Basic introduction of elbow

  Elbow in the pipeline system, elbow is a pipe fitting that changes the direction of the pipeline. According to the angle, there are three commonly used elbows: 45 ° and 90 ° 180 °, and other abnormal angle elbows such as 60 ° are also included according to the needs of the project. Elbow materials include cast iron, stainless steel, alloy steel, malleable cast iron, carbon steel, non-ferrous metals and plastics. The connection methods with the pipe include: direct welding flange connection, hot-melt connection, electric fusion connection, threaded connection and socket connection, etc. According to the production process, it can be divided into: welding elbow, stamping elbow, push elbow, casting elbow, butt welding elbow, etc. Other names: 90 degree elbow, right angle bend, love bend, etc.

 

        Elbow is a commonly used connecting pipe fitting in plumbing installation. It is used for the connection at the bend of the pipeline and to change the direction of the pipeline.

Other names: 90 ° elbow, right angle bend, love bend, stamping elbow, machine-made elbow, welding elbow, etc.

 

        Purpose: connect two pipes with the same or different nominal diameter to make the pipeline turn 90 °, 45 °, 180 ° and various degrees.

 

        Bending radius less than or equal to 1.5 times of pipe diameter belongs to elbow, and bending radius greater than 1.5 times of pipe diameter belongs to elbow.

 

        A connecting pipe fitting commonly used in pipeline installation, which connects two pipes with the same or different nominal diameter to make the pipeline turn at a certain angle, and the nominal pressure is 1-1.6mpa.

Production and processing method of pipe tee

 1. Forging

 

 

 

That is to use forging machine (rotary type, connecting rod type and roller type) to punch and stretch the end or part of the pipe to reduce the outer diameter.

 

 

 

2. Stamping

 

 

 

The taper core is used to expand the pipe end to the required size and shape. This operation is carried out on the punch.

 

 

 

3. Roller


 

For round edge processing, place the core in the pipe and press the outer circumference with rollers.

 

 

 

4. Rolling

 

 

 

It is suitable for the inner round edge of thick wall pipe. Generally, there is no mandrel.

 

 

 

5. Bulging

 

 

 

        The rubber is mainly put into the tube and compressed with a punch at the top to make the tube protrude and form; Filling the middle of the pipe with liquid and bulging the pipe into the required shape by the pressure of the liquid.

        In addition, there is another processing method of using mold to produce pipe tee. The mold includes upper mold and lower mold. The lower die is provided with a processing cavity, the upper die is provided with a processing block matching the shape of the processing cavity, and the processing cavity is a horizontal T-shape. In addition to the T-shaped intersection, the cross-section intersection of the processing cavity is semicircular, and the opening of the cross-section is located on the upper surface of the lower die, which changes the processing mode of the tee pipe and processes two semicircular tee pipe fittings one by one. The opening of the pipe joint is welded to increase the contact surface between the two and reduce the difficulty of welding. In addition, the semicircular tee fitting is easy to be placed on the ground without swinging, which further improves the processing stability. It avoids the situation that the traditional nozzle is easy to roll in the processing process.

Comparison of flange materials

 The material of carbon steel flange is not intended to be carbon steel, but we all know that the performance of carbon steel is relatively poor, which is vulnerable to corrosion by external factors, thus affecting the service performance of carbon steel flange. Therefore, carbon steel flange can be put into use only after some treatment during production. Commonly used treatments are mainly divided into metal plating or rust paint.

　　Carbon steel flange is used in a special field, so it requires smooth material and other characteristics. It can be used under high pressure without distortion. Because carbon steel has few burrs, its friction is also very small, which can be more applied to equipment.

Preparations for carbon steel flange measurement

 With the rapid development of domestic and foreign pipeline construction, pipeline pressure test has become an essential and important link. Before and after the pressure test, each section of pipeline must be cleaned by ball cleaning, usually 4 ~ 5 times. Especially after the pressure test, the water stored in the pipeline is difficult to clean, and the cleaning times will be more. Before the measurement of carbon steel flange, it is necessary to make certain preparations, measure according to certain methods and methods, and determine different measurement methods according to specific conditions to ensure the accuracy of measurement.

　　The following describes the preparations for carbon steel flange measurement:

　　1. Before measurement, according to the position of large flange, first draw the sketch of each connecting large flange of the equipment and number it continuously, so that the fixture can be installed according to a certain way and principle, so as to ensure normal use.

