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What are reducers

What are reducers?

Reducer is also called reducing pipe. The diameters of pipe orifices at both ends are different. It is used to connect pipes or flanges with different diameters for reducing. The product types include concentric reducer and eccentric reducer. The centers of both ends of concentric reducer are on the same axis. It is generally used for reducing the diameter of gas or vertical liquid pipeline. The nozzle circumference at both ends of the eccentric reducer is inscribed. It is generally used for horizontal liquid pipeline to prevent effusion while reducing the diameter.

Classification of reducer

According to the shape, the reducer can be divided into concentric reducer and eccentric reducer. If the center of the ports at both ends of the reducer is in the same straight line, it is called concentric reducer. If the center of the circle is not on the same straight line, it is called eccentric reducer.

What is an eccentric reducer

An eccentric reducer is designed with two female threads of different sizes with centers so that when they are joined, the pipes are not in line with each other, but the two pieces of pipes can be installed so as to provide optimum drainage of the line.

An eccentric reducer fitting is manufactured with the smaller outlet off center to the larger end, which allows it to align with only one side of the inlet. The reducer must be installed with straight side up so that it can prevent trapping air at the pump suction. The eccentric pipe reducers allow simple connection of different sized pipes.

Buyer’s Guide
Factors to consider are as follows:

  • Whether seamless or welded or forged;
  • Size and dimension;
  • Wall thickness;
  • Construction material;
  • Forming type: press-forming for metal reducers;
  • Reducers: hot forming for carbon steel reducers;
  • Tested and verified for durability, accuracy and precision;
  • Superior strength;
  • Leak & corrosion resistance.

Materials used:

  • Rubber
  • Plastic
  • Cast Iron
  • Stainless steel
  • Copper
  • Nickel
  • Aluminum
  • Alloy etc.

Diagrammatic representation of eccentric reducer:
eccentric reducer - What are reducers
Uses of eccentric reducers:

  • Keeping big pipes and small pipes together.
  • Reducing noise and vibration at the same time.
  • Requires less installation space.
  • Absorbs pipe wall and fluid borne noise.
  • Less turbulence or material entrapment.
  • Reduces stress.
  • Protects against start-up surges.
  • Eliminates electrolysis.
  • Filled eccentric reducers are used on slurry and abrasive applications which in turn prevent the collection of material that can settle in the arches.

What are concentric reducers

Concentric reducers are used to join pipe or tube sections on the same axis. They provide an in-line conical transition between pressurized pipes of differing diameters. A pipe reducer can be a single diameter change or a multiple diameter change. The pipes cannot recognize what the outside configuration of the pipe reducer looks like. The pipe flow is affected by the inside diameter conical transition configuration which can be axially moved and externally reconfigured to provide for more economical reducer fittings. Thus, concentric reducers connect pipes of unequal size but have a common centerline. In other words, it is a type of pipe fitting with different size ends to join pipes of different diameter that joins pipe sections on the same axis.
Concentric reducers are designed with the small and large diameters on opposite ends and joined by a cone shaped transition section. They are available in both seamless and welded construction.

Materials used:

  • Stainless steel
  • Carbon steel
  • Alloy steel
  • Alloy titanium
  • Copper
  • Nickel
  • Cast Iron
  • Brass
  • Bronze
  • Rubber
  • Ceramic

Buyer’s Guide
Factors to consider are as follows: 

  • Whether seamless fittings or welded fittings or forged;
  • Size and dimension;
  • Wall thickness;
  • Material of construction;
  • Forming type: press-forming for metal reducers;
  • Reducers: hot forming for carbon steel reducers;
  • Tested for durability, accuracy and precision.

Diagrammatic representation of concentric reducer:
concentric reducer - What are reducers

How to take measurements of concentric reducers?

Get the measurements of outer diameter (OD) and inner diameter (ID) , height (H), and the total dimension (T1, T2).
Uses of concentric reducers:
Some uses of concentric reducers are as follows:

  • Concentric reducers will transition gracefully between the piping and the pump.
  • The concentric reducers help in transporting slurries or abrasive liquids.
  • They are useful in services where cavitation is present.
  • When transporting between flanges or pipes of different ratings and wear protection is necessary, concentric reducers are ideal.

Relationship among diameter, pressure and flow of reducer

Relationship between pipe diameter, pressure and flow velocity: it can be calculated by Bernoulli equation of fluid mechanics. If the pipe diameter suddenly increases and the flow remains unchanged, the pipe pressure decreases. The pipe diameter increases, the pressure decreases and the flow rate decreases. When the pipe diameter becomes smaller, the pressure increases and the flow rate increases.

