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Concentric reducer | Concentric size head

 

Reducer series Concentric reducers, also known as concentric head size tolerances shall comply with the provisions of Table 4.2.2-3.

 

Reducers are also called size heads. They are used to connect pipes of different sizes. Generally, they are divided into concentric reducers and eccentric reducers. When the diameters of the two ports are set to concentric circles, they are Concentric reducers are called, and the projection of the eccentric reducer is a small circle cut in the outer circle.

 

        The manufacturing process of concentric reducers is the simplest. Thicker-walled tubes are used as the blanks, and one-port diameter can be expanded or equal-walled tubes can be used as the blanks, and the diameter of one port can be reduced. Whether flaring or shrinking, it is generally pressed with a mold.

At present, the eccentric die is widely used in the country to suppress the eccentric reducer step by step. The eccentric reducer with more than three stages produced by this process will produce a serious gap in the eccentric end of the small head, and the internal wall will become a tumor with uneven wall thickness and ellipse. phenomenon. When an eccentric reduction pipe is replaced by a truncated concentric reducer truncated pipe structure, since the oblique section is not a round surface but an elliptical surface, there is a problem that the end face and the straight pipe are misaligned and cannot be completely connected. If a new pressing process is adopted, that is, the concentric reducer is pressed first with a concentric die, and then the pressed concentric reducer is placed in the eccentric die to press the integral type into the required eccentric reducer. The surface is smooth, the small head is even, the wall thickness is uniform, roundness is qualified, and less raw materials are used. The quality of concentric reducers shall comply with the current national standard “Steel Butt-weld Seamless Fittings” GB/T 12459-2005 and shall meet the following requirements: 1) The roundness of concentric reducers shall not be greater than that of the corresponding end The diameter of 1%, and allowable deviation of ± 3mm, concentric reducer at both ends of the center line should coincide, the allowable deviation of the eccentricity is ± 5mm.2)

 

 

 The appearance of concentric reducers should be free from cracks, heavy skin, and the wall thickness should be greater than the wall thickness of the large-diameter end pipe section. 12459-2005 Concentricity reducer standard deviation permissible DN15-65 Caliber: +1.6 -0.8 Inner diameter: ±0.8 Height : ±2DN80-100 Caliber:±1.6 Inner diameter:±1.6 Height:±2DN125-200 Caliber:+2.4 -1.6 Inner diameter:±1.6 Height:±2DN250-450 Caliber:+4 -3.2 Inner diameter:±3.2 Height:±2DN500- 800 Caliber: +6.4 -4.8 Inner diameter: ±4.8 Height: DN500-600 ±2 DN650-750 ±3 DN800 ±5 Wall thickness 87.5% of the wall thickness not less than the nominal wall thickness The deviation is the sum of positive and negative absolute values. However, the roundness below 500 is generally within 4 mm.