1. According to the chemical industry standard, the integral flange (IF), threaded flange (Th), plate flat welding flange (PL), butt welding flange (WN), neck flat welding flange (SO), socket welding flange (SW), butt welding ring loose sleeve flange (PJ/SE), flat welding ring loose sleeve flange (PJ/RJ), liner flange cover (BL (S)), flange cover (BL).
  2. According to the standard of petrochemical industry: threaded flange (PT), butt welding flange (WN), flat welding flange (SO), socket welding flange (SW), loose sleeve flange (LJ), flange cover (no note).
  3. According to the standard of machinery industry: integral flange, butt welding flange, plate flat welding flange, butt welding ring plate loose sleeve flange, flat welding ring plate loose sleeve flange, flanged ring plate loose sleeve flange, flange cover.
  4. According to the national standard: integral flange, thread flange, butt welding flange, neck flat welding flange, neck bearing insert welding flange, opposite welding ring with neck loose sleeve flange, plate flat welding flange, opposite welding ring plate loose sleeve flange, flat welding ring plate loose sleeve flange, flanged ring plate loose sleeve flange, flange cover.

What is the difference between butt welding flange and flat welding flange?
The butt welding flange is the pipe diameter and wall thickness of the interface end, which is the same as the pipe to be welded, just like two pipes.
The flat welding flange is a concave platform that is slightly larger than the outer diameter of the pipe at the interface, in which the pipe is welded.
The welding performance of butt welding is better and the corrosion is small.
Flat welding and butt welding are the welding methods when flange and pipe are connected. Only one side welding of flat welding flange does not need welding pipe and the inner mouth of flange connection, and the welding installation of welding flange requires flange double-sided welding. Therefore, flat welding flange is generally used for low and medium pressure pipeline, butt welding flange is used for medium and high pressure pipeline connection, butt welding flange is generally at least PN2.5MPa, butt welding is used to reduce stress concentration, the general butt welding flange is also called nipple flange with neck flange. Therefore, the installation cost, labor cost and auxiliary material cost of welding flange should be higher, because of an additional process.
Welding flange is not all need internal and external double-sided welding, there are no special requirements generally only outside welding, flat welding is better welding, because the pipe and flange are good vertical, the pipe will not oblique.

What are the characteristics of the principle of flat welding flange?
Flat welding flange is a kind of flange which is connected with container or pipe by fillet weld. It belongs to any flange. According to the integrity of the connection between the flange ring and the straight cylinder section, the design is checked according to the integral flange or loose flange respectively. There are two kinds of flange rings with and without neck. Compared with the flange with neck butt welding, the flat welding flange has the advantages of simple structure and less material use, but the rigidity and sealing property are not as good as those with neck butt welding flange. Flat welding flanges are widely used in the connection of medium and low pressure vessels and pipes.
The characteristics of flat welding flange: flat welding flange not only saves space and reduces weight, but also ensures that the joint will not leak, and has good sealing performance. The compact flange size is reduced because the diameter of the seal is reduced, which will reduce the section of the sealing surface. Secondly, the flange gasket has been replaced by the sealing ring to ensure the matching of the sealing surface of the seal face. In this way, only a small amount of pressure is required to press the tight cover. With the reduction of the required pressure, the size and quantity of bolts can be reduced accordingly, so a new product with small size and light weight (70% less than the weight of traditional flanges) is finally designed. Therefore, flat welding flange type is a relatively high quality flange product, which reduces the quality and space, and plays an important role in industrial use.
Sealing principle of flat welding flange: the two sealing surfaces of bolts extrude flange gasket and form seal, but this also leads to the damage of seal. In order to keep the seal, it is necessary to maintain a huge bolt force, so the bolt has to be bigger. Larger bolts have to match larger nuts, which means that larger diameter bolts are needed to create conditions for upper tightening nuts. However, the larger the diameter of the bolt, the more suitable the flange will become bent, by increasing the wall thickness of the flange part. The whole device will require a great deal of size and weight, which will become a special problem in the offshore environment, because in this case, weight is always the main issue that people must pay attention to. Moreover, fundamentally speaking, the flat welding flange is an invalid seal, which requires 50% of the bolt load to squeeze the gasket, while only 50% of the load is used to maintain the pressure.
The problem of flat welding flange has always been a topic of concern to people, it is related to the production cost or economic benefits of companies and enterprises, so the sealing principle of flat welding flange is constantly improved and improved.
However, the main design disadvantage of flat welding flange is that it can not guarantee no leakage. This is the deficiency of its design: the connection is dynamic, and periodic loads such as thermal expansion and fluctuating periodic loads will cause the movement between flange surfaces, affect the function of flange, thus impair the integrity of flange, and eventually lead to leakage. No product can be without defects, but try to control the deficiencies of the product to the minimum, so the company in the production of flat welding flange as far as possible to improve the performance of the product, so that it plays a role.

Are there interfaces for flanges of different sizes to join together?
Flange is a standard, according to different pressure levels, different specifications of the flange, there is a clear number of bolts and bolt size, bolt hole is also a standard size. If the difference between the outside diameter is not large, the diameter and diameter of the bolt hole can be unified, it can be connected. If the specification difference is great, can not be directly connected, can use the size of the head as a transition.
Flange, also known as flange flange or flange flange. The flange is the connecting parts between the pipe and the pipe, for the connection between the end of the pipe; Also useful in the equipment import and export flange, for the connection between two equipment, such as reducer flange. Flange connection or flange joint is a detachable connection which is connected by flange, gasket and bolt as a group of combined sealing structure. Pipe flange means a flange used for piping in a piping installation. When used on equipment means an inlet and outlet flange of equipment. There are holes in the flange and bolts make the two flanges join together. Gasket seals between flanges. The flange is divided into thread connection (thread connection) flange, welding flange and clamping flange. Flange are used in pairs, low pressure pipe can use wire flange, more than 4 kg of pressure using welding flange. Add a gasket between the two flanges and tighten with bolts. Different pressures have different flange thicknesses and they use different bolts. Pumps and valves, and pipe connection, these equipment and local equipment, also made corresponding flange shape, also known as flange connection. All in two plane peripheral use bolt connection at the same time closed connecting parts, generally known as “flange,” such as ventilation pipe connection, this kind of parts can be called “flange parts.” But this connection is only a partial equipment, such as flange and pump connection, it is not good to call the pump “flange parts.” Relatively small, such as valves, can be called “flange parts.”