A flange connects pipes, valves, pumps, and other equipment to form a piping system. It also provides easy access for cleaning, inspection, or modification. Flanges are usually welded or screwed onto the pipe end and are then sealed with a gasket. Welding neck, slip-on, blind and socket weld flanges are some common types of flanges.
ASME B16.5 is a standard that covers pressure and temperature ratings, dimensions, tolerances, marking, and material requirements for forged or rolled 304 stainless steel lap joint ASME B16.5 flanges for use in pressure systems at ambient and higher-temperature service conditions. This standard covers forged or rolled 304 Stainless Steel LJ ASME B16.5 Flanges with nominal pipe sizes from NPS ½” to NPS 24” for leaks class rating 150# to 2500
Class 150# Leaks
The Class 150# leak is defined as a condition where the internal pressure in the piping system is less than that of the atmosphere by more than 3 psi (0.21 kg/cm2) through a circular orifice 1/16” (1.6 mm) in diameter in the body of a forged or rolled 304 stainless steel lap joint ASME B16.5 flange when tested following the provisions of Paragraph UG-121(a) of Appendix A-20A of the ASME Boiler and Pressure Vessel Code.
Class 300# Leaks
The Class 300# leak is defined as a condition where the internal pressure in the piping system is less than that of the atmosphere by more than 3 psi (0.21 kg/cm2) through a circular orifice 1/8” (3.2 mm) in diameter in the body of a forged or rolled 304 stainless steel lap joint ASME B16.5 flange when tested per the provisions of Paragraph UG-121(a) of Appendix A-20A of the ASME Boiler and Pressure Vessel Code
Class 400# Leaks
The Class 400# leak is defined as a condition where the internal pressure in the piping system is less than that of the atmosphere by more than 3 psi (0.21 kg/cm2) through a circular orifice 3/16” (4.8 mm) in diameter in the body of a forged or rolled 304 stainless steel LJ ASME B16.5 flange when tested per the provisions of Paragraph UG-121(a) of Appendix A-20A of the ASME Boiler and Pressure Vessel Code
Class 600# Leaks
The Class 600# leak is defined as a condition where the internal pressure in the piping system is less than that of the atmosphere by more than 3 psi (0.21 kg/cm2) through a circular orifice 1/4” (6.4 mm) in diameter in the body of a forged or rolled 304 stainless steel lap joint ASME B16.5 flange when tested following the provisions of Paragraph UG-121(a)of Appendix A-20A of the ASME Boiler and Pressure Vessel Code.
Class 900# Leaks
The Class 900# leak is defined as a condition where the internal pressure in the piping system is less than that of the atmosphere by more than 3 psi (0.21 kg/cm2) through a circular orifice 5/16”(7 .9mm ) in diameter in the body of forged or rolled 304 stainless steel LJ ASME B16.5 flanges when tested per the provisions of paragraph UG-121(a)of Appendix A-20A of the ASME Boiler and Pressure Vessel Code.
Class 1500# leaks
The Class1500 # leak is defined as a condition where the internal pressure in the piping system is less than the atmosphere by more than 3 psi (0.21 kg/cm2) through a circular orifice 3 / 8 ”( 9.5 mm ) in diameter in the body of forged or rolled 304 stainless steel lap joint ASME B 16.5 flange when tested.
Class 2500# leaks
The Class 2500# leak is defined as a condition where the internal pressure in the piping system is less than the atmosphere by more than 3 psi (0.21 kg/cm2) through a circular orifice 1/2” ( 12.7 mm ) in diameter in the body of forged or rolled 304 stainless steel LJ ASME b 16.5 flanges when tested.
It is essential to understand how different classes of flanges are used based on the size of the leak acceptable for a given application.
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