Guide to Flanges

In this introduction to flanges, we'll cover the different types of flange attachment methods, which flanges to choose for a variety of applications, and an overview of pressure and temperature ratings and how they apply to different types of piping systems.

What Are Flanges and How Do They Work?

A flange is a protruding rim, lip, or rib that is used to increase strength or provide an attachment method to connect pipes, valves, and other equipment to form a piping system and to create an easy access point for cleaning, inspection, or modifications.

Flange Attachment Methods and Purposes

Flanges can be welded or screwed on, depending on the type of flange and piping system requirements. When selecting a flange type, some important aspects include pressure capacity, pipe size, and intended application.

Ring or slip-on flanges have a center hole, and they slide onto a pipe end. The flange face extends beyond the pipe end to be welded into place.

Lap-joint flanges are similar to slip-on flanges but are used in conjunction, which means that the flange doesn't have contact with the medium in the pipe. These flanges don't require welding, which allows them to rotate freely to line up with the mating flange.

Threaded flanges are often used for smaller pipe sizes and do not require welding, which makes them a convenient option'however, they are not suitable for piping systems with thin walls.

Socket weld flanges are used for small, high-pressure applications. The pipe is inserted into one end, then a fillet weld is applied around the outside of the flange. An expansion gap is required between the flange and pipe to reduce weld stress.

Weld neck flanges feature a long, tapered hub that provides reinforcement and improved distribution of stress for use in high-pressure, sub-zero, or elevated-temperature applications.

Blind flanges are flat, with no bore, and are used to finish off a piping system.

Common Flange Materials

Flange material can affect everything from connection methods to pressure rating, so it is an important consideration. While there are a variety of options, the best flange material varies by application requirements.

Some common flange materials include:

Steel ' The Most Common Flange material, is preferred for strength

Stainless Steel ' Preferred for its higher resistance to corrosion and rust

Aluminum ' Lightweight material ideal for corrosion resistance

Ductile Iron ' A lower-cost option for backing flanges that can be used because the flange doesn't come in contact with the medium

Flanges come in a variety of surface finishes, which determine the roughness or smoothness of the finished flange face. Flange faces may offer a smooth finish or can have serrations'small grooves on the flange face. The appropriate finishing technique depends on the intended service use.

The AWWA standard finish is between 24-55 serrations per inch and is suitable for a range of applications. Serrations may be continuous spirals or evenly spaced concentric grooves. Other finishing options include a mill (or rolled) finish and surface flanges that offer no finishing except where machining is required.

Coatings protect the flanges from corrosion or damage through shipping, storage, and use. These coatings include:

Light oil or other rust-prohibiting material

Zinc

Paint

Epoxy

With competitive price and timely delivery, MIDAS sincerely hope to be your supplier and partner.

Galvanized

Outside of flange material and coatings, it is also important to differentiate between the different flange material sources.

Import ' These are popular due to their lower cost, but in some cases, like for government projects, they may not be appropriate.

Buy America ' This standard provides a preference for domestically produced materials, but there are provisions that allow for materials to be sourced from a list of approved countries if it is a small enough part of the total contract, domestic product availability is low, or the price is too high.

Domestic ' These flanges meet AIS (American Iron & Steel) standards, which allows imported raw components of the metal, but requires that the flange material be melted and manufactured in the United States.

How Are The Most Common Flanges Used?

To determine the correct flange for your application, consider flange size and attachment method, materials used to manufacture the flange, the pressure class rating, bolt hole size and placement, and which standards your flanges must meet. Refer to flange dimensions when selecting your pipe fittings'most often listed as outside diameter (OD), inside diameter (ID), bolt hole diameter and spacing, and thickness (T). Refer to flange dimensional tolerances if necessary specifications aren't available, or consider a custom-machined fitting.

Slip-On Flanges

Slip-on or ring flanges are often used for high-temperature, low-pressure piping systems and can be used in applications with higher flow rates. Also called a 'ring flange,' this style flange slides onto a pipe end through a center hole and the flange face extends beyond the pipe. The flange is then welded into place for a secure fit. Ring flanges may be manufactured to ANSI and AWWA standards, are available in Class 150 through , and are available in flat face or raised face styles.

