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Pipe flanges are basically plates or rings used to connect pipes, valves and other piping equipment to form a piping system.
General Flange is a domestic manufacturer of flanges with precision machining capabilities.
· ASTM A105/A105M
· ASTM A350 LF2
· ASTM A182 F11, F22, F304, F316
· ASTM A694 F52, F60, F65, F70
· ASME B16.5
· MSS SP-44
A pipe flange connects piping and components in a piping system by use of bolted connections and gaskets. Most commonly used flanges are weld neck flange, slip on flange, blind flange, socket weld flange, threaded flange and lap joint flange (RTJ Flange). This type of connection in a pipe flange allows for ease of disassembly and separation for repair and regular maintenance. Most common specification for carbon steel and stainless steel flange is ANSI B16.5 / ASME B16.5.
Metal flanges are commonly used for industrial, commercial, and institutional application. Steel pipe flanges are available in variety of styles and pressure classes. Metal flanges are classified from 150 to 2500 # rating. In addition to specifying pressure class, certain flanges such as weld neck flange & socket weld flange also require specifying the pipe schedule. This ensures the pipe bore will match the bore of the weld neck or socket weld flange.
SunnySteel offers wide variety of pipe flanges in carbon steel, stainless steel and nickel alloy. We can also provide special flanges such as long weld neck flange, special material request and high-yield pipe flanges.
There are six most commonly used flanges, also knows as ANSI Flange, ASME B16.5 Flange. However, these designs can be modified to meet the specific functions and requirements of the applications. Therefore, it’s essential to understand the pressure at the flagged joint, the required strength, and the size of pipes involved. With the correct information comes six types of flanges that an individual can choose from. These include:
Blind Flange:These flanges do not have a bore. It is used to blind off a flange or even a valve. When used at the end of a pipe or fitting, it provides an easy to open access for further extension of the pipe. The blind flange and its bolts are stressed more than any other flange.
Lap Joint Flange:This flange is used with a lap joint stub end fitting. It is similar to a slip-on flange, but with two differences. The radius and the flat face, both allow the flange to secure against the stub end fitting. This is useful where alignment of bolt holes is difficult, such as with spools to be attached to flanged nozzles of vessels. A lap joint is used in low pressure applications and not suitable where high external of heavy loads are present.
Slip-on Flange:A slip on flange is designed to slip over the end of pipe. It allows for easy positioning before welding. Both the inside and outside of the pipe is welded on the slip on flange. See picture on the right. The pipe is generally inserted all the way, inside the slip on flange, leaving only the gap equivalent to wall thickness of pipe. These flanges are also knows as ANSI Flange or ASME B16.5 Flange
Socket Weld Flange:This is similar to a slip-on flange, except they have a bored and counter bore. The counter bore allows the pipe to fit into the socket/counter bore. The bore of the flange is the same diameter as the inside of the pipe. These flanges were first designed for small diameter, high pressure pipe.
Threaded Flange:It is similar to a slip-on Flange, but has internal threads. It is normally used for low pressure and not used where temperature or stress is very high. Threaded flange is also called screwed flange or screwed-on flange. This type of flange is used where welding is not an option. Threaded flange is most commonly used on low pressure applications and smaller pipes (up to 4" nominal).
Weld Neck Flange:This flange type is designed to be connected by a butt weld connection to the pipe or equipment requiring a flanged joint. Welding neck provides good service under variety of temperature and pressure applications. A weld neck flange must specifiy the pipe schedule for the bore. Due to the welding neck, it is a popular choice on pressure vessels and for creating man-holes etc. These flanges are also knows as ANSI Flange or ASME B16.5 Flange
Pipe flanges are manufactured in all the different materials like stainless steel, cast iron, aluminium, brass, bronze, plastic etc. but the most used material is forged carbon steel and have machined surfaces.
In addition, flanges, like fittings and pipes, for specific purposes sometimes internally equipped with layers of materials of a completely different quality as the flanges themselves, which are "lined flanges".
The material of a flange, is basically set during the choice of the pipe, in most cases, a flange is of the same material as the pipe.
All flanges, discussed on this website fall under the ASME en ASTM standards, unless otherwise indicated. ASME B16.5 describes dimensions, dimensional tolerances etc. and ASTM the different material qualities.
Additionally, the flanges can be modified to form other types, depending on application and functions. These unique designs are made to incorporate specific needs and applications, like reducing flanges to answer to size and orifice flanges to incorporate orifice mounting:
Spectacle blind flange:A spectacle flange is a specialty flange made of two metal discs attached in the middle by a small section of steel. Spectable flanges get their name because they look like a pair of reading glasses, or spectacles. Spectacle and line blind flanges are similar to a blind flange but different because they fit between two flnges. Spectacle blind gets their name from similarity to pair or eye glasses. Once side of spectacle blind is fully closed for complete flow shutt off, whereas the other end is open for full flow. In this setup the blinds can be rotated without having to take the system apart. It also gives visual confirmation if the line is open or close.
