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Content archived on 2024-04-15

DEVELOPMENT OF ACOUSTIC EMISSION (AE) TESTING METHODS FOR ANALYSIS AND ON LINE MONITORING OF STRESS CORROSION CRACKING (SCC) UNDER OPERATING CONDITIONS IN THE CHEMICAL INDUSTRY

Objective

CORROSION IS A VERY COSTLY PROBLEM IN THE CHEMICAL INDUSTRY,AND ONE OF THE MAIN DAMAGE MECHANISMS IS STRESS CORROSION CRACKING(SCC).THE OBJECTIVE IS TO STUDY THE ABILITY OF ACOUSTIC EMISSION TESTING(AET) TO DETECT SCC DAMAGE ON LARGE CHEMICAL STRUCTURES AND TO CONCEIVE AN ON-LINE MONITORING SYSTEM.THE FOLLOWING ASPECTS WILL BE INVESTIGATED:
BASIC RELATIONSHIP BETWEEN SCC AND AE FOR DIFFERENT CORROSION SYSTEMS IN LABORATORY EXPERIMENTS.
PRACTICAL TESTS ON SMALL VESSELS AS AN INTERMEDIATE STEP FOR STUDYING OTHER SIGNIFICANT PARAMETERS FOR TRANSFERABILITY.
CONCEPTION OF AN ON-LINE MONITORING SYSTEM FOR LARGE VESSELS AND DEMONSTRATION OF THE EFFICIENCY OF THE SYSTEM IN PRACTICAL SERVICE CONDITIONS.
In laboratory experiments, it has been possible to characterise signals for extraneous sources, eg solution boiling and recrystallisation, and to distinguish these from real acoustic emission (AE) activity from stress corrosion cracking (SCC) crack growth, allowing detection and location of SCC. A good qualitative correlation between AE activity and SCC damage has been achieved.

The need was clarified for small scale vessels to be as representative as reasonably practicable of full scale, but it was recognised that some compromise will be necessary between the desire to reproduce the operating environment and the need for accelerated tests to provide useful results. Positive results have been obtained on small vessels confirming the capability for detection and location of AE and SCC, within the limitations of size and geometry so far investigated. Detection and monitoring capabilities now require a quantitative correlation of the AE data with the extent of SCC damage.
RP IND AND INSA ARE MAINLY CONCERNED WITH THE FIRST TASK CONSISTING IN CHARACTERIZING THE RELATIONSHIP BETWEEN AE SIGNALS AND THE DIFFERENT SOURCES LIKELY TO OCCUR DURING STRESS CORROSION CRAKING.THE PROGRESS OF THE EXPERIMENTAL WORK IS ON TIME.
THE EQUIPMENT PURCHASE BY RP IND (SLOW STRAIN RATE MACHINES) WAS ADAPTED AND PERFECTED TO OBTAIN SCC IN WELL DEFINED AND REPRODUCIBLE CONDITIONS,SIMILAR TO CRACKING IN SERVICE CONDITIONS (AUSTENITIC STAINLESS STEEL IN HOT MGCL2 SOLUTION).
SUITABLE ACOUSTIC EMISSION INSTRUMENTS HAVE BEEN PURCHASED AND ADAPTED FOR SCC MONITORING.SPECIFIC SIGNAL PROCESSING SOFTWARES HAVE BEEN DEVELOPED TO FIND MEANINGFUL INFORMATION ON SCC PHENOMENON.ICI AND SOLVAY,IN AGREEMENT WITH IZFP,ARE PREPARING SIMULATION TESTS ON SMALL VESSELS.

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Coordinator

Rhône-Poulenc Industrialisation SA
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25 Quai Paul Doumer
92408 Courbevoie
France

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