Steel pipe flanges are specified as per ANSI B16.5. Pipe flanges are commonly used for industrial, commercial, and institutional application. Steel pipe flanges are available in variety of styles and pressure classes. Most commonly used flanges are weld neck flange, slip on flange, blind flange, socket weld flange, threaded flange and lap joint flange.
Metal flanges are classified from 150 to 2500. In addition to specifying pressure class, certain flanges such as weld neck flange & socket weld flange also require specifying the pipe schedule. This ensures the pipe bore will match the bore of the weld neck or socket weld flange.
Trupply offers wide variety of metal flanges in carbon steel, stainless steel and nickel alloy. We can also provide special flanges such as long weld neck flange, special material request and high-yield pipe flanges.
Select the flange type below for online shopping. We carry wide variety of flange in stock for immediate shipment.
What is the difference between Class 150 and 300 flange?
Video below shows the difference between different classes of a flange using slip on flange as an example. Same principle applies to weld neck flange, blind flange or any other flange manufactured as per ASME B16.5 standard.
*see video transcript at the end of page
Steel Pipe Flange Types
As common as it may seem to many people, a lot of customer ask what is a flange? Trupply has created a demonstration video to explain different types of flanges, its features and how they are used on the pipe. Metal flanges are manufactured as per ASME B16.5. These flanges are also called ANSI Flanges.
*see video transcript at the end of page
Flange Pressure & Temperature Rating
The table below shows pressure and temperature rating of a carbon steel pipe flange from 150# to 2500#.
*Video transcript for difference between 150, 300 & 600 # flange
Today we’ll talk about a slip on flange and different pressure ratings of a flange, we’ll use a slip on flange as an example. This is a 2 inch raised face slip on flange, and you can see it goes on a 2 inch pipe, this is a 2 inch pipe sample. It goes right here and then you weld it. When we talk about a raised face flange, we’re talking about a 1/16 lip on the back end, that you can see right here. The same flange, if it comes in a flat face, there’s no lip on the backside and you can see the difference between a raised face and a flat faced flange.
All flanges come with a marking on the side, and you can read right here, the size of the flange, the pressure rating, what specification it conforms to, and the country of origin. The difference between 150 pound and 300 pound and a 600 pound flange is mainly the outer diameter, the number of bolts, and the bolt circle. This is a 300 pound flange, raised face slip on. You can see it goes on a 2 inch pipe, because it’s a 2 inch flange, but this has more bolts, you can see right here. The bolt size stays the same for this 2 inch flange, it’s the 5/8 bolt size, but the number of bolts are higher, it went from 4 to 8 bolts.
Same thing, if you jump from 300 to 600 pound flange, again, this is for a 2 inch, you can see right here. This portion stays the same. This outer diameter is slightly bigger, this bolt circle is slightly bigger, it’s a thicker flange, you can see right here if you compare it with this one, 300 pound, but if you compare it with 150 pound, you can see the 600 pound is much thicker. Also know the difference that for 150 pound and 300 pound, the raised face is 1/16, but when you go up to 600 pound, the raised face is about a quarter inch, it’s much thicker on the back end.
In summary, the main difference between 150 pound, 300 pound, and a 600 pound flange is the number of bolt changes, the outer diameter changes, the bold circle diameter changes, and the flange gets thicker. Thank you.
*Video transcript for flange types
Today we’ll talk about different flanges such weld neck flange, slip on flange and blind flange etc. These are all steel pipe flanges. This is a slip on flange and this is a 2 inch flange, 150 pound. All flanges that we are showing you today for the purpose of this video are 150 pound flanges. 2 inch flange, this is a 2 inch pipe sample, and you see the slip on flange is the easiest one, you just slide it on and then you weld it. This is a raised face flange, and the raised face flange, on the backside of the flange, right here, you can see that has a lip, a 1/16 inch lip. This is also a slip on flange, but this is a flat face, and we are showing you as an example that this does not have a raised face, this is a flat faced flange slip on flange.
