Tesco Steel & Engineering manufactures reducing flanges — a flange that carries the outside diameter, bolt circle, and thickness of the larger pipe but a smaller bore, so it joins two different pipe sizes at one flanged joint without a separate reducer. Available as weld-neck, slip-on, and threaded reducing flanges to ASME B16.5. A105, SS 304/316/321, Duplex, Monel, Inconel, and Hastelloy. Class 150 to 2500, PN1 to PN400. ISO 9001:2015 certified. Made in India.
Stainless Steel & Alloy Reducing Slip-On Flange
Reducing flanges and expander flanges are the two ways to change pipe size at a flange. Tesco Steel & Engineering manufactures reducing flanges to ASME B16.5 in the full material range — see the flange dimensions charts and our standard weld-neck and slip-on flanges.
| Type | Connection to Smaller Pipe | Use |
|---|---|---|
| Weld-Neck Reducing | Tapered hub butt-welded to the smaller pipe | Higher-pressure / cyclic service; best flow |
| Slip-On Reducing | Smaller pipe slips into the bore, fillet-welded | Lower-pressure lines; easier fit |
| Threaded Reducing | Smaller pipe screwed into a tapered thread | Small-bore, no-weld connections |
| Solution | How It Changes Size | Best For |
|---|---|---|
| Reducing Flange | Large flange pattern with a smaller bore — one fitting | Stepping down to a smaller pipe at a flanged joint |
| Reducer + Standard Flange | Concentric reducer welded to a flange — two parts | Where layout allows & flow must stay smooth |
| Expander Flange | Small pipe welded, hub expands up to a larger flange | Stepping up to a larger flange / equipment |
A reducing flange is the simplest way to step down to a smaller pipe at a flange; an expander flange steps up; a reducer-plus-flange is used where a smoother flow transition or larger size change is needed.
| Reducing Flanges are available in the following specifications: | |
|---|---|
| Size | 1/2"NB to 56"NB |
| Class | 150#, 300#, 3000#, 6000#, 9000# |
| Sch (Schedule) | XS, XXS, STD & Schedule 20, 40, 80, 160 |
| Pressure Ratings | PN 1 - PN 400 |
| Stainless Steel Reducing Flange | ASTM A 182 F - 304 / 304H / 304L / 316 / 316H / 316L / 316Ti, 309, 310, 317L, 321, 347, 904L |
| Duplex Steel Reducing Flange | ASTM A 182 - F 51, F 53, F 55 |
| Alloy Steel Reducing Flange | ASTM A 182 - F5, F9, F11, F21, F22 & F91 |
| Carbon Steel Reducing Flange | ASTM A 105 |
| Low Temp. Carbon Steel Reducing Flange (LTCS Reducing Flange) | A 350 LF2 |
| Copper Nickel (Cu-Ni) Reducing Flange | C70600, 90/10, C71500, 70/30, C71640 |
| Nickel Reducing Flange | UNS N02200, UNS N02201 |
| Monel Reducing Flange | UNS N04400, UNS N05500, Alloy 20 |
| Inconel Reducing Flange | UNS N06600, UNS N06601, UNS N06625, UNS N08800, UNS N08810, UNS N08825 |
| Hastelloy Reducing Flange | UNS N10276, UNS N06022, UNS N10665, UNS N06455 |
| Titanium Reducing Flange | Gr. 1, Gr. 2, Gr. 3, DTH 3.7035, DTH 3.7055 |
| Other Services | Hot Dip Galvanized (GI) Reducing Flange Sand Blasting on Reducing Flange Shot Peening on Reducing Flange Epoxy Coating on Reducing Flange FBE Coating on Reducing Flange |
Joins two pipe sizes in a single flange — no separate reducer — saving a component, a weld, and space.
Weld-neck, slip-on, and threaded reducing flanges for welded or screwed connection to the smaller pipe.
A105, LTCS, SS 304/316/321, Duplex, Monel, Inconel, and Hastelloy for corrosive and high-temperature service.
Large-end OD, bolt circle, and facing to ASME B16.5 so it bolts to standard mating flanges and gaskets.
