Flange

Flange

The Flange is the second most used joining method after welding. Flanges are used when joints need dismantling. It Provides flexibility for maintenance.

Flange Connects the pipe with various equipment and valves. Breakup flanges are added in the pipeline system if regular maintenance is required during plant operation.

Flange Materials Specification

Dimensions from carbon steel and stainless steel flanges are defined in the ASME B16.5 standard. The material qualities for these flanges are defined in the ASTM standards.

These ASTM standards, define the specific manufacturing process of the material and determine the exact chemical composition of pipes, fittings, and flanges, through percentages of the permitted quantities of carbon, magnesium, nickel, etc., and are indicated by “Grade”.

For example, a carbon steel flange can be identified with Grade F9 or F11, a stainless-steel flange with Grade F316 or Grade F321 etc..
Below you will find as an example a table with chemical requirements for fittings ASTM A403 Grade WP304, WP304L, WP316L and a table with frequent Grades, arranged on pipe and pipe-components, which belong together as a group.

As you may be have noted, in the table below, ASTM A105 has no Grade. Sometimes ASTM A105N is described; “N” stands not for Grade, but for normalized.

Normalizing is a type of heat treatment, applicable to ferrous metals only. The purpose of normalizing is to remove the internal stresses induced by heat treating, casting, forming etc.

Carbon Steel Flanges

The Carbon Steel Flanges are available in various dimensions. Exhibiting the properties such as high strength, high toughness, excellent fatigue strength, superior chemical resistance and high stress-corrosion cracking resistance, these flanges are ideal for connecting various pipes and are significant while support is required for mechanical parts.

• ASTM A105, ASTM A350 LF1, LF2 CL1/CL2, LF3 CL1/CL2
• ASTM A694 F42, F46, F48, F50, F52, F56, F60, F65, F70

Stainless Steel Flange

Stainless Steel Flanges are corrosion resistant and have a wide variety of uses. We carry a variety of threaded flanges, weld neck flanges and slip-on flanges and of course, we can custom build stainless steel flanges to your specifications.

• ASTM A182 F304/304L, F316/316L, F316H, F310, F321, F44 (UNS S31254)
• ASTM A403 WP316/316L
• ASTM A403 WP304/304L
• ASTM A182 F304, F304L, F316, F316L, F321

316 / 316L

316/316L is the most commonly used austenitic stainless steel in the chemical process industry. The addition of molybdenum increases general corrosion resistance, improves chloride pitting resistance and strengthens the alloy in high-temperature service.

Through the controlled addition of nitrogen, it is common for 316/316L to meet the mechanical properties of 316 straight grade while maintaining a low carbon content.

Applications of flanges

Flanges are integral parts of many engineering and plumbing projects.

In many applications, engineers need to find a way to close off a chamber or cylinder in a very secure fashion, usually, because the substance inside must differ from the substance outside in composition or pressure.

They do this by fastening two pieces of metal or other material together with a circle of bolts on a lip. This “lip” is a flange.

Plumbing

You can connect two sections of metal piping by soldering or welding them together, but pipes connected in this way are very susceptible to bursting at high pressures.

A way of connecting two sections of pipe more securely is by having flanged ends that you can connect with bolts. This way, even if gases or liquids build up to high pressures inside the pipe, it will often hold with no problem.

Mechanics

In order to connect two sections of a large, enclosed area, it is often best to used flanges and bolts. An example of this is the connection between the engine and the transmission in an automobile.

In this case, both the engine and the transmission contain a number of moving parts that can easily get damaged if they get dust or other small objects inside of them. By connecting the outer casings of the engine and transmission in this way, engineers protect the inner workings of both.

Electronics

Flanges have a specific purpose in cameras and other electronic devices. Though flanges in such items do not usually have to sustain high pressures, they do have to hold tight so they can keep out harmful particles.

These flanges are usually found connecting two different materials, such as the glass of a lens and the rest of the body of the camera.

TYPES OF FLANGES

The most used flange types in Petro and chemical industry are:

• Welding Neck Flange
• Slip On Flange
• Socket Weld Flange
• Lap Joint Flange
• Threaded Flange
• Blind Flange

SPECIAL FLANGES

Except for the most used standard flanges, there are still a number of special flanges such as:

• Orifice Flanges
• Long Welding Neck Flanges
• Weld flange / Nipoflange
• Expander Flange
• Reducing Flange

Weld-neck

Complete with a tapered hub, these flanges are recognizable and used in high-pressure environments. The flange is particularly useful under repeat bending conditions.

Slip-on

A flange which is slipped over the pipe and welded both inside and outside to increase strength and prevent leakage. A favorite for engineers compared to the weld-neck due to their lower cost.

Socket-weld

With a static strength equal to the Slip-on flange, the Socket-weld is connected with the pipe with 1 fillet weld on the outside of the flange. Due to corrosion issues, some processes do not allow this flange.

Lap-joint

Used in conjunction with a lap joint stub end, the flange is slipped over the pipe but not fastened, unlike the slip-on. Instead, the flange is held in place by the pressure transmitted to the gasket by the flange pressure against the back of the pipe lap.

Threaded

Used in special circumstances, the threaded flange can be attached to the pipe without being welded. These are usually positioned on pipes with a deep wall thickness, used to create the internal thread.

Blind

Manufactured without a bore, these flanges are used to blank off the end of piping, valves and pressure vessel openings. They are also most suitable for high pressure-temperature applications.

References:

https://hardhatengineer.com/types-flanges-used-piping/

http://www.wermac.org/flanges/flanges_pipe-connections_pipe-flanges.html

http://www.sunnysteel.com/flange-material.php

https://blog.miragemachines.com/6-of-the-most-common-flange-types-used-in-the-oil-and-gas-industry