NDTnet 1998 Aug, Vol.3 No.8

Abstract

Acoustic Emission (AK) on vertical storage tanks is a condition assessment technique which is more and more widely used. It is an empirical based technique of which the claims look very promising. The test results are amongst others reported as AE ratings and indicative recommendations:

A grade	very minor	no maintenance necessary
B grade	minor	no maintenance necessary
C grade	intermediate	some maintenance is needed
D grade	active	give priority in maintenance schedule
E grade	highly active	give highest priority inmaintenance schedule

However, in order to justify a maintenance strategy on AK, quantified validation is required. To this end an AE usergroup collected information of a representative population of storage tanks of which both the AE-gradings had been determined as well as their actual condition in a full follow-up inspection programme. A representative test population means that the percentage of product and crude oil tanks per AE class resembles the scores that are obtained on the larger number of tanks, which are normally scheduled for periodic inspection.

On the basis of the follow-up (FU)inspections, the tanks were classified into three groups:

FU1/2	No or minor damage/no repair
FU3	damage/some repair
FU4	damage/major repair/new floor

Within our population of 150 tanks, the A-grades (no repair required), showed to have perfect predictive power, since all these tanks (=50) required no repair. Also for the other AE-grades the correlation has been quantified and are given in the paper. They indeed show that major repair requirements correlate very well the highest AE ratings. The established figures can be used for risk assessment.

It has been shown how this technique can contribute to both cost and risk reduction in refinery maintenance programmes.

Abstract Source:
Book of Abstracts, 7th European Conference on Non-Destructive Testing, 26-29 May 1998, ISBN: 87-986898-0-00

Full-Text Source:
Proceedings of the 7th European Conference on Non-Destructive Testing, 26-29 May 1998, ISBN:

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