Concentric and eccentric butt weld reducers to ASME B16.9 in carbon steel, alloy steel and stainless steel, from 1/2 inch to 48 inch.
- Standard: ASME B16.9, ASME B16.25, ASTM A234, ASTM A403
- Grades: WPB, WP5, WP11, WP22, WP91, WP304, WP304L, WP316, WP316L, WP321
Specifications
| Outer diameter | 1/2" x 3/8" - 48" x 40" |
|---|---|
| Wall thickness | SCH 10 - XXS, matching pipe |
| Schedule | SCH 10 to XXS, STD, XS |
| Length | End to end per ASME B16.9 |
| Ends | Bevelled to ASME B16.25 |
| Surface treatment | Black, varnish, galvanized, epoxy coated |
| Manufacturing process | Seamless or welded, formed |
| Pressure rating | Per ASME B16.9 wall thickness and ASME B31.3 |
Concentric versus Eccentric Reducers
A concentric reducer has its two ends on a common centerline, so the reduction is symmetrical. It is used in vertical lines and in horizontal lines where neither the top nor the bottom elevation must be maintained. An eccentric reducer has its two ends offset, so one side of the reducer is flat, which allows it to keep either the bottom of the line or the top of the line at a constant elevation. The orientation of the flat side matters: in a pump suction line the flat side is normally placed on the bottom so the line stays self-draining and no gas pocket forms. In a line carrying liquid with entrained gas or in a liquid seal arrangement, the flat side may be placed on top so gas can escape. Specifying the flat side orientation incorrectly is a common error that can cause pump cavitation or trapped gas.
Sizing and Ordering
A reducer is designated by large end size by small end size, for example 6 x 4 inch. The wall thickness or schedule must be stated for each end, since the two ends frequently have different schedules and the fitting must match the adjoining pipe at both ends. The overall length, or end to end dimension, is fixed by ASME B16.9 for each size combination, so it does not need to be specified unless a non-standard length is required. For eccentric reducers the orientation of the flat side should be indicated on the order or on a drawing, since the fitting cannot be rotated after installation without cutting it out.
When should I use an eccentric reducer instead of a concentric one?
Use an eccentric reducer whenever one side of the line must stay at a constant elevation. The classic case is a pump suction line, where the flat side is placed on the bottom so the line drains and no gas pocket forms at the reducer. Use a concentric reducer in vertical lines, or in horizontal lines where elevation change does not matter, since it is usually cheaper and easier to align.
Do reducers come with the same schedule at both ends?
Not necessarily. Reducers are made with the same schedule at both ends, or with different schedules to match the adjoining pipe at each end. Since the schedule of the large pipe and the small pipe often differ, state the schedule required at each end when ordering. If only one schedule is stated, the mill may supply that schedule at both ends, which could create a mismatch at the weld.
Materials
- Carbon steel
- Alloy steel
- Stainless steel
Typical applications
- Pipeline size transitions
- Pump suction and discharge piping
- Refinery and petrochemical piping
- Steam and condensate lines
- Horizontal piping where self-draining is required
Inspection & testing
- Dimensional inspection per ASME B16.9
- Radiographic or ultrasonic examination
- PMI on alloy and stainless steel
- Hardness testing
- Third-party inspection (SGS, BV, TUV)
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