Pressure bending is the most commonly used bending method for pipe bend

At present, compression bending is the most commonly used pipe bend method in China. Most of the equipment used are general mechanical presses or hydraulic presses, as well as special bending presses. The common roll bending equipment is the bending machine. The three roll rolling machine continuously bends the slab according to the principle that three points determine a circle. The three roll plate rolling machine has two driving rollers and one holding down roller.

　　The relative distance between the holding down roll and the driving roll can be changed by adjusting the up and down position of the holding down roll.

　　In the production of pipe bend stretch bending, the plate is placed between the drive roll and the holding down roll, and the drive roll rotates in the positive and negative directions to make the plate move back and forth. By adjusting the holding down roller to press it down gradually, the plate can be bent into cylindrical surface, conical surface and hyperboloid with small curvature. One end of the pressing roller can be raised to facilitate unloading of the workpiece. In addition, there are four roll and multi roll rolling machines. Four roll rolling machines are used to roll thick plate cylinders. Multi roll rolling machines with more than four rolls gradually pipe bend welded pipes into complex profiles with multiple pairs of rollers.

　　For bending parts with high accuracy requirements, large length and radius of curvature requirements and small transverse size requirements, stretch bending can be carried out on a special stretch bending machine. During the bending process, the whole thickness of the plate is affected by tensile stress, so only elongation deformation is generated. The deformation caused by elastic recovery after unloading is small, which is easy to ensure the bending accuracy.

Common faults of flange

 　In the continuous production of modern industry, flange leakage will inevitably occur due to the influence of medium corrosion, scouring, temperature, pressure, vibration and other factors. Due to the error of processing size of sealing surface, aging of sealing elements and improper installation and fastening, it is very easy to cause flange leakage. If the flange leakage problem cannot be solved in time, the leakage will expand rapidly under the scouring of the medium, resulting in the loss of materials and the destruction of the production environment, leading to the shutdown of the enterprise and huge economic losses. If it is toxic, harmful, flammable and explosive medium leakage, it may also cause major accidents such as personnel poisoning, fire and explosion.

　　The traditional methods to solve flange leakage are to replace sealing elements, apply sealant or replace flanges and pipes, but this method has great limitations, and some leakage can not be solved on site due to the requirements of working environment safety. Polymer composites can now be used for on-site plugging, in which the more mature youfushi blue system is applied. It is a very ideal method, especially in flammable and explosive occasions, which shows its unique advantages. Polymer composite technology has the advantages of simple construction process, safety and low cost. It can solve most flange leakage problems for enterprises, eliminate potential safety hazards and save maintenance costs for enterprises.

What are the differences between cold forging and hot forging of flanges

 The cold forging of flange is forged at low temperature, and the size change of flange is very small. When forging below 700 ℃, the formation of oxide scale is less, and there is no decarburization on the surface. Therefore, as long as the deformation energy is within the forming energy range, cold forging is easy to obtain good dimensional accuracy and surface finish. As long as the temperature and lubrication cooling are well controlled, the warm forging below 700 ℃ can also obtain good accuracy. Cold die forging, cold extrusion, cold heading and other plastic processing. Cold forging is the forming process of materials below the recrystallization temperature and forging below the recovery temperature. In production, forging without heating blank is used to be called cold forging. Cold forging materials are mostly aluminum and some alloys, copper and some alloys, low carbon steel, medium carbon steel and low alloy structural steel with low deformation resistance and good plasticity at room temperature. Cold forging has good surface quality and high dimensional accuracy, which can replace some cutting. Cold forging can strengthen the metal and improve the strength of the flange.

　　The development of cold forging technology is mainly to develop high value-added products and reduce production costs. At the same time, it is constantly infiltrating or replacing in the fields of cutting, powder metallurgy, casting, hot forging, sheet metal forming process and so on. It can also be combined with these processes to form a composite process.

　　The hot forging of flange is: during hot forging, large flange with complex shape can be forged because the deformation energy and deformation resistance are very small. The flange with high dimensional accuracy can be hot forged in the temperature range of 900-1000 ℃. In addition, attention should be paid to improving the working environment of hot forging. The service life of forging die is shorter than that of forging in other temperature ranges, but it has large degree of freedom and low cost. The purpose of hot forging flange is mainly to reduce the deformation resistance of metal, so as to reduce the forging pressure required for bad material deformation and greatly reduce the tonnage of forging equipment; Change the as cast structure of the flange material ingot. After recrystallization in the hot forging process, the coarse as cast structure becomes a new structure of fine grains, reduce the defects of as cast structure and improve the mechanical properties of the steel.