This is a 2 inch flange, but this is a threaded pipe flange. You can see the pipe threads here. If you have a 2 inch pipe and you have a thread on it, then you simply thread it in. That’s the only difference between a slip on or a threaded flange. Again, this is also a raised face, so it has a 1/16 lip on the backside. A 150 pound, 2 inch, threaded flange.
This is a socket weld flange. 2 inch, raised face, 150 pound socket weld flange. Remember, all flanges have a stamping here that shows the size, the pressure rating, the country of origin, the specification, the material. A socket weld flange, if you can see right here, has a little socket. The pipe goes in here and it fits in the socket and then you can weld it. You can see from the backside, this is a standard schedule pipe, this is a standard bore socket weld flange, and it’s very flush from the backside.
On the socket weld flange, you have to specify the pipe schedule. The pipe schedule, this is a 2 inch nominal pipe, and this is a standard schedule pipe, and this is a standard schedule socket weld flange. The pipe schedule and the bore of the socket weld flange has to match so that there is no raised face, there is no protrusion on the backside. The difference between a socket weld flange that has a bore of schedule 40 or schedule 80 is that this inner bore will change so it matches the bore of the pipe. That’s what you’re trying to do.
Remember, on a socket weld flange, other than specifying if it’s a 150 pound or 300 pound, you also have to mention if it is for a schedule 40, schedule 80, schedule 120, schedule 160, what is the schedule of the pipe where you’re trying to use this socket weld flange.
This is a weld neck flange, this is a very popular flange, a lot of people use it. Again, as the name says, it has a welding neck right here. 150 pound flange, it has four bolts, again, raised face, it has a little lip on the backside, the stamping on the side. The way the weld neck flange is used is you take a pipe, again, this is a 2 inch pipe, and you have to have a bevel. This does not have a bevel, but if you are installing, you’ll have a bevel, and then you just butt it up right like this and then you make a weld. That’s how it is installed and it’s called a weldneck flange, this is a welding neck of the flange.
On the weldneck also, you have to specify the bore, so if you specify the schedule, whether it’s for schedule 40, schedule 80 and so on, that will determine the size of the bore here. Again, this is also, that once you weld it, you don’t want your pipe to be thicker than the flange; that will not be good for the flow. Once you specify the right schedule of the flange that matches the schedule of the pipe, if you look from the inside, it will be almost flush. You won’t be able to see any edge sticking out. A weld neck pipe flange.
This is a lap joint flange. The difference between a lap joint flange and a slip on flange, I want to show you a slip on flange, which looks very similar. From the outside, it almost looks like the same. But you look on the backside, it has a little radius and a little end right here. Some people confuse it that this is a flat faced flange. It is not. If you look at the difference, if you just look at the backside, you will see that this is different because it has a little radius. I’ll show you right now why it has a little radius, that lap joint flange.
For example, I have the same flange in stainless steel, this is a stainless steel 304 flange. Whenever you’re using a lap joint flange, you use a stub end. The radius is for the stub end, so you do like this and that’s why it’s called a lap joint flange. You need to have a stub end and that is the purpose of that little radius right there.
This is a blind flange, and as the name says, there is no bore in it, just a blind flange. Again, 2 inch, 150 pound, blind flange, no bore in it. This is a 2 inch one. Again, it’s hard to see how the 2 inch fits on it, but the outer diameter matches what a 2 inch flange is.
This is another example of a stainless steel flange. We carry both carbon steel, stainless steel, nickel alloys flanges and this is a 304 flange; it’s also available in 316. This is A105 forged material also available in A105 normalized, you just have to specify what flange you want. Thank you.
Fabricator Tip (Using Two Hole Pins)
The number of bolts used to join any standard flange pair is always divisible by four. It is important to ensure that when piping is fabbed in a shop that it fit in the field. A common designation in pipe spool drawings is "2HU", which means to the fabricator that there should be "two holes up" at the vertical quarter point of a flange. Another way of saying this on piping drawing is to note that "bolt holes straddle center-line." Because the number of holes is divisible by four, if any of the bolt holes of a flange straddle the center line, then they all do. If our spool was simply a straight length of pipe with a flange on each end, you would still want the flanges to have the same orientation with respect to each other in order to ensure there there was consistency among the spools. This will assure fit-up in the field.