Storage practice for volatile liquids (e.g., naphtha): which roof configuration is commonly used on cylindrical tanks to minimize vapor losses and reduce emissions?

Introduction / Context:
Volatile hydrocarbons like naphtha generate significant vapor above the liquid surface. Managing these vapors is essential to reduce product losses and atmospheric emissions. Tank roof design is therefore a key environmental and safety control in storage terminals and refineries.

Given Data / Assumptions:

• Cylindrical atmospheric storage tank.
• Stored liquid is volatile (high vapor pressure).
• Goal is to minimize breathing and working losses from vapor space.

Concept / Approach:
A floating roof (either external or internal) rests directly on the liquid surface, keeping vapor space volume minimal across operating levels. This reduces vapor-generation area and limits evaporation and emissions. By contrast, fixed or conical/flat roofs leave a vapor space whose composition changes with temperature and liquid level, causing greater breathing losses.

Step-by-Step Solution:

Verification / Alternative check:
Industry guidance and emission inventories consistently show lower losses for floating roof tanks compared to fixed roof tanks storing high-volatility products.

Why Other Options Are Wrong:

• Conical, flat, or generic fixed roofs maintain a headspace, increasing vapor losses unless combined with internal floating covers and vapor control systems.

Common Pitfalls:
Ignoring rim-seal integrity and deck fittings (sources of residual emissions); overlooking wind effects on external floating roofs; not considering internal floating roofs under fixed covers in strict-weather locations.

Final Answer:
Floating