Pipe Bend Centerline Radius
and Size Guide

Defining CLR and R/D

Centerline radius (CLR or R) is the radius of the curved pipe centerline in a continuous sweep. It determines the location of the circular arc and is useful for design, manufacturing and fit checks. An R/D ratio divides the CLR by a stated diameter. Because DN is only a nominal designation, an engineering drawing should tell you whether D refers to actual OD, the finished ID or a nominal reference.

Do not call a pocket body’s connection offset a centerline radius. Even if a dimension on the drawing happens to be labeled R, its meaning must be verified from that manufacturer’s notation.

Proposed Radius Schedule DN50–DN400

Candidate common catalog for the five pipe-based families. Manufacturing and lining feasibility not yet approved. All dimensions in millimetres.

The three options—Compact, Standard and Extended—are a provisional product-standardization proposal. They require approval for tooling, metal grade, wall thickness, liner construction, hardfacing access and final flow area. DN150 R600/R1000 appear in older Polimak basalt-bend pricing records, but that does not validate all other entries.

Multiple Radius Options for One Diameter

For a single nominal size, more than one CLR can satisfy the same total angle. A smaller CLR occupies less space but can concentrate directional change; a larger CLR occupies more space and may increase particle sliding along the outer wall. The best choice depends on actual solids, velocity, route and maintenance objective. Larger CLR should not automatically be described as gentler or longer-lasting.

30°, 45° and 90° Bend Geometry

Bend Angle

The bend angle means the change in conveying direction. In a continuous circular sweep, centerline arc length is L = R × θ, with θ in radians, before tangents. For 90°, θ = π/2; for 45°, π/4; for 30°, π/6.

Tangents and End Connections

Real assemblies normally extend beyond the mathematical arc. Specify inlet and outlet straight lengths, flange positions, external insulation, support points and removal clearance. Two elbows with the same radius and angle can have different installed dimensions.

Segmented Bends and Nominal Radius

A segmented elbow uses a sequence of mitered joints to approximate the desired turn. Its nominal centerline radius is a design reference; the material path is composed of straight segments, not a continuous arc. The engineering drawing must state segment lengths, number of miters and final face-to-face or face-to-center dimensions.

Why Pocket Elbows Do Not Have a Conventional CLR

The pocket elbow has a cast chamber and two connecting axes rather than a single constant-radius curved passage. Choose its DN, 45°/90° configuration and flange standard, then specify the flange-to-center offsets and body envelope. Compare space claims using identical reference points, not CLR values.

Straight Tangents and Space Requirements

Check available space around adjacent equipment, insulation, bolting, supports and lifting. A replacement bend must match the existing connection planes and remove safely, even when it has a favorable nominal envelope. How to measure.

Download Current Approved Dimensions

The schedule above is a draft. Production release will identify the approved radii for each material and pipe wall, plus signed-off dimensional drawings by configuration. The technical documents page lists how to request the current revision.

Request a Radius Outside the Listed Range

Custom requests can be reviewed separately if you provide the required installed envelope and operating conditions. An enquiry does not mean the combination is buildable or suitable until engineering confirms it. Request a radius review.