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.

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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
• 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.

Categories: Breastfeeding, Pumping
March 11,

Finding the right size for your breast flange or shield will help you ensure appropriate milk output and have the most comfortable pumping sessions possible. Don&#;t know what size breast shield you need? Find out more below!

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What is a flange?

A flange, or breast shield, is the cone shaped funnel that fits directly over your nipple, areola, and breast. When using the correct size, it forms a seal between your breast and the plastic or silicone, which then creates a vacuum to extract milk.

Many manufacturers will also make smaller inserts or cushions that go within an existing breast shield size. These reduce the opening of the tunnel where the nipple enters. They are often less expensive than a full flange or breast shield.

Why size matters

Using the correct size flange or breast shield will help optimize milk output. If a flange is too small, it could restrict the tissue, potentially causing clogged milk ducts. If the flange is too large, it may not remove all the milk, which could contribute to a lower milk supply. Using an ill-fitting flange can also cause nipple pain or injury.

Flange sizes range from about 13mm up to about 36mm, depending on brand. That measurement has nothing to do with the opening of the flange, but is the size of the beginning of the flange tunnel. That is because breast shield size is about nipple size, not breast/chest size.

Breast pumps typically come with 1 or 2 sets of breast shields. They will most likely be around 21-28mm. These are a good place to start. In addition to the included size(s), some brands like Cimilre, have certain guarantees to help you get the size you need by offering you a third size option, free of charge! Outside of these guarantees, additional sizes typically require an out-of-pocket purchase or using a possible insurance benefit covering replacement parts.

How to measure your flange size

To determine the best flange size for you, you&#;ll need to measure your nipple. Take a tape measure or ruler and measure the diameter of your nipple in millimeters. We recommend measuring vertically (up and down) and horizontally (left to right) and using the larger of those 2 measurements. Do not include measurements for your areola, the larger part around your nipple. Many manufacturers make their own, printable, measuring tools!

Not just the numbers

The size of your nipple is not the only thing that matters. You also want to pay attention to what happens to your nipple once the pump is on and suction is applied to your body. Everyone&#;s body reacts differently- stretching longer vs wider. It is okay if your nipple touches the side of the flange tunnel, as long as it still moves easily and does not cause any friction, discomfort, or damage.

Once you have your nipple diameter, you select the next largest size flange offered by your pump manufacturer, closest to or even the same size as your nipple diameter.

Examples:

• Using a Cimilre S6, measuring 14mm. Next size is a 16mm flange.
• Using Elvie, measuring 16mm. Next size is the 17mm insert.
• Using a Lansinoh SmartPump 3.0, measuring 22mm. Next size is the 25mm flange.
• Using a Medela PIS MaxFlow, measuring 18mm. Next size is the 21mm flange.
• Using a Spectra S2, measuring 14mm. Next size is the 16mm.
• Using a Willow, measuring 19mm. You have a few options: Trying the 19mm or 21mm insert in the 24mm shield, or trying the 21mm or 24mm shield alone.
• Using a Zomee Z2, measuring 20mm. Start by trying the 21mm. You could also try the 24mm.

Keep in mind, breasts are not identical. Each breast/nipple may require a different size flange. In fact, your flange size may even change throughout your pumping journey. Before you replace your pump parts, it&#;s a good idea to remeasure to confirm you are still using the correct size.

If you feel the sizes offered by the manufacturer of your breast pump will not work for you, reach out to them and ask them what they suggest! Some manufacturers, like Lansinoh, recommend PumpinPals, while others are ok with you using any other flange or insert if they DO NOT offer the size you need. It is best to ask the manufacturer directly where to look because using off-brand replacement parts may undermine the warranty for your pump.

The proper fit

Signs of an incorrect fit:

• Significant pain while pumping
• Breast/chest/areolar/nipple discomfort between pumping sessions
• A delayed let-down (over 2-3 minutes)
• Recurrent plugged ducts, with other causes ruled out

Signs of a correct fit:

• The flange fits comfortably around your nipple
• Only your nipple and little to none of your areola enter the tunnel when pumping
• Your nipple moves freely when pumping
• Any rubbing against the side of the tunnel is fluid and comfortable. There should not be any friction or pulling on the nipple from the sides of the tunnel.
• After pumping, your breasts feel soft and emptied
• Your milk supply remains the same or improves
• Overall, your pumping sessions are comfortable and free of pain

A final note

Finding and using the correct size flange is important to ensure your pumping experience is as successful and comfortable as possible. Spending time to determine your flange size will go a long way toward helping you meet and exceed your breastfeeding and pumping goals. If you have questions about the size of your flange fit or pumping, reach out to support.

Still looking for a breast pump? We can help you get your free breast pump through insurance!

 

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