Versatile Pipe Size Transition Solutions
Reducing flanges are designed to reduce the size of a pipe joint, allowing them to be connected with smaller pipes or tubes.
Versatile Pipe Size Transition Solutions
Reducing flanges are designed to reduce the size of a pipe joint, allowing them to be connected with smaller pipes or tubes.
Reducing Flanges are versatile steel flanges engineered to connect pipes of varying diameters, adhering to ASME B16.5 standards as of August 23, 2025, 05:48 PM PDT. These Pipe Size Transition Flanges facilitate seamless flow transitions in industrial systems.
Available in sizes from 1/2” to 48”, Reducing Flanges support pressure ratings from Class 150 to 2500 and temperature tolerances up to 600°C, depending on the material, making them suitable for diverse applications.
Reducing flanges are a specialty flange that are most often used on projects that require the fitting together of different sized pipes.
Our range of plate flanges can be availed in different dimensional specifications depending upon the requirements and their applications.
Crafted through forging or machining, these flanges ensure durable transitions, with coatings like 3LPE or galvanizing enhancing corrosion resistance as of August 2025. Their design optimizes industrial piping efficiency.
A reducing flange consists of a flange with one specified diameter having a bore of a different and smaller, diameter. Except for the bore and hub dimensions, the flange will have dimensions of the larger pipe size.
Compared to standard flanges, Reducing Flanges offer greater flexibility for diameter adjustments, boasting a service life of 15–35 years with proper maintenance and protective coatings.
Reducing Flanges effectively tackle challenges such as mismatched pipe sizes and flow inefficiencies, providing reliable industrial piping solutions as of August 23, 2025.
ASME B16.5 Reducing Flanges
Reducing flanges are designed for when there is a change in the pipe size.
The predominate flange (dimensions) matching the larger pipe size (NPT) but having a smaller bore matching the smaller pipe size (NPT). These flanges normally come in blind, slip-on, threaded and weld neck flanges.
They are available in all pressure classes and provide a good alternative to connecting two different sizes of pipe. This type of flange should not be used if an abrupt transition would create unwanted turbulence, such as at a pump.
There are several types of reducing flanges including weld-neck reducing flanges, slip-on reducing flanges and threaded reducing flanges.
Ideal for high-pressure, high-temperature applications such as power plants, refineries, and oil pipelines, offering superior strength and reliability.
Designed for easy installation without extensive welding, making them perfect for low-pressure systems such as water treatment and pipelines.
A welding-free option for low-pressure, low-temperature setups. Especially suitable for small-scale systems and easy maintenance requirements.
Reducing Flange can be fabricated using a reducing spool with concentric or eccentric reducer & desired flange at each end OR it could be a single flange with internal reduced bore to connect different sized fittings on either sides.
Designed for use in changing diameters in a piping system. A reducing flange consists of a flange with one specified diameter having a bore of a different and smaller, diameter
Except for the bore and hub dimensions, the flange will have dimensions of the larger pipe size.
The most common type, featuring a raised sealing surface that concentrates the bolting force on a smaller area.
Has a flat sealing surface, commonly used with cast iron flanges and for low-pressure applications.
Features a groove for metal ring gaskets (oval or octagonal), providing metal-to-metal sealing.
Features matching tongue and groove surfaces, providing self-alignment and confined gasket area.
Flange faces have to be smooth enough to ensure a tight, leak-free seal for bolted flanges.
| Flange Face Type | Flange Face Type | Flange Face Type |
|---|---|---|
| Type A: flat face | Type D: groove face | Type G: O Ring recess |
| Type B: raised face | Type E: spigot | Type H: O Ring groove |
| Type C: tongue face | Type F: recess |
| ASME B16.5 | Pipe Flanges NPS 1/2 - 24 |
| ASTM A105 | Forged Carbon Steel |
| ASTM A350 LF2 | Low-Temperature Service |
| ASTM A182 | High-Temperature Service |
| ASTM A694 | High-Pressure Transmission |
| DIN EN 1092-1 | European Standard PN 2.5-400 |
Most commonly used, forged with machined surfaces
Corrosion resistant, grades 304, 316, etc.
High-temperature and high-pressure applications
Cast iron, aluminum, brass, bronze, plastic
| Material Category | Fittings (ASTM Grade) | Flanges (ASTM Grade) | Valves (ASTM Grade) | Bolts & Nuts (ASTM Grade) |
|---|---|---|---|---|
| Carbon Steel | A234 Gr WPA | A105 | A216 Gr WCB | A193 Gr B7 A194 Gr 2H |
| A234 Gr WPB | A105 | A216 Gr WCB | ||
| A234 Gr WPC | A105 | A216 Gr WCB | ||
| Carbon Steel
Alloy (High-Temperature) |
A234 Gr WP1 | A182 Gr F1 | A217 Gr WC1 | A193 Gr B7 A194 Gr 2H |
| A234 Gr WP11 | A182 Gr F11 | A217 Gr WC6 | ||
| A234 Gr WP12 | A182 Gr F12 | A217 Gr WC6 | ||
| A234 Gr WP22 | A182 Gr F22 | A217 Gr WC9 | ||
| A234 Gr WP5 | A182 Gr F5 | A217 Gr C5 | ||
| A234 Gr WP9 | A182 Gr F9 | A217 Gr C12 | ||
| Carbon Steel
Alloy (Low-Temperature) |
A420 Gr WPL6 | A350 Gr LF2 | A352 Gr LCB | A320 Gr L7 A194 Gr 7 |
| A420 Gr WPL3 | A350 Gr LF3 | A352 Gr LC3 | ||
| Austenitic Stainless Steel | A403 Gr WP304 | A182 Gr F304 | A182 Gr F304 | A193 Gr B8 A194 Gr 8 |
| A403 Gr WP316 | A182 Gr F316 | A182 Gr F316 | ||
| A403 Gr WP321 | A182 Gr F321 | A182 Gr F321 | ||
| A403 Gr WP347 | A182 Gr F347 | A182 Gr F347 |
ASTM standards define the specific manufacturing process of the material and determine the exact chemical composition of pipes, fittings and flanges, through percentages of the permitted quantities of carbon, magnesium, nickel, etc., and are indicated by "Grade".
The usual materials of flanges include stainless steel, carbon steel, aluminum and plastic. The choice of the material largely depends on the purpose of the flange. For example, stainless steel is more durable and is necessary for heavy use. On the other hand, plastic is more feasible for use in the home because of its reasonable price and easy installation. The materials used for flanges are under the designation of the American Society of Mechanical Engineers.
The most common materials for pipe flanges (forged grades) are: ASTM A105 (carbon steel high temperature to match A53/A106/API 5L pipes), A350 Grades LF1/2/3 (carbon steel low temperature to match A333 pipes), A694 Grades F42 to F80 (high yield carbon steel to match API 5L pipe grades), ASTM A182 Grades F5 to F91 (alloy steel flanges to match A335 pipes), A182 Grade F304/316 (stainless steel flanges to match A312 SS pipes), A182 Gr. F44/F51/F53/F55 (duplex and super duplex to match A790/A928 pipes) and various nickel alloy grades (Inconel, Incoloy, Hastelloy, Monel).
The material qualities for these flanges are defined in the ASTM standards.
Metal flanges are classified from 150 to 2500 # rating for different pressure applications.
Incoloy 825 Flange
Industries Using
The basic application of the Reducing Flange to connect pumps, pipes, valves, and other equipment, often using butt welds, to make a pipework system.
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