MONPAC™ was developed between Physical Acoustics Corporation and the Monsanto Chemical Company over many years from more than 2000 tests on metal process industrial equipment. It became the de-facto industrial standard (IChem.E International Process Safety Group) for in-service testing of LPG spheres, cryogenic tank walls and stainless steel plant, and is used by the oil and process industry world-wide.
Additions to the procedure and analyses based on Physical Acoustics’ experience and software led to the IPAC™ test. The method provides the following benefits:
- On-stream test (no need to remove product);
- 100% volumetric test for developing defects;
- Identification of flaws that only develop during operation;
- Rapid testing (15m diameter sphere in 4 days);
- Identification of spheres that need inspection and repair, leaving good spheres on-line and saving on shut down costs.
FRP/GRP Vessels and Pipelines
The acoustic emission test method is designed to detect defects and damage in metal and composite equipment. Deformed materials produce sound waves, that is, acoustic emission. The deformation is usually local, at a crack tip or point of corrosion, and occurs during loading or over stressing. The sound waves produced travel along the surface and in the equipment. The general procedure consists of subjecting the equipment to increasing stress while monitoring with sensors that are sensitive to acoustic emission caused by stressed defects.
In-service equipment is typically tested to 10% over the maximum operating load used in the previous six months. Pressure may be increased on-stream, using nitrogen or other gas, or by a hydro test.
IRT Sphere Leg Test
Corrosion may be active and unseen underneath fire protection. If water has penetrated, over a period of time, the corrosion damage can threaten structural integrity, with potentially disastrous consequences. Several spheres have collapsed as a result of such corrosion.
Automated crawlers are utilised to obtain B-Scan or C-Scan UT thickness information on the shells of the vessels. This provides up to millions of thickness readings for a comprehensive corrosion mapping inspection report.
Stress Corrosion Cracking (SCC)
Acoustic Emission techniques are able detect the early stages of stress corrosion cracking.
Once present, SCC is difficult to eradicate, and is otherwise detectable only by sectioning and microanalysis. AE inspection can identify and locate SCC before leaks occur, providing plant management the opportunity to plan replacement components prior to major failures and process interruptions.
Active SCC and corrosion pitting is detectable on-line using AE. The effectiveness of any steps taken to stop the process may be ascertained by re-testing or continuous monitoring.