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Vacorda Lessons: knowledge about flange

Author:vacorda    Source:vacorda.com    Date: 2018-05-11 16:16:29

Flanges are the parts that connect the shaft to the shaft and are used for the connection between the pipe ends. They are also used for flanges on the equipment inlet and outlet, for the connection between two devices, such as the reducer flange. Flange connection or flange joint refers to the detachable connection of flanges, gaskets and bolts as a set of combined sealing structures. Due to its excellent performance, flanges are widely used in chemical, construction, water supply, drainage, petroleum, light and heavy industry, refrigeration, sanitation, plumbing, fire protection, power, aerospace, shipbuilding and other basic projects.

All of our vacorda measuring instruments need them. In order to make it more clear about the flanges when the customer use our measuring instruments. Here we give you some brief introduction about the flanges.


1. Basic introduction of flange

Pipe flanges and their gaskets and fasteners are collectively referred to as flange joints.

 flange joints

2.1. Application: Flange joints are a kind of parts that are used widely in engineering design and cover a wide range of aspects. It is an indispensable part of piping design and fitting valves, and it is also an essential component of equipment and equipment components (such as manholes, sight glass level gauges, etc.). In addition, flange joints are often used in other professions such as industrial furnaces, thermal engineering, water supply and drainage, heating and ventilation, and self-control.


2.2. Material: Forged steel, WCB carbon steel, 316L, 316, 304L, 304, 321, chromium molybdenum steel, chromium molybdenum vanadium steel, molybdenum titanium, rubber lining, lined with fluorine material.


2.3. Classification: Flat welding flange, with neck flange, butt welding flange, ring connection flange, socket flange, and blinds.


2.4. Implementation standards: There are GB series (national standards), JB series (mechanical department), HG series (chemical department), ASME B16.5 (American standard), BS4504 (British standard), DIN (Germany standard), JIS (Japanese standard).


2.5. The international standard flange flange system: There are two main systems for international standards for pipe flange:

European pipe flange system represented by German DIN (including the former Soviet Union)

American pipe flange system represented by American ANSI pipe flange.

2. Types and features of common used flange

1. Plate flat welding flange (Chemical standard HG20592, national standard GB/T9119, mechanical JB/T81).

Plate flat welding flange


Easy to draw, simple to manufacture, low cost, widely used.


Due to poor rigidity, it cannot be used in chemical process piping systems where there are supply, demand, flammability, explosives, and high vacuum levels, and in highly hazardous locations.

The sealing surface type has flat and protruding surfaces.

2. Slip-on flange with neck

Slip-on flange with neck is a standard system of national standard flange. It is one of the expressions of national standard flange (also called GB flange) and it is one of the commonly used flanges on equipment or pipelines.

 Slip-on flange with neck drawingSlip-on flange with neck


The installation on the spot is more convenient, and the welding seam can be omitted.


The neck-flanged neck has a low neck height, which improves the rigidity and load-bearing capacity of the flange. Compared with butt welding flanges, the welding work load is large, the welding rods are high in consumption, and cannot withstand the high temperature and high pressure and the repeated bending and temperature fluctuations.

3. Welding flange with neck

The sealing surfaces with neck butt welding flanges are:

Raised face (RF), concave face (FM), convex face (M), facet (T), groove face (G), full face (FF).

Welding flange with neck


The connection is not easily deformed, has good sealing effect and is widely used. It is suitable for pipelines with large temperature or pressure fluctuations or high temperature, high pressure and low temperature pipelines, and also for conveying expensive media, inflammable and explosive media, toxic gas pipelines.


The flanges with neck butt welded flanges are bulky, heavy, expensive, and difficult to install and position, making it easier to bump in transit.

4. The integral type flange

The integral flange is a flange connection. It is also a kind of flange with neck welded steel pipe. Materials contains carbon steel, stainless steel, alloy steel and so on.

The integral type flangedrawingThe integral type flange

It mostly used in high pressure pipelines, the production process is generally casting. Generally, it is a protruding surface (RF). If it is used under flammable, explosive, high and extremely hazardous working conditions, the sealing of the convex and concave surfaces (MFM) and the groove surface (TG) other than the RF surface may be selected. The form of the face.

5. Socket welding flange

The socket welding flange is a flange that is bolted to one end and the other end of the steel pipe.

Socket welding flange drawingSocket welding flange

Sealing surface form:

Raised surface (RF), concave-convex surface (MFM), grooved surface (TG), and ring-connected surface (RJ).


Application range:

Boiler pressure vessels, petroleum, chemicals, shipbuilding, pharmaceuticals, metallurgy, machinery, food and other industries.

Commonly used in PN ≤ 10.0MPa, DN ≤ 40 in the pipeline.

6. Threaded flange

Threaded flanges are made by machining the internal bore of a flange into a pipe thread, and are connected to a threaded pipe to make a connection. This is a non-welding flange.

Threaded flange


Compared with the flat-welded or welded flanges, the threaded flanges are easy to install and maintain, and can be used on pipelines that are not allowed to be welded on site. Alloy steel flanges have sufficient strength but are not easy to weld or have poor welding performance. Threaded flanges are also available.


In the event of a sharp temperature change in the pipeline or a temperature higher than 260°C below -45°C, it is recommended not to use a threaded flange to prevent leakage.



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