Tank Assessment with Acoustic Emission

Applus RTD offers Acoustic Emission (AE) testing of aboveground storage tanks. This complements their already broad range of specialised, non-intrusive inspection services.

Brief Description

AE tank assessment is a specialised procedure for assessing corrosion damage in tanks. Corrosion processes and scale fracture produce AE signals, detected by externally placed sensors. Recorded data are evaluated to exclude noise and provide a measure of corrosion damage to the floor. The main benefit of this test is to survey a number of tanks to help determine inspection needs and priorities.

Testing requires monitoring a static tank along the following lines:

  • Record and evaluate AE data from a tank under static, low noise conditions.
  • Fill to greater than 50% capacity, isolate the tank and allow at least 12-hours settling time.
  • Mount sensors on the tank (8-24 depending on tank size) and connect to an AE system.
  • Calibrate, check that monitoring conditions are OK, record AE data for at least one hour.
  • Pack up equipment, evaluate recorded data.


Effectiveness of Method

Using AE to assess the condition of tank bottoms has developed over the last 15-years or so. A study of the method, published in 1998, showed how AE test results compared to internal inspection findings for 148 tanks. These held a variety of products from crude oil to distillates and blended products.

The study showed that AE testing was able to tell the difference between a good? tank and one with corrosion damage. As the chart shows, there is uncertainty in determining the amount of damage but there is a clear correlation between the AE grade and severity of damage. In particular, test reliability was highest for good? tanks.


Capabilities

  • Most tanks tested within one day, minimum disruption to operations.
  • Provides information about floor condition to aid in scheduling internal inspections.
  • Permanent record of test data, ability to monitor condition over time.


Limitations

  • Qualitative assessment only. Does not give an exact measure or location of corrosion damage.
  • Detects on-going corrosion, may not accurately assess previous damage.
  • Requires good test conditions, susceptible to wind and other noise sources.


Preparation

  • Fill and isolate the tank 12-hours or more before testing.
  • Provide construction details and operating and maintenance history.


Services Required

  • Access to the tank shell and necessary permits.
  • 110V AC electrical power.

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