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 info@veraciousinc.com 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 : Info@veraciousinc.ca

Alberta279 Nolan Hill Dr. NWCalgary, Alberta Canada T3R 0T1Phone: 1(800)-281-0604Email : Info.west@veraciousinc.ca

3312-29 Ave Regina, SKCanada S4S 2P2Phone: (306) 351–1499Email : Info.west@veraciousinc.ca

USA

East Point Mall Baltimore Maryland. Zip code : 21224 USAPhone :1(800)-281-0604Email : Info@veraciousinc.com

Ontario

150 King Steet W Suite 200 Toronto ON Canada M8X 1B3Phone (416) 640 5364 Fax (416) 981 3933 Email : Info@veraciousinc.com

Saskatchewan

www.veraciousinc.com ISO 9001:2015 Certified