This specification covers the polyethylene pipe grade material, dimensions, design equations for pressure ratings applicable to mitered-bends (elbows) which provide the change in direction in piping and pipeline systems. This standard specification describes mitered-bends fabricated from axially extruded, solid-wall, standard or custom polyethylene (PE) pipe, for nominal pipe sizes (NPS) from 2-inch to 65-inch diameters (63mm to 1651-mm) in both Iron Pipe Sizes (IPS) and Ductile Iron Pipe Sizes (DIPS). The mitered-bends are fabricated by sequentially heat-fusion joining two or more miter-cut gore-pipe segments, using a qualified fusion-joining procedure specification (FPS). The pressure rating of mitered-bends is affected by the gore-pipe segments wall thickness, the R/D ratio of the radius of curvature, and the magnitude of the miter-cut angle. The miter-bend pressure rating formula using the derived geometric strength ratio (GSR) is included in the standard. The miter-bends may be internally reinforced or externally reinforced. Within this standard, any single miter-angle cut is limited to 22.5-degrees or less. The preferred R/D ratios are 1.0, 1.25, 1.5, 2.0, 3.0, 5.0. The mitered-bends are designed to have a sufficiently long tangent end length to enable heat-fusion joining using standard polyethylene pipe fusion equipment when the mitered-bend is clamped in the machines fixed jaw.
Polyethylene pipe has been sold for 50-years. There are no standards for pressure rated elbows. Novice fabricators are not educated in pressure-vessel design, and, require a published design basis in order to provide miter-bends with uniform pressure ratings between fabricators.
Keywordsmiter-bend, elbows; elbow components; pipe directional change; gore pipe; gore segments; pressure rating; PE4710; miter-cut; miter-angle; R/D ratio; intrados; extrados; geometric strength ratio; GSR; internally reinforced; externally reinforced; miter-bend calculations;
The title and scope are in draft form and are under development within this ASTM Committee.Back to Top
Draft Under Development