Difference between flange class and flange schedule
Maybe you heard of flange class and flange schedule,sometimes confused what flange class and flange schedule is,are they the same?
You maybe know a little about flange,flange class is a pressure-temperature rating that defines maximum allowable working pressure of the flange. Flange class is usually in 150#, 300#, 600#, 900#, 1500# and 2500# in standard ASME/AWWA,large diameter flanges that is 24″ to 60″ are available up to 900# class.The rating is higher,and the flange can withstand higher pressure and temperature.Check the following pictures,there are some size in class 150 and class 300.you can see there are some difference in diameter for same size in different class..
Same in other standard,like EN 1092-1 PN10,PN16,PN25,PN40,JIS standard Flange 5K,10K,16K.20K. All these are flange class.what’s flange schedule?
Check the above pictures again, for Weld Neck Flange.The word “E” refer to Diameter at Weld Bevel.This is neck where pipe is going to weld.If the pipe is having schedule 40,then flange must have same schedule so that there will be no miss match in internal diameter of flange and pipe.”E” is same as Pipe OD and “B” is same as Pipe ID. Pipe schedule is same as flange schedule, and pipe thickness (schedule) equal to the date (E-B)/2. Schedule is commonly abbreviated to SCH.Flange schedule usually appears in weld neck flange and socket welding flange.
Whether the same class flange could have a different schedule?Of course,if same class flange is used with different schedule pipe, the flange schedule will also be changed according.
When flange class and schedule appears in the same request description.you should be able to understanding means.if client request weld neck flange,but didn’t offer flange schedule in request,should check with client what pipe schedule/thickness is welded with the weld neck flange.If flange schedule is wrong to produce,there will be a miss matching in internal diameter of flange and pipe.
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