Effect of Precompression on Thickness of Pipe During Bending

2009 ◽  
Vol 131 (3) ◽  
Author(s):  
A. V. Kale ◽  
H. T. Thorat
Keyword(s):  
Cross Section ◽  
Wall Thickness ◽  
Horizontal Plane ◽  
Circular Cross Section ◽  
Thickness Variation ◽  
Parallel Plates ◽  
Thickness Change ◽  
Maximum Deformation ◽  
Curved Pipes ◽  
Tension And Compression

Straight pipes with a circular cross section are processed into smooth bends by various pipe bending techniques. After bending, the initial circular cross section is deformed with thickness change. These changes from ideal are normally referred to as “ovality” and “thinning.” Their influence on the subsequent behavior of curved pipes is not yet fully understood. The aim of this paper is to present a factual method to reduce thinning of the wall thickness of pipe during bending. A new mechanism is developed for bending of pipes. This mechanism has a provision of precompression (radial squeeze) of the pipe along the directrix of maximum deformation during bending. This is achieved by clamping the pipe using two parallel plates from top and bottom. In fact, the pipe is wrapped using two rollers—one from inside and one from outside in the horizontal plane—and two plates parallel to the horizontal plane—one from the top and one from the bottom. Experimentation is carried out on this mechanism, and thicknesses are measured at the grid points along the length of the pipe. From the experimental values of thicknesses on the tension and compression sides, dimensionless variations in wall thickness of various groups of pipes are computed for different precompression values. In order to represent the thickness at any point, a mathematical equation is derived. Analytical values of thickness variations on tension and compression sides are computed using this equation. Experimental and analytical results are compared, and its methodical approach is presented in this paper. Results show that precompression reduces thickness variation of the pipe after bending.

The Bending of Curved Pipes With Variable Wall Thickness

2003 ◽  
Vol 70 (2) ◽  
pp. 253-259 ◽  
Author(s):  
V. P. Cherniy
Keyword(s):  
Cross Section ◽  
Wall Thickness ◽  
Shell Theory ◽  
Neutral Line ◽  
Radius Of Curvature ◽  
Curved Pipes ◽  
Variable Wall Thickness ◽  
Previous Solution ◽  
Variable Wall ◽  
Thin Shell Theory

A general solution is presented for the in-plane bending of short-radius curved pipes (pipe bends) which have variable wall thickness. Using the elastic thin-shell theory, the actual radius of curvature of the pipe’s longitudinal fibers and displacement of the neutral line of the cross section under bending are taken into account. The pipe’s wall thickness is assumed to vary smoothly along the contour of the pipe’s cross section, and is a function of an angular coordinate. The solution uses the minimization of the total energy, and is compared to our previous solution for curved pipes with constant wall thickness.

Improved Prediction of External Pressure Collapse of Seamless Pipe

2009 ◽  
Author(s):  
Josef Navarro ◽  
Philip Cooper
Keyword(s):  
Cross Section ◽  
Wall Thickness ◽  
Design Method ◽  
External Pressure ◽  
Thickness Variation ◽  
Seamless Pipe ◽  
Line Pipe ◽  
Collapse Pressure ◽  
Average Wall Thickness ◽  
Improved Design

Seamless pipe typically features well controlled average wall thickness around its cross-section, but is prone to significant local thickness variation arising from the manufacturing process. Pipeline design codes, such as DNV OS-F101, provide little guidance on how to treat thickness variation whilst designing for collapse resistance. Standard practice is to consider minimum wall thickness across the whole cross-section, an assumption that two dimensional finite element simulations have proven conservative. This justifies the need for an improved design method. A program of simulations has been carried out to investigate the effect of wall thickness variation on collapse pressure. A modification to the DNV OS-F101 collapse design equation using average wall thickness over the whole crossection together with a fabrication factor is presented based on the results of this study. The fabrication factor de-rates the collapse pressure according to the amount of thickness variation present. The correction has been calibrated for thickness variations up to the maximum permitted by typical line pipe specifications. A number of FE trials demonstrate that the proposed formula predicts simulated collapse pressures with 98% accuracy. Adopting this method could provide significant wall thickness savings for deep water flowlines which in turn could lead to a reduction in steel costs and transportation and lay vessel requirements.

scholarly journals COMPARATIVE ANALYSIS OF TEST RESULTS OF DRIP LATERALS WITH CIRCULAR AND ELLIPTIC CROSS SECTION

2019 ◽  
Vol 31 (3) ◽  
pp. 735-739
Author(s):  
Dimitar Georgiev ◽  
Veselin Karasinkerov
Keyword(s):  
Cross Section ◽  
Wall Thickness ◽  
Circular Cross Section ◽  
Internal Diameter ◽  
Irrigation Season ◽  
Elliptic Cross Section ◽  
Hydraulic Test ◽  
Small Water ◽  
Head Losses ◽  
Elliptic Cross

