Forged Flanges
“A flange is a forged ring of steel designed to connect mechanically sections of pipe or join pipe to a pressure vessel, pump, valve or any other piece of equipment.”
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.
| Standards | ASME B16.5, ASME B16.47 Sr. A & B, ASME B16.36, ASME B16.48 MSS SP44, AWWA, API 6A, EN 1092-1, DIN Standards, & Custom Drawings |
| Size | ½” (DN15) – 60” (DN1500) |
| Class Pressure | Class 150#, 300#, 600#, 900#, 1500#, 2500#, PN6, PN10, PN16, PN25, PN40, PN100 |
| Type | Slip on, Weld Neck, Blinds, Long Weld Necks, Socket Weld, Threaded, Orifice, Line Blanks, Spectale Blinds |
| Flange Face Type | Flat Face (FF), Raised Face (RF), Ring Type Joint (RTJ), Tongue & Groove and custom |
| Grades | ASTM A182, F304, F304L, F316, F316L, F51, F53, F347, Inconel 625, Monel 400, Hastelloy C276, A105/N, A350, LF1, LF2, LF3 CL1/2, A694 |
Slip-on
Blind
Lap-Joint
Socket Weld
Threaded
Weld-Neck
SLIP-ON FLANGE
The flange is slipped over the pipe and is settled by welding at both top and base side of the flange. They are used to provide sufficient strength to the connection and prevent leakage. This flange is favoured over weld neck flanges as less accuracy is required when cutting pipe to length, the cost to produce is lower but there is nearly the same outcome.
BLIND FLANGES
This is a flange without a bore. Also called a blanking flange, it is used to fix or seal an end of a piping framework or shut off a piping system or vessel opening. Inspection of vessels or piping system is easier and it is simpler to access it. A blind flange can be supplied with or without hub depending on the requirements.
LAP-JOINT FLANGES
This is again similar to a slip-on flange, but it has a radius at the intersection of the bore and the flange face to accommodate a lap stub end. The face on the stub end forms the gasket face on the flange. This type of flange is used in applications where sections of piping systems need to be dismantle quickly and easily for inspection or replacement.
SOCKET WELD FLANGES
This is similar to a slip-on flange in outline, but the bore is counter-bored to accept pipe. The diameter of the remaining bore is the same as the inside diameter of the pipe. The flange is attached to the pipe by a fillet weld around the hub of the flange. An optional interval weld may be applied in high stress applications. Its biggest use is in high pressure systems such as hydraulic and steam lines.
This is similar to a slip-on flange in outline, but the bore is threaded, thus enabling assembly without welding. This obviously limits its application to relatively low pressure piping systems. The flange may be welded around the joint after assembly, but this is not considered a satisfactory method of increasing its applications.
WELD-NECK FLANGES
As is the name, this is a flange attached by welding neck of flange to a pipe. It is expensive because of its long neck, but more suitable for high stress applications because the neck provides important reinforcement to the flange. The bore of the flange matches the bore of the pipe, reducing turbulence and erosion.
Groove Flanges
Long Neck
Orifice
Spectacle
GROOVE FLANGES / TONGUE FLANGES
A groove flange is constantly paired with a tongue flange.
The tongue flange has the face with a raised ring (i.e. the tongue). One flange has a machined raised ring (also called the tongue) and the other one has machined groove depression (also called the groove). Those two flanges should match perfectly with each other.
Tongue-and-groove facings are standardized in both large and small types. They are mainly used for pump covers and valve bonnets.
Tongue-and-groove joints have the advantage of being self-aligning and act as a reservoir for the adhesive. Major machining operation are not necessary especially thanks to the scarf joint keeping the axis of loading in line.
LONG WELD NECK FLANGES
The long neck guides the pipe into the flange itself and provides reinforcement that a standard weld neck flange cannot. Long weld-neck flanges also are used in situations expansion bends or changes the pipe because of the high pressure. The Long Weld Neck Flange also provides reinforcement in places where a standard or conventional weld neck flange cannot do so.
ORIFICE FLANGES
The function of an orifice flange is to provide access to a line for metering of gases or liquids. An orifice plate is clamped between a pair of flanges when installed in a line and the whole assembly is referred to as an orifice flange union. Jack-screws within the assembly facilitate removal of the orifice plate. The orifice plate, the metering device, consists of a thin plate with a concentric, square edge, circular hole in the centre. Two pressure tap-holes are drilled in each flange to measure pressure difference through the orifice.
SPECTACLE FLANGES
This is a pressure retaining plate with one solid end and one open end connected with a web or tie-bar. In normal operation, the open end forms the seal between two flanges and permits normal flow of fluid through pipe work. If the solid end is swung into position it effectively blanks of the pipe and halts the flow.
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.
Raised Face (RF)
Flat Face (FF)
Ring Type Joint (RTJ)
Raised Face (RF)
The Raised Face Flange 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 RF flange is to concentrate more pressure on a smaller gasket area and thereby increase the pressure containment capability of the joint.
Flat Face
The Flat Face (FF) 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. ASME B31.1 says that when connecting flat face cast iron flanges to carbon steel flanges, the raised face on the carbon steel flange must be removed, and that a full face gasket is required. This is to keep the thin, brittle cast iron flange from being sprung into the gap caused by the raised face of the carbon steel flange.
Ring type Joint (RTJ)
The Ring Type Joint flanges are typically used in high pressure (Class 600 and higher rating) 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.
An RTJ flange may have a raised face with a ring groove machined into it. This raised face does not serve as any part of the sealing means. For RTJ flanges that seal with ring gaskets, the raised faces of the connected and tightened flanges may contact each other. In this case the compressed gasket will not bear additional load beyond the bolt tension, vibration and movement cannot further crush the gasket and lessen the connecting tension.
