High pressure butt-welded flanges

High-pressure butt-welded flanges are suitable for pipelines with high pressure or temperature fluctuations or for high-temperature, high-pressure and low-temperature pipelines, as well as for pipelines that are expensive, flammable, and explosive. The high-pressure butt-welding flange is not easy to be deformed, has good sealing and is widely used. The nominal pressure PN is about 16 MPa.
Butt weld flanges are suitable for pipelines with high pressure or temperature fluctuations or for high temperature, high pressure and low temperature pipelines, as well as for pipelines that are expensive, flammable and explosive. The welding flange is not easy to be deformed, sealed well, and widely used. The nominal pressure PN is about 16 MPa. The butt joint size of the flange changes with the nominal pressure, which makes the equal-diameter flange often unable to dock. The actual work of ordering, manufacturing, storage, installation, overhaul and maintenance is very troublesome. It is adopted for 0.25 and 0.6 MPa flanges. The 1.0 MPa butt size and the thickness are still in the original three specifications, thus simplifying the docking size.
Production standard for high-pressure butt-welded flanges: Since the nominal diameter of the container cylinder and the nominal diameter of the pipe represent different sizes, the container flanges and pipe flanges of the same nominal diameter are also different in size. Can not substitute for each other. In addition to flat welding and butt welding flanges, there are cast steel flanges, cast iron flanges, looper flanges, threaded flanges, etc. In addition to GB9119.7-88, the standard for pipe flanges is: Standards of the Ministry of Chemical Industry HG20592~HG20602-97; Sinopec Standard SH3406-96. Among them, the Ministry of Chemical Industry is divided into the European system and the American system. The European system is commonly used in China. Because the operating pressure is not high, the diameter is not large, A-type flat welding flange, flat sealing surface can be used, and the gasket material is made of asbestos rubber sheet. The connecting bolt is made of Q235-A and the 2″ and 4″ flanges are used.
High-pressure butt-welded flanges, also known as split flanges, are a type of flange. The flange is a part that connects the pipe to the pipe and is connected to the pipe end. There are holes in the flange, and the bolts make the two flanges tightly connected. Butt weld flanges and their gaskets and fasteners are collectively referred to as flange joints. Flange joints are an essential component in equipment and equipment components, and are also indispensable parts in piping design and pipe fittings. A butt weld flange is a flange that has a neck and is transitioned by a round pipe and is butt welded to the pipe. Butt weld flange is one of the flanged pipe fittings. It is widely used and promoted in different fields and industries. The applicable range is different in use, and the environment to be used is different. It needs to be used according to certain conditions. The welded flange is suitable for steel pipe connections with a nominal pressure not exceeding 2.5 MPa. It plays an important role and value in the link of the pipe, but the nominal pressure must be guaranteed to be within a certain range.
The processing of high-pressure butt-welded flanges is called “five-step walk”. By strictly monitoring the precise five steps, we can produce high-quality butt weld flanges. Let’s take a look at the five steps.
In the first step, the annealing temperature has reached the specified temperature.
The welding flange treatment is generally a solution heat treatment, which is commonly referred to as “annealing”. The temperature range is generally 1040 degrees Celsius to 1120 degrees Celsius. It can also be observed through the observation hole of the annealing furnace. The flanged pipe fittings in the annealing zone should be It is in an incandescent state, but there is no softening sagging.
In the second step, the welding flange is used to process the water vapor in the casting furnace.
On the one hand, check whether the material of the furnace body is dry. When the furnace is installed for the first time, the material of the furnace body must be dried. Second, is there any excessive water stain on the flanged pipe fittings entering the furnace, especially if the flanged pipe fittings are free? Don’t leak into it, or else destroy the atmosphere of the road.
The third step is the sealing of the furnace body.
The soldering flange bright annealing furnace should be sealed, isolated from the outside air, using hydrogen as a shielding gas, and only one exhaust port is open. The inspection method can be applied to the joint gap of the annealing furnace with soapy water. Look at whether to run, the most easy place to run is the place where the annealing furnace enters the pipe and the place where the pipe is discharged. The sealing ring in this place is particularly easy to wear, and it is often checked frequently.
The fourth step is to protect the gas pressure.
In order to prevent micro-leakage on the welding flange, the protective gas in the furnace should maintain a certain positive pressure. If it is hydrogen shielding gas, it is generally required to be above 20kBar.
The fifth step is to anneal the atmosphere.
For the welding flange, pure hydrogen is generally used as the annealing atmosphere, and the purity of the atmosphere is preferably 99.99% or more. If another part of the atmosphere is an inert gas, the purity can be slightly the first point. But absolutely must not contain too much oxygen and water vapor.
Butt welding flange is one of the flanges, and it has been applied in various fields. According to the range applicable to the welding flange e in use, the environment to be used is different, and it needs to be used according to certain conditions. . Butt welding flange has corresponding rigidity and elasticity requirements and reasonable butt welding thinning transition, the welding joint is away from the joint surface, the joint surface is free from the welding temperature deformation, it adopts a more complicated squat body structure, suitable for pressure Pipes with high temperature fluctuations or pipes with high temperature, high pressure and low temperature are generally used for the connection of pipes and valves with PN greater than 2.5 MPa; they play an important role and value in the links of pipes, but must be guaranteed in use. The pressure is in a certain range. The sealing surface of the welding flange e can be made into a smooth type, a concave-convex type and a groove type, and the smooth type butt welding flange e has the largest application amount. Mostly used in the case of moderate media conditions, such as low pressure non-purified compressed air, low pressure circulating water, it has the advantage that the price is relatively cheap. Butt weld flange e is suitable for pipelines with high pressure or temperature fluctuations or high temperature, high pressure and low temperature pipelines, and also for pipelines that are expensive, flammable and explosive. The welding method used for the flange and pipe connection of the welding flange e is butt welding. The welding is similar to the welding of the pipe and the pipe. Generally, the pipe diameter is small, the argon arc welding is used to make the bottom, the cover is hand welded, and the pipe diameter is large. Only double-sided welding is used.

