Community Research and Development Information Service - CORDIS

Inspection and surveillance of metallic pressure vessels during the proof test

In Europe, every pressure vessel has to undergo qualification tests both at the final acceptance stage before its first usage and on a periodic basis during its life span (every ten, five or three years). Current practice, as specified by regulations, is to perform an hydraulic proof test, to verify that the vessel is able to withstand the maximum service pressure.

To overcome the numerous drawbacks of this kind of proof tests, industrialists would prefer to replace hydraulic tests by pneumatic tests, associated with an effective surveillance method. Gas, unlike water, is highly compressible and a large amount of energy is stored in the vessel during the test. If an undetected defect moves significantly, the expansion of the gas makes the pneumatic test dangerous.

The aim of the project is to give industrialists the means to implement pneumatic proof tests in the best conditions through the development and the validation of an operational procedure using Acoustic Emission Testing (AET) associated with a surveillance system. Acoustic Emission (AE) is a phenomenon of energy release in the shape of transient elastic waves, resulting from local microdisplacement (i.e. cracks progress) inside a material subject to stress.

In order to reach this objective, four main actions were carried out simultaneously, on the basis of 3 main materials chosen by the project's industrial partners (fine grain carbon steel St52.3, austenitic stainless steels 316 and 304L).

Execution of numerous pressurization tests on three main types of structure :
- Tubes
- Small stainless steel vessels, of volume generally around 200 litres
- True pressure devices

Development of a computer-aided decision system

To guarantee the safety of pneumatic tests, a multitude of different types of data must be processed, analysed and interpreted in real time. To overcome the human factor and reduce reaction time as much as possible when faced with a risk of bursting, a computer-aided decision system had to be developed which would quickly reveal local microdisplacements within the structure, indicating defects development. The benefits of this action were really demonstrated after the tests carried out on small structures, through the quantity and quality of data collected. A new data analysis conception has led to a first software version developed using Matlab, and validated by all proof tests and burst tests carried out in laboratory on small vessels made of stainless steel 304L.

Creation of a "European " database

In addition to storage of all AE data collected during the various pressure cycles, creation of a less technical and more informative database has been started, intended for the project's industrial partners. The E.D.A.M.P. database, developed using Access 97, allows industrialists to find the main information concerning the pressure vessels tested during the project.

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