A guide to flanges
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What is a flange?
A flange is the protruding rim that enable pipes, valves and other equipment to form a connection. Flanges also increase strength at the joint. They enable you to create a piping system while also allowing for fast disassembly. By providing access points, inspections or modifications can be carried out with relative ease.
How you make a pipe-flange connection varies. It depends on the type and the requirements of your piping system. Some are weld-on pipe flange, while others can be screwed on. The type of flange you choose will also depend on issues such as pressure capacity and application. But first, let&#;s look at common flange types.
Different types of pipe flanges
While specialty pipe flanges are available, there are six main types. Here they are, along with how to secure the flange on a pipe.
Threaded flanges
They&#;re used in low-pressure systems on smaller pipes with thick walls. They also make it easy to connect and disconnect pipe systems without disrupting the entire system for maintenance or to make adjustments. To attach the flange on a pipe, the bore&#;s female thread is screwed onto the pipe&#;s external threads. These flanges are not welded on.
Typical use:
- Flammable, hazardous or explosive applications where welding is dangerous
- Ideal in restricted spaces where welding flange to pipe can&#;t be carried out
Socket weld flanges
The simple design is intended for small-size and high-pressure piping that do not transfer highly corrosive fluids. Socket weld flanges are attached by inserting the pipe into the socket and applying one fillet weld around the outside of the flange. First, the pipe is inserted in the socket of the flange. When it reaches the
bottom of the flange, the pipe is lifted out slightly by 1/16" (1.5mm) and welded. This gap allows for thermal expansion created by welding, minimizing the probability that the weld will crack. Not suitable for highly erosive or corrosive applications, as the gap is vulnerable to corrosion between the pipe end and the socket&#;s shoulder.
Typical use:
Lap joint flanges
Slides over the pipe and used with a stub end. Also known as loose-ring flanges, and back-up flanges. These flanges are used on piping fitted with lapped pipe or with lap joint stub ends. With the stub end, the lap joint flange is typically used in systems requiring frequent dismantling for inspection and cleaning. Another advantage is its ability to swivel and align with bolt holes. As the flange never comes into contact with the fluid, the flange is highly durable and can be re-used.
Not recommended in extreme or high-pressure temperature applications.
Typical use:
- Low-pressure applications
- When flange needs frequent dismantling for maintenance
Slip-on flanges
These low-pressure flanges are thinner than most other flanges. With an inside diameter slightly larger than the pipe&#;s outside diameter, the flange slips onto the pipe. A fillet weld is applied at the top of the flange and at the bottom. The welds enhance strength and prevent leakage. Also known as hubbed flanges. Installation of slip-on pipe flanges is easy and therefore low cost.
The speed at placing the flange on the pipe saves costs, but those savings are reduced with the additional costs of two fillet welds which are needed for proper installation.
Typical use:
- Cooling and firefighting water lines
- Process lines for oil, gas and steam
Blind flanges
The lack of an inner hole enables blind flanges to seal off the end of pipe systems, preventing flow. This makes it easier and more cost efficient to carry out pressure tests. The blind flange connection is also an ideal pipeline flange. You can stop the flow of fluid and safely add new pipes or new lines to the pipeline.
Without blind flanges, shutdowns and repairs would be incredibly difficult to handle. While shutoff valves solve the problem of stopping flow, the location of the valve can be a problem. For example, if the valves are a mile or two away, then you&#;re looking at a significant amount of wasted fluid.
Blind flanges are installed with bolts, so they&#;re also easy to remove.
Typical use:
- Testing pipe pressure
- Creating access points to piping systems
- Seal a piping system temporarily to make repairs, or permanently
Welded neck flanges
Also known as weld bend flanges. Their long necks are butt welded to a pipe. The flange&#;s bore matches that of the pipe, reducing turbulence and erosion. This flanged connection relocates stress to the pipes, ensuring a decrease in high-stress concentration at the bottom of the flange. When installing, weld neck pipe flanges must be positioned parallel at the time of fitting. Flanges at opposite ends of a pipe should typically have the same bolt-hole direction too.