How is the pressure rating of the flange divided

 　Common flanges are used in different places, so the pressure grade is different to a certain extent. For example, large stainless steel flanges are mainly used in high temperature resistant pipelines in chemical engineering, so it is necessary to

　　The material has high requirements for pressure bearing function.

　　Therefore, customers often require forged flanges. Because the data is forged, the arrangement density is improved and its pressure bearing ability is enhanced.

　　There are clear grade requirements for the compression resistance of large stainless steel flanges in domestic and world specifications. Large stainless steel flanges are generally divided into PN25, pn6, PN10, PN16, PN25, PN40, etc

　　Wait. PN10 and PN16 are the most commonly used.

The flange can meet the connection between pipes

 Compared with the traditional pipe, the composite pipe improves the corrosion resistance, wear resistance, heat conduction function of the pipe, adheres to the purity of pipe data, and extends the service life of the pipe. When the pipe rack and engine are installed, flange will not affect the hoisting of hoisting equipment and the height of pipeline. Generally speaking, in the process of steel production, from electric furnace steel to stainless steel

　　The energy consumption per ton of steel is 280 kg;. It is the axial length compensation of common axial bellows expansion joint and pipeline.

　　Flange Street connects all kinds of containers. It is the most basic and common process pipeline connection method. Sometimes it is necessary to put the elbow in the narrow area, such as the part about the pipe, because the radius of curvature of the bend is small, generally 6 and 40.

　　The flange can completely meet the interconnection between pipes, bring us a close connection effect, and also bring ultra-high product functions. It can effectively reduce the leakage and leakage, so that we can easily get the best application conditions and win the best product functions through the use of new parts. The traditional method does not crack in the welding process. For general drainage pipes, the primary presentation pipe shall be of type, and the drainage riser and drainage branch pipe shall be selected.

Welding of flange

 1. Flat welding flange: only the outer layer needs to be welded, and the inner layer does not need to be welded; It is generally used in medium and low pressure pipelines, and the nominal pressure of the pipeline shall be less than 0.25MPa. There are three types of sealing surfaces for flat welding flanges, namely lubrication

　　Type, concave convex type and tenon groove type, among which lubricating type is most widely used, and the price is affordable and cost-effective.

　　2. Butt welding flange: the inner and outer layers of the flange shall be welded. It is generally used in medium and high pressure pipelines. The nominal pressure of the pipeline is between 0.25 ~ 2.5MPa. The sealing surface of butt welding flange connection is concave convex,

　　The device is complex, so the labor cost, device method and auxiliary material cost are relatively high.

　　3. Socket welding flange: generally used in pipes with nominal pressure less than or equal to 10.0MPa and nominal diameter less than or equal to 40mm.

　　4. Loose flange: it is generally used in pipes with low pressure but corrosive medium, so this kind of flange has strong corrosion resistance, and the raw materials are mainly stainless steel.

　　This connection is mainly used for the connection of cast iron pipe, rubber lined pipe, non-ferrous metal pipe and flange valve. Flange connection is also used for the connection between process equipment and flange.

Characteristics of carbon steel tee and butt welded tee

 Carbon steel tee is generally used for the installation of regulating valve and is used for drainage.

　　Butt welded tee is a steel elbow formed by hot pressing or forging. Its connection form is to directly butt weld the tee with the steel pipe. The main manufacturing standards of butt welded tee are generally GB / t12459, GB / T13401, ASME b16.9, sh3408, sh3409, Hg / t21635, Hg / t21631 and SY / t0510.

　　Butt welding tees generally include equal diameter tees, reducing tees, etc., and the materials are carbon steel, alloy steel and stainless steel.

　　When the chromium content in the steel reaches about 1.2%, the chromium reacts with the oxygen in the corrosive medium to form a thin oxide film (self passivation film) on the steel surface. The seamless tee can prevent the further corrosion of the steel matrix. In addition to chromium, the commonly used alloy elements include nickel, molybdenum, titanium, niobium, copper, nitrogen, etc, In order to meet the requirements for the structure and performance of concentric reducers for various purposes. Certain production and processing processes are adopted in the production of carbon steel tee to ensure good function and performance in production and processing.