Reducing Flange:Reducing flanges are designed for when there is a change in the pipe size. A reducing flange changes the line size without adding an extra fitting. The reduction in a reducing flange is always abrupt compared to a reduction that can be achieved by concentric butt weld reducer. A reducing flange is commonly available as threaded reducing flange or slip on reducing flange. A 6" by 4" reducing slip on flange will have the flange dimension (outer diameter, bolt circle diameter) of an 6" flange but the hole of a 4" flange. This allows it to mate to an 6" pipe via flanged connection but connect a 4" pipe instead.
Orifice Flange:Orifice flanges are for metering the volumetric flow rate of liquids and gasses through a pipe. This flange is normally available in weld neck, slip-on, and threaded flanges. Orifice flange is a special flange and is always used in pairs. It is used in conjunction with orifice plate for measure flow of liquids and gases in a piping system. Orifice flanges are pre-drilled with tapped holes made in the flange rims to accommodate metering pipe. The flange that makes up the orifice flange is usually a welding neck flange. Slip on and threaded flange are also used sometimes as end connection. In an orifice flange, the pipe must be drilled to accommodate the tapped hole through which the pressure is sensed. The picture above illustrates the working of orifice flange in a welding neck flange arrangement.
Weldoflange / Nipoflange:A weldoflange is an olet connection, it is simular to a nipoflange, both are used for a branch connection on a pipe.
Expander Flange:An expander flange is similar to a weld neck flange but with the hub expanding to a larger size (one or two sizes).
Custom flanges:Our experts are exceptional at machining custom flanges for life. We have experience helping engineers, estimators, purchasing agents and more with their custom flanges.
Anchor flange:An anchor flange is a device to restrain pipe movement in a piping system,it looks like a weld neck flange but has two hubs on the both sides to weld with the pipes,but there is no bolt bores on the anchor flanges.
Standard Connection Flange:This flange is normally used for nozzles on pressure vessels and rarely used with pipe.
Flange face provides a mean to mate the flange with sealing element, usually a gasket. Even though there are many face types, most common flange face types are following;
1. Raised Face
2. Flat Face
3. Lap Joint
4. Ring Joint
5. Tongue and Grove
There are two type of flange face finishes for Raised Face and Flat Face Flanges;
1. Smooth finish
2. Serrated finish (serrated concentric grooves, serrated spiral grooves)
Both serrated finishes have grooves 1/16" deep with 24 to 60 groves per inch.
The back end of raised face flange has a lip that is 1/16" high for pressure classes 150#, 300# and 600#. For flange 900# or higher, the lip is 1/4" thick. Picture above shows a raised face flange.
The back end of a flat face flange, is flat. People sometime confuse it with lap joint flange, however the flat face flange does not have round edges on the bore. Picture above is an example of a flat face flange. compared it to picture from raised flange flange to observe the difference. Flat face is commonly used on cast iron flanges and as mating flanges to pumps and valves in low pressure application.
A ring joint face design has a grooved slot in which a metal ring gasket is inserted to creating a seal with mating flange. The metal ring is available in oval or octagonal shape. Most common material for ring joint gasket is 316 stainless steel which makes it ideal for corrosive applications. The picture above illustrates the ring type gaskets and the ring joint grove finish on the flange.
Lap joint face is used on lap joint flange. It looks similar to flat face flange but has a groove in the bore for mating stub end.
Tongue and groove face has a small contact area for the sealing element providing good gasket compression under low bolt loading. The groove slot acts like an oring groove and provide a good containment means for the gasket. This is ideal under high pressure application. The picture above illustrates the tongue and groove face flange.
Flanges and their joints – Circular flanges for pipes, valves, fittings and accessories, PN designated – Part 1: Steel flanges
This European standard specifies requirements for circular steel flanges in PN designations PN 2,5 to PN 400 and nominal sizes from DN 10 to DN 4000. This standard specifies the flange types and their facings, dimensions, tolerances, threading, bolt sizes, flange face surface finish, marking, materials, pressure/ temperature ratings and flange masses.
Flange faces have to be smooth enough to ensure a tight, leak-free seal for bolted flanges.
A bolted flange connection is a complex combination of many factors (Flange, Bolts, Gaskets, Process, Temperature, Pressure, Medium). All these various elements are interrelated and depend upon one another to achieve a successful result.
The reliability of the flanged joint depends critically upon competent control of the joint making process.
Remember the types of flanges described in the beginning of this article? (Welding Neck, Slip-On, Threaded, Socket Weld, Lap-Joint and Blind), well those were the standard types, now you’ll see that the types of flanges available in the type of the flange is very similar to them, so all the “pros” and “cons” described there can be applied here.
The types divided the flanges in three groups: loose, integral and optional. Below I’ll describe these types according to the Code.
This type covers those designs in which the flange has no direct connection to the nozzle neck, vessel, or pipe wall, and designs where the method of attachment is not considered to give the mechanical strength equivalent of integral attachment.