Butt weld flanges are typically made using forging or forging processes. When made of steel or steel, the following requirements must be met:

1. The welding flange should be ultrasonically flawed without delamination defects;
2. It should be cut into strips along the rolling direction of the steel, bent into a ring by bending, and the surface of the steel forms a cylindrical surface. The steel plate shall not be directly machined into a neck butt weld flange; the butt weld of the ring shall be subjected to post-weld heat treatment and 100% ray or ultrasonic inspection, and the radiographic inspection conforms to the Class II requirements of JB4730, and the ultrasonic flaw detection conforms to JB4730. Level I requirements.
In the actual application process, the high pressure butt welding flange is used for pipe connection, which is usually suitable for pipe connection with pipe diameter of 32-315 mm. When installing the socket type telescopic short pipe joint, it must be fixed by using the anchor pipe clamp to avoid the position of the socket pipe due to the influence of thermal expansion and contraction. If it is used in vertical vertical pipe, long-distance collection pipe network and buried pipeline between floor and floor, at least one socket type telescopic short pipe part shall be installed. If it is used on the pipe, it can be easily disassembled by loosening the screws and then rotating the pipes on both sides and then tightening. The reason is that the socket type telescopic short tube can not only eliminate the thermal expansion and contraction caused by the temperature change of the drainage process, but also facilitate the reliable connection with the branch pipes of each floor, so that the installation of the pipeline is more Simple and convenient.
This high-pressure butt-welded flange is a flange product with good performance, which can show good performance and function in practical use, and can overcome the shortcomings of the traditional butt-welded flange. This high-pressure butt-welded flange is a reliable connection for two large-diameter pipes, usually consisting of two flanges plus several fastening bolts. It is actually made of carbon steel. Low carbon steel has good plasticity and weak strength. It can be added with carbon to make it harder. At this time, the plasticity will decrease and the strength will increase.
This high-pressure butt-welded flange plays a good value and role in use. Use in the right way and method can effectively avoid a series of quality problems during use. This type of flange may have a corresponding size reduction problem during use because the diameter of the seal is reduced and the cross section of the seal surface is reduced. At present, such a high-pressure butt-welded flange is sealed with a sealing ring to ensure a good match between the sealing surface and the sealing surface.
Source: China High Pressure Butt-Welded Flange Manufacturer – Yaang Pipe Industry Co., Limited (www.yaang.com)

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