Flanges can either be forged or cast. Both manufacturing methods have their advantages and disadvantages, depending on the application you have in mind for your flange. Below, we will delve into the advantages and disadvantages of both forged steel flanges and cast iron flanges.

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CAST IRON FLANGES

Casting is the process in which the metal is heated until molten then poured into a mold or vessel to create the desired shape. They are often used in cases that are too large, complicated, or other wise not suitable for forgings. Some of the advantages of flanges manufactured in this way include lower costs of production, the ability to make more intricate parts at lower costs, as well as having no true upper limit on size when it comes to your part.

There are, however, some drawbacks to cast iron flanges. The most important of these being how susceptible they are to internal defects. Due to this, cast flanges are not suitable for high pressure applications or applications in which the probability of corrosion is high. Despite advancement of casting technology and computer optimization of the casting process and designs, it is still difficult to meet the standards required for petrochemical industry applications.

FORGED STEEL FLANGES

Forging is the application of mechanical and thermal energy to steel billets or ingots to cause material to change its shape while still in solid form. Forgings offer consistency in composition and structure.  Due to the nature of the production of forged flanges, the production costs are higher than that of cast flanges. Though they cannot have the complex shapes that cast flanges can be made in, their internal structure is more compact and therefore seldom have the defects the often affect cast flanges. Forging eliminates defects found in casting such as shrinkage, porosity, cavities, or cold pour issues.

Tips:What are the flanges?

Flanges are an integral part of the Piping industry. These Flanges are used to form a link between two different Pipes. Flat (FF), elevated (RF), ring joint (RTJ), lap joint (M&F), tongue, and groove (T&G) are the 6 styles of flange faces needed. Multi-faced flanges need different gaskets and should never be matted to avoid joint leakage. The flanges RF and FF may have various finishing forms (i.e. roughness at the top of the surface): flat, lined, and serrated. Although flanges themselves have specific pound scores that reflect the levels of pressure and temperature to which they can operate, the individual flange faces vary depending on the context within which they are to be used.

Various types of flange faces are used to seat the sealing gasket content as the contact surfaces. The faces are panels which matt with flanges, funnels or valves. Flange faces must be smooth enough to ensure that the flanges are fastened together to maintain a stable, leak-free seal.

As a wholesaler, you are critical to the success of the PVF industry.  Complimenting your offering with pipe flanges means you can:

• Improve supply chain efficiency and customer service with various types & materials
• Meet diverse customer needs for both low pressure & high pressure piping systems
• Support your customization needs for specific project requirements 
• Provide consistent & compliant product to ensure system compatibility and reliability

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What is a Pipe Flange?

Pipe flanges connect piping and the components of a piping system such as valves, fittings, pipe with each other and specialty items using 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.

Contact us to discuss your requirements of OEM cast iron flange. Our experienced sales team can help you identify the options that best suit your needs.

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Components of a Pipe Flange

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 manufactured from 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, and pounds.  While they are available in several diameters, the larger flanges are available in the higher pressure class/rating.

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Types of Flange Facing

Flanges also have several types of facing which 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 °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 in commercial, industriall and institutional applications.  Always consult your project manager prior to installing any pipe flange into any application.

Blind flanges

• 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 is used 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

• 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

• 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 flanges

• Have 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.

Raised Face or Flat Faced?

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

What Alloys Do Pipe Flanges Come In?

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:

Brass

• Domestic
  
  • Leaded
  • Lead Free
• Import
  • Leaded 
  • Lead Free
• Classes 150, 250 & 300

Stainless Steel

• ANSI  
• MSS
• 150 LB
• 300 LB
• Weldneck
• Blind
• Threaded
• Plate (Tube OD Slip-on, Bling, IPS Slip-on Bevel x Square and IPS Slip-on Square x Square)
• Slip-on
• Socket Weld
• Lap Joint

Chrome-Plated Brass

• Floor

Ductile Iron

• Standard
• Galvanized

PIPE FLANGES FREQUENTLY ASKED QUESTIONS

Can a stainless steel flange be put with carbon steel pipe?

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Absolutely not, it would cause galvanic corrosion.  Always consult your project team to ensure a proper, safe installation. Does Merit's offering of pipe flanges come with flange protectors? Yes. Do ANSI Flanges come in raised face (RF) and flat-faced (FF)?  Yes, Merit's ANSI Flanges are raised face.  The raised face can be machined off to make it the flat-faced style. Can a flange be identified without stampings on the sides? Yes, traditionally, the bolt dimensions, OD and thickness can identify which class the flange is.