This type covers designs where the flange is cast or forged integrally with the nozzle neck, vessel or pipe wall, butt welded thereto, or attached by other forms of arc or gas welding of such a nature that the flange and nozzle neck, vessel or pipe wall is considered to be the equivalent of an integral structure. In welded construction, the nozzle neck, vessel, or pipe wall is considered to act as a hub.
This type covers designs where the attachment of the flange to the nozzle neck, vessel or pipe wall is such that the assembly is considered to act as a unit, which shall be calculated as an integral flange, except that for simplicity the designer may calculate the construction as a loose type flange provided none of the following values is exceeded: g0 = 5/8″ (16 mm), B/g0 = 300, P = 300 psi (2 MPa) and operating temperature = 700°F (370°C).
Pipe flanges are manufactured in all the different materials like stainless steel, cast iron, aluminium, brass, bronze, plastic etc. but the most used material is forged carbon steel and have machined surfaces.
Flanges are welded to pipe and equipment nozzle. Accordingly, it is manufactured from the following materials;
· Carbon steel
· Low alloy steel
· Stainless steel
· Combination of Exotic materials (Stub) and other backing materials
The list of materials used in manufacturing is covered in ASME B16.5 & B16.47.
· ASME B16.5 -Pipe Flanges and Flanged Fittings NPS ½” to 24”
· ASME B16.47 -Large Diameter Steel Flanges NPS 26” to 60”
Commonly used Forged material grads are
· Carbon Steel: – ASTM A105, ASTM A350 LF1/2, ASTM A181
· Alloy Steel: – ASTM A182F1 /F2 /F5 /F7 /F9 /F11 /F12 /F22
· Stainless Steel: – ASTM A182F6 /F304 /F304L /F316 /F316L/ F321/F347/F348
· ASME B16.1 – Gray Iron Pipe Flanges and Flanged Fittings: Classes 25, 125, and 250
· ASME B16.5 – Pipe Flanges and Flanged Fittings: NPS 1/2 through NPS 24 Metric/Inch Standard
· ASME B16.20 – Ring Joint Gaskets and Grooves for Steel Pipe Flanges
· ASME B16.21 – Nonmetallic Flat Gaskets for Pipe Flanges
· ASME B16.24 – Cast Copper Alloy Pipe Flanges and Flanged Fittings: Classes 150, 300, 600, 900, 1500, and 2500
· ASME B16.34 – Large Diameter Steel Flanges (NPS 26 through NPS 60)
· ASME B16.36 – Orifice Flanges
· ASME B16.42 – Ductile Iron Pipe Flanges and Flanged Fittings: Classes 150 and 300
· ASME B16.47 – Large Diameter Steel Flanges (NPS 26 Through NPS 60)
· ASTM A105 – Specification for Carbon Steel Forgings for Piping Applications
· ASTM A182 – Specification for Forged or Rolled Alloy Steel Pipe Flanges, Forged Fittings, and Valves and Parts for High Temperature Service
· ASTM A193 – Specification for Alloy Steel and Stainless Steel Bolting Materials for High Temperature Service
· ASTM A194 – Specification for Carbon and Alloy Steel Nuts for Bolts for High Pressure and High Temperature Service
· ASTM A694 – Specification for Carbon and Alloy Steel Forgings for Pipe Flanges, Fittings, Valves, and Parts for High-Pressure Transmission Service
· ASTM A707 – Specification for Flanges, Forged, Carbon and Allow Steel for Low Temperature Service
· AWWA C115 – Standard for Flanged Ductile Iron Pipe with Ductile-Iron or Gray-Iron Threaded Flanges
· ISO 5251 – Stainless steel butt-welding fittings
· MSS SP-6 – Standard Finishes for Contact Faces Pipe Flanges and Connecting End Flanges of Valves and Fittings
· MSS SP-9 – Spot Facing for Bronze, Iron and Steel Flanges
· MSS SP-25 – Standard Marking Systems for Valves, Fittings, Flanges, and Unions
· MSS SP-44 – Steel Pipeline Flanges
· MSS SP-53 – Quality Standards for Steel Castings and Forgings for Valves, Flanges and Fittings and Other Piping Components – Magnetic Particle
· MSS SP-54 – Quality Standards for Steel Castings and for Valves, Flanges and Fittings and Other Piping Components – Radiographic
· MSS SP-55 – Quality Standards for Steel Castings and for Valves, Flanges and Fittings and Other Piping Components – Visual
· MSS SP-75 – High Test Wrought Butt Welding Fittings
· MSS SP-106 – Cast Copper Alloy Flanges and Flanged Fittings Class 125,150, and 300
· ASME B16.5 and ASME B16.47 cover pipe flanges up to NPS 60 (B16.5 from 1/2″ to 24″ and B16.47 from 26″ to 60″). ANSI
· B16.47 covers two series of flanges, Series A is equal to MSS SP-44-44, and Series B is equal to API 605 (API 605 has been canclled).
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