What is a concentric reducer?

The primary structural feature of a concentric reducer is its concentric design. This structure ensures that the flow direction of the fluid remains unchanged as it passes through the reducer, maintaining a relatively stable flow state. The characteristic of a concentric reducer lies in the fact that the centerlines of its two ends (the larger and smaller openings) are perfectly aligned. When viewed from the side, it exhibits a symmetrical conical structure, resembling a bell or funnel. This design ensures smooth fluid transition within the pipeline, minimizing the generation of vortices and turbulence, making it particularly suitable for applications with stringent requirements for fluid flow.

Differences Between Concentric and Eccentric Reducers

The primary difference between concentric reducers and eccentric reducers lies in the position of the centerlines at both ends: the centerlines of a concentric reducer are aligned on the same straight line, forming a symmetrical conical shape, suitable for vertical pipes or applications requiring high fluid symmetry; whereas the centerlines of an eccentric reducer are not aligned on the same straight line, with one side transitioning in a straight line, commonly used in horizontal pipes to prevent gas accumulation or liquid stagnation.

Concentric Reducer Specification

Features of Stainless Steel Concentric Reducers

High Corrosion Resistance: The composition of stainless steel makes it resistant to corrosion from a wide range of chemical media, making it ideal for use in industries such as the chemical, petroleum, and food processing.

Hygienic and Non-Toxic: The smooth surface resists bacterial growth and is easy to clean, meeting food-grade and sanitary standards.

High Strength and Durability: Withstands high pressures and temperatures for a long service life.

Excellent Weldability: Easily welds to stainless steel pipes, creating a tightly sealed piping system.

Concentric Reducer Weight Calculation Formula

The steel pipe reducer weight formula is 0.02466 * S <(D+d)/2 – S> * H / 1000
D = Large end diameter in mm.
d = Small end diameter in mm.
S = Large end Thickness in mm.
H = Height from end to end.

If we want to calculate the weight by formula, we need to know above 4 factors. Where can you get them? Usually we get the them from pipe reducer dimensions.

ASME B16.9 Concentric Reducer Dimension

ASME B16.9 Concentric Reducer Weight

Stainless Steel Concentric Reducer Manufacturing Process:

1. Hot Rolling (Extruded Seamless Steel Tubing): Round tube blank → Heating → Piercing → Three-roll oblique rolling, continuous rolling, or extrusion → De-burring → Sizing (or reducing diameter) → Cooling → Straightening → Hydrostatic testing (or non-destructive testing) → Marking → Storage

Hot rolling is a processing method performed above the recrystallization temperature of the metal material. For stainless steel, this typically means temperatures exceeding 1000°C. The stainless steel tube blank is heated to high temperatures and then repeatedly rolled through rollers to reduce its diameter and thin its wall thickness, ultimately forming the desired-sized tubing.

2. Cold drawing (rolling) seamless steel tubes: Round tube blank → Heating → Piercing → Heading → Annealing → Acid washing → Oil coating (copper plating) → Multiple cold drawing (cold rolling) → Blank tube → Heat treatment → Straightening → Hydrostatic testing (inspection) → Marking → Storage.

Cold drawing is performed below the recrystallization temperature, typically at room temperature. Using hot-rolled tubes as raw material, the tubes are drawn through a die to further reduce their diameter and wall thickness. To ensure smooth drawing operations, annealing is typically performed between drawing intervals.

How to make a reducer？

Reducers are pipe fittings designed to meet pipe diameter requirements. Common forming processes include reducing/expanding, or both. Stamping can also be used for certain reducer sizes.

a. Reducing/Expanding Forming

The reducing/expanding forming process involves placing a tube blank of the same diameter as the larger end of the reducer into a die. Pressing is performed along the tube blank’s axial direction, causing the metal to move along the die cavity and shrink. Depending on the size of the reduced diameter, this process can be performed in a single press or multiple presses.

b. Stamping

In addition to using steel pipe as raw material to produce reducers, some sizes can also be produced using steel plate using a stamping process. The die used for drawing is designed based on the reducer’s inner surface dimensions. The blanked steel plate is then stamped and stretched using the die.

Common Applications

Chemical and petrochemical industries

Food and beverage processing

Pharmaceutical industry

Water treatment and desalination

Oil and gas transportation

Pulp and paper and sugar industries

Marine and offshore engineering

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Concentric and Eccentric Reducer are two types of reducer. Reducer is fittings to change the pipe diameter in the same direction. There are two types: concentric reducer, usually used for vertical pipelines. Eccentric reducer, usually used for horizontal pipelines.

Concentric and Eccentric Reducer

Eccentric Reducer

In horizontal pipelines, if use eccentric reducer, there are two installations: top level TF (Tops flat) and bottom flat bf (bottom flat). For example:

1. Bottom Flat Eccentric Reducer is common in the pipe gallery, to maintain the line on the same elevation. If you use a concentric reducer or a top flat eccentric reducer, the Tube gallery support will be changed.
2. The Top Flat Eccentric Reducer is more suitable for the suction line of the pump, the top level of the pipeline, the bubble will not accumulate in the pipeline.

Some cartographic staff often indicate the variable T of the pipeline center line in the drawing. When the eccentric reducer is used in the vertical pipeline, the orientation of the eccentric reducer is also a very important problem. See below drawing

Reducer Drawing

The length of the reducer has little relation with the change of pipe diameter. Therefore, some of the larger diameter of the reducer may cause fluid sudden change. For example: 6 “-2 1/2” of the reducer length is 140 mm, in such a short distance, pipe diameter is from 168.3 mm to be 73 mm. In the design phase of a piping system, piping design engineers will certainly consider such issues.

The alternative is to increase the use of the reducer, for example:

• NPS 6 – NPS 5 (L=140 mm)
• NPS 5 – NPS 4 (L=127 mm)
• From NPS 4 to NPS 3½, L=102 mm
• From NPS 3½ to NPS 3, L=102 mm

In the above scenario, the total distance from 6 “to 2 1/2” is extended to 573 mm, and the smooth transition of the fluid is ensured. In practice, similar examples may never have occurred.

Reducer Weight Chart

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