Distillation trays: how are bubble caps typically secured in place on the tray?

Introduction / Context:
Bubble-cap trays use risers and caps with slots to disperse vapor into the liquid on the tray. Mechanical attachment must resist vibration, thermal cycling, and two-phase flow forces, while allowing maintenance and replacement. Understanding the typical fastening method helps during inspection and turnaround planning.

Given Data / Assumptions:

• Conventional bubble-cap hardware (risers, caps, and decks).
• Industrial towers with access for bolting and bar installation.
• Need for secure yet removable retention.

Concept / Approach:
A common method is to use a hold-down bar spanning across the top of caps or engaging cap lugs, fastened by bolts to the tray deck or through brackets. This prevents caps from lifting or rotating under vapor thrust. The bolted hold-down system also allows disassembly for cleaning or replacement. Permanent methods such as welding to the deck are generally avoided due to maintenance implications and potential deck distortion.

Step-by-Step Solution:

Verification / Alternative check:
Tray hardware catalogs depict bolted hold-down bars as standard accessories for bubble-cap trays.

Why Other Options Are Wrong:

• Rivets and spot welding hinder maintenance and are not standard for removable caps.
• Hold-down bar without bolts is incomplete; bolts provide the clamping force.

Common Pitfalls:
Improper torque leading to loose hardware; mixing cap models with incompatible hold-down systems.

Final Answer:
Both (b) and (c)