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Veracious Canada Inc In
Partnership with Advanced NDT Solutions Presents
High Temperature Hydrogen Attack As per API 941
Veracious Canada Inc150 King Street W, suite 200 Toronto, ON Canada M8X 1B3
Phone: +1(416) 640 5364 [email protected] www.veraciousinc.com
ISO 9001:2015 certified
HTHA in HAZ
High Pressure Hydrogen @ Elevated Temperatures
High temperature hydrogen attack is a form of damage commonly observed in steels exposed to high pressure hydrogen at elevated temperatures. The damage occurs as hydrogen atoms diffuse into steels, react with carbon, form methane gas internally in the material, which results in decarburization and fissuring (micro-cracking). This damage leads to loss of tensile strength and toughness. More importantly, it can cause catastrophic failure without prior warning, especially if occurring in the weld H.A.Z.
Sample Client Equipmentabove CS curve
Historical Hot Spots Arising during plant operation
Injection Points
Hot Hydrogen Stripping Process
Welds & HAZ – most likely damage locationFocus to inspect high percentage as HTHA can be localised in Welds & HAZ
Base Material
Significant change in wall thicknessNozzle to shell with SS cladding
Requires cleaning to achieve reliable inspection results
Establish Work Scope
Mark Test Locations
Prepare Surface
Measure Backscatter
No Backscatter Isolated B/S
not ID connected
ID connected
Backscatter
Significant
Attenuation
0.31 dB/mm
Thruwall B/S
or loss of BW
Velocity Ratio
Spectrum Anal. No HTHA No HTHA
Examine 4
additional
spots
B/S at 1 or 2
spots only
B/S at 3 or
more spots
Ratio < 0.555
on elbow
Ratio 0.555 or
more on elbow
Ratio > 0.553
not an elbow
Ratio > 0.553
not an elbow
Velocity
Ratio
No Variation
in Ratio
No HTHA
Velocity
Ratio is
Higher at
Backscatter
Locations
No HTHA
Possible HTHA
Remove Sample
or surface
metallography
No HTHA
Velocity Ratio
Possible HTHA
Remove Sample
or surface
metallography
Figure 8.2
Possible HTHA
Remove Sample
or surface
metallography
AUBT Backscatter – Base Material & HAZ
Velocity Ratio – Selected Locations on each weld
Spectral Analysis on all suspect locations
PAUT Sectorial Array – Confirmation
Weld & HAZ – PAUT / High Frequency Shearwave
TOFD – Screening of Welds & HAZ
Evaluating HTHAExtensive research has been carried out to investigate a reliable means to evaluate equipment that fall into the category of high risk potential for HTHA damage. ANS has adopted a (AUBT) multiple ultrasonic technique approach as outlined in API 941, that includes industry accepted techniques and in addition supplemental Phased Array & TOFD technology to further evaluate and characterize suspect damage. With field replication as final step.
Actual Severe HTHA Damage Signals
Technique #1: The ultrasonic backscattering technique is based upon the principle that
ultrasound will be scattered by changes in the grain boundaries resulting from the
presence of hydrogen damage. The extent of this damage can be directly correlated
to a through-wall depth value of affected material thickness and its location in relation
the ID/OD surfaces. Using a combination of 10 Mhz and 5 MHz transducers.
Pattern #1: Continuous decrease of backscattering from OD to ID surface.
Pattern #2: Large discrete reflections but no hydrogen attack.
Pattern #3: Hydrogen attack which has progressed to mid-wall.
Pattern #4: Hydrogen damage at the internal surface.
LocationRatio
Results
Individual Measurements for information purposes only
SW P1 SW P2 P2-P1 LW P1 LW P2 P2-P1
1 0,548 16,13 32,37 31,31 9,47 18,38 8,91
VELOCITY RATIO MEASUREMENTS
Comparing transit time relationship between the ultrasonic velocities of longitudinal and shear-wave.
Ratio = Velocity L / Velocity S
Velocity Guidelines (Expected Values)The ratio for carbon steel is in the range of 0.542 to 0.550Hydrogen can be present if the ratio is > 0.550
When severely attacked the ratio is > 0.560Note 1: for pipe bends the ratio maybe higher than 0.553 due to manufacturingNote 2: damage will not be reliably detected if less than 15% of the wall thickness
Clean Sample
8.91us/16.23us = .548
LocationRatio
Results
Individual Measurements for information purposes only
SW P1
SW P2
P2-P1LW P1
LW P2 P2-P1
1 0,567 14,72 29,99 15,27 8,81 17,47 8,66
Recent research has revealed that utilization of a high frequency shear-wave examination of welds and the HAZ can also help detect HTHA damage. This technique utilizes a pitch catch ultrasonic technique utilizing a pair of 10MHz 45º /60º shear-wave probes.
Spectrum Analysis generally is only utilized after we have seen evidence of backscattering ; Velocity Ratio > 0.560
Spectrum analysis uses Fast Fourier Transform (FFT) to convert the signal readout from amplitude versus time to amplitude versus frequency. This technique compares spectra of back-wall echoes measured from suspect locations with a "clean" reference spectrum taken from a "no damage" area. This follow-up technique is used because of its speed and sensitivity to HTHA.
Phased Array UltrasonicsThis can be a very useful tool in confirming HTHA damage
TOFD – Time of Flight DiffractionThis can be a very useful tool in detecting HTHA damage
TOFD scans on heat exchangers revealed multiple signals in weld body suggesting possible HTHA.
Further Evaluation with AUBT techniques to confirm.
API Reporting Data Sheet
PAUT Scan with & without TFM 40mm ID
PAUT Scan with & without TFM 40mm OD
PAUT Scan with & without TFM 50mm ID
PAUT Scan with & without TFM 50mm OD
PAUT Scan with & without TFM 60mm ID
PAUT Scan with & without TFM 70mm OD
PAUT Scan with & without TFM 70mm Cal StepWith 1mm FBH
PAUT Scan with & without TFM 75mm OD
PAUT Scan with & without TFM 80mm Cal Step with 1mm FBH
HTHA Miscellaneous Field Data
VR = 0.580
HTHA damage observed in piping
Backscatter signals with Velocity Ratio (VR) confirmation
Field Replication - Confirmation
Veracious Canada Inc
1101 Britannia Road EMississauga ON Canada L4W 3X1Phone (416) 640 5364 Fax (416) 981 3933Email : [email protected]
Alberta279 Nolan Hill Dr. NWCalgary, Alberta Canada T3R 0T1Phone: 1(800)-281-0604Email : [email protected]
3312-29 Ave Regina, SKCanada S4S 2P2Phone: (306) 351–1499Email : [email protected]
USA
East Point Mall Baltimore Maryland. Zip code : 21224 USAPhone :1(800)-281-0604Email : [email protected]
Ontario
150 King Steet W Suite 200 Toronto ON Canada M8X 1B3Phone (416) 640 5364 Fax (416) 981 3933 Email : [email protected]
Saskatchewan
www.veraciousinc.com ISO 9001:2015 Certified