Today, let's explore the world of flanges! Let's take a look at the types of flanges and the forms of their sealing surfaces.
Flange Basic Introduction
Pipe flanges, their gaskets, and fasteners are collectively referred to as flange joints.
application:
Flange joints are a widely used component in engineering design. They are essential parts for piping design, pipe fittings, and valves, and are also indispensable components in equipment and equipment parts (such as manholes, sight glasses, and liquid level gauges). In addition, flange joints are frequently used in other disciplines such as industrial furnaces, thermal engineering, water supply and drainage, heating and ventilation, and automatic control.
Material:
Forged steel, WCB carbon steel, stainless steel, 316L, 316, 304L, 304, 321, chromium-molybdenum steel, chromium-molybdenum-vanadium steel, molybdenum-titanium steel, rubber-lined, and fluoropolymer-lined materials.
Classification:
Flat-face flanges, neck flanges, butt-welding flanges, ring flanges, socket flanges, and blind flanges, etc.
Implementation Standard:
The series include GB (National Standard), JB (Ministry of Machinery), HG (Ministry of Chemical Industry), ASME B16.5 (American Standard), BS4504 (British Standard), DIN (German Standard), and JIS (Japanese Standard).
International pipe flange standard system:
There are two main international pipe flange standards: the European pipe flange system, represented by German DIN (including the former Soviet Union), and the American pipe flange system, represented by American ANSI pipe flange.
12 types of flanges and sealing surface forms
1. Plate-type flat welding flange
Plate-type flat welding flange (Chemical Standard HG20592, National Standard GB/T9119, Machinery JB/T81).
advantage:
It is easy to source materials, simple to manufacture, low in cost, and widely used.
shortcoming:
It has poor rigidity and therefore should not be used in chemical process piping systems with supply and demand requirements, flammability, explosiveness, and high vacuum requirements, or in highly hazardous or extremely dangerous situations.
Sealing surfaces can be flat or raised.
2. Necked flat welding flange
Necked slip-on flanges belong to the national standard flange system. They are one type of national standard flange (also known as GB flanges) and are one of the commonly used flanges on equipment or pipelines.
advantage:
On-site installation is relatively convenient, and the process of patting and kneading the weld seam can be omitted.
shortcoming:
The neck height of a slip-on flange is lower, which improves the flange's rigidity and load-bearing capacity. Compared with a weld neck flange, it requires more welding work, consumes more welding rods, and cannot withstand high temperature and pressure, repeated bending, and temperature fluctuations.
3 Weld neck flange
The sealing surface types of weld neck flanges include:
Raised face (RF), concave face (FM), convex face (M), tenon face (T), groove face (G), flat face (FF).
advantage:
The connection is not easily deformed, has a good sealing effect, and is widely used. It is suitable for pipelines with large temperature or pressure fluctuations, or pipelines with high temperature, high pressure and low temperature. It is also used for pipelines that transport expensive media, flammable and explosive media and toxic gases.
shortcoming:
Weld neck flanges are bulky, heavy, expensive, and difficult to install and position. Therefore, they are more susceptible to damage during transportation.
4. Integral flange
An integral flange is a type of flange connection. It is also a type of weld neck steel pipe flange. Materials include carbon steel, stainless steel, and alloy steel.
In various domestic standards, IF is used to denote integral flanges. They are mostly used in high-pressure pipelines. The manufacturing process is generally casting.
In flange types, an "IF" designation is used to indicate the type of integral flange.
Generally, raised face (RF) is used. However, in flammable, explosive, or highly hazardous operating conditions, sealing surfaces such as raised face (MFM) and tongue and groove face (TG) can be selected in addition to RF.
5. Socket welding flange
A socket weld flange is a flange that is welded to a steel pipe at one end and bolted to the other end.
Sealing surface type:
Raised face (RF), MMF (Matching Face), Tongue and Groove (TG), Ring Joint (RJ)
Application scope:
Industries include boilers and pressure vessels, petroleum, chemical, shipbuilding, pharmaceutical, metallurgy, machinery, stamped elbows, and food processing.
It is commonly used in pipes with PN≤10.0MPa and DN≤40.
