The choice between concentric and eccentric is a process decision, not a drafting habit. Concentric reducers are the default for vertical lines and general service: the cone is symmetrical, flow stays centred, and supports see a predictable load. Eccentric reducers are specified on horizontal lines — flat side up on pump suction to stop vapour pockets forming at the crown, flat side down in pipe racks so the bottom of the line stays level from size to size.
A reducer is ordered as large end x small end, with the schedule of each end where they differ. The length of the reducer is fixed by ASME B16.9 for each size combination, so the layout does not change between suppliers.
| Item | Range / Options |
|---|---|
| Types | Concentric reducers (catalogue execution) |
| Standards | ASME B16.9 (catalogue reducer record — concentric) |
| Size range | Confirmed per product at enquiry — catalogue execution: seamless concentric reducers in A234 WPB, Sch 80 – 160 |
| Wall thickness | Per end, confirmed per product at enquiry — state the schedule of each end on the enquiry |
| Materials | ASTM A234 WPB in the execution above; other grades confirmed per product at enquiry |
| Options | NACE / HIC-tested executions listed — confirm on enquiry |
Forming a True Cone
Reducers are pressed or formed so the transition is a smooth, centred cone (or a true offset cone for eccentric patterns) with wall thickness maintained through the transition — thinned or wrinkled transitions change the pressure rating of the whole joint. On an order, each end carries the schedule of the pipe it joins, and the two ends may differ. State both walls on the enquiry: whether a specific pair of end walls can be formed and bevelled as one reducer is assessed for the specific product before order.
Where Each Pattern Belongs
- Concentric — vertical lines, discharge lines, general process transitions, anywhere the centreline must stay put.
- Eccentric, flat top — horizontal pump suction lines, so gas cannot collect at the top of the reduction.
- Eccentric, flat bottom — pipe rack and sleeper runs, keeping the bottom of pipe level and drainage predictable.
Part of the Line List
Reducers bridge the sizes that elbows and tees run between. Send the complete fitting list for a line with the enquiry: the end schedules at each joint are assessed and confirmed item by item for the specific products before order — the end schedules are the detail that decides whether site welding goes smoothly.
Frequently Asked Questions
Which side should be flat on an eccentric reducer?
Flat side up (flat top) on pump suction lines so vapour cannot pocket; flat side down (flat bottom) on rack runs to keep the invert level. The catalogue execution on this site is the concentric pattern; state an eccentric requirement, with the duty or an FT / FB mark, on the enquiry and it will be assessed for the specific product before order.
Can the two ends have different schedules?
Yes — the two ends of a reducer commonly carry different schedules, a heavier large end and a lighter small end, or the reverse. State both schedules on the enquiry; the combination is assessed for the specific product before order.
Do you make swage nipples as well?
Swage nipples are a small-bore forged type named in the supplier's official classification of forged fitting types. They are not one of the catalogue executions referenced on this site, so a swage requirement is assessed for the specific product before order — the forged fittings page names the classification and the catalogue examples.
Related Products
Forged Fittings
The forged small-bore family — catalogue examples: a socket weld elbow and an NPT plug in A105.
Send Your Specification
Tell us the size, schedule or pressure class, material grade and quantity for the butt weld reducers you need. MOQ and lead time are confirmed in the quotation for your exact specification.