Flange is the abbreviation of flange, which is the transliteration of flange. It was first proposed by an Englishman named Elchard in 1809, and the casting method of flange was also proposed at the same time. However, it was not widely used for quite a long time afterwards. It was not until the beginning of the twentieth century that flange was widely used in various mechanical equipment and pipeline connections.

What is flange?

Flange, also known as flange flange or flange. It usually refers to a metal body with several fixed holes opened around it for connecting other parts. It is widely used in various mechanical equipment and pipeline connections. Flange is a part that connects shafts to each other and is used for connecting pipe ends; there are also flanges used on the inlet and outlet of equipment, which are used for connecting two equipment, such as reducer flanges.

Classification of flanges?

1. According to the chemical industry (HG) standards:

Integral flange (IF), threaded flange (Th), plate slip-on flange (PL), necked butt-weld flange (WN), necked slip-on flange (SO), socket-weld flange (SW), butt-weld ring loose flange (PJ/SE), slip-on ring loose flange (PJ/RJ), lined flange cover (BL(S)), flange cover (BL).

2. According to the petrochemical industry (SH) standards:

Threaded flange (PT), butt-weld flange (WN), slip-on flange (SO), socket-weld flange (SW), loose flange (LJ), flange cover (not noted).

3. According to the machinery (JB) industry standards:

Integral flange, butt-weld flange, plate slip-on flange, butt-weld ring plate loose flange, slip-on ring plate loose flange, flange plate loose flange, flange cover.

4. According to national (GB) standards:

Integral flange, threaded flange, butt-weld flange, flat-weld flange with neck, socket-weld flange with neck, butt-weld ring-neck loose flange, plate-weld flange, butt-weld ring-plate loose flange, flat-weld ring-plate loose flange, flanged ring-plate loose flange, flange cover.

Flange standards

Flanges are widely used as a connector internationally, which requires a unified standard. For example, there are currently two main standard systems for pipeline flanges, namely the European pipe flange system represented by German DIN (including the former Soviet ｕｎｉｏｎ) (DIN, GB, JB, HG20592) and the American pipe flange system represented by American ANSI pipe flange (including ANSI, GB, HG20615). In addition, there are Japanese JIS pipe flanges, but they are generally only used for public works in petrochemical plants and have little impact internationally. Here is a brief introduction to pipe flanges from various countries:

1. European flange system

European flange system: German DIN (including the Soviet ｕｎｉｏｎ)

★ Nominal pressure: 0.1, 0.25, 0.6, 1.0, 1.6, 2.5, 4.0, 6.4, 10.0, 16.0, 25.0, 32.0, 40.0, Mpa;

★ Calculated diameter: 15~600mm;

★ Flange structure type: flat welding plate type, flat welding ring loose sleeve type, rolled edge loose sleeve type, butt welding rolled edge loose sleeve type, butt welding ring loose sleeve type, butt welding type, neck thread connection type, integral type and flange cover;

★ Flange sealing surfaces include: flat surface, concave surface, concave and convex surface, tongue and groove surface, rubber ring connection surface, lens surface and diaphragm welding surface;

★ The OCT pipe flange registration standard issued by the Soviet ｕｎｉｏｎ in 1980 is similar to the German DIN standard.

2. American flange system

American flange system: US ANSI B16.5 "Steel pipe flanges and flange fittings"

Nominal pressure: 150psi (2.0Mpa), 300psi (5.0Mpa), 400psi (6.8Mpa), 600psi (10.0Mpa), 900psi (15.0Mpa), 1500psi (25.0Mpa), 2500psi (42.0Mpa);

★ Calculated diameter: 6~4000mm;

★ Flange structure type: strip welding, socket welding, threaded connection, loose sleeve, butt welding and flange cover;

★ Flange sealing surface: concave surface, concave and convex surface, tongue and groove surface, metal ring connection surface.

3. JIS (Japanese Standard) pipe flange

JIS pipe flange: It is generally only used for public works in petrochemical plants, has little influence internationally, and has not formed an independent system internationally.

Attached GB (National Standard) System

my country's national standard system for steel pipe flanges GB.

