Siting of large hazardous-chemical storage tanks: what is a commonly cited safe spacing range between two adjacent tanks, expressed as multiples of tank diameter?

Introduction / Context:
Spacing between large above-ground tanks storing hazardous chemicals is a fundamental layout decision. Adequate separation limits fire escalation, allows firefighting access, and provides room for maintenance and inspection.

Given Data / Assumptions:

• Vertical cylindrical atmospheric tanks in a tank farm.
• Flammable or otherwise hazardous contents.
• Generic spacing guidance; actual projects must check local codes/standards and risk assessments.

Concept / Approach:
Many plant standards express minimum tank-to-tank spacing as a fraction or multiple of tank diameter. A shell-to-shell distance around one tank diameter, sometimes up to 1.5D, offers fire separation and access while keeping plot area reasonable. Tighter spacing risks domino effects; much wider spacing consumes land and piping unnecessarily.

Step-by-Step Solution:

Verification / Alternative check:
Company engineering practices and risk-based standards often quote minimum spacing near 1D, with increased distances in congested or high-inventory services.

Why Other Options Are Wrong:

• 2.5–3.5D, 4–5D, 6–8D: these are far larger than typical baseline requirements and are rarely used except in special risk scenarios or where land is abundant.

Common Pitfalls:
Ignoring dike/containment requirements; forgetting foam-monitor access; not adjusting spacing for relief load interaction or vapor cloud hazards.

Final Answer:
1 to 1.5 times the tank diameter