Offset steel transitions with the flat-side position defined
We supply carbon steel eccentric butt weld reducers for two-size pipe connections. The smaller opening is offset, with one straight side positioned to the piping drawing. Each item identifies the large and small pipe sizes, end walls and required length.
| Size order | Large-end NPS × small-end NPS |
|---|---|
| Material | Required carbon steel grade, including A234 WPB orders |
| Construction | Specified seamless or welded fitting route |
| Large-end connection | Required OD, wall and weld-end preparation |
| Small-end connection | Required OD, wall and weld-end preparation |
| Length and alignment | Adopted B16.9 row or approved special fitting drawing |
Check the two opening diameters and end-to-end length against the adjoining pipework. The offset column gives the ideal geometric difference between the two centerlines.
| Large × small NPS (in.) | Large-end OD (mm) | Small-end OD (mm) | End-to-end length H (mm) | Calculated offset (mm) |
|---|---|---|---|---|
| 2 × 1 | 60.3 | 33.4 | 76 | 13.45 |
| 2-1/2 × 2 | 73.0 | 60.3 | 89 | 6.35 |
| 3 × 2 | 88.9 | 60.3 | 89 | 14.30 |
| 4 × 3 | 114.3 | 88.9 | 102 | 12.70 |
| 6 × 4 | 168.3 | 114.3 | 140 | 27.00 |
| 8 × 6 | 219.1 | 168.3 | 152 | 25.40 |
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ASME B16.9 layout reference, cross-checked in the Weldbend metric reducer tables. For the ideal straight-side geometry, offset = (large OD − small OD) ÷ 2; dimensional tolerances and wall transitions remain on the accepted drawing. Wall thickness and pressure rating stay on the fitting line.
A B16.9 eccentric reducer is an identified fitting pattern. A welded transition assembled from plate, straight pipe or several cut pieces has a different fabrication and acceptance route.
The pipe class identifies the required material and wall, while the equipment detail locates the nozzle. Those references are reconciled at the reducer’s small end, fixing the bore and connection position together with the size pair.
A nonstandard taper, attachment or mixed end preparation is recorded on the fitting drawing. Those features are reviewed with the adopted design and examination requirements instead of being treated as an unmarked change to a standard reducer.
The straight side can establish a top or bottom alignment in a horizontal line. The piping drawing specifies that orientation for the process arrangement.
The table’s calculated offset comes from outside diameters. Different end walls change the inside surfaces, so an intended internal top or bottom alignment is checked on the actual fitting and weld detail.
The smaller end, adjoining flange and straight approach length form one nozzle connection. Suction conditions, nozzle loads and operating performance belong to the pump arrangement.
An eccentric fitting can form part of the selected suction layout. Flat-side orientation and the approach piping follow the pump and process detail; no universal orientation is imposed for every fluid or installation.
The offset can preserve a required top or bottom line through a size change. Support elevations, flange centers and weld-end walls are coordinated with that chosen reference.
The inspection datum follows the specified straight side and end planes. Its relationship to the small opening identifies the offset direction used on the isometric. The offset direction is measured from that datum.
Checks locate both openings and the end-face relationship against the selected reducer pattern. A project-specific flange or nozzle interface is checked from the same reference, keeping the offset direction right at fit-up.
Outside diameters, end walls and any bore transition are read together at each end. That check distinguishes outside flat-side geometry from the internal alignment required for the actual adjoining pipes.
Where the drawing requires orientation marks, their reference stays tied to the flat side and fitting item. The package carries that mark, so the receiver can place the fitting without guessing.
Orders containing both reducer patterns retain the full type and size pair on their package references. Eccentric and concentric items stay distinct even at the same end diameters and length.
Our offer states the eccentric body, two end walls and preparation before any separately requested flange, coating or fabricated assembly work. Required dimensional and material records follow those identified supply lines.
Nominal DN labels do not identify every pipe diameter series. The order states the actual ODs at both ends and the adjoining pipe standard; a DN100 designation alone can leave a 108.0 or 114.3 mm connection unresolved.
Mixed end preparation needs an identified detail for each opening. It is a separate supply requirement, not an assumption carried by the eccentric reducer name or by one wall-schedule entry.
A flange and its attachment are separate items unless included in the offer. The assembly detail identifies the flange face, bore, orientation and weld scope as well as the eccentric body.
A standard reducer supplies a pipe-size transition, not a calibrated measuring or control element. A required flow restriction needs its own hydraulic design and identified device or special fitting specification.
The reducer’s internal lining and external coating are specified separately. The fitting order identifies the coating scope, weld-end termination and any later joint treatment; the pipe’s finish description alone does not define those surfaces.
Handling follows the agreed method for the fitting or assembled spool. A machined weld lip is not a rated lifting point, and contact that damages the bevel must be assessed before the fitting is released for welding.
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Provide both pipe sizes and end walls, material, construction, required length and quantities with the flat-side position or isometric. Add the destination for an itemized fitting supply quote.