Floating Roof Correction (FRC) or Floating Roof Adjustment (FRA)? They Are Not the Same.

One of the most frequent mistakes in inventory calculations and custody transfer operations is using the terms Floating Roof Correction (FRC) and Floating Roof Adjustment (FRA) interchangeably, when in fact they correspond to two different calculations, with specific objectives and application criteria.

API MPMS Chapter 12.1.1 clearly establishes that:

Floating Roof Correction (FRC) corrects the volume displaced by the weight of the floating roof when this effect is not incorporated in the Calibration Table.
Floating Roof Adjustment (FRA) corresponds to a secondary adjustment that only applies when the Calibration Table already incorporates the FRC and the observed density (or observed API) is different from the reference density (or reference API) used during calibration.

Although both concepts are related to the behavior of the floating roof, they are not interchangeable. Applying the incorrect calculation can generate volumetric differences that affect inventories, balances, and custody transfer reconciliations.

In this infographic we summarize in a practical way:

What each concept is.
When it should be applied.
How it is calculated.
Which variables are involved.
A decision diagram to select the correct calculation.

At BZ Consulting, we recognize the importance of correctly applying the criteria established by the API MPMS standards, ensuring that our Tank Calibration, Inspection, and Loss Control services are developed with technical rigor, traceability, and in accordance with the best industry practices.

BZ Consulting, “The value of experience.”