pipes placed with their axes across the direction of the air flow. The result found for plain pipes, namely, that H/ κ θ is a function of V d/ v only (where H is the heat loss per unit length from a pipe of diameter d at a temperature excess θ over air of thermal conductivity κ and kinematic viscosity v, moving at velocity V), requires modification in the case of gilled pipes. In the former case, H is the heat loss per unit length, and is thus equivalent to the product of the circumference and the heat loss per unit area. The latter interpretation, when dealing with the results for the gilled pipes, does not give systematic results, if the heat loss per unit area is calculated on the total exposed area of the pipe. Moreover, in defining the surface emitting heat, the quantity d, the pipe diameter, is only unambiguous for plain pipes. In the case of gilled pipes, it is found that the most consistent treatment of the results is obtained if d is taken to be the “effective diameter” of the pipe, i.e. the total exposed area per unit length divided by π If the interpretations just explained are given to the quantities H and d, then it is found that to a first approximation, the relationship between H/ κ θ and V d/ v is the same for a gilled and a plain pipe. The observations have also been analysed from the point of view of the temperature of the edge of the gill, relative to that of the air and that of the pipe.

Plain End Pipe and Specials Versus Bell and Spigot Pipe and Solid Sleeves

Plain End Pipe and Specials Versus Bell and Spigot Pipe and Solid Sleeves

Load-Deflection Relations for Large Plain, Corrugated, and Creased Pipe Bends

Abstract This paper presents the results of tests made on 10-in. and 14-in. seamless steel pipe loaded in the same manner as the simple cases shown on pages 526 to 529, “Piping Handbook,” by Walker and Crocker. Comparison has been made between calculated deflections and the results of tests in the six cases for a plain pipe bend. The relation between the results of tests on corrugated and creased pipe bends and the calculated results for plain pipe bends of the same dimensions are shown. Such calculations are included as are necessary to show the method of analysis by which the load-deflection relations of a plain quarter-bend and its tangents are determined.