ASME B16.47 is a standard established by the American Society of Mechanical Engineers (ASME). Its full name is "Large Diameter Steel Flange (NPS 26 to NPS 60)". This standard includes A series (mainly in English units) and B series (using metric units). It mainly regulates the size, pressure-temperature rating, material, manufacturing, inspection and other aspects of large diameter steel pipe flanges. ASME B16.47 High Hub Blind Flange refers to a large diameter high-neck blind flange that meets this standard.
Structural features
High neck design: Unlike ordinary blind flanges, high-neck blind flanges have a higher neck structure. This high neck part is usually conical, gradually tapering from the flange disc to the end. The presence of the high neck increases the overall strength and rigidity of the flange, which can better withstand loads such as pressure, bending moment and torque in the pipeline system, effectively reduce stress concentration, and improve the reliability of the flange in high pressure, high temperature or vibration environments.
Blind structure: As a blind flange, its center is solid and there is no channel for fluid to pass through. It is mainly used to close the end of the pipeline, prevent the flow of the medium in the pipeline, and play the role of isolation and blocking. During the maintenance, overhaul or renovation of the pipeline system, the high-neck blind flange can be easily installed and disassembled to achieve isolation operations on specific pipe sections.
Sealing surface form: Common sealing surface forms include raised face (RF), ring joint surface (RTJ), etc. The raised face sealing surface is an annular area that is higher than the plane of the flange body. When installed, it needs to be matched with a suitable gasket (such as rubber gasket, metal spiral wound gasket, etc.), and the gasket is deformed by tightening the bolts to achieve sealing; the ring joint surface is specially designed to match the metal ring gasket, with better sealing performance, suitable for high pressure, high temperature and working conditions with extremely high sealing requirements.
Bolt hole distribution: There are several bolt holes evenly distributed on the circumference of the flange, and the number, diameter and spacing of the bolt holes are strictly in accordance with the ASME B16.47 standard. These bolt holes are used to install bolts. By tightening the bolts, the high-neck blind flange can be tightly connected with the matching flange to ensure the sealing effect and connection reliability.
Material selection
Carbon steel: such as ASTM A105, which is a commonly used carbon steel material with good strength and toughness and relatively low cost. It is suitable for general industrial piping systems, can withstand certain pressures and temperatures, and is widely used in the transportation of media such as water, steam, and air.
Alloy steel: For example, ASTM A350 LF2, a low-temperature alloy steel, has alloy elements added to enable it to maintain good mechanical properties in low-temperature environments. It is often used in low-temperature piping systems, such as the storage and transportation of liquefied natural gas (LNG), to prevent brittle fracture under low-temperature conditions.
Stainless steel: Stainless steel materials such as ASTM A182 F304 and F316 have excellent corrosion resistance. It is widely used in piping systems in the chemical, food, pharmaceutical and other industries to prevent the corrosion of the flange by the medium and ensure the long-term stable operation of the piping system.
Application scenarios
Oil and gas industry
In the piping system of offshore oil platforms, high-neck blind flanges are often used to close the ends of pipelines or isolate different process units. Due to the harsh offshore environment, the pipeline system needs to withstand high pressure, high temperature and severe vibration. The high neck design and high strength characteristics of the high neck blind flange can meet these harsh working conditions and ensure the safe operation of the pipeline system.
During the construction and maintenance of long-distance natural gas pipelines, high neck blind flanges can be used to temporarily or permanently block the ends of the pipelines. During the segmented pressure test, overhaul or renovation of the pipeline, the installation of high neck blind flanges can effectively isolate the pipe sections, prevent natural gas leakage, and ensure construction safety.
Chemical industry
In the pipeline system of large chemical plants, high neck blind flanges are widely used for pipeline connections for transporting various corrosive media and high pressure fluids. For example, in the distillation unit of the refinery, the inlet and outlet pipelines of the chemical reactor, etc., the use of high neck blind flanges can ensure the sealing and safety of the pipelines and prevent the leakage of media from causing harm to the environment and personnel.
In the chemical production process, it is sometimes necessary to regularly clean, overhaul or replace equipment for certain pipelines. The detachability of high neck blind flanges makes these operations more convenient and quick, reduces downtime and improves production efficiency.
Power Industry
In high-temperature and high-pressure pipeline systems such as steam pipes and water supply pipes in power plants, high-neck blind flanges can withstand high temperatures and high pressures to ensure the stable operation of the pipeline system. For example, in the steam pipe connection between the boiler and the steam turbine, the use of high-neck blind flanges can effectively prevent steam leakage and improve energy efficiency.
During the maintenance and overhaul of power equipment, high-neck blind flanges can be used to isolate the pipeline system and provide a safe working environment for maintenance personnel. At the same time, its high strength and reliability can also meet the requirements of long-term operation of the power system.