6 Threaded Flange
A threaded flange is a type of non-welded flange where the inner hole of the flange is machined into a pipe thread and used to connect with a threaded pipe.
advantage:
Compared to flat-face or weld neck flanges, threaded flanges are easier to install and maintain, and can be used on pipelines where welding is not permitted on-site. Alloy steel flanges have sufficient strength but are difficult to weld or have poor weldability; in such cases, threaded flanges can also be chosen.
shortcoming:
In cases of rapid temperature changes in pipelines or temperatures above 260°C or below -45°C, it is recommended to avoid using threaded flanges to prevent leaks.
7. Loose flange with welding ring
Welded ring loose flanges are movable flange plates, usually used in water supply and drainage fittings. When the manufacturer ships the expansion joint, each end has a flange, which is directly bolted to the pipes and equipment in the project.
effect:
The purpose of using a weld neck loose flange is generally to save materials. Its structure is divided into two parts: one end of the pipe part connects to the pipeline, and the other end is made into a weld neck ring. The flange is made of a lower grade material, while the pipe part uses the same material as the pipeline, thus achieving the purpose of saving materials.
advantage:
1. Cost savings. When the pipe material is special and expensive, welding flanges of the same material is costly.
2. Those that are inconvenient to weld or process, or require high strength. Such as plastic pipes and fiberglass pipes.
3. Facilitates construction. For example, it can help to align the flange bolt holes during connection or prevent changes in the flange bolt holes when replacing equipment in the future.
shortcoming:
1. Low stress tolerance.
2. Low strength at the weld ring (especially when the thickness is less than 3mm)
8. Flat-welded ring loose flange
A slip-on flange is a movable flange that can be directly bolted to pipes and equipment in the project.
The purpose of using a flat-welded ring loose flange is generally to save data. Its structure is divided into two parts: one end of the pipe is connected to the pipeline, and the other end is made into a flange, with the flange part fitting on the flange.
advantage:
1. Easy to weld, easy to process, or requires high strength, such as plastic pipes and fiberglass pipes.
2. Facilitates construction, such as making it easy to align flange bolt holes during connection or preventing changes in flange bolt holes when replacing equipment in the future.
3. When prices are high, save costs. When the pipe material is special, welding flanges of the same material is costly.
shortcoming:
They have low stress tolerance.
The weld ring has low strength (especially when the thickness is less than 3mm).
9 Flange Cover
Also known as a blind flange or blind plate. It is a flange without a hole in the middle, used to seal pipe ends.
Its function is the same as that of welded end caps and threaded pipe caps, except that blind flanges and threaded pipe caps can be removed at any time, while welded end caps cannot.
Flange cover sealing surface:
Flat (FF), Raised (RF), MFM, Tongue and Groove (TG), Ring Joint (RJ)
10 Lined Flange Cover
A lined flange cover is a type of blind flange where the side closest to the medium is welded with stainless steel, forming a single unit. Lined flange covers are used as blind flanges on pipelines carrying corrosive media. The difference between a lined flange cover and a regular flange cover is the addition of a corrosion-resistant lining on the surface in contact with the medium.
11. American Standard Neck Welding Flange
A slip-on flange with a neck is attached to the end of a pipe. Its main function is to connect pipes to each other. Slip-on flanges have holes for bolts to pass through, allowing two flanges to be tightly connected, and a gasket is used to seal between the flanges.
A gasket is placed between the sealing surfaces of the two flanges. After tightening the nuts, the specific pressure on the gasket surface reaches a certain value, causing it to deform and fill the unevenness on the sealing surface, ensuring a tight and leak-proof connection. Flange connections are detachable connections. Based on the components being connected, they can be divided into vessel flanges and pipe flanges. Necked slip-on flanges are suitable for steel pipe connections with a nominal pressure not exceeding 2.5 MPa.
Necked slip-on flanges are used for butt welding flanges to pipes. They have a reasonable structure, high strength and rigidity, and can withstand high temperature and pressure, repeated bending and temperature fluctuations, with reliable sealing performance. Necked slip-on flanges with a nominal pressure of 0.25～2.5MPa use a raised face sealing surface.
12 American Standard Welding Flanges
ASME (American Standard) flanges are parts used to connect pipes to each other, attached to the pipe ends. ASME welding flanges are manufactured using two methods: forging and casting.
ASME welding flanges can be divided into necked ASME welding flanges and non-necked ASME welding flanges, depending on whether they have a neck.
An ASME (American Standard) welding flange consists of two flanges and a gasket, fastened together with bolts. The flange has perforations for the bolts to secure the two flanges tightly together.
A gasket is used to seal between the flanges.
Chart Explanation