　　2. During installation, the carbon steel flange may have different outer diameters, staggered joints (non concentric) and unequal gasket thickness, so the machined fixture shall correspond to the carbon steel flange on the side and cannot be interchanged. Therefore, measuring the size and number of each part is the key to fixture processing and installation

　　3. When measuring, it is best to arrange three people, two of whom measure, one of whom proofreads and fills in the form. The measuring tool is vernier caliper. If there is no condition, external caliper and steel ruler can be used Measurement is a detailed work and the premise of fixture installation. The measurement and record must be prepared without error, and the form must be filled in carefully and clearly In the actual measurement work, we should cooperate with each other and be able to cooperate and use according to the correct principle.

Maintenance method of elbow

 1. Elbows stored for a long time shall be inspected regularly. The exposed processing surface shall be kept clean, dirt shall be removed, and stored neatly in a ventilated and dry place indoors. Stacking or outdoor storage is strictly prohibited. Always keep the elbow dry and ventilated, keep the device clean and tidy, and store it according to accurate storage methods.

　　2. During installation, the elbow can be directly installed on the pipeline according to the connection mode and installed according to the use position. Generally, it can be installed at any position of the pipeline, but it needs to be easy to operate. Note that the medium flow direction of the stop elbow should be upward under the longitudinal valve disc, and the elbow can only be installed horizontally. Pay attention to the tightness of elbow during installation to prevent leakage and affect the normal operation of pipeline.

　　3. When the ball valve, stop valve and gate valve of elbow are used, they are only fully open or fully closed, and are not allowed to adjust the flow, so as to avoid erosion of the sealing surface and accelerated wear. There is a reverse sealing device in the gate valve and upper thread stop valve. The hand wheel is screwed to the top position to prevent the medium from leaking from the packing.

What are the principles in the production process of carbon steel elbow

 The carbon steel elbow mainly adopts the polygonal ring shell or the closed polyhedral sector shell with polygonal sections at both ends, which is filled with the interior of the pressure transmission medium. Under the internal pressure, the polygonal section under the internal pressure gradually becomes round and eventually becomes a ring shell. According to the needs, a ring shell can be cut into 90 degree elbows, 4 or 6 60 degree elbows or other standards. This process is suitable for making elbows. The ratio of length to diameter is greater than 1.5, which is the manufacturing method of large elbows.

　　Set the pressure and flow of water in front of the carbon steel elbow to be the same, and the pressure loss will occur when the water flows through the pipe. If the loss is greater, the pressure out of the elbow will be smaller, 90DEG; The bend is equivalent to two 45DEG elbows. If the radius of the bend is the same, that is, the impact of the water rushing out of the elbow on the ground will be smaller.

　　Now, the frequency of using carbon steel elbow in various pipelines is also higher and higher, and people gradually begin to pay attention to the price. Under such circumstances, we see more opportunities. It is also this situation that enables the development of carbon steel elbow, and the momentum of development is very good. The carbon steel elbow still has great characteristics. For example, as long as the raw materials are flat plate and developable surface. The accuracy is simple and easy to install and weld.

Application of flange in different fields

 　Stainless steel flanges will not produce corrosion, pitting, corrosion or wear. Stainless steel is also one of the strongest building metal materials. Because stainless steel has good corrosion resistance, it can make structural parts permanently maintain the integrity of engineering design.

　　Chrome stainless steel flange also integrates mechanical strength and high extensibility, which is easy to process and manufacture parts, and can meet the needs of architects and structural designers.

　　All metals react with oxygen in the atmosphere to form an oxide film on the surface. Unfortunately, the iron oxide formed on ordinary carbon steel continues to oxidize, expanding the corrosion and finally forming holes. The carbon steel surface can be guaranteed by electroplating with paint or oxidation resistant metals (e.g. zinc, nickel and chromium), but as is known, this protection is only a thin film.

　　Application field of stainless steel flange: stainless steel flange is widely used in petroleum, chemical industry, nuclear power station, food manufacturing, construction, shipbuilding, papermaking, medicine and other industries. It is used differently in different industries and shows its value in various industries.

Characteristics of high pressure flange

 1. Sealing mode: the core of the high-pressure self tightening flange is a unique new metal to metal sealing, that is, the sealing is formed by the elastic deformation of the sealing lip (T-Arm) of the sealing ring, which belongs to hard sealing; A strong rigid body is formed by the combination of the sleeve, ferrule and sealing ring, so that the strength of the connecting part is far greater than that of the base metal of the pipeline. When under pressure, the rib and lip play the role of strength and sealing respectively, which can not only self tighten and seal, but also reinforce the pipeline, greatly enhancing the overall strength of the connecting parts

　　2. Tensile property: in most cases, the high-pressure self tightening flange in the connection can bear tensile load better than the pipe itself; The destructive test shows that the flange is still intact without leakage after the pipeline fails to bear the tensile load.

　　3. Bending resistance: a large number of tests show that the flange will not leak or loosen when it bears large bending load. Actual tests: the high-pressure self tightening flange of DN15 specification is welded on the pipe and subjected to multiple cold bends. The connection of the high-pressure self tightening flange will not leak and the bolts will not loosen.