1. Nominal pressure: 0.25Mpa~42.0Mpa

★ Series 1: PN1.0, PN1.6, PN2.0, PN5.0, PN10.0, PN15.0, PN25.0, PN42 (main series)

★ Series 2: PN0.25, PN0.6, PN2.5, PN4.0

Among them, PN0.25, PN0.6, PN1.0, PN1.6, PN2.5, PN4.0, a total of 6 grades of flange sizes belong to the European flange system represented by the German flange, and the rest are the American flange system represented by the American flange.

In the GB standard, the maximum nominal pressure level of the European flange system is 4Mpa, and the maximum nominal pressure level of the American flange system is 42Mpa.

2. Nominal diameter: 10mm~4000mm

3. Flange structure:

① Integral flange ② Unit flange

★ Threaded flange;

★ Welded flange, butt-welded flange;

★ Neck-welded flange, neck-welded socket-welded flange, plate-welded flange: loose flange, butt-welded ring loose flange with neck, butt-welded ring loose plate flange, flat-welded ring loose plate flange, plate-type flip-over loose flange

★ Flange cover (blind hole flange).

4. Flange sealing surface: flat surface, concave surface, concave-convex surface, tongue-and-groove surface, ring connection surface

Flange assembly

1. Before assembling the flange, the flange surface must be cleaned, especially the sealing surface.

2. When assembling the flat plate welding flange, the pipe end should be inserted into the flange inner diameter thickness of 2 ≤ 3, and then the flange should be spot welded with the pipeline. If it is a horizontal pipe, the flange should be spot welded from above, and then the flange position should be checked and corrected from different directions with a 90° angle ruler so that its sealing surface is perpendicular to the center line of the pipeline, and then the second point under spot welding is correct.

3. Check and correct the flange position from the left and right directions with a 90° angle ruler, spot weld the third and fourth points after passing, and complete the spot welding and fixing of the flange.

4. As far as the assembly of the flange pair is concerned, the bolt holes of the mounting flange should be aligned with the corresponding bolt holes of the fixed flange and parallel to the fixed flange, and the deviation shall not be less than 1.5% of the outer diameter of the flange per thousand., and not more than 2mm.

5. When selecting the matching flange of the equipment or valve component, attention should be paid to whether the flange of the original equipment or valve component is consistent with the flange connection size used in the pipeline.

Commonly used soft gasket materials

Rubber sheet and rubber cotton sheet are the most commonly used flange soft gasket materials.

1. Industrial rubber sheet

Rubber sheet is commonly known as industrial rubber sheet, also known as industrial vulcanized rubber sheet or rubber sheet.

2. Rubber cotton sheet

Rubber cotton sheet, also known as asbestos rubber sheet, is generally used as a gasket for equipment and pipeline flange sealing. The medium can be water, steam, air, various gases, ammonia, alkali liquid and oil, etc.

Flange connection

1. The flange connection should be kept on the same axis, the center deviation of the bolt hole should not exceed 5% of the aperture, and the bolt should be freely perforated. The connecting bolts of the flange should have the same specifications, the installation direction should be the same, and the bolts should be tightened symmetrically and evenly.

2. Bevel washers of different thicknesses should not be used to compensate for the non-parallelism of the flange. Do not use double washers. When large-diameter washers need to be spliced, they should not be butt-jointed with flat ports, but should be in the form of beveled loops or mazes.

3. To facilitate the installation and removal of the flange, the fastening bolts and the flange surface shall not be less than 200 mm.

4. When tightening the bolts, they should be symmetrical and intersecting to ensure uniform force on the gasket.

5. Bolts and nuts should be coated with molybdenum disulfide, graphite oil or graphite powder for subsequent removal: stainless steel, alloy steel bolts and nuts; pipeline design temperature is 100℃ or below 0℃; open-air facilities; atmospheric corrosion or corrosive media.

6. Metal gaskets such as copper, aluminum and mild steel should be annealed before installation.

7. Direct buried flange connection is not allowed. Flange connections for buried pipelines should have inspection wells. If buried is necessary, anti-corrosion measures should be taken