Detailed introduction of the reducer

Pipe reducer for connection between pipes of two different pipe diameters. According to the shape, it is divided into two types: concentric small head and eccentric reducer. The different diameter pipe material includes stainless steel reducer (alloy steel, carbon steel reducer).

The calculation method of the expansion arc length of the different diameter reducer:

Concentric reducers, with a large head radius of R1, a small head radius of R2, and a height of H, these three data are known on sheet metal drawings. Decomposition of the expansion arc length of the reducer:
For the convenience of calculation, the radius of the large arc is RD, the angle of expansion is α, the radius of the arc of the small head is RX, (R1—R2)=(ΔR), and L is the length of the side projection of the reducer.
(RD-RX)=L=[(H)^2+(ΔR)^2]^(0.5)
RD = (R1 × L) ÷ (ΔR),
RX=(R2×L)÷(ΔR),
The angle of expansion is α = [180 × (ΔR)] ÷ (L × π), and the unit is degree.
The heterocentric reducer should be developed according to the sheet metal drawing.
Concentric reducers, with a large head radius of R1, a small head radius of R2, and a height of H, these three data are known on sheet metal drawings.
Production of seamless reducer
A reducer (reducing pipe) is a type of pipe used for pipe diameter. The forming process usually adopted is a reduction press, a diameter expansion press, or a reduction and diameter expansion press. For certain sizes of different diameter pipes, press forming can also be used.

Reduced diameter / expanded diameter forming

The reduction forming process of the reducer is to put the blank of the diameter of the large end of the reducer into the forming die, and the metal is moved along the cavity and contracted by pressing along the axial direction of the blank.
The reduced diameter forming process of the reducer is to put the blank of the same diameter as the large end of the reducer into the forming mold, and the metal is moved along the cavity and contracted by pressing in the axial direction of the blank. According to the size of the reducer of the reducer, it is divided into one or more press forming. The diameter reduction of the concentric reducer is to use a tube blank smaller than the diameter of the large end of the reducer, and the inner die is formed along the inner diameter of the tube. The diameter expansion process mainly solves the problem that the reducer having a large reduction diameter is not easily formed by the diameter reduction, and sometimes the method of expanding the diameter and reducing the diameter is used according to the material and product forming requirements.
In the process of reducing or expanding the deformation and deformation, it is determined according to different materials and the diameter of the diameter to determine the use of cold or hot pressing. In general, cold pressing is used as much as possible, but in the case of severe work hardening caused by multiple reductions, thick wall thickness or alloy steel material, hot pressing is suitable.

Stamping forming of reducer:

In order to make the service life of the reducer longer, the quality of the product is better. Many people usually use the following techniques in the production of the reducer. Let me introduce the stamping method for the reducer:

  • (1) Because the die guarantees the size and shape accuracy of the stamping part during stamping, and generally does not damage the surface quality of the stamping part, and the life of the die is generally long, so the quality of the stamping is not disordered, the interchangeability is good, and it has the same “Characteristics.
  • (2) Stamping is generally free of chip scraps, material consumption is less, and no other heating equipment is needed, so it is a material-saving, energy-saving processing method, and the cost of stamping parts is lower.
  • (3) Stamping can process parts with large size range and complicated shape, such as stopwatch from small to clock, large to automobile longitudinal beam, cage parts, etc., plus cold deformation hardening effect of material during stamping, strength of stamping And the stiffness is higher.
  • (4) The production efficiency of the different diameter pipe stamping processing is high, and the handling is convenient, and it is easy to realize mechanization and automation. This is because the stamping relies on the die and the punching equipment to complete the processing, and the number of strokes of the ordinary press is up to several tens of minutes per minute. Second, the high-speed pressure can reach hundreds or even thousands of times per minute, and each punching stroke may get a punch.

The internal pressure of the concentric reducer:

Under the action of internal pressure, the bending moment caused by the area pressure difference at the end of the concentric reducer causes the big end to be relatively open and the small end is relatively contracted. (2) The inner surface of the eccentric side of the eccentric reducer under the internal pressure and the eccentricity The hoop stress on the outer surface of the side central portion is the largest. 5 The above theoretical results have been verified by finite element numerical analysis and experiments. The experiment also shows that the bending radius and the tube section radius of the ring shell increase under the action of internal pressure, while the tube wall thickness changes little.
The concentric diameter reducer is formed by using a tube blank smaller than the diameter of the large end of the reducer, and is formed by expanding the inner diameter of the tube with the inner die. The diameter expansion process mainly solves the problem that the reducer having a large reduction diameter is not easily formed by the diameter reduction, and sometimes the method of expanding the diameter and reducing the diameter is combined according to the material and product forming requirements.
The hoop stress formula and the meridional stress formula of the concentric reducer under internal pressure are derived. Under the corresponding structural parameters, the hoop stress formula of the different diameter elbow can be transformed into the hoop stress formula of the concentric reducer, the eccentric reducer, or the equal diameter bend. Based on this, the ultimate pressure type of the reducer is derived. The entire process is formed by the radial compression of the tube blank and the stretching process of the branch portion. Different from the hydraulic bulging tee, the metal of the hot-pressed three-way branch pipe is compensated by the radial movement of the tube blank, so it is also called the radial compensation process.
In the process of reducing or expanding the diameter of the concentric reducer, it is determined according to the different materials and the diameter of the pipe, and cold or hot pressing is determined. Under normal circumstances, cold pressing is used as much as possible, but in the case of severe work hardening caused by multiple reductions, thick wall thickness or alloy steel material, hot pressing is preferred.
Concentric reducer hot press forming is to divide the tube blank larger than the diameter of the three-way, about the diameter of the three-way diameter, and open a hole in the portion of the stretched branch pipe; the tube blank is heated, placed in the forming mold, and The tube is filled with a die of a tensile branch pipe; under the action of pressure, the tube blank is radially compressed, and in the process of radial compression, the metal flows toward the different diameter pipe member and forms a branch pipe under the drawing of the die.

Eccentric reducer process pipe flow design:

The eccentric reducer is internally cut at the ends of the nozzle, and is generally used for horizontal liquid pipes. When the eccentric pipe reducer is cut upward, it is called top flat installation. It is generally used for pump inlet, which is good for exhausting. The cut point is down to the bottom. It is generally used for adjusting the valve installation and using the drain. The concentric reducer facilitates fluid flow and has less interference with the fluid flow regime when the diameter is reduced, so the gas and the vertically flowing liquid conduit use concentric reducer diameter reduction. Because the eccentric reducer is flat on one side, it is good for exhausting or draining, which is convenient for driving and overhauling. Therefore, the horizontally installed liquid pipeline generally uses an eccentric 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 ±3 mm; the allowable deviation of the reducer size shall comply with the provisions of Table 4.2.2-3.
The flowmeter of the corresponding caliber can be selected according to the actual flow rate of the process pipeline corresponding to the flow rate in the above table, and the flowmeter with the same caliber specification as the process pipeline can be selected as much as possible. The inlet of the pump inlet reducer should be installed so that the gas does not accumulate at the variable diameter to avoid cavitation due to improper installation. When the horizontal inlet pipe of the pump is reduced in diameter, an eccentric reducer should be used. When the pipe is pumped horizontally from bottom to top, the reducer should be “flat”; when the pipe is pumped horizontally from top to bottom, the reducer should be “bottom flat” to prevent gas from being at the pump inlet reducer. Accumulation, eccentric reducers are also installed in a “top flat” manner, even if the pipe is pumped horizontally from top to bottom. The pump that transports the medium with impurities at the end or side suction, when the suction speed is lower than the sedimentation speed of the impurities, the diameter of the reducer should be the same as the diameter of the nozzle that is inserted into the tank.

The stress distribution of the reducer:

The bending moment caused by the area pressure difference at the end of the different diameter tube causes the big end to be relatively open and the small end to shrink relative to each other.

The standard of the reducer:

There are two main systems for the international pipe flange standard, namely the European pipe flange system represented by German DIN (including the former Soviet Union) and the American pipe flange system represented by the American ANSI pipe flange. In addition, there are Japanese JIS pipe flanges, but they are generally only used for public works in petrochemical plants, and have little impact internationally. Now introduce the national pipe flanges as follows:

  1. European system pipe flange represented by Germany and the former Soviet Union
  2. American system pipe flange standard, represented by ANSI B16.5 and ANSI B 16.47
  3. British and French pipe flange standards, the two countries have two casing flange standards.

In summary, the internationally accepted pipe flange standard can be summarized as two different, non-interchangeable pipe flange systems: a European pipe flange system represented by Germany; the other is represented by the United States. American pipe flange system.
IOS7005-1 is a standard promulgated by the International Organization for Standardization in 1992. This standard is actually a standard for pipe flanges that combines two series of pipe flanges from the United States and Germany.