Typical use:
- Piping systems with repeating bends
- In conditions with wide fluctuations in temperature and pressure
- Volatile and hazardous fluids
Flange types: at a glance
Type
Pressure capacity
Pipe sizes
Use for
Threaded
Low
Small
Attaching without welding
Lap joint
Low
All
Systems that need frequent disassembly
Slip on
Low
All
Low installation cost; easy assembly
Blind
Very high
All
Flow pressure testing; closing pipes
Welded neck
High
All
High-pressure systems; extreme temperatures
The flange face is the area on the head where your gasket will go. The three most common types are:
- Raised face (RF)
- Ring type joint (RTJ)
- Flat face (FF)
Flanges with different faces should not be mated. For example, a raised face to flat-face flange connection will result in leakage from the joint, per ASME code B31.3.
Raised face flanges
The most common type is the raised face flange. Its name comes from the raised gasket surface, above the bolting circle face. The raised face concentrates more pressure on a smaller gasket area. In turn, this increases the joint&#;s pressure containment capability.
The height of the raised face is determined by the flange&#;s pressure rating. Likewise, the higher the pressure rating, the bigger the flange diameter, the more bolts needed and the thicker the flange.
Flat face flange
Raised face vs. flat face flange, also called full face flange, isn&#;t an issue. They play different roles. Instead of a raised face, this is a flat surface. Consequently, the gasket surface is the same plane as the bolt frame, covering the flange from its inside diameter to outside diameter.
- Full face is designed to avoid the bending that flanges undergo as bolts are torqued.
- Cast iron can break during this process, which is why this material is often used to make flat face flanges. The design prevents this problem from happening.
Ring-type-joint face flange
High temperature, high-pressure flanges or rather, flanges used in extreme environments, utilize a ring-type-joint face. These flanges often have a raised face with a ring groove machined into it. They can also have grooves cut into their faces with steel ring gaskets. The flanges seal when the bolts are torqued, compressing the gasket between the flanges into the grooves.
Ring joint flange vs raised face
The purpose behind a raised face flange is to concentrate more pressure on a smaller gasket area, increasing the joint&#;s ability to contain the pressure. Ring-type-joint face flanges don&#;t use gaskets. The groove within the flange enables the ring to center itself when the bolts are torqued. As the process pressure increases, so, too, does the sealing pressure.
Face flanges: at a glance
Typically used:
Raised face flange
Flat face flange
Ring-type- joint face
Process plants (chemical, etc.)
l
Oil & gas
l
l
Valves
l
Cast-iron equipment
l
Low-pressure water pipe systems
l
Severe applications: high pressure and high temperature (up to 1,382&#;F/ 750&#;C)
l
The pipe flange face is vulnerable to damage during handling and transport, so you need to think about flange covers. This flange cover shown here is made of durable and flexible polyethylene. It protects both raised and flat face flanges, along with full-face gaskets.
Flange protectors are also critical. The studded full face flange protector here is also made of polyethylene and provides full coverage by inserting the lugs firmly into the bolt holes.
Understand more about flange covers in our guide, Why Flange Covers are Essential.
The raised face flange protector shown here has an adhesive backing for fast application.
You can learn more about flange protection in Pipe & flange protection: a quick buyer&#;s guide.
Flange materials
Whether steel pipe flanges or a plastic flange, you should base the material you choose on its application. Typically, the materials should match your pipe material, but again, it depends on your application. For example, if your piping system is used for air or other non-corrosive applications, then your flanges and pipes may not need to be of the same corrosion-resistant material as acidic or caustic liquids.
Otherwise, if you&#;re interested in say, carbon steel slip-on flanges, you need to match the grade steel you choose to the pipe. Common flange materials include:
Carbon steel
Carbon-steel flanges are alloyed primarily with carbon. Carbon steel has a high hardness and strength that increases with carbon content but lowers ductility and melting point. Carbon steels range from mild and low, with 0.16&#;0.29% carbon to ultra-high carbon steel, with around 1&#;2% carbon. Steels with carbon content above 2% are considered cast iron.
