Polyethylene Pipe Fittings and Sweep Bends Manufactured in Canada for Gas, Water, Mining, Industrial and Plumbing applications

Plate Stress:VM-z Surface(kPa)

ALLOWABLE STRESS 8.0 MPa

5.113x10³[P:47]

5.050x10³
4.986x10³
4.923x10³
4.859x10³
4.796x10³
4.733x10³
4.669x10³
4.606x10³
4.542x10³
4.479x10³
4.415x10³
4.352x10³
4.288x10³
4.225x10³
4.161x10³
4.098x10³
4.035x10³
3.971x10³
3.908x10³

3.844x10³[P:187]

 
Finite element analysis is a computer based analysis of hoop stresses at full pressure operation of a bend using a computer generated model of a long sweep bend.

The model is an accurate replication of every mechanical property and wall thickness variation within the Pipestar sweep bend.

The maximum hoop stress at full pressure rating is 5.113 Megapascals. The maximum allowable hoop stress is 8.0 Megapascals for PE3408.

A 90 degree sweep elbow is 1/4th of a torus or doughnut shape. It is one of the most useful and widely used shapes in pressure vessel and pipeline construction. In straight pipe, the walls are equal and hoop stresses are uniform. When straight pipe of a given DR is forged into a Sweep Bend using the Pipestar process, a natural redistribution of materials occurs, with minimal tolerable thinning at the outside (the "extrados"), and slight thickening at the inside crotch (the "intrados").

Interestingly, this is a natural compensation with the change in hoop-stresses due to the change in geometry. The torus hoop-stresses on the outside (extrados) become lower, and the inside (intrados) stresses intensify. The changes in both wall thickness and hoop-stress re-distribution offset one another such that the fitting remains fully pressure rated. In quick-burst tests, it typically takes about 15% more pressure to forcibly burst a Sweep Bend than to burst straight pipe.

A fabricated, segmented elbow with its notch, stress-intensification-factor requires a thicker wall pipe segment to maintain a pressure equal to pipe main. Unlike fabricated elbows, the forged long Sweep Bends do not require thicker wall pipe to adjust for the minimal tolerable thinning during bending. The smooth change in geometry redistributes hoop-stresses in direct proportion to resulting changes of wall thickness for the R/D ratio's customarily used. It has a Working Pressure Rating (WPR) equal to that of straight pipe of the same DR. Dynamic fluid or slurry flow behaviour within a Sweep Bend is vastly superior to a fabricated elbow.