Log in

Login to your account

Username *
Password *
Remember Me

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.

Grade 91 Steel - How Did We Get Here? Part 2

grade91_cover-image
Read Part 1 Part 2: Type IV Cracking and Inspectability The current concerns with Grade 91 are fundamentally and firmly rooted in inspectability of Type IV damage; while sensitivity of the material can be managed (see for example [1]), Type IV cracking is perhaps the Achilles heel of Grade 91.  At a high level, the thermal cycle(s) due to welding will create a thin band of material in the heat affected zone (HAZ) with properties much closer to Grade 9 than Grade 91.  While full re-normalization and tempering of the entire component after welding can greatly improve the situation, simple (subcritical) post-weld heat treatment (PWHT) does not.  Damage is overwhelmingly concentrated in this thin band of material during high temperature operation, such that when failure finally occurs, it has an almost brittle appearance since there has been little if any creep deformation or damage outside of the HAZ (see Figure 3...
Continue reading
4
  657 Hits
  0 Comments
657 Hits
0 Comments

Grade 91 Steel - How Did We Get Here? Part 3

grade91_cover-image
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...
Continue reading
3
  593 Hits
  0 Comments
593 Hits
0 Comments

EPRI Publishes "Roadmap to Integrity Evaluation and Repair of Nuclear Plant Piping"

epri-logo
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...
Continue reading
2
  443 Hits
  0 Comments
443 Hits
0 Comments

Turnaround Critical Path Reviews – Recommendations and Examples

critical-path-review-for-TA
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...
Continue reading
3
  376 Hits
  0 Comments
376 Hits
0 Comments