A cartridge tray system packages multiple contacting trays into a removable preassembled bundle for towers where internal panel assembly is impractical. Its value comes from controlled workshop assembly and rapid installation, but its success depends on accurate spacing, structural load transfer, shell clearance, peripheral sealing, nozzle coordination and lifting design. Unlike a tray manway or removable access panel, the cartridge changes the support and installation philosophy of the complete tray stack.

A tunnel-cap tray uses elongated fixed caps to route vapor through raised openings and discharge it into the tray liquid. The construction can provide stable liquid retention, a useful operating range and resistance to fouling or solids without movable components. Its reliability depends on accurately controlling riser height, cap clearance, orientation, internal free area and cleanability. Properly engineered, the tunnel cap is a distinct high-reliability tray option—not simply a rectangular version of a conventional bubble cap.

A side-to-side baffle tray creates an alternating transverse liquid path using segmental plates mounted from opposite shell sides. Its large vapor windows and simple surfaces provide strong fouling resistance, but the design must still control plate coverage, spacing, slope, discharge-edge geometry and landing position. The best applications are quench and wash zones where uninterrupted operation and solids passage are more important than achieving high separation efficiency on every level.

A disc-and-donut tray uses alternating central discs and annular baffles to create large, changing vapor and liquid passages. Its open construction provides strong resistance to plugging and a practical route for solids, but performance depends on the balance between central and annular free area, correct liquid interception, controlled vapor velocity and adequate mechanical support. It is most valuable where fouling resistance and continuous operation justify accepting less stage efficiency than a conventional crossflow tray.

Directional fixed valves convert part of the upward vapor flow into controlled lateral momentum. Their orientation can promote liquid movement and reduce stagnation, but only when each valve zone follows the engineered hydraulic map. Reversed panels may still fit the tray mechanically while creating backmixing, wall accumulation, uneven froth and increased entrainment. Clear orientation drawings, permanent panel marks and field verification are therefore essential parts of fixed-valve tray quality control.