Just receieved some information from one of our other refineries. The purpose for going from a the 150# to the 300# class was to eliminate using 4 bolt flanges (3" and below for 150# flanges). The concern was a reliability of a flange if one bolt is lost (due to damage, corrosion, or defective...
BigInch,
Thanks. Great information. When I see these types of changes in specifications, I scratch my head and say why did they do this. As you said I see no advantage to going to the higher class to to provide more available bolt load for seating stress. Typically at these smaller flanges...
Based on your replies there is no basis for using the 300# flanges for the smaller sized pipe for 150# service. If this was a cut and paste mistake than it appears to be infectious because I have found this in specifications from Foster Wheeler, "Ford, Bacon & Davis", CB&I/TPA and in old Mapco...
Many engineering pipe specifications will specify the use of 300# flanges for pipe diameters of 3" and below for pipe classes specified for 150# service. Does anyone know the basis of this? I havve heard it is to provide the smaller pipe more structural strength and resistance to vibration issues.