Alloy steel
Just as you can enhance properties in plastics with additives, you can alloy steels with other elements to enhance the properties of your chose steel. Common alloys include molybdenum and chromium. Through different elements, you can increase a steel&#;s strength, ductility, corrosion resistance, and machinability.
Stainless steel
Stainless steel is alloyed with chromium in amounts above 10%. It&#;s chromium that gives stainless steel a higher corrosion resistance than carbon steel, which easily oxidizes from air and moisture exposure. Stainless steel is ideal for corrosive applications that also require high strength. Different grades of stainless steels yield different outcomes. You can learn more in our guide, Understanding stainless-steel grades.
Cast iron
When iron is alloyed with carbon, silicon, and other alloyants, the result is cast iron. Cast irons have good fluidity, castability, machinability, and wear resistance. They tend to be brittle to a degree with low melting points.
Aluminum
This is a low-density metal with medium strength. Malleable and ductile, it&#;s more corrosion resistant than typical carbon and alloy steels. Aluminum is suitable for flanges that need both strength and low weight, such as for irrigation applications.
PVC
A PVC flange is low cost and durable. PVC pipe flanges also have the advantage of being both chemical and corrosion resistant. Additives can make PVC more flexible and softer. PVC flange connections can provide extra protection to underlying pipes. They&#;re also popular for water-treatment processes, favored by the agricultural industry and used in domestic plumbing. Lightweight and easy to install, PVC flanges are perfect for PVC pipe systems.
Gasket materials
For all flange types excluding ring-type-joint faces, you&#;ll need gaskets. Choose them based on factors such as operating temperature, the fluid being conveyed by the pipeline, flange type, size, pressure class or rating and other specifications. First, however, you need to know material properties, which can be enhanced with additives.
Suitable for
EPDM
Natural rubber/SBR
Neoprene
Nitrile
Butyl
Silicone
Keytones
l
Hot & cold water
l
Alkalis
l
Acids & bases
l
l
Heat
l
l
Oils
l
Hot oils
l
Ozone
l
l
l
Weather resistance
l
l
l
Abrasion resistance
l
l
Low-moisture permeability
l
Low-gas permeability
l
l
Seawater applications
l
l
High temperatures
l
Low temperatures
l
Vibration suppression
l
General chemical resistance
l
Animal fats
l
Flange sizes
Flange dimensions are determined by the nominal pipe size (NPS) and the pressure class that your application requires. The higher the pressure rating of the class, the higher the size and dimensions of the flange. Typically, a 1/2" pipe flange will belong to the 150-pound pressure class. For threaded flange, a 4" pipe flange is the largest size available.
Large diameter flanges are in higher pressure classes. Below are the different classes:
Pressure classes
- 150 lbs
- 300 lbs
- 400 lbs
- 600 lbs
- 900 lbs
- lbs
- lbs
Size standards
Flange types and sizes vary, but they&#;re manufactured according to the standards set by organizations. For example, a long weld neck flange ASME B16.5 conforms to ASME standards, and might differ slightly from another standard. ASME B16.5 swivel flange dimensions &#; a type of weld neck flange &#; have equivalents in EN and MSS standards.
(If you see, for example, ANSI 150 swivel flange dimensions, this is incorrect. ANSI at one time published standards and started working with ASME in . At the time standards appeared as ANSI/ASME, but by , ASME had taken over standards.)
So your first task is determining the standard you&#;ll work to, which will likely follow what&#;s commonly used in your area.
Size standards are set according for each pressure class.
The example here is a threaded flange, both raised face and flat face, according to ASME B16.5. The pressure class is 150.
Sizes: inches
Flange NPS
I.D.
O.D.