　　4. Compression resistance: in normal pipeline application, high pressure self tightening flange will not bear overload compression; When higher compression loads occur, the maximum load on the high-pressure self tightening flange is determined by the ultimate strength of the pipeline.

Preparation for carbon steel flange measurement

 With the rapid development of domestic and foreign pipeline construction, the carbon steel flange blind plate has become an indispensable and important part of the pipeline pressure test. Before and after the pressure test, each section of the pipeline must be cleaned by passing the ball, usually 4-5 times. Especially after the pressure test, it is difficult to clean the water stored in the pipeline, and the cleaning times will be more. The construction method of repeatedly welding the head at the ball receiving place has the following problems: first, increasing the labor intensity of workers; Second, the repeated welding head method has high consumables, requires many times of large-scale equipment and high cost. In view of the problems of high labor intensity, high consumables, many times of large-scale equipment and high cost caused by the repeated welding head method at the launching point when the ball cleaning is carried out after the pressure test of long-distance pipeline, a new simple quick opening large-scale flange blind plate construction method is proposed. Before the measurement of carbon steel flange, certain preparations shall be made, and the measurement shall be carried out according to certain ways and methods. Different measurement methods shall be determined according to specific conditions to ensure the accuracy of measurement.

　　Preparation before measurement:

　　1. before measurement, according to the position of the large flange, the sketch of each connecting large flange of the equipment shall be drawn and numbered continuously, so that the fixture can be installed in a certain way and principle to ensure normal use.

　　2. during installation, the carbon steel flange may have different outer diameters, staggered joints and unequal gasket thickness, so the machined fixture should correspond to the carbon steel flange on the side and cannot be interchanged. Therefore, measuring the size and number of each part is the key to fixture processing and installation

　　3. when measuring, it is better to arrange three people, two of whom measure, one of whom proofreads and fills in the form, and the measuring tool is vernier caliper. If there is no condition, the external caliper and steel ruler can be used Measurement is a meticulous work and a prerequisite for fixture installation. Measurement and recording must be prepared without error and the form must be filled out carefully and clearly In the actual measurement work, we should cooperate with each other and be able to cooperate and use according to the correct principle.

Equal diameter hot pressing pipe tee forming process

 Equal diameter hot pressing pipe tee forming process the thickness of the equal diameter tee and the reducing tee is used to express the detailed reducing main type, while the American Standard reducing tee uses Sch to express the pressure of the reducing tee. Before the reproduction of American Standard reducing tee and pressing cold extrusion, we must implement the wall thickness of reducing tee before further cold extrusion of reducing tee. If we don't know the wall thickness of the reducing tee, what if we make the cold extrusion reducing tee to meet the customer's requirements. This is a huge difference in wall thickness between our most common national standard reducing tee and American Standard reducing tee.

Desulfurization process of carbon steel elbow

 Desulfurization of carbon steel elbow in oxygen converter is difficult and uneconomical. In recent years, the supply of high-quality metallurgical coke is insufficient, the sulfur content of coke is the highest, and the sulfur content of heavy oil injected to strengthen blast furnace smelting is also high, which makes the quantity and cost of low-sulfur molten iron meeting the requirements of steelmaking increasingly problematic. Practice has proved that the carbon steel elbow is a good way to solve the above contradictions by taking off the bowl of molten iron outside the furnace between the blast furnace and the converter.

　　It can improve the technical and economic indicators of ironmaking and carbon steel elbow at the same time. It is particularly important for the converter to simplify operation and realize automatic control. It is developing rapidly in many countries. The basic principle of desulfurization outside the furnace of carbon steel elbow is the same as that of desorbing inside the furnace. That is to use elements or compounds with greater affinity to sulfur than iron and sulfur to transform iron sulfide into more stable, rarely soluble or completely insoluble sulfide in molten iron; At the same time, create good dynamic conditions to accelerate the diffusion of sulfur in molten iron of carbon steel elbow to the reaction area and expand the reaction area between desulfurizer and molten iron. ASTM 440 is called high-strength carbon steel elbow.

　　It includes Mn-Cu high-strength low-alloy steel profiles, plates and bars. It is mainly used for riveting or bolting (non welded) bridges and buildings. Generally, welding is not suitable. However, the material can also be welded after taking certain measures. Since it contains a minimum of 0.2% Cu, its atmospheric corrosion resistance is about twice that of carbon structural steel without Cu. The minimum yield strength of steel plate with thickness less than 19mm is 345MPa.

