Pipe flanges connect piping and the components of a piping system such as valves, fittings, pipe with each other and specialty itemsusing bolted connections and gaskets. They can be installed in several fashions including: welding, lapping or screwing.
There are several benefits to using a pipe flange including: it provides a secure connection between pipes, valves & other equipment; it allows for quick disassembly by providing installation or modification access points; and it increases the strength at the joint.
The application and type of flange determine the way in which the connection is made. Always consider the fluid being conveyed through a pipeline, the operating temperature, flange type, size, pressure class/rating and other specifications prior to installation. This ensures safety during installation and operation of the piping system.
A pipe flange has several components: a unique bolt pattern, connection type (e.g. socket weld, threaded, slip on, etc.) and face. They have varying bolt patterns that are based on the type of flange and its diameter.It is important to note that flanges do require a gasket to make the seal except for ring-type joint faces.
Pipe flanges can be manufacturedfrom a casting (cast from a mold) or forging(using energy to change the shape of billet/ingot). They also come in various pressure ratings: 150, 300, 600, 900, 1500 and 2500 pounds. While they are available in several diameters, the larger flanges are available in the higher pressure class/rating.
Flanges also have several types of facingwhich include:flat face, ring-type joint, lap joint, tongue & groove and raised face. The facing is the area that is used to seal the flange.
Industry
Flat-Full Face
Raised Face
Ring-Type Joint Face
Cast-Iron Equipment
X
High Pressure/High Temperature (up to 1382°F/750°C)
X
Low-Pressure Water Pipe Systems
X
Process Plants (Chemical, etc.)
X
Oil & Gas
X
X
Valves
X
The face itself can be serrated or smooth. There are several industries that traditionally require a specific type of facing.
Types of Pipe Flanges
There are several types of pipe flanges in a piping system; but there are 6 main types – blind, lap joint, slip on, socket weld, threaded and weld neck. Each of them has properties that determine their use incommercial,industriall and institutional applications. Always consult your project manager prior to installing any pipe flange into any application.
Blind flanges have no center hole and are used to seal off a piping system. As a result, one can easily execute pressure tests cost effectively.
Lap Joint flanges use a stub end (Type A, B or C) and slide over the pipe. They are also known as loose-ring flanges and back-up flanges.Lap joint isused with lapped pipe and allow for frequent cleaning and inspection through dismantling. They are very durable and can be used because the fluid conveyed in the system does not come in contact with the flange.
Slip On flanges, also known as hubbed flanges, are thinner than other flanges and are traditionally used in low pressure systems. This type slips onto the pipe and the fillet weld is applied at both the top and bottom of the pipe flange. These welds provide extra strength and prevent leakage. While the installation is low cost and easy, the welding does add cost to its installation.
Socket Weld flanges are designed for small size, high-pressure piping systems that do not carry corrosive fluids. The pipe is inserted into the socket and a single fillet weld on the outside of the flange is applied.
Threaded flanges are used in applications that are low pressure on smaller, thick walled pipes. Given their threaded connection, they do make it easy to disconnect the piping system.
Weldneck flangeshave a long neck that is butt welded to pipe. This type is also known as a weld bend flange. Since the bore of the neck matches that of the pipe, it reduces erosion and turbulence.
There are other types of flanges including: orifice, reducing, ductile iron backup, copper solder joint and many more.
What are the Applications of Pipe Flanges?
Type
Traditionally Used In
Blind
Creating piping system access points
Permanent seal to a piping system
Pipe pressure testing
Temporary seal for system repairs
Lap Joint/Loose Ring
Frequent dismantling for maintenance
Low-pressure applications
Slip-On/Hubbed
Cooling water lines
Firefighting water lines
Oil, gas & steam process lines
Socket Weld
Hydraulic pipes
Threaded
Applications that are flammable, hazardous, or explosive & cannot be welded due to safety concerns
Restricted space where welding is not feasible
Small pipe sizes
Weld Neck/Weld Bend
Conveyance of volatile and hazardous fluids
Piping systems with bends that are repeating
System conditions that have wide fluctuations in pressure & temperature
Flanges are available in several alloys including: copper, brass, stainless steel, carbon steel, titanium, aluminum, superalloys, tool steel and alloy steel. Each alloy carries specific attributes:
Alloy
Attributes
Alloy Steel
Iron-based with <4% Chromium
Resistant to wear & tear
Strong
Aluminum
Ideal for lightweight requirements
Great weight-to-strength ratio
Corrosion resistant due to surface microscopic oxide layer
Brass
Highly conductive
Copper, Tin and Zinc alloy
Nonmagnetic
Corrosion resistant
Resists higher heat & electric conductivity compared to other metals
Carbon Steel
Low & high carbon steels available
Ductility, impact strength, wear resistance and hardness determine its need
Copper
Nonmagnetic
Compared to other materials, can sustain greater loads
Corrosion resistant
Can handle high-temperatures
Stainless Steel
Corrosion resistant
Durable
Withstands pressure & high temperatures
Super Alloys
Tolerates severe conditions
Material makeup includes Nickel & Cobalt
Resists acid corrosion & high temperatures
Titanium
Lightweight
Strength is exceptional
High heat resistance
Very costly
Tool Steel
Made from tool steel billets/ingots
Impact resistance & robustness is strengthened because it includes carbon & other alloys that react with iron
Durable
Merit offers several types of flanges in various alloys:
