Presented at the 10th International NDE Conference in Nice, France in 2013, this paper outlines new methods and technologies for obtaining representative samples without tendon can disassembly, and a more robust and reliable test slate to evaluate corrosion failure modes including MIC, water, corrosive ions, and the presence of oxidized ferrous debris. Methods developed in response to a containment tendon failure, and the resulting corrective action plan to evaluate an entire assembly of tendons.

1. Advanced methods for
sampling and analysis of
post-tensioned concrete
tendon greases
Rich Wurzbach
ASNT Level III, Infrared and Thermal Testing
Laboratory Lubricant Analyst (LLA-I)
MRG Labs, York, Pennsylvania, USA

2. Overview
 Background of tendon grease testing
 Failures of post-tension tendons
 Comparison of as-found conditions,
failures, to routine grease testing
 Root-Cause failure analysis and corrective
actions
 Enhanced sampling methods
 Expanded grease analysis techniques

3. Background
 Some nuclear containment designs
include ungrouted post-tension concrete
tendons
 Tendon sheaths and anchorhead areas
are filled with a corrosion protection
grease
 ASME Section XI, IWL-2525 Table 1
contains guidance for corrosion protection
grease testing, requires 125g sample
minimum

4. Table IWL-2525-1

5. Status of referenced tests
 ASTM D992 was withdrawn in 1983
 Current version of ASTM D4327 allows for
testing of all three ions, but IWL-2525-1
specifies this for nitrates only, requires two other
tests to be performed.
 APHA tests are for environmental and
wastewater; often requires samples being split
between labs, or being run by inexperienced
personnel, may require refrigeration of prepared
sample
 Total alkalinity test does not fall within the scope
of current ASTM standard.

6. Sampling Challenges
 Quantity required for current IWL-2525
test slate requires disassembly of tendon
anchors can, disturbing anchor area
during sampling
 Harvesting of grease may disturb position
of buttonheads, hiding broken strand
indications
 Invasive nature of sampling requires costly
logistical support, equipment, time,
scaffold, etc.

7. Tendon Anchor and Can

8. Containment Tendon Grease
 Tendon failure at US
nuclear power plant
prompts RCFA, CAR
 IWL, Section IX
requires 125g grease
 Test slate for 2 grams
grease developed; tool
for sampling remotely

9. Grease thief and T-handle
 Provide method to sample grease near anchor without
disassembly
 Design consistent with ASTM D7718 Standard
Practice for Obtaining In-Service Samples of
Lubricating Grease
 T-handle and stinger probe allow sampling grease
from face of anchor
 Results from Small Volume Test (SVT) correlated to
disassembly method (large volume sample)
 Sampling saved ~US$500,000 in maintenance costs

10. Water – D95 (IWL-2525)
 Uses distillation glassware
 Per ASTM: “The amount of water as determined
by this test method…to the nearest 0.05 or 0.1
volume%”, which is 500-1000ppm.
 Per Noria Training: D95 “is fairly cumbersome
and requires a comparatively large sample to
ensure accuracy, which is why it is rarely used in
production-style oil analysis labs today”

11. Water – Karl Fischer (SVT)
 Per ASTM: KF allows “direct determination
of water in the range of 10 to 25,000” ppm
 Can be performed on grease via “oven
method” to eliminate interferences and
improve accuracy
 Only a small volume of grease required
(about ¼ gram)

12. Water Testing Comparison
Image courtesy Noria Corporation, USA Images courtesy Metrohm USA
SVT
IWL

13. Total Alkalinity Testing
 Uses an “ASTM Modified” procedure.
 Per ASTM: “determination of acidic or basic
constituents in petroleum products and
lubricants soluble or nearly soluble in mixtures
of toluene and isopropyl alcohol.”
 Per ASTM: “This test method is not suitable
for measuring the basic constituents of many
basic additive-type lubricating oils. Test
Method D4739 can be used for this purpose.”
Visconorust contains basic detergents

14. Total Alkalinty Comparison
 Method developed using 0.5 grams
grease and smaller solvent amount
 Grease fully dissolves, acidification
process followed
 Titration performed with both colorimetric
and potentiometric (D4793) methods,
correlating results
 Titration performed per IWL-2525 and new
small volume method, correlating results

15. Ion testing
 Two of three methods in IWL-2525 allow
for ion-specific electrodes
 New method for small volume ion-specific
electrode method under development
 Can create more repeatable, reliable, and
quicker test for ions, Chloride, Nitrate and
Sulfide

16. SVT Small Volume Test Slate
 Ferromagnetic Iron (ppm) – tested with a Hall-effect
sensor
 Metals spectroscopy – multiple elements, ppm (iron,
calcium, etc)
 Moisture, ppm
 Total Base Number (alkalinity) – using 0.5g sample
 Red oxide count (corrosion particulate by microscope or
direct-imaging sensor
 Die Extrusion Index – evaluating unexpected softening or
hardening of the grease
 Microbial content – quantification of ATP by grease thin-
film extraction

17. Analysis Techniques
Sample is received. fdM+ is run Grease Thief Analyzer is performed and substrate is made
Two strips are used to make
a dilution to run RDE/ICP.
One Strip is used
for FT-IR.
One Strip is Dissolved in Green
RULER solution to run RULER.

18. Ferrographic analysis and Red
Oxide quantification

19. Results
 Data compiled for 500 tendon locations
 Strongest correlation between related
parameters (Calcium and TBN, Red
Oxides and Ferrous Debris)
 Some high Red Oxides were found in
higher Total Alkalinity locations
 Multiple potential failure modes likely
contributor to lack of consistent correlation

20. Results

21. Results

22. Results

23. Results

24. Analysis of Data
 Not a clear single failure mode
represented by correlated data
 Several tendons identified for further
testing: high ATP (microbial), several high
Red Oxides, & high Red Oxide/Low TBN
 Testing showed majority of tendons in
good condition, small percentage
candidates for disassembly and inspection
 Advanced statistics package used for
ranking metrics

25. Analysis of Data
 Dispersion analysis: failed tendon
exceeded 2σ outside the mean for the
failed tendon for three parameters
Data analysis by Dr. David Polk, Polk-Lepson Research, USA http://www.polk-lepsonresearchgroup.com/

26. Analysis of Data
 Regression analysis performed using Red
Oxides as the dependent variable (actual
measure of corrosion) and assigning
weighting factors for scoring
 Failed tendon and one other scored 5, and
twelve others scored as 4.
Data analysis by Dr. David Polk, Polk-Lepson Research, USA http://www.polk-lepsonresearchgroup.com/

27. Summary
 Tendon failure modes require reliable and
cost-effective method for sampling and
analysis
 Using new sampling tools per ASTM
D7718 without tendon can removal
 Small volume testing methods shown to
be equivalent or superior to traditional
testing
 Additional failure modes detectable with
small volume test slate