Reducers can be classified according to core dimensions such as structural form, manufacturing process, connection method, material, and pressure rating. Different classifications correspond to different application scenarios and technical requirements. The systematic and clear classification system is as follows:
I. Classification by Structural Form
(The most important classification, which determines fluid flow characteristics)
1. Concentric Reducer
- Structural Features: The axes of both ends are completely coincident, forming a symmetrical conical shape (similar to a funnel), with wall thickness tapering uniformly from the large end to the small end.
- Core Advantages: Fluid flows along the central axis with uniform resistance distribution and no risk of local liquid accumulation.
- Limitations: When transitioning from a large diameter to a small diameter, low-pressure vortex easily forms at the center (which may cause gas locking in gas-liquid two-phase flow).
- Application Scenarios: Vertical pipelines, single-phase gas/liquid pipelines (such as power plant steam pipelines, water supply risers), and straight pump discharge sections requiring axis alignment.
2. Eccentric Reducer
- Structural Features: The axes of both ends are parallel but not coincident (the axis of the small end is offset to one side). It is divided into flat-bottom type (bottom of the small end aligned with the bottom of the large end) and flat-top type (top of the small end aligned with the top of the large end). The flat-bottom type is dominant in industry.
- Core Advantages: The flat-bottom eccentric reducer has no bottom step in horizontal pipelines, preventing liquid accumulation, material buildup, or solid particle deposition.
- Limitations: Lateral pressure difference exists during fluid flow, and resistance is slightly higher than that of concentric reducers.
- Application Scenarios: Horizontal pipelines, pipelines for fluids containing solid particles/slurries (such as crude oil transmission, mineral slurry pipelines), and gas pipelines (to prevent explosions caused by liquid accumulation).
II. Classification by Connection Method
(Matching pipeline installation technology)
1. Butt Weld Reducer
- Structural Features: Pre-fabricated bevels (V-type/U-type) at both ends for direct welding with pipelines.
- Core Advantages: Strong tightness, high pressure resistance, suitable for high-temperature and high-pressure conditions.
- Application Scenarios: Mainstream connection method in industry (medium and high-pressure pipelines with DN ≥ 50).
2. Flanged Reducer
- Structural Features: Flanges (raised face / male-and-female face) at one or both ends, connected to pipelines/equipment by bolts.
- Core Advantages: Easy disassembly and convenient equipment maintenance (such as inlets and outlets of pumps, heat exchangers).
- Application Scenarios: Equipment connections and pipelines requiring frequent maintenance (DN50~DN300).
3. Threaded Reducer
- Structural Features: Small-size reducers (DN ≤ 50) with threads (G/NPT) at both ends for screwed connection.
- Core Advantages: Convenient installation without welding.
- Application Scenarios: Low-pressure civil pipelines (domestic water pipes, household gas pipes).
4. Socketed Reducer
- Structural Features: Made of plastic materials (PVC/PPR), with a socket at one end and a spigot at the other, connected by adhesive or hot fusion.
- Application Scenarios: Civil water supply and drainage pipelines (DN15~DN100).
III. Classification by Material
(Matching conveyed medium and service environment)Consistent with the material system of tees and elbows, mainly divided into:
- Metal Reducers: Carbon steel (20#, Q235), stainless steel (304, 316L), alloy steel (12Cr1MoVG), cast iron, copper.
- Non-Metal Reducers: PVC/UPVC, PPR, PE (PE80/PE100), FRP.
IV. Classification by Pressure Rating
(Matching pressure resistance requirements of piping systems)
- Low-pressure Reducers: PN ≤ 1.6 MPa / Class 150 (civil water supply/drainage, household gas).
- Medium-pressure Reducers: PN 2.5~6.3 MPa / Class 300~600 (urban gas mains, chemical process pipelines).
- High-pressure Reducers: PN ≥ 10.0 MPa / Class 900~2500 (long-distance oil pipelines, power plant steam pipelines).
V. Classification by Diameter Change Direction
- Reducer (Conical Reduction): Large end → small end (diameter decreases, e.g., DN200×DN100), used to increase fluid velocity.
- Expander (Conical Enlargement): Small end → large end (diameter increases, e.g., DN100×DN200), used to reduce fluid velocity and stabilize pressure.
Core Principles of Classification
The essence of reducer classification is accurate selection — to choose the corresponding structure and process type according to pipeline orientation (horizontal/vertical), fluid type (single-phase/two-phase, particle-containing/pure), pressure rating, and installation requirements, so as to ensure safe and efficient fluid transportation.
