Piping cost fraction in fluid-processing units For a fluid-processing section such as distillation, the installed cost of process piping is roughly what percent of fixed capital investment (FCI)?

Introduction / Context:
Cost distribution within a plant varies with process type. Fluid-processing units (distillation, absorption, extraction) tend to require extensive piping, valves, and instrumentation, increasing the piping fraction of fixed capital compared with solids-handling plants.

Given Data / Assumptions:

• Typical refinery/chemical fluid-processing unit.
• Installed piping cost as a percentage of FCI.
• Screening-level estimating, not a detailed take-off.

Concept / Approach:
Rules of thumb place piping in fluid plants in the ~15–25% range of FCI, depending on complexity and pressure rating. A mid-range representative value is about 22%, which aligns with many textbook tabulations for fluid services with moderate complexity.

Step-by-Step Solution:

Verification / Alternative check:
Historic plant summaries and estimating manuals show higher piping fractions for fluid services relative to solids plants (often <10%).

Why Other Options Are Wrong:

• 4% or 13%: More typical of solids handling or very simple services; low for complex fluid units.
• 34%: High for average units; may occur in exceptional high-pressure or highly integrated plants but not as a typical figure.

Common Pitfalls:
Applying a single fraction across all units; pressure class, metallurgy, and layout congestion can shift piping percentages materially.

Final Answer:
22