Classification of Reducers

Reducers (also known as reducer couplings) are classified according to highly consistent dimensions and logical criteria, focusing on key attributes including structural characteristics, manufacturing process, connection method, material properties, pressure rating, and diameter change direction. Different classification dimensions correspond to different application scenarios and technical requirements. The systematic and clear classification system is as follows:

I. Classification by Core Structural Characteristics

(The most basic classification, which determines fluid adaptability)

1. Concentric Reducer
   • Structural feature: The axes of both ends are completely coincident, forming a symmetrical conical (funnel) shape, with wall thickness tapering uniformly from the large end to the small end.
   • Key characteristics: Fluid flows along the central axis with uniform resistance distribution and no lateral pressure difference.
   • Application scenarios: Vertical pipelines, single-phase gas/liquid pipelines (such as power plant steam risers, vertical water supply sections), and straight pump discharge pipelines requiring axis alignment.
2. Eccentric Reducer
   • Structural feature: 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 small end aligned with bottom of large end) and flat-top type (top of small end aligned with top of large end). The flat-bottom type is dominant in industry.
   • Key characteristics: The flat-bottom design eliminates bottom steps and avoids liquid or solid accumulation.
   • Application scenarios: Horizontal pipelines, pipelines for fluids containing solid particles/slurries (such as crude oil transmission, slurry pipelines), and gas pipelines (to prevent safety hazards caused by liquid accumulation).

II. Classification by Connection Method

(Matching pipeline installation technology)

1. Butt Weld ReducerPre-fabricated bevels at both ends for welding connection with pipelines. Features strong tightness and high pressure resistance; the mainstream type for industrial pipelines (DN ≥ 50).
2. Flanged ReducerWith flanges at one or both ends for bolted connection. Easy to disassemble; used for equipment connections (inlets and outlets of pumps, heat exchangers, etc.).
3. Threaded ReducerSmall size (DN ≤ 50) with threaded ends for screwed connection without welding. Suitable for low-pressure civil pipelines (domestic water pipes, household gas pipes).
4. Socketed ReducerExclusive to plastic materials, with socket-and-spigot structure, connected by adhesive (PVC) or hot fusion (PPR). Used for civil water supply and drainage.

III. Classification by Material Properties

(Matching conveyed medium and service environment)

1. Metal Reducers
   • Carbon steel reducers (20#, Q235B): For non-corrosive media (water, oil, steam), low cost.
   • Stainless steel reducers (304, 316L): For corrosive media (acid, alkali, seawater) and hygienic applications (food, pharmaceutical).
   • Alloy steel reducers (12Cr1MoVG): For high-temperature and high-pressure media (power plant steam, chemical cracking gas).
   • Cast iron reducers (HT200, QT450-10): For low-pressure gravity flow pipelines (drainage in old buildings).
   • Copper reducers (T2, H62): For pipelines requiring high thermal conductivity (air conditioning, domestic hot water).
2. Non-Metal Reducers
   • PVC/UPVC reducers: Acid and alkali resistant, for low-pressure civil drainage.
   • PPR reducers: Hygienic and non-toxic, for domestic hot and cold water systems.
   • PE reducers (PE80/PE100): For buried gas and water supply networks.
   • FRP reducers: For highly corrosive media (concentrated nitric acid, hydrochloric acid).

IV. Classification by Pressure Rating

(Matching pressure resistance requirements of piping systems)

1. Low-pressure ReducersPN ≤ 1.6 MPa / Class 150, used in civil water supply/drainage, household gas, farmland irrigation, etc.
2. Medium-pressure ReducersPN 2.5~6.3 MPa / Class 300~600, used in urban gas mains, chemical process pipelines, heating networks, etc.
3. High-pressure ReducersPN ≥ 10.0 MPa / Class 900~2500, used in long-distance oil pipelines, power plant main steam pipelines, oil and gas production pipelines, etc.

V. Classification by Diameter Change Direction

1. ReducerDiameter changes from large to small, used to increase fluid velocity (e.g., reactor feed pipes, fire sprinkler branches).
2. ExpanderDiameter changes from small to large, used to reduce fluid velocity and stabilize pressure (e.g., pump discharge pipelines, ends of steam pipelines).

VI. Classification by Nominal Diameter

1. Small-size ReducersDN ≤ 100 (or below 4 inches), mainly connected by injection molding, threading or socketing. Used in civil or small-flow industrial pipelines.
2. Medium-size ReducersDN 100~DN 600 (4″~24″), mainly formed by press welding or seamless extrusion. Used in industrial medium-pressure pipelines.
3. Large-size ReducersDN ≥ 600 (above 24 inches), mainly fabricated by rolled welding or casting. Used in large-flow low-pressure pipelines for municipal and mining applications.

Core Classification Logic

All classification dimensions of reducers ultimately serve accurate selection. The appropriate reducer type is chosen based on pipeline orientation (horizontal/vertical), fluid properties (single-phase/two-phase, particle-containing/pure), pressure, temperature, and installation requirements, to ensure safe, efficient and economical fluid transportation.