Industry expert Tony Paulin, president of Paulin Research Group, called for field confirmation of pipe stress deflections and fatigue indications predicted by commonly available analysis software. Paulin said, “Checking piping displacements throughout the plant life cycle can be easily done using inexpensive laser scanning technology when used properly.” Paulin made his comments at HxGN Live in Las Vegas in June.
Although laser scanning has been used in selected applications for confirming predicted or expected pipe behavior, it is not a standard inspection practice by construction or maintenance. This use would represent an entirely new “best practice” for the construction, commissioning, operations and maintenance stages of a plant life cycle.
According to Amadeus Burger, president of longtime provider of plant scanning services CSA, laser scanning has been used before by individual process plant owners concerned with hot to cold displacement and in the nuclear industry to confirm containment vessel distortion during repair. The bulk of his scanning work is in nuclear power generation, a high-accountability industry.
The regular confirmation of predictions during the full life cycle of pipe would be new. Typical applications could include:
- Confirming deflection of pipe during start-up and commissioning. This implies CAESAR II and other analysis results are delivered for construction use.
- Inspection of predicted pipe fatigue failure points. Paulin Research Group uses CAESAR II along with FEATools to determine a piping system’s proximity to time of failure based on correlations with observed crack first appearance data obtained from full-size piping fatigue tests conducted at Paulin’s office in Houston.
- Detection of damage. Damage from creep, upsets, earthquakes, storms and other events become evident from overlaying current scans on prior ones. “The first thing we look at after an earthquake are pipe supports,” said Dan Edgar, principal engineer, Senior Flexonics Pathway Inc. “If they are displaced beyond their cold or hot positions, we know there is damage.”
Cycle failure pinhole leak
There is no guarantee piping will remain in an “as-built” condition through the plant life cycle. Paulin said, “If the satisfaction of piping code compliance indicates that a piping system is safe to operate, then comparisons to analysis predictions provide a readily available verification of that compliance through the life of the facility. This ongoing verification seems prudent and reasonable considering the routine number of field modifications, support errors, weight errors and input errors that occur in the hurried world of plant construction.”
The comparison to analysis predictions by owner/operators implies deflections can be delivered to them in usable form. CAESAR II exports its data in a neutral file format (.CII) and the analysis report as well as a (.OUT) file. These files can be used for confirmation with the proper comparison software.
So there is no technical obstacle to this new practice. With so many obvious benefits, Paulin’s call to action might be quickly answered.
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