Ring-type joint flanges are similar to ring or slip-on flanges, but are preferred for high-pressure applications as this type is paired with a gasket for improved sealing.

Lap-Joint Flanges

Lap-Joint flanges, also called back-up or backing flanges, are paired with stub ends or angle face rings. The backing flange slides over the pipe end, and welding is not required. This solution is ideal for ensuring flange bolt holes line up correctly as the backing rings are able to rotate to match bolt holes'connect the stub end and backing flange, line up the connection points, then align the bolt holes to complete the installation. Lap-Joint flanges are suitable for piping systems that require regular maintenance or that are dismantled often.

Threaded Flanges

Threaded flanges attach to pipes with threaded ends, no welding is required'making threaded flanges ideal in small spaces or areas where welding is not possible. This convenient option is often used for smaller diameter pipe sizes and high-pressure applications, but should not be used in a piping system with thin walls. Threaded flanges are available in a variety of materials and dimensions to meet a wide range of specifications.

Blind Flanges

Blind flanges are available with the same thicknesses and bolt hole patterns as other flange types, but are manufactured with no bore. They are used to finish off a piping system and can create an efficient, leak-proof seal when paired with a gasket and properly seated.

Weld-Neck Flanges

Weld-neck flanges feature a long, tapered hub that is welded to the pipe. Weld-neck flanges are used for high-pressure and sub-zero to high-temperature applications to distribute piping system stress and provide reinforcement.

Socket Weld Flanges

Socket weld flanges offer a higher fatigue strength over a slip-on flange when used for small pipe sizes and high-pressure applications. Choose socket weld flanges based on class and pressure rating, as well as pipe schedule. To assemble, the pipe is inserted into one end, then retracted slightly to form an expansion gap to reduce weld stress. Then, a fillet weld is applied around the outside of the flange. This assembly allows smooth fluid flow with no leakage.

Reducing Flanges

Reducing flanges are used in pipe-to-pipe connections when there is a change in pipe size. The bore matches the smaller pipe size so the larger and smaller pipes fit together properly. Reducing flanges are available in weld-neck, slip-on, and threaded styles.

Flanged Pump Connectors

Flanged pump connectors include flanges on either end of a hose'generally made of flexible braided steel or stainless steel'and are used to absorb pump vibration and reduce stress on the piping system. They're also suitable when adjusting for minor misalignment. Pump connectors are also available with male X male threaded ends.

Overview of Flange Types and Benefits

Type of FlangePressure CapacityBenefits and UsesSlip-On FlangeLowLower-cost option; fits over the pipe for a snug fitLap-Joint FlangeLowEasier bolt hole alignment; good for applications that require frequent dismantlingThreaded FlangeLowNo-weld attachment for small-diameter applicationsBlind FlangeHighestTo seal off piping systems and provide easy accessWeld-Neck FlangeHighReduces pipe stress in high-pressure applicationsSocket Weld FlangeHighSmooth fluid flow, no leakage

Common Piping and Flange Standards

Flange standards cover everything from dimensions, materials, maximum pressure capabilities, temperature ratings, manufacturing technique, and other technical details. These classifications help determine which flange is appropriate for which applications.

There are a variety of piping standards, including these most common standards:

ANSI/ASME (American National Standards Institute and American Society of Mechanical Engineers) is the industry standard for pipeline flanges in the United States.

MSS (Manufacturers Standardization Society) is a standard used in steel pipelines.

API (American Petroleum Institute) covers large diameter carbon steel flanges used in high-pressure oilfield applications.

AWWA (American Water Works Association) is a set of waterworks industry standards that cover water treatment and supply.

DIN ('Deutsches Institut für Normung' German Institute of Standardization) is a European metric standard that is used internationally, often in maritime applications.

ANSI Flange Temperature and Pressure Ratings

Flanges are rated based on the maximum pressure they can withstand at a particular temperature. There are seven main ANSI pressure ratings, from #150 to #. Flange performance is determined by the rating'generally, the lower the class number, the lower the pressure capability. This rating may be listed in a number of ways, including pressure rating, #, Lb(s), or class. This means that 300 Lb, 300#, and Class 300 all refer to the same pressure class or rating.

