Flange is the interconnecting part between pipe and pipe, used for the connection between pipe ends; it is also useful for the flange on the inlet and outlet of the equipment, used for the connection between two equipment, by flange, gasket and The three bolts are connected to each other as a detachable connection of a combined sealing structure. The main materials are: carbon steel, alloy steel, low temperature steel, and stainless steel.
Marine flanges are flanges used on ships and are currently the most important form of ship pipeline connection. Its advantages are high bonding strength, convenient disassembly and assembly, wide application range, and it can be applied to almost all pipeline connections.
Marine flanges are divided into:
Plate flat welding flange (PL), neck butt welding flange (WN), neck flat welding flange (SO), socket welding flange (SW), integral flange (IF), threaded flange (Th ), butt welding ring loose flange (PJ/SE), flat welding ring loose flange (PJ/RJ), lining flange cover (BL (S), flange cover (BL).
Commonly used sealing surface forms: flat surface (FF), raised surface (RF), concave-convex surface (MFM), tongue and groove surface (TG), ring connection surface (RJ).
The implementation of standards-about the standard codes of marine flanges:
1. ISO International Standard/GB National Standard
2. CB Soviet Standard/Industry Standard
3. JIS Japanese Standard/CBM Foreign Trade Standard
Since the Japanese standard system was introduced in large quantities when my country began to build export ships in the 1980s, the CBM standard that conforms to the JIS standard is currently widely used, and now the world’s operating ships built by Japan account for the majority, so the JIS standard It is still the universal standard in the world. But from the perspective of the country's entire standard system, the CBM standard should be a transitional standard and should be gradually cancelled.
In addition, according to the requirements of the National Standardization Committee in 2004, the marine flange standards will have major changes, mainly in two to three years. The current 15 national standards on flanges will be integrated into 6-7 standards. Pay attention to these changes in actual work.
Marking of flange standards
Marine flanges are generally standard products. According to most current standards, the marking composition of flanges is as follows:
Name + pressure level + diameter + standard number
The pressure grade and diameter are expressed by numbers, the diameter is expressed by three digits, and 0 is added for less than three digits, and the diameter over 1000mm is expressed by four digits; the pressure is expressed by the MPa value magnified by 10 times.
For example: pressure rating PN=0.5MPa, nominal diameter DN=100mm, CBM1012 standard flange, its mark is:
Lap welded steel flange 5100 CBM1012-81
Pressure rating PN=1.6 MPa, nominal diameter DN=50mm, GB2506 standard flange, its mark is:
Marine lap welded steel flange 16050 GB 2506-1989
However, the new standard has changed the requirements for flange marking, that is, the pressure rating and diameter are moved to the back of the standard number.
Common faults of flanges
In the continuous production of modern industry, flanges are affected by factors such as medium corrosion, scouring, temperature, pressure, vibration, etc., and leakage problems will inevitably occur. Due to the error of the sealing surface processing size, the aging of the sealing element and the improper installation and tightening, etc., it is very easy to cause the leakage of the flange. If the flange leakage problem cannot be treated in time, the leakage will rapidly expand under the erosion of the medium, causing loss of materials and destruction of the production environment, causing the company to stop production and cause huge economic losses. If toxic, harmful, flammable and explosive media leaks, it may also cause serious accidents such as personnel poisoning, fire and explosion. The method to solve flange leakage is to replace the sealing element and apply sealant or replace the flange and pipeline.
In addition, because the flange has good comprehensive performance, it is also widely used in chemical, construction, water supply, drainage, petroleum, light and heavy industry, refrigeration, sanitation, plumbing, fire fighting, electric power, aerospace, and other basic projects.
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