Concentric and eccentric reducers
Reducers join pipes of two sizes. Concentric reducers keep a common centreline; eccentric reducers keep one side flat.
About reducers
Use concentric reducers in vertical lines and most process runs. Use eccentric reducers on pump suctions (flat side up, to avoid trapping air) and on pipe racks where the bottom of pipe must stay level.
Length H is fixed by the large-end size in ASME B16.9.
- Concentric reducers
- Eccentric reducers
- Swage nipples (MSS SP-95)
- Fabricated reducers for large sizes
What the dimensions mean
Every letter used in our tables, marked on the drawing.
- HOverall length, end to end
- ODLarge-end and small-end outside diameters
Need reducers? Get a price from the manufacturer.
Send size, schedule, grade and quantity. We usually reply within one working day.
Dimension finder
Pick a size to see the values on the drawing, then send it to us for a price.
Fitting dimension finder
Choose a fitting and size. The letters on the drawing show exactly what each ASME B16.9 dimension measures.
Dimensions in mm per ASME B16.9 (short stub end per MSS SP-43).
Dimension table
| Size | OD at bevel | Reducer H | |
|---|---|---|---|
| 3/4" (20 NB) | 26.7 | 38 | Quote |
| 1" (25 NB) | 33.4 | 51 | Quote |
| 1-1/4" (32 NB) | 42.2 | 51 | Quote |
| 1-1/2" (40 NB) | 48.3 | 64 | Quote |
| 2" (50 NB) | 60.3 | 76 | Quote |
| 2-1/2" (65 NB) | 73.0 | 89 | Quote |
| 3" (80 NB) | 88.9 | 89 | Quote |
| 3-1/2" (90 NB) | 101.6 | 102 | Quote |
| 4" (100 NB) | 114.3 | 102 | Quote |
| 5" (125 NB) | 141.3 | 127 | Quote |
| 6" (150 NB) | 168.3 | 140 | Quote |
| 8" (200 NB) | 219.1 | 152 | Quote |
| 10" (250 NB) | 273.0 | 178 | Quote |
| 12" (300 NB) | 323.8 | 203 | Quote |
| 14" (350 NB) | 355.6 | 330 | Quote |
| 16" (400 NB) | 406.4 | 356 | Quote |
| 18" (450 NB) | 457.2 | 381 | Quote |
| 20" (500 NB) | 508.0 | 508 | Quote |
| 24" (600 NB) | 609.6 | 508 | Quote |
| 30" (750 NB) | 762.0 | 610 | Quote |
| 36" (900 NB) | 914.0 | 610 | Quote |
Dimensions in mm per ASME B16.9 (stub-end short pattern per MSS SP-43).
Grades
| Material | Fitting specification | Notes | |
|---|---|---|---|
| Carbon steel | ASTM A234 WPB, WPC | Seamless and welded | Quote |
| Low-temperature carbon steel | ASTM A420 WPL6, WPL3 | Impact tested to -46°C (WPL6) | Quote |
| High-yield pipeline | MSS SP-75 WPHY 42 to 70 | For API 5L line pipe | Quote |
| Chrome-moly | ASTM A234 WP5, WP9, WP11, WP22, WP91 | Normalised and tempered | Quote |
| Austenitic stainless | ASTM A403 WP304/304L, WP316/316L, WP321, WP347, WP310S | Class S, W and WX | Quote |
| Super-austenitic | ASTM A403 WP904L, WPS31254 (guide) | Seamless and welded | Quote |
| Duplex and super duplex | ASTM A815 WPS31803, WPS32205, WPS32750, WPS32760 (guide) | Ferrite and A923 tests on request | Quote |
| Titanium | ASTM B363 WPT1, WPT2, WPT7, WPT12 (guide) | Grade 5 on enquiry | Quote |
| Nickel alloys | ASTM B366 WPNCMC, WPNICMC, WPHC276, WPNC, WP20CB (guide) | Seamless and welded | Quote |
| Copper-nickel | 90/10 and 70/30 to EEMUA 146 or project spec (guide) | Seamless and welded | Quote |
Ends, marking, testing and packing
Ends and bevels
Bevelled to ASME B16.25, normally 37.5° ± 2.5° with a 1.6 mm root face, or to your weld-end detail. Wall thickness matched to the pipe schedule.
Marking
Each fitting is marked with Teshi mark, grade, size, schedule, heat number and standard, traceable to its material certificate.
Testing
- Dimensional and visual inspection
- PMI on alloy fittings
- RT of welded fittings (WX class), IGC for stainless
- Impact tests for WPL6 and WPHY
Finish and packing
Stainless and nickel alloys solution annealed, pickled and passivated. Carbon steel varnished or painted. Packed in wooden cases, seaworthy for export.
Questions buyers ask
When should I use an eccentric reducer?
On pump suctions, flat side up, so air is not trapped; and on pipe racks where the bottom of pipe must stay level.
Get a quotation from the manufacturer
Send your BOQ, drawing or tender reference. You deal directly with the manufacturer.
- Reply from our estimation team, usually within one working day
- Carbon steel to titanium on one order
- EN 10204 3.1 or 3.2 certificates, third-party inspection welcome
- ISO 9001:2015 certified and IBR approved, since 1971
Drawings and BOQ spreadsheets are easiest by email. Mention your project name.