Geometric Integrity Assessment of Petroleum Storage Tank using Total Station Technology in Compliance with API 653 Standards

Abstract

This study presents a comprehensive inspection report on a storage tank (B1) at the CNR base in Abidjan, Ivory Coast. Utilizing Total Station surveying techniques with a Kolida reflectorless total station. The investigation focused on key parameters such as base settlement, roundness (ovality), verticality, and base level assessments in compliance with API 653 standards. This study focuses on the geometric integrity assessment of petroleum storage tanks using Kolida KTS 442 reflectorless total station technology, with the objectives of : Present a comprehensive measurement workflow aligned with API 653, demonstrate how total station–derived data supports detection of deformation parameters—such as settlement, out-of-roundness, and verticality deviations and evaluate compliance with API 653 tolerance limits . The inspection methodology involved the use of a total station instrument and its assessories. Temporary control points were established within the tank premises on which Total station was set up. The circumferential level of the tank base was determined for nine(9) points at a marked interval of 2.5meters from each point. Two different set of readings were determined for check purpose. The ovality inspection was carried out by coordinating the nine (9) points marked around the circumference with 2.5m intervals and also coordinating randomly smaller intervals between the 2.5m marks for better circumference. The instrument was used to generate the coordinates of at least one point each from the five couches of the tank vertically upwards. The base level of eight points was taken round the tank B1 circumference. The difference between the highest and lowest base level reading for tank B1 was 3cm. With the mean vertical angle of the four points taken in tank B1, only one point has a high value of  00⁰ 02’ 46.46” which is quite different from all other values and this made the mean deflection angle to get to 00⁰ 01’ 41.46”. The tank B1 was found to be within allowable deviation. The verticality for four point on the tank had an excess of 1^st = 0° 0' 59.42", 2^nd = 0° 0' 24.28",  3^rd = 0° 1' 41.48", 4^th = 0° 0' 43.14" which is within the allowable standard. Total station inspection of storage tank cannot be said to be complete when there is no available initial or subsequent data of the tank under inspection which will serve as basis of comparison for any deviation. Hence it was recommend that a search be made for previous records and all inspection reports be kept safe for ease of access in case of subsequent inspection.