Details:

Alternative Title:
Testing and Recommended Practices to Improve Nurse Tank Safety: Phase 3
Creators:
Enyart, Darrel ; Russell, Alan M. ; Chumbley, Scott
Enyart, Darrel ; Russell, Alan M. ; Chumbley, Scott Less -
Corporate Creators:
Iowa State University
Corporate Contributors:
United States. Federal Motor Carrier Safety Administration. Office of Analysis, Research and Technology
Subject/TRT Terms:
[+]
Anhydrous Ammonia Annealing FMCSA Freight Transportation Hazardous Materials Highway Safety Leakage Motor Carriers Nurse Tanks Residual Stress Safety And Human Factors Stress Corrosion Tanks (Containers) Tank Trucks Testing Vehicle Safety Vehicles And Equipment
Publication/ Report Number:
FMCSA-RRR-16-013
DOI:
https://doi.org/10.21949/1502552
Resource Type:
Tech Report
Geographical Coverage:
United States
TRIS Online Accession Number:
01675624
Edition:
Final Report, May 2015-March 2016
Contracting Officer:
Goettee, David
Corporate Publisher:
United States. Federal Motor Carrier Safety Administration
Abstract:
This report summarizes findings from a re-examination of 411 tanks that were relocated of 532 previously examined anhydrous ammonia (NH3) nurse tanks using the single-beam side-angle ultrasonic nondestructive evaluation method. There were 532 tanks examined previously in phase II of this research (conducted in 2012). In comparison to the earlier study, the Phase III effort (conducted in 2015) provided better training to its undergraduate student examiners majoring in material science and deliberately attempted to discriminate between ultrasonic indications that resulted from stress corrosion, almost exclusively perpendicular to the weld seam, versus those more likely caused by issues in the geometry of the weld seam. Important findings include: Growth rate of many existing perpendicular indications found in the Phase II and Phase III studies were slower than observed by the constant stress laboratory tests conducted as part of Phase II. Even though indication growth of existing perpendicular cracks was less than found in the constant stress laboratory tests, there were numerous new perpendicular indications found to have developed in the 3 years since the Phase II survey. Perpendicular cracks were the only ones single-beam ultrasound could reliably distinguish. A phased-array approach would be necessary to try seeing into the weld seams for distinguishing parallel cracks. Growth of existing indications and development of new indications were both disproportionately greater in newer tanks. Possible reasons why newer tanks are having more problems are discussed in the body of this report. There was a decrease in shell wall thickness following the 1997 American Society of Mechanical Engineers (ASME) change in guidance, which may be associated with the increase in the number of indications in newer tanks. Tank wall thickness measurements showed 5 percent of tanks inspected were near or below thickness standards that would be applied if the tanks were missing their ASME data plates, which would make them subject to 5-year periodic testing. Post-weld heat treatment (PWHT, annealing) reduces residual stresses remaining in steel after welding and is associated with dramatic reductions in both initiation of indications and their subsequent growth.
Format:
PDF
Collection(s):
Federal Motor Carrier Safety Administration
Main Document Checksum:
[+]
urn:sha256:b1c49ba3f011f32268c3a1e23ff92339b3441052b30666c54e948f19a9461b11
Download URL:
https://rosap.ntl.bts.gov/view/dot/36238/dot_36238_DS1.pdf
File Type:

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