AWWA Flange Standards, Ratings, and Size Range

This table lists flanges by AWWA standard, class and drill pattern, PSI rating, and size to assist in determining the appropriate flange based on these specific requirements.

StandardClass/Drilling PatternPSI RatingRing/Slip-On Size RangeBlind Size RangeHub Size RangeAWWA C207 SteelClass B, # psi4' ' 144'4' ' 72'N/AAWWA C207 SteelClass D, # psi (4' ' 12'), 150 psi (all other sizes)4' ' 144'4' ' 72'4' ' 96'AWWA C207 SteelClass E, # psi4' ' 144'4' ' 72'4' ' 96'AWWA C207 SteelClass F, # psi4' ' 48'4' ' 48'N/AAWWA C228 Stainless SteelClass SA, # psi (SPFH Series)2' ' 12'2' ' 8'N/AAWWA C228 Stainless SteelClass SB, # psi2' ' 72'2' ' 72'N/AAWWA C228 Stainless SteelClass SD, # psi (4'' 12') 150 psi (all other sizes)2' ' 72'2' ' 72'N/AAWWA C228 Stainless SteelClass SE, # psi2' ' 72'2' ' 72'N/AAWWA C228 Stainless SteelClass SF, # psi4' ' 48'4' ' 48'N/A

The best flange style, material, and rating will ultimately depend on the intended application. We manufacture standard and custom flanges to meet the highest quality standard. Our full line of flanges can be viewed here.

If our standard flanges don't meet your requirements our Custom Machining Shop allows the manufacture of custom parts as well as modifications to stock items, so you can get exactly what you need.

Four Things You Need to Know About Flanges

Four Things You Need to Know About Flanges

1. What is a Flange?

Flange is a major component that is used for connecting two pipes. A flange connects the ends of two pipes through threading or welding. Flanges are classified into two big categories according to attended modes: threaded connection (screwed threaded) flanges and welding flanges. If two pipes are arranged to be connected, a pair of flanges, a gasket and several bolts and nuts are required to complete the flange joint. First, one must place the gasket between two sealing faces. Then, one should tighten the bolts. When the gasket surface pressure reaches a certain level, it would be deformed to fill the uneven parts of the sealing surface to achieve the perfect leak tightness.

Mechanical components are indispensable in many mechanical types of equipment. Flanges all work together to drive the industrial process to proceed at a smooth pace. With the great variety of the mechanical fittings, flanges are popular in many situations. A flange is generally an extension of a structure, and is usually used to increase the strength of a structure, to keep a particular object in place or to combine two parts together.

It should be mentioned that these flange pieces should be designed and manufactured under some regulations. Otherwise, these fitting would result in poor performance, even leading to the unexpected industrial accidents. In fact, there are two main organizations responsible for most standards. The flanges fittings are mainly set by the American National Standards Institution and American Petroleum Institute, so the dimensions of the flanges are restrictively regulated.

2. What are Flanges made of?

The manufacturing materials for producing flanges are generally easy to access. Flanges can be made from stainless steel, carbon steel, aluminum and plastic. These are all in great demand. As a matter of fact, every material holds its advantages and disadvantages. For instance, the stainless steel is able to be with good durability, being used in situations requiring good tolerance.

Varying on the different manufacturing materials and required dimensions, flanges can be made into a wide range of the types. Most of the time, this fitting is used to attach two ends of the pipes together. At this moment, some securing bolts are needed during the connecting process. It is important to consider the specific requirements, the faces of the flanges vary. Generally, the face is designed to be a tongue and groove. For instance, there is a kind of the flange which is called the ring joint. A flange fitting generally covers the entire face, this includes the internal and external portions of the bolts. The slim surface would give great benefit to the whole operating process.

3. How do you Classify Flanges?

The shape is the most obvious method to classify the different types of flanges. However, there are other ways to classify flanges, which are: ' 

Grade of Material 

The Type of Flange face (raised, flat, ring joint, male and female, tongue and groove, lap joint)

The flange finish (smooth, serrated, stock)

The dimensions of flanges (nominal size and pressure rating)

4. How Many Types of Flanges are Available?

Shinsei Industry Sdn Bhd produces a wide range of flanges, here are a few common types of flanges: '

Slip-on Flanges

Blind Flanges

Lap-Joint Flanges

Socket Weld Flanges

Threaded Flanges

Weld-Neck Flanges

Orifice Flanges

Groove Flanges / Tongue Flanges

Long Neck Flanges

Spectacle Flanges

Expanding flanges

Reducing flanges

Swivel ring flanges

Overall, flanges are available in different sizes and materials, and each type of flange makes its own contribution in the development of the entire industrial process.

