Pipe Reducer Offset Calculator

Inputs

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Actual outside diameter of the large end.
in
Actual outside diameter of the small end.
in
End-to-end axial length between the large and small end planes.
in
Choose concentric, a flat-side eccentric reducer, or enter a custom centerline offset.
Simple longitudinal seam allowance added to the shell area estimate.
in

Results

Default result
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Centerline offset(e)
1.0625in
Pass

Centerline shift between the large and small ends. Concentric reducers use zero; flat-side eccentric reducers use (OD1 - OD2) / 2.

Also computed

Flat-side offset((OD1-OD2)/2)1.0625in

Offset needed to keep one outside side flat: (OD1 - OD2) / 2.

Offset / flat-side offsetPass1x

1.0 means a one-side-flat eccentric reducer; 0.0 means concentric.

Long side lengthPass8.2774in

Longest side profile true length = sqrt(L^2 + (radius difference + offset)^2).

Short side length8in

Shortest side profile true length = sqrt(L^2 + |radius difference - offset|^2).

Long-short difference0.27742in

Difference between long and short side profile lengths.

Maximum side taperPass14.88°

Steepest side taper angle measured from the reducer axis.

Pipe reducer side profile axial length offset Long/short side lengths are profile true lengths. Fitting standards and shop flat patterns are separate checks.
Method notes 3 notes
  • Flat-side eccentric offset is e = (OD1 - OD2) / 2. Concentric reducers use e = 0.
  • Long side = sqrt(L^2 + (DeltaR + e)^2); short side = sqrt(L^2 + |DeltaR - e|^2).
  • This is reducer geometry only. It does not provide ASME fitting dimensions, manufacturer reducer length charts, wall thinning, end prep, weld gap, bevel, hydrostatic code acceptance, flow loss, triangulated eccentric flat patterns or shop fabrication allowances.

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