Flanges (Introduction to ASME B16.5)
-Flanges are most often used to connect pipes that have diameter greater than 2”.
-A flange joint consist of 2 matching disk of metal separated by a gasket that are bolted together to achieve a strong seal with the gasket material.
1.Type of Flanges
-Blind or Blank Flange
-Lap Joint Flange
-Slip-On Flange
-Socket Welding Flange
-Threaded Flange
-Welding Neck Flange
2.Pipe Flanges & Flanged Fittings
2.1.Scope
a.General
-Pressure-Temperature ratings
-Materials
-Dimensions
-Tolerances
-Markings
-Testing
-Methods of designating opening for pipe flanges and flanges fittings in sizes NPS ½-24
-Rating Classes: Class 150, Class 300, Class 400, Class 600, Class 900, Class 1500, Class 2500
-Flanges and flanged fittings may be: Cast, Forged, Plate material (for blind flanges and certain reducing flanges only)
b.References
b1.Referenced standards
-Standards and specifications adopted by reference in the standard
-A flange/flanged fittings manufactured in accordance with earlier editions of the reference standards and in all other respects conforming to this standards will be considered to be in conformance with this standard
b2.Codes and Regulations
-A flange/flanged fitting used under the jurisdiction of the ASME Boiler and Pressure Vessel Code, the ASME Code for Pressure Piping or a government regulation shall be subject to any limitation of that code or regulation.
2.Pressure Temperature Rating (P-T Ratings)
a.Rating basis
-Ratings are maximum allowable working gauge pressure at temperatures
-For intermediate temperatures, linear interpolation is permitted
b.Ratings of Flanged Joint
-Use of ratings for flanged joints not conforming to these limitations is the responsibility of the user.
-Requirement for alignment and assembly of joints are not given in the standard
-For flanges in a flanged joint that do not have same P-T ratings, the rating of the joint at any temperature is the lower of the two flange ratings at that temperature.
c.Rating Temperature
d.Temperature consideration
d1.Flange attachment
-Socket welding and Threaded flanges are not recommended for service above 500 deg F or below –50 deg F if severe thermal gradients or thermal cycling are involved
d2.High temperature service
-At temperatures at the creep range, gradual relaxation of flanges, bolts and gaskets may progressively reduce bolt loads.
-When used above 400F, CL150 joints may develop leakage unless care is taken to avoid imposing severe external loads or severe thermal gradients. For other classes, similar consideration should be given above 750 deg F.
d3.Low temperature service
-User should recognize that some material listed in the rating tables undergo insufficient decrease in toughness at low temperature that they cannot safely sustain shock loadings, sudden changes in stress or temperature, or high stress concentrations.
