Understanding Pipe Flanges

are attachments to pipes that serve a wide array of purposes. For instance, they may help in attaching other items to pipes. Then they also serve as a cushion to bolster strength in the pipes. Finally, if you are looking to provide any blockage to a pipe, you are quite likely to deploy .

User Profile

The user profile of pipe is quite extensive. Suffice it to say that any entity that has something to do with pipes is likely to use these . Thus, whether it is merely the pipelines running through your house or ones far more vast such as those that carry gas between countries or even continents, they are very likely to deploy . Broadly, any situation where there is a relatively wide scale deployment of pipes would see in operation.

Materials they are made of
Flanges for pipes are made with a wide variety of materials. These include plastic, stainless steel, bronze, aluminum, cast iron, and brass. The most common material deployed to make flanges for pipes is in fact forged carbon steel that has been thoroughly machined on its surface.

You may be have noted, in the table below, A105 has no Grade. Sometimes A105N is described;
“N” stands not for Grade, but for normalized. Normalizing is a type of heat treatment, applicable to ferrous metals only. The purpose of normalizing is to remove the internal stresses induced by heat treating, casting, forming etc.

Chemical requirements composition, %
Chemical elements Grade F304 (A) Grade F304L (A) Grade F316L (A-B)
Carbon, max 0.08 0.035 0.035
Manganese, max 2.00 2.00 2.00
Phosphorus, max 0.045 0.045 0.045
Sulfur, max 0.03 0.03 0.03
Silicon, max 1.00 1.00 1.00
Nickel 8-11 8-13 10-15
Chrome 18 – 20 18 – 20 16 – 18
Molybdenum 2.00-3.00

(A) Carbon 0.040% max. is necessary where many drawing passes are required, as with outside
diameter <0.5 inch (12.7 mm), or nominal wall thickness <0.049 inch (1.2 mm).
(B) On pierced tube, Nickel may be 11 – 16.00%.


ASTM standards define the specific manufacturing process of the material and determine the exact chemical composition of pipes, and flanges, through percentages of the permitted quantities of carbon, magnesium, nickel, etc., and are indicated by “Grade”.

Material Fittings Flanges Valves Bolts & Nuts
Carbon Steel A234 Gr WPA A105 A216 Gr WCB A193 Gr B7
A194 Gr 2H
A234 Gr WPB A105 A216 Gr WCB
A234 Gr WPC A105 A216 Gr WCB
Carbon Steel
A234 Gr WP1 A182 Gr F1 A217 Gr WC1 A193 Gr B7
A194 Gr 2H
A234 Gr WP11 A182 Gr F11 A217 Gr WC6
A234 Gr WP12 A182 Gr F12 A217 Gr WC6
A234 Gr WP22 A182 Gr F22 A217 Gr WC9
A234 Gr WP5 A182 Gr F5 A217 Gr C5
A234 Gr WP9 A182 Gr F9 A217 Gr C12
Carbon Steel
Alloy Low-Temp
A420 Gr WPL6 A350 Gr LF2 A352 Gr LCB A320 Gr L7
A194 Gr 7
A420 Gr WPL3 A350 Gr LF3 A352 Gr LC3
A403 Gr WP304 A182 Gr F304 A182 Gr F304 A193 Gr B8
A194 Gr 8
A403 Gr WP316 A182 Gr F316 A182 Gr F316
A403 Gr WP321 A182 Gr F321 A182 Gr F321
A403 Gr WP347 A182 Gr F347 A182 Gr F347

ASTM Materials for flanges & fittings

ASTM International, known until 2001 as the American Society for Testing and Materials (ASTM), is an international standards organization that develops and publishes voluntary consensus technical standards for a wide range of materials, products, systems, and services.

One important aspect to remember is that there are individual layers of materials that often line pipe flanges, giving them the name of “line flanges”. These materials differ considerably, based on factors such as the material of the tube itself and the item(s) they would carry within them.

Industrial application
As mentioned previously, any industry that deploys pipes extensively would see flanges for pipes being used. So whether it is the oil and gas industry, waterways especially water treatment and movement of water of varying temperatures such as hot water in our homes or offices, sewage lines, nuclear facilities, or even cryogenic industries, flanges witness extensive industrial application.

There are some advantages that come with deploying pipe flanges. We look at them below.

  • They bolster the overall strength of pipes
  • They make it easy to attach other items to pipes
  •  In case a pipeline needs to be blocked, flanges for pipes prove very handy
  • Cleaning pipes and systems becomes a whole lot easier when you have these flanges
  • Anytime you need to make modifications to the piping system you would be happy there were these flanges in place!
  • Pipes need regular inspections from time to time to ensure that they are functioning well with no possible issues anywhere. Again, it is thanks to pipe flanges that such checks become much easier.

—Kinds of pipe flanges—

Flanges for pipes can be of many types. We look at some of them below.

Welding neck flanges
– They are typically flanges with elongated hubs that taper off. These flanges commonly find usage in high-pressure situations, fending off dishing thanks to the tapered hub that reinforces strength.

Slip-on flanges
– Unlike welding neck flanges, these flanges prove handy for low-pressure situations. They are very cost efficient and can easily be welded in their place that is typically at the end of pipes.

– These flanges prove very handy when the pressure in flow needs to be tested. They also make it simple to access pipelines once they have been sealed off. Blind flanges come in a lot of varieties allowing them to fit pipes of many sizes and can easily be used to close off pipe ends.

Threaded flanges
– These are unique flanges that do not require welding onto pipes. Instead, as the name suggests, they are threaded to the bore and tapered off such that there is a seal formed between the pipe and the . From a utility perspective, they are ideal for low-pressure situations or small tubes and should not be used where there is high pressure or significant throughput.

Socket weld flanges
– Like threaded flanges these are suitable for small pipes but with a crucial differentiator in that they can handle high-pressure throughput quite adeptly. Their design is similar to slip-on flanges but with greater strength, especially when internally welded.

Lap joint flanges
– Like socket weld flanges above, lap joint pipe flanges are also similar to slip-on flanges with a key differentiator being a curved radius at the bore. They are suitable for low-pressure situations as well as for piping where disassembly is rather frequent.


Related products maybe you like
Understanding Pipe Flange
Most common flange types
Welding Neck Flange
Flange types
Threaded Flange

Leave a Reply

Your email address will not be published. Required fields are marked *