Lately, the drip irrigation systems find more and more application, which led to the production of a new type of drip laterals – with flat to elliptic cross section and comparatively small thickness of the wall – from 0.2 to 0.9 mm, compared to the conventional ones with circular cross section and wall thickness over 1 mm. The main advantage of the first type is that they are comparatively cheap and are offered in the form of small rolls, the length of the hose being from 500 to 3500 m which makes their transportation to warehouses, assembly and disassembly very convenient. With the smaller thickness of the walls, the laterals have almost clenched form and are intended to be used for one irrigation season, while those with higher thickness, with elliptic form, may be used for several seasons. The inside welded emitters are flat and have a very small water-stopping head area compared to the annular water-stopping cross section of the cylindrical drippers in the conventional circular type of laterals. This is connected with the smaller head losses in the movement of water in them, which is an important advantage. The paper presents and analyses the results of the hydraulic test of the two types of drip hoses – with circular and elliptic cross section, in order to find the head losses for different lengths - 40, 60 and 80 m and heads in the beginning of 6, 8, 10, 12, 14 and 16 m, as well as the coefficients of uniformity for both types. The following hoses of both types were tested: JUNIOR, with circular cross section and internal diameter of 13.8 mm, nominal diameter 16 mm, thickness of wall 1.1mm, cylindrical type of drippers with a flow rate of 2.1 l/h and interval between nozzles 0.30 m (Irritec, Italy); DP Line (D5), with elliptic cross section, with the same sizes and intervals but with a wall thickness 0.6 mm and flat type of drippers (Irritec, Italy). The results indicate that irrespectively of the elliptic form of the cross section which is with a very small hydraulic radius, the head losses are almost equal to those with the circular cross section with cylindrical drippers, which is due to the minor head losses because of the flat nozzles in them. The values of the absolute coefficient of uniformity and the calculated one according to the method of Christiansen for all options are presented. The test is performed for zero slope, while modelling is performed for slopes 1% and 2%. The analysis of the data indicates that for zero slope of the terrain the increase of head leads to increase of the coefficients of uniformity for the three tested lengths of laterals; for 1% are observed very small tendencies for reduction of those coefficients, while for 2% the coefficients have higher values compared to the other slopes, again with slightly expressed tendency for change. The higher values in the 2% slope are due to the additional head caused by the geodetic level difference of the terrain.

Heat-Transfer Analysis of Visco-Elastic Giesekus Fluid in a Duct Between Parallel Plates and in a Straight Pipe of a Circular Cross-Section

2015 ◽  
Author(s):  
Sara N. AlMelhi ◽  
Lyes Khezzar ◽  
Mohamed Alshehhi ◽  
Abdelkader Filali
Keyword(s):  
Heat Transfer ◽  
Cross Section ◽  
Numerical Solutions ◽  
Numerical Technique ◽  
Circular Cross Section ◽  
Heat Transfer Analysis ◽  
Rheological Parameters ◽  
Parallel Plates ◽  
Straight Pipe ◽  
Finite Element Software

This work aims to conduct numerical simulation to investigate the convective heat transfer of viscoelastic fluids obeying Giesekus model flowing either along straight pipe of circular cross-section or within the space between parallel plates with constant heat flux thermal boundary condition and neglected viscous dissipation. The numerical technique used is based on finite element software (ANSYS Polyflow 14.0) and the obtained numerical solutions are compared against the analytical solution available in literature. The effect of the rheological parameters on the heat transfer enhancement is discussed.

scholarly journals OPTIMIZATION OF BELLOWS AND TUBES CUTTING BY DISC KNIFE TO ACHIEVE THE MINIMUM BURR SIZE

2021 ◽  
Vol 2021 (6) ◽  
pp. 5373-5380
Author(s):  
RADEK CADA ◽  
◽  
PAVEL LOSAK ◽  
Keyword(s):  
Cross Section ◽  
Wall Thickness ◽  
Cutting Tool ◽  
Circular Cross Section ◽  
Minimum Size ◽  
Optimal Size ◽  
Outer Diameter ◽  
Burr Size ◽  
Metal Bellows

The paper solves the determination of the optimal size of the shear gap when dividing components with a circular cross section (hydroformed metal bellows and tubes) with a disc knife to achieve the smallest burr size on the divided surfaces. The analyzes were performed on bellows with an outer diameter of 15 mm and a wall thickness of 0.4 mm. During the experiments, the size of the shear gap between the inner disc knife and the outer knife was changed, and the pressing force of the inner disc knife was changed. The experiments were carried out using a cutting tool after 20,000 cuts and after 120,000 cuts. The optimal size of the cutting gap was determined, allowing the minimum size of the burr to be achieved, thus reducing the time to remove it by brushing or tumbling in the subsequent operation. The mentioned procedure can be applied to analogous cases of division.

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