What is the difference between the flange pressure class and schedule? 

To answer this question, you should know about the flange rating. You must have heard about 150 class flange or 300 class or 600 class flanges. What is this class? Flange class is a combination of pressure-temperature rating that defines maximum allowable working gauge pressure of the flange. Here pressure is in a bar & the temperatures in degrees Celsius.

Based on this calculation, flanges are available in 150#, 300#, 400#, 600#, 900#, 1500# and 2500#. Large diameter flanges that is 24″ to 60″ are available up to 900# class. In simple terms, you can know that higher the rating, heavier the flange and can withstand higher pressure and temperature. Look at this image for your easy understanding.

Weld neck flange schedule

Weld neck flange schedule

Now you know what flange class is. But what about flange schedule. Many people have asked me this question whether the same class flange can have a different schedule?  Answer is yes.Now look at this flange image. This is weld neck flange. This is neck where pipe is going to weld. If you pipe is having schedule 40 then your flange must have same schedule so that there will be no miss match in internal diameter of flange and pipe. Now if same rating flange is used with schedule 80 pipe, you flange schedule will also change to 80. So, now you know that flange class and schedule are two different things.

Contact Haihao Group for more information if you need any kinds of flanges.Email:sales@haihaogroup.com