Becht Engineering Blog

Read Part 1 or Read Part 2 Part 3: Allowable Stresses While inspectability has been at the center of recent concerns, other issues such as chemistry control, ductility and excessive oxidation have also come under scrutiny.  Perhaps most interesting is that while all of the preceding concerns have been debated, it has also been found that existing ASME allowable stresses for Grade 91 are not conservative relative to newer data techniques.  This is beautifully illustrated in Figure 5 from [2], where the continual drop in allowable stress is plotted as more and more short term test data is removed from the analysis.  The good news is that “new” material is not worse than older material (at least from a statistical and data analysis perspective).  The bad news, as discussed in [2] and can be seen in Figure 6, is that even more modern techniques like “region-splitting” do not capture the apparent...

EPRI has just published the report “Roadmap to Integrity Evaluation and Repair of Nuclear Plant Piping” EPRI report number 3002013156, dated December 2018, prepared by Becht Nuclear Services, under EPRI Project Manager T. Eckert. The methods and criteria for the evaluation of degraded and non-conforming conditions in piping systems in nuclear power plants are dispersed among a number of ASME XI Code sections, Appendices, Code Cases, and US NRC regulatory requirements, generic letters, and inspection manual sections. This multitude of requirements makes it necessary to have this roadmap to help the engineer make the right fitness-for-service evaluation and the right repair decision. The EPRI road map addresses the fitness-for-service evaluation methods and criteria for the two most common damage mechanisms in nuclear power plant piping systems: Wall thinning, and cracking. The roadmap also addresses non-conformance caused by overloads, i.e. operating loads that exceed the design loads. Regarding repairs of nuclear plant...

Critical Path Analysis, Schedule Optimization or Cold Eyes Review  (call it what you want) are all designed to check your Turnaround (TA) Schedule for logic, manpower and equipment efficiencies that can affect the duration of the TA Schedule.  When margins are high you can have unit-down-days that are worth upward of $1MM/day.  For this type margin it pays to have experienced third-party TA Field Supervision/Managers (as are all our Becht Advisors) to facilitate these sessions.  When Becht reviewers conduct these assessments, everyone in the review is told up front that there are no "stupid questions" - as there may be some who are afraid to ask a question.  We have found that these questions frequently lead to schedule or manpower savings. Other times, we just get people to look at doing a task a different and more efficient way. The reviewers not only evaluate the schedule to save time but also...

"When You're Stuck, You're Stuck" Over years of normal operation - like cycling and wear and tear - High Energy Pipe support friction can increase causing distress in these critical systems. Friction is a common phenomenon which is widely understood and considered in both piping analysis and support design.  Generally, a piping analyst models a piping system with a friction coefficient on all base type supports of 0.3 for steel on steel or lower if a low friction sliding surface will be used, and hits “run” on his design software program.  The stresses are evaluated, loads on supports determined, and the analysis is off to support design.  The support designer takes the loads (which include friction) and designs the support.  No errors were made, the calculations are correct, and everything should work. But what happens in the field after years of operation and cycling? That depends on several variables, including the...