Flange connection is a common pipe connection method, which is widely used in various pipe systems, especially in pipe systems that require high pressure or high temperature environments. The advantages of flange connection are its reliability and detachability, which is especially suitable for occasions where it is inconvenient to use other connection methods such as welding, threading or crimping. This article will explain in detail the definition of flange, the steps and precautions of flange connection, etc., to help you understand How to connect flange to pipe and ensure the safety and stability of the connection.
Definition and types of flanges
A flange is a disc-shaped component used to connect pipes, valves, pumps and other equipment. It usually has multiple holes for connecting to other equipment through bolts. Flanges seal and connect pipeline systems through the combination of bolts and gaskets. According to different working conditions and uses, flanges have many different types and standards, mainly including:
1. Weld Neck Flange
This flange has a tapered long neck and is suitable for high-pressure and high-temperature pipeline connections. After welding, it can ensure the uniform distribution of pressure inside and outside the pipeline and reduce stress concentration.
2. Slip-on Flange
The slip-on flange does not have a tapered long neck. It can be slid into the pipeline during installation and then fixed by welding. It is suitable for medium and low pressure environments and is easy to install.
3. Butt Weld Flange
This flange is designed for direct welding with the pipeline, and it is tightly connected by welding. It is usually used in pipeline systems that require higher pressure and stability.
4. Blind Flange
Blind flange is used to close the end of the pipeline and is not connected to other pipelines. It is usually used to seal the pipeline during maintenance to prevent material leakage.
5. Flat Flange
This flange is used for low pressure and simpler connection methods. It is connected through a flat sealing surface.
There are many standard types of flanges, including ANSI, DIN, JIS, GB, etc. Each standard differs in size, number of bolt holes, sealing method, etc. When selecting a flange, the appropriate flange type should be selected according to the pressure level of the pipeline, the type of medium, and the use environment.
Basic steps for flange connection
The process of connecting flange to pipeline is relatively simple, but in order to ensure the firmness and sealing of the connection, certain steps and requirements must be followed. The following are the basic steps for connecting flange to pipeline:
1. Preparation
Before starting the connection, you first need to check the specifications of the pipeline and flange to ensure that their size, pressure rating and material match. At the same time, you also need to prepare other accessories such as bolts, nuts, gaskets and necessary tools. Commonly used tools include wrenches, sealants, welding equipment, etc.
2. Processing of pipeline ports
Make sure that the ports at both ends of the pipeline are flat, clean and burr-free. If it is a welded flange (such as a weld neck flange), the port of the pipeline needs to be finely processed to ensure that the welding surface is smooth and there are no defects such as pores and cracks during welding.
3. Assembly of flange
For loose flanges, slide the flange into the pipe port, make sure it is flat with the pipe end face and fixed well. If a welded flange is used, align the flange with the pipe port and perform the welding operation.
For welding flanges, first butt the pipe and flange, and weld the flange and pipe together through appropriate welding processes to ensure that there are no defects in the weld and the welding quality meets the standards.
4. Install gaskets
Place gaskets between the flange sealing surfaces where the flange and the pipe are connected. Gaskets are usually made of flexible materials (such as rubber, asbestos, metal, etc.), have good sealing properties, and can effectively prevent liquid or gas leakage. Make sure that the gasket is of appropriate size and can cover the entire sealing surface.
5. Install bolts
Align the bolt holes on both sides of the flange and insert the bolts one by one. The bolts should be evenly distributed to avoid being too tight on one side and too loose on the other side. After the nuts are installed, they should be tightened manually, but not too tight to prevent damage to the gasket or flange sealing surface.
6. Tighten the bolts evenly
Use a wrench to tighten the bolts on the flange alternately and evenly step by step. It is best to tighten in diagonal order to ensure that the pressure is evenly distributed and avoid flange deformation. Certain torque requirements should be followed when tightening. Flanges and pipes of different specifications need to determine the appropriate torque value according to the standard.
7. Check the tightness
After installation, perform a pressure test or water tightness test to ensure that there is no leakage at the flange connection. If leakage is found, recheck the bolt tightness or replace the gasket.
Precautions for flange connection
1. Choose the right flange type
Choose the right flange type according to the working pressure, working environment and medium type of the pipeline. For example, high temperature and corrosion resistant materials should choose flanges suitable for high temperature or corrosive environments, commonly used are stainless steel flanges, carbon steel flanges, etc.
2. Cleaning and inspection
Before connection, make sure that the flange, gasket and pipe port are kept clean to avoid impurities affecting the sealing. The sealing surface of the flange should be flat and smooth to avoid cracks, deformation or unevenness.
3. Torque control
The bolts should be tightened evenly to avoid excessive local force. Overtightened bolts may cause flange deformation or damage to the gasket, while overly loose bolts may cause leakage. When tightening, a torque wrench can be used to ensure that the standard torque is reached.
4. Gasket selection
The choice of gasket should be determined according to the type, temperature and pressure of the medium. For example, the gasket material used for gas pipelines is different from that used for liquid pipelines. Common gasket materials include rubber, polytetrafluoroethylene (PTFE), metal gaskets, etc.
5. Avoid over-tightening
The bolts of the flange should not be over-tightened, otherwise it may cause permanent damage to the flange and gasket, resulting in seal failure.
6. Regular inspection and maintenance
After the flange is connected, regularly check its sealing and bolt tightening, especially in an environment with large pressure and temperature changes. During long-term use, the gasket may age or wear, so it needs to be replaced regularly.
As an efficient and reliable pipeline connection method, flange connection is widely used in many industries such as petroleum, chemical, electricity, and food. Correct flange connection can not only ensure the sealing of the pipeline system, but also improve the safety and reliability of the system. Through the introduction of this article, we understand the basic steps and precautions of flange connection. Whether it is in the selection of flange type, the operating process during installation, or in the later inspection and maintenance, it is necessary to strictly follow the relevant standards and operating specifications to ensure the firmness of the connection and the long-term stable operation of the system.