Manufacturing method of reducer

The roundness of the reducer shall not be greater than 1% of the outer diameter of the corresponding end, and the allowable deviation shall be ± 3mm. The materials of reducer shall comply with SY/T 5037, GB/T 9711, GB/T 8163, American Standard ASTM A106 / A53 GRB, API 5L, apt5ct, ASTM A105, ASTM A234, ASTM A106, DIN German standards and customer requirements standards.
Reducer is a kind of pipe fitting used at pipe diameter change. The commonly used forming process is reducing pressing, expanding pressing or reducing plus expanding pressing. Stamping can also be used for reducing pipes of some specifications.

Reducing / expanding forming

The reducing forming process of reducing pipe is to put the pipe blank with the same diameter as the large end of reducing pipe into the forming die, and press along the axial direction of the pipe blank to make the metal move along the die cavity and shrink. According to the size of reducing pipe, it can be divided into one-time pressing forming or multiple pressing forming. As shown in the schematic diagram of reducing forming of concentric reducer.
Expanding forming is to expand the diameter of the tube blank along the inner diameter of the tube blank with an internal die. The expanding process mainly solves the problem that the reducer with large variable diameter is not easy to form through reducing. Sometimes, the expanding and reducing methods are combined according to the forming needs of materials and products.
In the process of reducing or expanding deformation pressing, cold pressing or hot pressing is determined according to different materials and reducing conditions. Generally, cold pressing shall be adopted as far as possible, but hot pressing shall be adopted for severe work hardening caused by multiple diameter changes, wall thickness deviation or alloy steel materials.

Stamping forming

In addition to using steel pipe as raw material to produce reducer, some specifications of reducer can also be produced by steel plate stamping process. The shape of the die used for drawing refers to the size design of the inner surface of the reducer, and the blanking steel plate is stamped and stretched by the die.

Application of eccentric reducer and concentric reducer

How to apply eccentric reducer

The diameter of the orifices at both ends of the eccentric reducer is different. It is used to connect pipes or flanges with different diameters for diameter reduction. The orifices at both ends of the eccentric reducer are centered on the same axis. When reducing, if the position of the pipe is calculated based on the axis, the position of the pipe remains unchanged. It is generally used for reducing the diameter of gas or vertical liquid pipes. The nozzle circumference at both ends of eccentric reducer is inscribed, which is generally used for horizontal liquid pipeline. When the tangent point of the pipe orifice of the eccentric reducer is upward, it is called top flat installation. It is generally used for the pump inlet to facilitate exhaust. When the tangent point is downward, it becomes bottom flat installation. It is generally used for the installation of the regulating valve and exhaust. Eccentric reducers are conducive to fluid flow and have little interference with fluid flow pattern during reducing. Therefore, concentric reducers are used for reducing gas and vertically flowing liquid pipelines. Because one side of the eccentric reducer is flat, which is conducive to exhaust or liquid discharge and convenient for start-up and maintenance, the liquid pipeline installed horizontally generally uses eccentric reducer.

How to apply concentric reducer

Concentric reducers will not produce corrosion, pitting, corrosion or wear It can give full play to its good role and performance in the industry. Concentric reducer plays an important role and performance in certain industries and fields, and shows certain advantages and characteristics in use. Concentric reducer is also one of the strongest metal materials for construction. Concentric reducer steel resistant to weak corrosive media such as air, steam and water and chemical corrosive media such as acid, alkali and salt Also known as stainless acid resistant steel In practical application, the steel resistant to weak corrosion medium is often called concentric reducer, while the steel resistant to chemical medium is called acid resistant steel. Due to the difference in chemical composition between the two, the former is not necessarily resistant to chemical medium corrosion, while the latter is generally stainless.

Whether the eccentric reducer at the inlet of centrifugal pump is installed on the top or bottom?

The horizontal eccentric reducer at the inlet of centrifugal pump is generally arranged at the top level, but when the reducer is directly connected with the upward bend elbow, the bottom level arrangement can be adopted. The reducer shall be close to the pump inlet. The reason for top flat installation is to prevent gas from accumulating in the eccentric reducer and entering the centrifugal pump, resulting in cavitation damage to the pump. When the inlet diameter of the horizontal suction centrifugal pump is changed, the top flat installation is adopted for the pipe from bottom to top, and the bottom flat installation is adopted for the pump from top to bottom (top flat installation is also adopted to prevent gas accumulation at the pump inlet). The bottom flat installation is adopted for the medium with impurities and the suction speed is lower than the impurity sedimentation speed. The principle is that no air bag is formed.
It is generally “flat at the bottom from the top and flat at the top from the bottom”.

Source: China Pipe Reducer Manufacturer – Yaang Pipe Industry Co., Limited (

(Yaang Pipe Industry is a leading manufacturer and supplier of nickel alloy and stainless steel products, including Super Duplex Stainless Steel Flanges, Stainless Steel Flanges, Stainless Steel Pipe Fittings, Stainless Steel Pipe. Yaang products are widely used in Shipbuilding, Nuclear power, Marine engineering, Petroleum, Chemical, Mining, Sewage treatment, Natural gas and Pressure vessels and other industries.)

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