Factors to Consider When Choosing Flanges for Your Project

Gas and oil plants are complex, large environments with thousands of miles of interconnected piping. For any flange or product to perform correctly, choosing the right type of flange for the job is fundamental. The flange must fit perfectly into the pipe joint to conduct its functions properly. A minor mistake during the flange selection may affect an application resulting in an expensive error.

This blog will discuss the factors associated with selecting the correct flange for the proper application to ensure maximum usability.

Types

It is often easy to spot the flange type by the way it looks. First, you must classify the top of the flange by deciding whether the flange has a socket weld, flat flange, lap joint, threaded bore, welded neck, groove, and tongue flange. Next, the bottoms are identified with the evaluation of whether they have a flat face, which is entirely flat, or a raised face which is a slightly raised section on the face of the flange.

All of this information is usually defined by the stamping on the outside diameter of the flange, provided this has not been completely painted over. It is important to keep an archive of your assembly components for future reference and maintenance.

Size

The flange size consists of factors that include the standard used (: JIS ' Japanese International Standard, ANSI ' American National Standards Institute, and DIN ' Deutsches Institut für Normung / European), the pressure level needed, and the actual overall outside diameter and thickness of the flange. Other factors in determining the full call-out include the number of bolt holes, outer diameter, inner diameter, bolt circle, and bolt hole diameter, but the nominal pipe size is typically universal.

Thickness

Depending on the flange thickness, it can be determined how high a pressure flange can handle, in any application thicker flanges can resist high pressures.

Bolt holes

Bolt holes help to measure the flange size and pressure class. The actual size of the bolt holes, the pitch circle diameter, and the number of bolt holes on the flange are three factors that need to be addressed. If the bolt is stronger and thicker, it can often correlate with higher pressure capabilities.

Standards

There are a lot of industry-defined standards from which you can choose the flanges. So the flanges help to choose based on the standard and application of the product. You can connect it to the three primary standards previously mentioned, including DIN, ANSI, and JIS.

Pressure class

Pressure class signifies the marginal pressure level under which the flange can safely function and sustain. Each standard comes with several pressure levels available, from high-pressure to low-pressure tolerance. The pressure levels of products connected to the flanges must be the same as those of valves and pipes in service. The most common industry pressure class is the modern ASME 150# per B16 spec.

Materials

It is crucial to choose a suitable material for a flange depending on the understanding and application the elements will encounter in an application that the piping system is using. The most common materials include chrome, nickel, carbon steel, duplex steel, stainless steel, etc.

Here are a few common ways to choose the flanges:

Define your specification and standard

Pipe flanges come in with standard blind, threaded, weld neck configurations. As fittings come into standard, oilfield dimensions become necessary for functional interchangeability.

Standard dimensions are the same for all materials used. However, the specifications are regularly updated, broadened, and revised.

Figure out the flange facing

Defining the facing of your flange is one of the first steps to order the industrial pipe fittings. The flange face is the sealing surface. The most common types of flange faces include:

. Full face
. Flat face
. Ring-type face
. Large female and male
. Lap joint
. Raised face

Pick put the correct pressure class

The pressure class of the flange standard determines its dimensions. The pressure class ratings may fall within 125 to 900 psi. The four factors which influence the pressure limits of the flange within the oil and gas industry include:

. Flange sizes
. Materials used
. External and internal temperatures
. Size of bolts, number, thickness, and dimensions

Conclusion

You may need to consult the fitting distributor to determine your project's right flange pressure class. For more information on sourcing suitable flanges for your project, you can reach out to Texas Flange.

If you would like more information about this product, please feel free to contact us. Recommend other popular products for you: API Flanges Manufacturer, API Flange Manufacturer, Advantages And Applications Of Water-Sealed Gate Valves

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