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Becht Engineering Blog

In this section of the site contributing authors submit interesting articles relating to the various services, industries and research & development efforts of Becht Engineering.

How To Quantify And Evaluate Oil Storage Tank Annular Plate Corrosion

annular_plates_cover-imag_20181008-172036_1 Failure of Oil Storage Tank Annular Plate
In the past ten years, there have been a few oil storage tank annular plate failures due to soil side corrosion and fatigue loading (filling and emptying) which has led to large spills. The corrosion tends to be localized in a groove fashion and the size of the flaw could vary from 3 feet to 12 feet in the circumferential direction. The location of the corrosion is also where the highest bending stress will occur during filling and emptying of tanks. See Figures 1 and 2 for the location of the failure on the annular plate.   Since the location of failure is under the tank, the corrosion flaws cannot be detected easily from the outside of the tank. It can only be detected if an internal inspection is done which would require the tank to be emptied and cleaned and this is very expensive. However, with UT shear wave technology...
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Reducing Loss of Primary Containment (LOPC's) in a Refinery

cover-LOPCs
Reducing Loss of Primary Containment (LOPC's) or commonly referred to as “leaks” in a refinery is a key factor to improve reliability.  Historically, most refiners reduced the high consequence leaks to avoid major incidents; however, lower consequence related leaks were not given high priority.  Today high reliability is required, and reduction of all leaks is desired due to greater legal and regulatory oversight of the industry.  Approximately 90% of the leaks occur in piping systems.  These leaks typically fall into 3 categories; internal corrosion, flange leaks and external corrosion.  Many refiners have programs in place for internal corrosion and programs for flanged joints; however, many lack comprehensive programs for external corrosion. To fully reduce LOPCs a comprehensive internal and external corrosion management system is necessary. Background Many refineries have had Mechanical Integrity related audits performed during the last decade.  These audits have found many areas for improvements and programs were initiated...
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CalOSHA Update – Damage Mechanism Reviews (DMR)

cal-osha
On May 18, 2017, the California Department of Industrial Relations’ Occupational Safety and Health Standards (CalOSHA) board approved a new regulation that changes how Process Safety Management (PSM) is handled for oil refineries within the state of California.  This regulation was approved in response to high-profile industry incidents in the state of California in the last 5 to 10 years.  The new regulation introduces a “refinery safety order” that will be enforced by the PSM unit within CalOSHA ( CLICK HERE for the regulation ).  Some key elements introduced in this regulation are: Damage Mechanism Reviews (DMR's) – Reviews that consider where corrosion, mechanical damage, environmental cracking, etc. are identified for process equipment; Hierarchy of Hazard Controls Analysis – A review to identify appropriate the most appropriate means for managing hazards; Human Factors Program – Analysis of personnel related factors such as employee fatigue, staffing levels, shift turnover, and training; Management...
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Evaluation of Corroded Pipe in Accordance with ASME B&PV Code Section XI - A Comparison of the Three Code Cases

Evaluation of Corroded Pipe in Accordance with ASME B&PV Code Section XI -
A Comparison of the Three Code Cases
The evaluation of wall thinning corrosion in steel pipes is addressed in three ASME XI code cases: N-513, N-597, and N-806. I have no ambition here other than to summarize in a table the differences between these three code cases. A brief commentary follows the table. The brief commentary... Line A – While these are Section XI Code Cases applicable to ASME III Class 2 and 3, technically, nothing would prevent from applying these Code Cases for B31.1 piping. Line B – There is no technical basis for limiting N-513 to moderate energy lines, i.e. pressure at or below 275 psi and (“or”, depending on the plant vintage) temperature at or below 200oF, other than the understandable reluctance to operate with hot water flashing to steam through a pinhole leak. Line D – It can be confusing that N-513 includes fracture mechanics consideration because it attempts to address cracks (so-called “planar...
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