Full pressure-class range with RF, RTJ, or FF facings for utility through to high-pressure lines.
Made to ASME B16.5 or your drawing — large size, reduced bore, type, and material — certified with EN 10204 3.1 MTC.
| Material | Properties | Typical Use |
|---|---|---|
| A105 Carbon Steel / A350 LF2 (LTCS) | Strong, economical; LF2 for low temp | Non-corrosive & low-temperature lines |
| SS 304 / 316 / 321 | Good corrosion resistance; 321 high-temp | Process, chemical & high-temperature service |
| Duplex 2205 / Super Duplex 2507 | High strength & chloride resistance | Seawater & offshore service |
| Monel 400 / Inconel | Excellent in HF, marine & high-temp | HF, seawater & high-temperature service |
| Hastelloy | Superior acid resistance | Aggressive chemical service |
| Industry | Typical Use | Why Reducing Flange |
|---|---|---|
| Oil & Gas | Size changes at flanged joints | One-piece step-down; full material range |
| Refinery & Petrochemical | Process & equipment connections | Saves a reducer; alloy grades |
| Power Generation | Steam & water-line size changes | SS 321 / alloy steel reducing flanges |
| Chemical Plants | Corrosive-line reductions | Monel / Inconel / Hastelloy |
| Water & Utilities | Pipe size transitions | Economical one-piece step-down |
| Pumps & Equipment | Connecting smaller branch lines | Compact flanged size change |
| Shipbuilding & Marine | Compact pipe routing | SS / Duplex corrosion resistance |
| Fertilizer & Process | Header-to-branch connections | Standard & custom sizes |
Q1. What is a reducing flange?
A reducing flange joins two different pipe sizes at a flanged connection. It has the outside diameter, bolt circle, and thickness of the larger flange but a smaller bore sized for the smaller pipe, so it bolts to the large mating flange while connecting to the smaller pipe — making the size change in one flange instead of a separate reducer plus flange.
Q2. What types of reducing flange are available?
Weld-neck reducing (tapered hub butt-welded to the smaller pipe, for higher pressure and best flow), slip-on reducing (smaller pipe slips into the bore and is fillet-welded), and threaded reducing (smaller pipe screwed into a tapered thread, for no-weld connections). All are made to ASME B16.5.
Q3. What is the difference between a reducing flange and an expander flange?
A reducing flange steps a line down — large flange pattern, smaller bore — to connect a smaller pipe. An expander flange steps a line up — the small pipe is welded and the hub expands out to a larger flange face. Both change pipe size at a flange; the choice depends on whether you are reducing or enlarging.
Q4. When should I use a reducing flange instead of a reducer plus a flange?
Use a reducing flange to save a component, a weld, and space when stepping down at a flanged joint and a smooth flow transition is not critical. Use a concentric reducer plus a standard flange where the flow must stay smooth (e.g. near a meter run) or where the size change is large.
Q5. How is a reducing flange sized?
By two sizes: the larger flange size (which sets the OD, bolt circle, thickness, and rating) and the reduced bore for the smaller pipe. Both must be specified, along with the type (WN/SO/threaded), class, and facing, so the flange bolts to the large mating flange and connects to the smaller pipe.
Q6. What classes, facings, and materials are available?
Class 150 to 2500 and PN1 to PN400, with RF, RTJ, or FF facings to ASME B16.5, in A105/LTCS, SS 304/316/321, Duplex, Monel, Inconel, and Hastelloy. The class, facing, and material are chosen for the service and the mating flange.
Q7. Does a reducing flange affect flow?
The bore changes abruptly at the flange, which creates some turbulence and pressure drop compared with a gradual concentric reducer. For most lines this is acceptable; where a smooth transition is needed (such as upstream of a flow meter) a reducer-plus-flange or expander flange is preferred.
Q8. Can reducing flanges be supplied to our drawing and certified?
Yes. We supply reducing flanges to ASME B16.5 or your drawing — large flange size, reduced bore, type, class, facing, and material — with EN 10204 3.1 material test certificates on request. Send your two pipe sizes and service conditions for a quote.