Stainless Steel Pipe Reducer for Butt-Weld Size Transition
The stainless steel pipe reducer is a butt-weld fitting used to connect pipes with different outside diameters in a welded piping system. Nonleak supplies concentric and eccentric reducers according to ASME B16.9 dimensional requirements, with 304/304L, 316/316L and duplex stainless steel options available for different project conditions.
As part of the butt-weld fittings range, this reducer helps create a smooth transition between larger and smaller pipe sizes. It is commonly used in water supply systems, HVAC pipelines, boiler systems, chemical processing lines, industrial process piping and equipment connection areas.
Concentric vs. Eccentric Butt Weld Reducer
Choosing the correct reducer type depends on pipeline layout, flow direction and installation space. In general, a concentric reducer keeps the pipe centerline aligned, while an eccentric reducer is selected when the pipeline needs a flat side to avoid air pockets, drainage issues or clearance problems.
| Type | Description | Typical Application |
| Concentric Reducer | Reduces pipe size while keeping both pipe centerlines aligned | Vertical pipelines, pump discharge, general process piping |
| Eccentric Reducer | Reduces pipe size with one side offset to create a flat-top or flat-bottom layout | Horizontal pipelines, pump suction, drainage-sensitive systems |
Key Advantages of Using Pipe Reducers
• Smooth Size Transition: Helps connect different pipe sizes in one welded piping system.
• Concentric and Eccentric Options: Supports different routing, flow and equipment layout requirements.
• Reliable Welded Connection: Butt-weld ends provide secure pipe-to-fitting connection after proper field welding.
• Wide Material Selection: Stainless steel and duplex grades are available for corrosion resistance and strength requirements.
Engineering Features of Butt-Weld Reducers
• Seamless or Welded Construction: Available according to size, wall thickness and project requirements.
• Accurate Formed Geometry: Supports stable diameter transition and dimensional consistency.
• Consistent Wall Thickness: Helps maintain strength across the reducing section and weld areas.
• Beveled Weld Ends: Prepared for standard butt-weld installation on site.
Material Options for Stainless Steel Pipe Reducers
Available materials can be selected according to media type, working environment, corrosion requirements and project specifications.
| Material Grade | Key Properties | Typical Applications |
| 304/304L | General corrosion resistance and good formability | Water supply, HVAC, general industrial piping |
| 316/316L | Better chloride resistance and chemical compatibility | Chemical processing, coastal environments, sanitary systems |
| Duplex 2205 | Higher strength and improved corrosion resistance | Industrial pipelines, marine systems, higher-pressure services |
| Duplex 2507 | Excellent resistance to chloride stress corrosion | Highly corrosive media and demanding process environments |
ASME B16.9 Pipe Reducer Standard Compliance
Nonleak manufactures stainless steel pipe reducer products according to project specifications and applicable butt-welding fitting standards, including ASME B16.9.
