Flange is a common connector in mechanical equipment, widely used in the connection of equipment such as pipelines, valves, pumps, boilers, etc. Its main function is to connect two sections of pipelines or equipment, or as an interface for disassembly and maintenance. Due to the wide variety of flanges, correctly determining the size of the flange is crucial to ensure the safety, sealing and reliability of the system. So, how to know flange size? This article will introduce the composition of flange size, measurement methods and common flange standards in detail.
Composition of flange size
The size of the flange can be classified according to the standard. Generally speaking, the main dimensions of the flange include the following aspects:
1. Flange diameter (Nominal Diameter, referred to as DN)
The diameter of the flange usually refers to the nominal diameter of the pipe connected by the flange. For example, DN50, DN100, etc. indicate that the flange is suitable for pipes with a diameter of 50mm and 100mm.
2. Flange bore (Bore)
The flange bore refers to the size of the circular hole in the middle of the flange, which determines the inner diameter of the pipe. The bore is usually equal to or slightly larger than the outer diameter of the pipe.
3. Flange Thickness
The thickness of the flange refers to the distance between the upper and lower surfaces of the flange, which is usually determined according to the working pressure, temperature and material of the pipeline.
4. Number of Bolt Holes and Hole Diameter
There are multiple screw holes on the flange for installing bolts to ensure the tightness of the flange connection. The number of holes and the size of the hole diameter are usually related to the diameter and type of the flange.
5. Bolt Circle Diameter (BCD)
The symmetrical distribution of bolt holes is the circular diameter of the center of the bolt hole. The size of the symmetrical distribution of bolt holes directly affects the strength and sealing of the flange.
6. Flange Pressure Rating
The pressure rating of the flange (such as 150, 300, 600, etc.) refers to the maximum working pressure that the flange can withstand, which is usually determined according to the material and manufacturing standards.
7. Flange Sealing Surface Type
The flange sealing surface is the contact surface when the two ends of the flange are connected to the pipeline. Different sealing surface types (such as flat surface, concave and convex surface, tongue surface, etc.) determine the sealing performance of the flange.
How to measure flange size
In engineering practice, knowing how to measure flange size is crucial for selecting and installing the right flange. Here are some common flange size measurement methods:
1. Measure flange outer diameter (OD)
Use a caliper or vernier caliper to measure the outer diameter of the flange. This size is usually the maximum diameter of the flange, which matches the connection size of the pipe.
2. Measure flange bore (Bore)
Use an inside diameter caliper or micrometer to measure the diameter of the middle hole of the flange. This size needs to match the outer diameter of the pipe to ensure a smooth connection.
3. Measure flange thickness (Thickness)
Use a thickness gauge or the depth measurement function of a caliper to measure the thickness of the flange. The thickness is usually related to the pressure rating, material, and working environment of the flange.
4. Measure bolt hole diameter (Bolt Hole Diameter)
Use a caliper or bore gauge to measure the diameter of the bolt holes on the flange. Generally speaking, the bolt hole diameter should match the selected bolt diameter.
5. Measure bolt hole center distance (BCD)
Use a caliper or protractor to measure the center distance of the bolt holes to ensure the symmetry of the bolt holes. The center distance of bolt holes is an important factor affecting the strength of flanges.
6. Measure the gap between the inner and outer planes of the flange
The sealing surface of the flange should be flat, without obvious unevenness. Use a special measuring tool (such as a flatness meter) to check the flatness of the flange and the gap between the inner and outer planes.
Flange standards and classifications
The size and type of flanges are usually specified by various standard specifications, and different countries and regions have different standard systems. Common flange standards include:
1. ISO standards
The International Organization for Standardization (ISO) has developed common flange standards, such as ISO 7005-1 “Industrial Pipe Flanges”, ISO 9001 Quality Management System, etc.
2. ANSI/ASME standards
The American National Standards (ANSI) and the American Society of Mechanical Engineers (ASME) have developed a series of flange standards, the most common of which are ASME B16.5 (flange standard for pipe connections) and ASME B16.47 (large diameter flange standard).
3. DIN standards
German standards (DIN) are also common reference standards for flange sizes and types, such as DIN 2576 and DIN 2631.
4. GB/T standards
The Chinese National Standards (GB) also have detailed regulations on flanges, such as GB/T 9119 (general pipe flanges) and GB/T 17185 (high-pressure flanges).
5. JIS Standards
Japanese Industrial Standards (JIS) include some flange size standards applicable to the Japanese market, such as JIS B 2220.
Depending on the standards, the size, material and design pressure rating of the flange may vary. Therefore, when selecting flanges, you must ensure that the standard that meets the project requirements is selected.
How to choose the right flange size
In practical applications, how to choose the right flange size according to demand is a key issue. The following factors need to be considered when choosing flange size:
1. Nominal diameter (DN) of the pipe
When choosing a flange, ensure that the nominal diameter (DN) of the flange matches the pipe diameter.
2. Working pressure
The pressure level of the flange should be selected according to the working pressure of the pipeline. Pipes with higher pressure need to choose flanges with thicker thickness and stronger pressure bearing capacity.
3. Temperature and material
In high temperature environments, the material of the flange needs to be able to withstand high temperatures. Common high temperature resistant materials include stainless steel, carbon steel, etc.
4. Installation method
The connection methods of the flange usually include butt welding, threading, loose sleeves, etc., and the appropriate flange needs to be selected according to the actual pipeline installation method.
Understanding the flange size and being able to accurately measure the various parameters of the flange is the premise for ensuring the safe and efficient operation of the pipeline system. By mastering the size composition, measurement methods and common standards of the flange, you can better select and install the flange to ensure the long-term stable operation of the equipment. When choosing a flange, you must comprehensively consider the working environment, pressure, temperature, material and other factors of the pipeline to ensure the safety and sealing of the connection.
