Q. What is Flanges ? Which Types of Flanges used In Fabrication...?
Flanges : A flange is a method of connecting pipes, valves, pumps and other equipment to form a piping system. It also provides easy access for cleaning, inspection or modification. Flanges are usually welded or screwed. Flanged joints are made by bolting together two flanges with a gasket between them to provide a seal.
Types :
1) WNRF Flanges (Weld Neck Flanges) :
The Welding Neck Flanges (WNRF) are often used for high-pressure applications. To order a weld neck flange, it is important to specify the pipe is being used for. This is because the inside diameter of the flange will match the inside diameter of your pipe or Fitting. Weld Neck Flanges are ideal for extreme fluctuations of temperature and in environments where there may be a lot of bending and handling of the flanges.Welding Neck Flanges are easy to recognize at the long tapered hub, that goes gradually over to the wall thickness from a pipe or fitting. The long tapered hub provides an important reinforcement for use in several applications involving high pressure, sub-zero and / or elevated temperatures. These flanges are bored to match the inside diameter of the mating pipe or fitting so there will be no restriction of product flow. This prevents turbulence at the joint and reduces erosion. This flange type will be welded to a pipe or fitting with a single full penetration, V weld (Butt weld).
Standards :
ANSI/ASME B16.5, B16.47 Series A & B, B16.48, BS4504, BS 10, EN-1092, DIN, ANSI Flanges, ASME Flanges, BS Flanges, DIN Flanges, EN Flanges, GOST Flange, ASME/ANSI B16.5/16.36/16.47A/16.47B, MSS S44, ISO70051, JISB2220, BS1560-3.1, API7S-15, API7S-43, API605, EN1092
Dimensional Tolerance As Per B16.5 and B16.47 as,
| Outside Diameter ≤ 24 = 1.6 mm | > 24 = ± 3.2 mm | Inside Diameter not applicable |
| Diameter of Contact Face 1.6 mm Raised Face = ± 0.8 mm 6.35 mm Raised Face, Tongue & Groove / Male-Female = ± 0.4 mm | Outside Diameter of Hub ≤ 12 = + 2.4 mm / - 1.6 mm | ≥ 14 = ± 3.2 mm |
| Diameter of Counterbore not applicable | Drilling Bolt Circle = 1.6 mm | Bolt Hole Spacing = ± 0.8 mm Eccentricity of Bolt Circle with Respect to Facing ≤ 2½ = 0.8 mm max. | ≥ 3 = 1.6 mm max. |
| Thickness ≤ 18 = + 3.2 mm / - 0 | ≥ 20 = + 4.8 mm / - 0 | Length thru Hub ≤ 18 = + 3.2 mm / - 0.8 mm | ≥ 20 = + 4.8 mm / - 1.6 mm |
Material :
For SS Material : ASTM/ASME A/SA182 F304, F304L, F316, F316L, ASTM/ASME A/SA351 CF8, CF3, CF8M, CF3M
For CS Material : ASTM/ASME A/SA105 A/SA105N & A/SA216-WCB, ASTM A105 / ASME SA105, A105N, ASTM A350 LF2 / ASME SA350, High Yield CS ASTM A694 / A694 (F52 F56 F60 F65 F70 F80)
For Alloy Steel Material : ASTM A182 / ASME SA182 F5, F9, F11, F12, F22, F91
The diagrammatic view of WNRF Flanges as shown below,
Pic.001
2) Slip On Flange :
The calculated strength from a Slip On flange under internal pressure is of the order of two-thirds that of welding neck flanges, and their life under fatigue is about one-third that of the latter. The connection with the pipe is done with 2 fillet welds, as well at the outside as also at the inside of the flange. A disadvantage of the flange is, that principle always firstly a pipe must be welded and then just a fitting. A combination of flange and elbow or flange and tee is not possible, because named fittings have not a straight end, that complete slid in the Slip On flange. Slip on flange are slipped over the pipe and welded to provide strength and prevent leakage. This SORF flange can sometimes have a boss or hub and can be made with a bore to suit either pipe or tube. The Slip on Flanges is at the low-cost end of the scale. SORF flanges are not required high accuracy when cutting the pipe to length.
