Series A Class 300 Flanges

Series A Class 300 flanges provide medium-pressure capability for large-diameter piping, covering the range from NPS 26 through NPS 60. The Class 300 rating permits working pressures significantly higher than Class 150, making these flanges suitable for process headers, turbine exhaust ducting, and main steam bypass lines in power generation facilities.

At Class 300, the flange body thickness and bolt sizes increase substantially compared to Class 150. The bolt count for a given NPS remains the same as Class 150 in the Series A pattern, but bolt diameters are larger and the flange cross-section is heavier to handle the increased internal pressure loading.

These flanges are critical components in large-scale process plants where column overhead lines, reactor effluent headers, and heat exchanger shell nozzles require robust flanged connections at pipe sizes beyond NPS 24. Proper bolt tensioning using hydraulic stud tensioners is essential at these sizes to achieve uniform gasket compression.