Pressure Vessels

Inspection by monitoring Acoustic Emission

ATTAR has been providing Acoustic Emission Testing (AET) of pressure vessels since 1986, offering AET as both an alternative and complementary method to conventional NDT. It offers a high level of plant safety and optimisation in maintenance planning. ATTAR’s experience in the application of AET on pressure vessels includes gas cylinders, spheres and other conventional pressure vessels. ATTAR are NATA accredited for AET and is a certified ‘Gas Cylinder Test Station’ in accordance with AS 2030 and AS 2337.

AET involves recording then analysing high frequency energy emitted by a vessel while it is being subjected to increasing stress levels exceeding those experienced during its normal operation. Acoustic emission sensors pick up transient stress waves (events) caused by defect changes such as cracks and corrosion over the whole vessel in one test, with relatively little process interruption. ATTAR’s ASNT SNT-TC-1A level II AE Technicians and Engineers interpret results to classify the condition of vessels.

Based on the level of AE activity, advice is given to facilitate follow up NDT or maintenance where necessary.

Equipment

ATTAR uses state of the art acoustic emission sensing equipment with neural network software which permits discrimination between active defects and background noise as well as identification of the location of defects or discontinuities in the structure under test.

While acoustic emission sensors are very sensitive to higher frequencies, they do allow testing to be conducted with operational noise present. Any interference from background noise is filtered by the AET Engineer, usually post test.

Testing Procedure

Acoustic emission sensors are mounted on the outside of the vessel or cylinder with pressure applied in stages, normally to 10% above normal operating pressure.

Pressure Vessels: Testing is conducted to ASME Boiler and Pressure Vessel Code article 12, Australian Standard AS 4037 Pressure Equipment, ASTM E569, ASTME650 and ASTME750 meeting the requirements of examination and testing Section 23.
Cylinders: Testing is conducted to ISO 16148; Gas Cylinders – Refillable seamless steel gas cylinders – Acoustic Emission testing for periodic inspection and ASTM E1419-02b; Standard Test Method for Examination of Seamless, Gas Filled Pressure Vessels using Acoustic Emission and similar Standards.
Gas Cylinder testing can be certified by ATTAR in accordance with AS 2030 and AS 2337.

Report

Test results are analysed for any potential anomalies. ATTAR reports include a diagram of the subject indicating severity and location of acoustic emission activity.

A pressure vessel indicating the location of AE sensors (numbered) and AE events.

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