Plant economics — understanding the Lang factor The ‘‘Lang factor’’ is defined as the ratio of fixed capital investment to the delivered cost of major equipment. For a solid–fluid processing chemical plant, what is the typical range of the Lang factor?

Introduction / Context:
Estimating the total capital required for a chemical process plant often starts from equipment quotes and then applies a multiplier to account for installation, buildings, piping, instrumentation, electricals, yard improvements, and indirect costs. This multiplier is known as the Lang factor. Knowing its typical range for various plant types helps engineers produce quick, order-of-magnitude estimates during pre-FEED and feasibility stages.

Given Data / Assumptions:

• Definition: Lang factor = fixed capital investment / delivered equipment cost.
• Plant type: solid–fluid processing chemical plant.
• We seek the most representative range used in preliminary cost estimating.

Concept / Approach:
The Lang factor varies with complexity and the amount of on-site fabrication. Fluid processing plants (e.g., refineries) typically carry higher factors due to extensive piping and instrumentation, whereas solid handling can add structure and materials handling but not always the same level of piping intensity as full fluid networks. Typical literature values cluster around the low- to mid-4s for solid–fluid plants when counting fixed capital (installed) relative to delivered major equipment.

Step-by-Step Solution:

Verification / Alternative check:
Cross-checks with classic cost-estimating references show factors in the ~4 to 5 band for many hydrocarbon/chemical services, with solid–fluid mixed duty often near the low- to mid-4s when counting complete fixed capital (installed).

Why Other Options Are Wrong:

Common Pitfalls:
Confusing ‘‘fixed capital’’ with ‘‘total capital’’ (which adds working capital) or applying a Lang factor meant for bare module cost methods. Also, using a single factor across very different plant types without adjustment can mislead early estimates.

Final Answer:
4.2 to 4.4