Bolt circle (BC)
Raised face (R)
Raised face (RF)
H
Raised face thickness (T)
T1
Flat face thickness (T2)
Bolt hole (B)
No. of bolt holes
½
0.93
3.50
2.38
1.38
.063
1.19
.62
.38
.56
.62
4
¾
1.14
3.88
2.75
1.69
.063
1.50
.62
.44
.56
.62
4
1
1.41
4.25
3.12
2.00
.063
1.94
.69
.50
.63
.62
4
1 ¼
1.75
4.62
3.50
2.50
.063
2.31
.81
.56
.75
.62
4
1 ½
1.99
5.00
3.88
2.88
0.63
2.56
.88
.62
.82
.62
4
2
2.50
6.00
4.75
3.62
0.63
3.06
1.00
.69
.94
.75
4
2 ½
3.00
7.00
5.50
4.12
0.63
3.56
1.12
.82
1.06
.75
4
3
3.63
7.50
6.00
5.00
0.63
4.25
1.19
.88
1.13
.75
4
3 ½
4.13
8.50
7.00
5.50
0.63
4.81
1.25
.88
1.19
.75
8
4
4.63
9.00
7.50
6.19
0.63
5.31
1.31
.88
1.25
.75
8
5
5.69
10.00
8.50
7.31
0.63
6.44
1.44
.88
1.38
.88
8
6
6.75
11.00
9.50
8.50
0.63
7.56
1.56
.94
1.50
.88
8
8
8.75
13.50
11.75
10.62
0.63
9.69
1.75
1.06
1.69
.88
8
10
10.88
16.00
14.25
12.75
0.63
12.00
1.94
1.13
1.88
Link to Ziheng
1.00
12
12
12.94
19.00
17.00
15.00
0.63
14.38
2.19
1.19
2.13
1.00
12
14
14.19
21.00
18.75
16.25
0.63
15.75
2.25
1.32
2.19
1.12
12
16
16.19
23.50
21.25
18.50
0.63
18.00
2.50
1.38
2.44
1.12
16
18
18.19
25.00
22.75
21.00
0.63
19.88
2.69
1.50
2.63
1.25
16
20
20.19
27.50
25.00
23.00
0.63
22.00
2.88
1.63
2.83
1.25
20
22
22.19
29.50
27.25
25.25
0.63
24.25
3.13
1.75
3.07
1.38
20
24
24.19
32.00
29.50
27.25
0.63
26.12
3.25
1.82
3.19
1.38
20
EN sizes: millimetres
DN
D
(diameter)
k
(PCD)
b
(thickness)
d2
(diameter of bolt hole)
Bolt size
No. of holes
Weight (kg)
10
90
60
16
14
M12
4
0.72
15
95
65
16
14
M12
4
0.81
20
105
75
18
14
M12
4
1.14
25
115
85
18
14
M12
4
1.38
32
140
100
18
18
M16
4
2.03
40
150
110
18
18
M16
4
2.35
50
165
125
18
18
M16
4
2.88
65
185
145
18
18
M16
8
3.51
80
200
160
20
18
M16
8
4.61
100
220
180
20
18
M16
8
5.65
125
250
210
22
18
M16
8
8.13
150
285
240
22
22
M20
8
10.5
200
340
295
24
22
M20
8
16.5
250
395
350
26
22
M20
12
24.1
300
445
400
26
22
M20
12
30.8
350
505
460
26
22
M20
16
39.6
400
565
515
26
26
M24
16
49.4
450
615
565
26
26
M24
20
63.0
500
670
620
28
26
M24
20
75.2
600
780
725
34
30
M27
20
124
700
895
840
38
30
M27
24
183
800
950
42
33
M30
24
29.7
900
46
33
M30
28
374
52
36
M33
28
492
60
39
M36
32
842
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Between the tubes and wires, mechanics and logistics, the whole pumping process can feel, well, like a process. But one thing can make it considerably easier: double-checking that you're using the right breast pump flange size.
It can make the difference between a frustrating struggle to express enough milk and a situation where you can more easily (and painlessly) produce plenty for your baby. Here's what you need to know about flange sizes to make the most of your pumping sessions.
