Fixed Valves Bubble cap trays are fixed valve trays. For a good portion of the history of fractionation trays, bubble caps were the only tray valve. Bubble caps remain in service throughout the industry in systems where low liquid flow rates and high variations in vapor flow and resistance to heavy fouling are required. Bubble caps come in a variety of shapes and sizes, from round (mushroom caps) to rectangular (brick or bread loaf caps) in both slotted caps and solid (FRI [fractionation research incorporated-type (FRI-type)] caps. While operating ranges are less than those allowed by moveable valve trays, significant increases in operating ranges and efficiency over sieve trays and bubble cap trays are possible using fixed valves extruded from the tray decks. Fixed valves offer lateral gas flow to inhibit fouling rather than the vertical gas flow of sieve trays, and higher mechanical strength than floating valve trays, with no moving parts to wear out. B.11—Float Valves with Two Weights
Fixed Valves Bubble cap trays are fixed valve trays. For a good portion of the history of fractionation trays, bubble caps were the only tray valve. Bubble caps remain in service throughout the industry in systems where low liquid flow rates and high variations in vapor flow and resistance to heavy fouling are required. Bubble caps come in a variety of shapes and sizes, from round (mushroom caps) to rectangular (brick or bread loaf caps) in both slotted caps and solid (FRI [fractionation research incorporated-type (FRI-type)] caps. While operating ranges are less than those allowed by moveable valve trays, significant increases in operating ranges and efficiency over sieve trays and bubble cap trays are possible using fixed valves extruded from the tray decks. Fixed valves offer lateral gas flow to inhibit fouling rather than the vertical gas flow of sieve trays, and higher mechanical strength than floating valve trays, with no moving parts to wear out. B.11—Float Valves with Two Weights
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