November 2020

Terminals and Storage

Maximize the value of tank laser scan data

API 653 Annex B is the standard for evaluating tank bottom settlement.

Trotter, B., PEMY Consulting

API 653 Annex B is the standard for evaluating tank bottom settlement. Section B2 requires shell settlement measurements (Z) with “maximum spacing of 32 ft around the circumference … [and] … there must be at least four equally spaced diametrical measurement lines.” It stipulates that out-of-plane settlement values (U) are computed as residuals from the best-fitting phase-shifted cosine curve. Tensile stress at the top of the shell above each measurement point is estimated by the negative second difference (S) of the U-series and compared to an upper bound (SMax) derived from the Euler-Bernoulli beam theory. Annex B warns against computing S values at spacings of less than 32 ft and suggests

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