What is a breast pump flange?
A breast pump flange is a funnel-shaped piece of plastic that fits over your nipple. It forms a vacuum seal around your areola, and then draws your nipple into its funnel to extract milk.
Most pumps come with a standard 24 millimeter (mm) flange. But they&#;re available in a wide range of sizes, generally anywhere from 21 to 36 mm. The size indicates the diameter of the small tube on the flange's narrow edge.
You can find different-sized flanges through your pump manufacturer, sites like Amazon or any baby supply store.
Why is flange size important?
The right flange fit will help you express as much breast milk as efficiently as possible. Your flange size generally depends on your breast tissue and skin elasticity. If your flange is too tight, it will constrict your breasts, which can cause clogged milk ducts that don&#;t release milk as quickly.
But if your flange is too loose, you won&#;t remove all the milk from your breast, which can lower your milk production. It can also cause unnecessary nipple pain and even injury to your nipple. If pumping hurts, it can impede your milk supply. You&#;re also less likely to stick with it.
Which flange size should you use? Check this flange size chart
To find your size, check the website of your pump's manufacturer. Most companies offer a size guide for flanges based on your nipple size. Here's an approximate guide you can use as a flange size chart:
- Up to 17 mm: 20 to 21 mm flange size
- 17 to 21 mm: 24 mm flange size
- 21 to 25 mm: 27 to 28 mm flange size
- 25 to 29 mm: 30 to 32 mm flange size
- 29 to 32 mm: 36 mm flange size
To measure your nipple diameter (its width), you'll need a ruler or a measuring tape. You can also estimate with coins: A dime is approximately 18 mm, a penny is 19 mm, a nickel is 21 mm and a quarter is 24 mm.
Before you measure, stimulate your nipple, either by rolling it between your thumb and finger or applying ice to it, to make sure you have its full size. Focus on its diameter at the base, and don&#;t include the areola. Remember to measure both of your nipples as they can be different sizes.
Flanges vary from company to company, so you may want to try a few out. You might find that another brand&#;s flanges work better with your body. It can take some time to find the ideal gear, but most pump and flange combos are totally fine.
Remember also that your nipple size (and hence your flange size) may fluctuate throughout your breastfeeding journey.
How to tell if you&#;re using the correct flange size
Most lactation consultants recommend using the "COMFY" test to help determine the right flange size. Here are the five major guidelines that the acronym stands for:
- Center nipples move freely. Your nipple should move freely in and out without touching the sides of the tunnel and without redness or pain.
- Only a little areola tissue should be pulled into the tunnel. You should see a bit of areola pulling into the tunnel with each pump cycle, but not too much or none at all.
- Motion of your breast is gentle and rhythmic. Your breasts should move back and forth every time the pump moves, but gently.
- Feels comfortable breast pumping. Your breast pump shouldn't cause any pain and tenderness.
- Yields well-drained breasts. Your pump needs to remove the majority of your milk from your breasts to keep up your milk production. Your breasts should feel noticeably softer and lighter once you&#;re done with your session.
How to tell if your flange is too big or small
Some signs that your flanges don't fit quite right include:
- Your breasts are moving too much or too little while pumping. Movement should be gentle, much like the movement of your nipple within the tunnel.
- Your nipple is rubbing the sides of the tunnel, causing discomfort.
- Your nipple and part of your areola are being pulled into the tunnel.
- Your nipples are red or white after pumping. This can indicate too small a flange.
- Your breasts still feel full after pumping. If they&#;re heavy and harder, that means all the milk hasn&#;t drained and your flange is possibly too big.
Finding the perfect flange can take a bit of perseverance, patience and trial and error, but it&#;s well worth your time and effort. If you&#;re having trouble, reach out to your doctor or a lactation consultant. He or she can share some advice as you go about your quest to find your perfect flange fit.
For more Flange Supplierinformation, please contact us. We will provide professional answers.
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