Standard : ANSI/ASME B16.5, B16.47 Series A & B, B16.48, BS4504, BS 10, EN-1092, DIN, ANSI Flanges, ASME Flanges, BS Flanges, DIN Flanges, EN Flanges, GOST Flange, ASME/ANSI B16.5/16.36/16.47A/16.47B, MSS S44, ISO70051, JISB2220, BS1560-3.1, API7S-15, API7S-43, API605, EN1092
Material :
For SS Material : ASTM/ASME A/SA182 F304, F304L, F316, F316L, ASTM/ASME A/SA351 CF8, CF3, CF8M, CF3M, DIN 1.4301, DIN 1.4306, DIN 1.4401, DIN 1.4404, DIN 1.4308, DIN 1.4408, DIN 1.4306, DIN 1.4409
For CS Material : ASTM/ASME A/SA105 A/SA105N & A/SA216-WCB, DIN 1.0402, DIN 1.0460, DIN 1.0619, Die Steel, ASTM A105 / ASME SA105, A105N, ASTM A350 LF2 / ASME SA350, High Yield CS ASTM A694 / A694 (F52 F56 F60 F65 F70 F80)
For Alloy Steel Material : ASTM A182 / ASME SA182 F5, F9, F11, F12, F22, F91
The diagrammatic view of WNRF Flanges as shown below,
Pic.002
3) Socket Weld Flange :
Socket Weld flanges were initially developed for use on small, size high pressure piping. Their static strength is equal to Slip On flanges, but their fatigue strength 50% greater than double-welded Slip On flanges. The connection with the pipe is done with 1 fillet weld, at the outside of the flange. But before welding, a space must be created between flange or fitting and pipe. The purpose for the bottoming clearance in a socket weld is usually to reduce the residual stress at the root of the weld that could occur during solidification of the weld metal. The image shows you the X measure for the expansion gap.
The diagrammatic view of WNRF Flanges as shown below,
Pic.003
4) Stud-Bend Flange :
A Stub End always will be used with a Lap Joint flange, as a backing flange. This flange connections are applied, in low-pressure and non critical applications, and is a cheap method of flanging. In a stainless steel pipe system, for example, a carbon steel flange can be applied, because they are not come in contact with the product in the pipe.
The diagrammatic view of WNRF Flanges as shown below,
Pic.004
5) Lap-Joint Flange :
Lap Joint Flanges have all the same common dimensions as any other flange named on this page however it does not have a raised face, they used in conjunction with a "Lap Joint Stub End". These flanges are nearly identical to a Slip On flange with the exception of a radius at the intersection of the flange face and the bore to accommodate the flanged portion of the stub end. Their pressure-holding ability is little, if any, better than that of Slip On flanges and the fatigue life for the assembly is only one tenth that of welding neck flanges. They may be used at all pressures and are available in a full size range. These flanges slip over the pipe, and are not welded or otherwise fastened to it. Bolting pressure is transmitted to the gasket by the pressure of the flange against the back of the pipe lap (Stub End).
The diagrammatic view of WNRF Flanges as shown below,
Pic.005
6) Threaded Flange :
Threaded Flanges are used for special circumstances with their main advantage being that they can be attached to the pipe without welding. Sometimes a seal weld is also used in conjunction with the threaded connection. Although still available in most sizes and pressure ratings, screwed fittings today are used almost exclusively in smaller pipe sizes. A threaded flange or fitting is not suitable for a pipe system with thin wall thickness, because cutting thread on a pipe is not possible. Thus, thicker wall thickness must be chosen...what is thicker ?
The diagrammatic view of WNRF Flanges as shown below,
Pic.006
7) Blind Flange :
Blind Flanges are manufactured without a bore and used to blank off the ends of piping, valves and pressure vessel openings. From the standpoint of internal pressure and bolt loading, blind flanges, particularly in the larger sizes, are the most highly stressed flange types
The diagrammatic view of WNRF Flanges as shown below,
Pic.007
Q. Types of Flange Faces...?
Different types of flange faces are used as the contact surfaces to seat the sealing gasket material. ASME B16.5 and B16.47 define various types of flange facings, including the raised face, the large male and female facings which have identical dimensions to provide a relatively large contact area. Other flange facings covered by these standards include the large and small tongue-and-groove facings, and the ring joint facing specifically for ring joint type metal gaskets.
Types :
1) Raised Face (RF) :
The raised face flange face is the most common type used in process plant applications, and is easily to identify. It is referred to as a raised face because the gasket surfaces are raised above the bolting circle face This face type allows the use of a wide combination of gasket designs, including flat ring sheet types and metallic composites such as spiral wound and double jacketed types.The purpose of a RF flange is to concentrate more pressure on a smaller gasket area and thereby increase the pressure containment capability of the joint.
2) Flat Face (FF) :
The flat face flange has a gasket surface in the same plane as the bolting circle face. Applications using flat face flanges are frequently those in which the mating flange or flanged fitting is made from a casting. Flat face flanges are never to be bolted to a raised face flange.
3) Ring Type Joint (RTJ):
This type is typically used in the most severe duties, for example, in high-pressure-gas pipe work. Ring-type metal gaskets must be used on this type of flange facing The ring type joint flanges are typically used in high pressure and/or high temperature services above 800°F (427°C). They have grooves cut into their faces which steel ring gaskets. The flanges seal when tightened bolts compress the gasket between the flanges into the grooves, deforming (or Coining) the gasket to make intimate contact inside the grooves, creating a metal to metal seal.
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