Flange O’Clock: Episode 2
Join our host John Barnett as he explains and demonstrates what pipe flange pressure classes are, and the differences between each of the pressure classes per ASME B16.5: 150#, 300#, 400#, 600#, 900#, 1500# and 2500#.
We thank you for watching and hope you found our video helpful! If there’s anything else you’d like to know, leave a comment and we’ll get your answer ASAP!
Haven’t seen Episode 1 yet on most common types of flanges?
In this episode of flange o’clock, we’re going to go over pipe flange pressure classes.
Before me I have one-inch raised face slip-on flanges. All three of these are 1 inch raised face flanges per B16.5. B16.5 allows for a class of 150, class 300, class 400, class 600, class 900, class 1500, and finally class 2500, which is available up to 12-inch. ASME B16.5 is the standard for pipe flanges from half inch to 24-inch nominal pipe size. B16.47 for 60-inch Series A and Series B have different pressure classes that we can go over in another video.
Different Pressure Classes for Flanges
The difference between these three flanges is the pressure class! This is a class 150, this is a class 300, and this is a class 600. The differences are in the dimensions except for the bore! You see this is a one inch pipe that can be placed in each of the flanges. So telling me it’s a one inch 4 bolt flange isn’t quite enough information. You can see that we have 1 inch 150 and 1 inch 300 have raised faces of a 1/16th inch. Contrast that with the 1/4 inch raised face height on the class 600. These dimensions can be found on pages 3 through 12 of the Texas Flange catalog.
Higher Flange Pressure Classes
Typically speaking, higher pressure classes are going to be heavier flanges. There are a couple exceptions to that. In class 400, small sizes up to three and a half inch nominal inclusive are identical to class 600 flanges. Likewise, class 900 flanges are identical to class 1500 flanges in all respects for half inch to the two and a half inch inclusive. So in this case, all three of these flanges have four bolt holes. That’s not enough to describe a flange completely. You can see the bolting chart on page 14 of our catalog. A 3 inch 150# flange has four bolt holes. Whereas a 3 inch 300# flange has eight bolt holes.
As we move from one pressure class to another we see that they get heavier and yes common sense dictates that they will be rated for a higher pressure but the 600 class, for instance, is not a 600 psi maximum service. When we say 150#, or 300#, or 600#, we’re referencing a class, not a maximum working pressure. I have here the A105 pressure temperature chart. So in the case of a 200 degree fahrenheit application, a class 150 flange would be good for 260 psig working pressure. In the case of a 600# flange at 400 degrees, your working pressure would be 1265 psig. Specifying the pressure class will help us ensure we get you the flanges you need when you need them!
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