 

Why should seamless steel pipe be strictly selected

      First of all, we know that there are many types of seamless steel pipes. High pressure boiler pipe is one of them. The use of high-pressure boiler pipe is often in high-temperature and high-pressure conditions for a long time. The pipe will undergo oxidation and corrosion under the action of high-temperature flue gas and steam. That is to test whether our steel pipe has long-term temperature, anti-oxidation and anti-corrosion performance, and has a good organizational stability.

　　Considering how he selects materials, we must first consider the product advantages and focus on quality, strictly select materials and real materials, so that when dealing with craft products, through strict selection, the production of real materials, the product bearing capacity of the selected products must be good, stable and solid, not easy to deform, with mature technology, quality assurance, sufficient inventory, timely delivery, cutting and smooth incision, Good bearing capacity, not easy to deform, various product specifications, strict selection of materials and quality assurance.

　　The seamless steel pipe also needs to pay attention to two ends. Due to the structure of the detection device, when the reserved cutting allowance at both ends is small, there is likely to be cracks or other missing parts at the end. If there is a tendency of cracks at the end, it will lead to crack propagation in a later installation.

　　Therefore, we should pay attention to a crack detection of seamless steel pipe, which is a very important link. When it comes to the dimensional change of high-pressure boiler caused by thermal expansion and cold contraction, there are two most common types: Rubber high-pressure boiler and metal high-pressure boiler tube.

 

Precautions for storage of seamless steel pipe

　In the building materials industry, the development of various pipelines is different. Due to their different characteristics, there is a certain distance between pipelines.

　　Seamless steel pipe is one of many pipes in this building materials industry. It is composed of strip steel after treatment. We understand the various characteristics of steel pipe, but in the building materials industry, the development of various pipelines is different. Due to their different characteristics, there is a certain distance between pipelines.

　　Square pipe is one of many pipes in the building materials industry. It is composed of strip steel after treatment. We understand the various characteristics of steel pipe, but due to the connection of steel pipe and other raw materials, the storage of steel pipe needs specific conditions.

　　When storing seamless steel pipes, we first need to choose a suitable place. We need to consider many external factors and steel pipe corrosion, so the place must be clean, boring and ventilated, harmful gases, seamless steel pipes can not appear, weeds and other sundries should be removed in time to keep the outer surface of steel clean.

　　If there is acid, alkali and salt in the warehouse, it is easy to react with the steel pipe and corrode the steel pipe, so try to cut it and don't let it touch it.

　　In addition, if it comes to expensive metal products, you can consider putting them in the warehouse. According to the geographical conditions, there is a sealed warehouse, but the ventilation setting is very good.

 

Executive standard and corresponding material of seamless steel pipe

1. GB / T8162-1999 (theoretical weight of seamless steel pipe and galvanized steel pipe for structure). It is mainly used for general structure and mechanical structure. Its representative material (brand): carbon steel, 20 and 45 steel; Alloy steel Q345, 20c galvanized steel pipe price r, 40Cr, 20CrMo, 30-35crmo, 42CrMo, etc.

　　2. GB / t8163-1999 (seamless steel pipe for fluid transportation). It is mainly used for conveying fluid pipelines on engineering and large equipment. The representative ceramic composite steel pipe material (brand) is 20, Q345, etc.

　　3. GB3087-1999 (seamless steel tubes for low and medium pressure boilers). It is mainly used for conveying low and medium pressure fluid pipes of industrial boilers and domestic boilers. The representative materials are 10 and 20 steel.

　　4. GB5310-1995 (seamless steel pipe for high pressure boiler). It is mainly used for high temperature and high pressure transmission fluid header and pipeline on the boiler of power station and Tianjin seamless steel tube nuclear power station. The representative materials are 20g, 12Cr1MoVG, 15CrMoG steel pipe scaffold, etc.

　　5. Gb5312-1999 (carbon steel and carbon manganese steel seamless steel tubes for ships). China seamless steel pipe network is mainly used for class I and II pressure pipes for marine boilers and superheaters. The representative materials are 360, 410 and 460 steel grades.

　　6. Gb1479-2000 (seamless steel pipe for high pressure chemical fertilizer equipment). It is mainly used in the high temperature and high pressure fluid pipeline of Tianjin steel pipe group. The representative materials are 20, 16Mn, 12CrMo, 12cr2mo, etc.

　　7. GB9948-1988 (seamless steel pipe for petroleum cracking). It is mainly used for boilers, heat exchange scaffolds, steel pipe pricers and fluid transmission pipelines in petroleum smelters. The representative materials are 20, 12CrMo, 1Cr5Mo, 1cr19ni11nb, etc.

　　8. GB18248-2000 (seamless steel pipe for gas cylinder). It is mainly used for making all kinds of gas welded steel pipes and hydraulic cylinders. Its representative materials are 37Mn, 34Mn2V, 35CrMo, etc.