• ASME B16.9 – Factory-made wrought butt-welding fittings
• ASTM A403 – Wrought austenitic stainless steel piping fittings
• EN 10253 – Butt-welding pipe fittings
• DIN 2616 – Steel butt-welding reducers, if required by project specification
• ISO / project-specific standards – Available upon request
Cross-section Diagram
Specification Table
| Nominal Pipe Size (NPS) | Outside Diameter at Bevel(mm) | End to end H(mm) | |
| Large End D | Small End D1 | ||
| 3/4 x 1/2 | 26.7 | 21.3 | 38.1 |
| 3/4 x 3/8 | 26.7 | 17.3 | 50.8 |
| 1 x 3/4 | 33.4 | 26.7 | 50.8 |
| 1 x 1/2 | 33.4 | 21.3 | 50.8 |
| 1-1/4 x 1 | 42.2 | 33.4 | 50.8 |
| 1-1/4 x 3/4 | 42.2 | 26.7 | 50.8 |
| 1-1/4 x 1/2 | 42.2 | 21.3 | 50.8 |
| 1-1/2 x 1-1/4 | 48.3 | 42.2 | 63.5 |
| 1-1/2 x 1 | 48.3 | 33.4 | 63.5 |
| 1-1/2 x 3/4 | 48.3 | 26.7 | 63.5 |
| 1-1/2 x 1/2 | 48.3 | 21.3 | 63.5 |
| 2 x 1-1/2 | 60.3 | 48.3 | 76.2 |
| 2 x 1-1/4 | 60.3 | 42.2 | 76.2 |
| 2 x 1 | 60.3 | 33.4 | 76.2 |
| 2 x 3/4 | 60.3 | 26.7 | 76.2 |
| 2 x 1/2 | 60.3 | 21.3 | 76.2 |
| 2-1/2 x 2 | 73 | 60.3 | 88.9 |
| 2-1/2 x 1-1/2 | 73 | 48.3 | 88.9 |
| 2-1/2 x 1-1/4 | 73 | 42.2 | 88.9 |
| 2-1/2 x 1 | 73 | 33.4 | 88.9 |
| 2-1/2 x 1/2 | 73 | 21.3 | 88.9 |
| 3 x 2-1/2 | 88.9 | 73 | 88.9 |
| 3 x 2 | 88.9 | 60.3 | 88.9 |
| 3 x 1-1/2 | 88.9 | 48.3 | 88.9 |
| 3 x 1-1/4 | 88.9 | 42.2 | 88.9 |
| 3 x 1 | 88.9 | 33.4 | 88.9 |
| 3-1/2 x 3 | 101.6 | 88.9 | 101.6 |
| 3-1/2 x 2-1/2 | 101.6 | 73 | 101.6 |
| 3-1/2 x 2 | 101.6 | 60.3 | 101.6 |
| 3-1/2 x 1-1/2 | 101.6 | 48.3 | 101.6 |
| 3-1/2 x 1 | 101.6 | 33.4 | 101.6 |
| 3-1/2 x 1-1/4 | 101.6 | 42.2 | 101.6 |
| 3-1/2 x 3-1/2 | 114.3 | 101.6 | 101.6 |
| 4 x 3 | 114.3 | 88.9 | 101.6 |
| 4 x 2-1/2 | 114.3 | 73 | 101.6 |
| 4 x 2 | 114.3 | 60.3 | 101.6 |
| 4 x 1-1/2 | 114.3 | 48.3 | 101.6 |
| 4 x 1 | 114.3 | 33.4 | 101.6 |
| 4 x 1/2 | 114.3 | 21.3 | 101.6 |
Dimensions and tolerances can be confirmed according to ASME B16.9, project drawings or customer-specific requirements.
For complete dimensional data for all sizes (DN10–DN2000), download our Butt-Weld Reducer Technical Documentation.
Key Applications
• Water Supply Systems: Pipe size transition in building and utility piping systems
• HVAC Systems: Diameter reduction in heating and cooling pipeline layouts
• Pump Connections: Concentric or eccentric transition for pump inlet and outlet piping
• Chemical Processing: Stainless steel reducer fittings for process media lines
• Industrial Process Piping: Size reduction for equipment connection and flow control areas
• Boiler & Heat Exchanger Systems: Pipe transition for equipment-related piping sections
Quality Assurance & Testing
• Material Traceability: Heat number and material records available on request
• Dimensional Inspection: Large-end diameter, small-end diameter, wall thickness and length checked before shipment
• Surface Finish Verification: Visual inspection for surface quality and forming defects
• Non-Destructive Testing: PT/RT/UT available according to project requirements
• Chemical Analysis: Material composition verification available when required
• Hydrostatic or Pressure Testing: Available according to application requirements
Custom Options
• Reducer Type: Concentric reducer and eccentric reducer available
• Special Materials: 304/304L, 316/316L, Duplex 2205, Duplex 2507 and other grades
• Custom Wall Thickness: Available according to pressure rating and project drawings
• End Preparation: Beveled ends, special weld preparation or customer-specified details
• Surface Treatment: Pickling, passivation, polishing or other finishing options
• Marking: Size, material grade, heat number, standard and customer logo available on request