Classification of different diameter pipes
Divided by material

  • Carbon steel: ASTM/ASME A234 WPB, WPC
  • Alloy: ASTM/ASME A234 WP 1-WP 12-WP 11-WP 22-WP 5-WP 91-WP911, 15Mo3 15CrMoV, 35CrMoV
  • Stainless steel: ASTM/ASME A403 WP 304-304L-304H-304LN-304N
  • ASTM/ASME A403 WP 316-316L-316H-316LN-316N-316Ti
  • ASTM/ASME A403 WP 321-321H ASTM/ASME A403 WP 347-347H
  • Low temperature steel: ASTM/ASME A402 WPL3-WPL 6
  • High Performance Steel: ASTM/ASME A860 WPHY 42-46-52-60-65-70
  • Cast steel, alloy steel, stainless steel, copper, aluminum alloy, plastic, argon leaching, PVC, PPR, RFPP (reinforced polypropylene).

Divided by production method

Can be divided into push, pressing, forging, casting and so on.
Divided by manufacturing standards
Can be divided into national standard, electric standard, ship standard, chemical standard, water standard, American standard, German standard, Japanese standard, Russian standard and so on.

The products of the reducer have the following characteristics:

The strength of the reducer is generally higher than that of the straight welded pipe. It can produce elbows with larger diameters with narrower blanks, and can also produce welded pipes with different pipe diameters with blanks of the same width. The strength of the reducer is generally better than that of the straight seam. The welded pipe is high, and the elbow with larger diameter can be produced with a narrow blank, and the welded pipe with different pipe diameter can be produced with the same width of the blank.
The different diameter pipe production process is simple, the production efficiency is high, the cost is low, and the development is fast. The main raw materials for the production of different diameter pipes account for a large proportion of the production cost of different diameter pipes, and the price changes directly affect the changes in production costs. If the same type of stainless steel stamping elbow is used for welding, it is necessary to carry out preheating at 300 °C or more and slow cooling at around 700 °C after welding. If the weldment cannot be post-weld heat treated, a reducer electrode should be used.

Application range of stainless steel reducer:

First, Application in mining and coal industry

  • (1) Mine: Mine filling, concentrate powder and tailings transportation are serious to the pipeline. The used powder conveying pipelines such as Panzhihua and Daye Mine have been used for less than one year. About 5 times.
  • (2) Coal: The coal transportation and long-distance pipeline coal transportation are generally carried out by wet method. It is required that the conveying pipe is both wear-resistant and corrosion-resistant. The pipe can be used as a long-life conveying pipe with considerable economic benefits.

Second, the application of different diameter pipe metallurgy and power industry

The transportation of pulverized coal, ash, mud, lime gypsum slurry, etc. in the metallurgical and electric power industries requires a large amount of metal pipes to be consumed each year. The ceramic composite pipe is used to replace other pipes, and has the characteristics of high wear resistance, long service life, convenient installation and remarkable economic benefits.
Introduction to anti-cracking technology of stainless steel reducer:
The production of stainless steel reducers is mainly based on pressing, but the pressing process will make the hardness and density of the steel larger, but if it is not heated, cracks will easily occur.
In the control of the variable diameter range, in general, the processing range of the stainless steel reducer is within one stage. For example, the reducer of 325-159 basically needs to be heated several times. First, the tube of 325 is pressed. The pressure of 325 is pressed into 273. This pressing also needs to be heated. The second diameter is 273 variable diameter 219. This time it is necessary to heat the tube to the specified temperature and then press. Then there is the process of 219 changing to 159, and each time the diameter is required to be heat treated.
Various materials have their own hardness and tensile strength, so it is determined that the pressing strength of each material is also different. The same type of stainless steel reducer, the material processing method and the program will be very different. For example, the reducer of ordinary carbon steel is formed after three heat treatments. However, the greater the hardness of the reducer of the alloy material, the more the number of presses and the number of times of heating, and the more complicated the forming process.
How to choose a reducer?
If the diameter of the different diameter pipe does not match the inner diameter of the process pipe, the corresponding diameter reduction or expansion process should be carried out. If the pipe is to be reduced, it should be considered whether the pressure loss caused by this will affect the process flow. In order to prevent the distribution of the flow field after the installation of the reducer, the pressure loss, and thus the measurement accuracy of the electromagnetic flowmeter, the required central cone angle α is not more than 15°, and the smaller the better.
Source: China Stainless Steel Reducer Manufacturer – Yaang Pipe Industry Co., Limited (www.yaang.com)

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