presentation for api 934f
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API 934FTRANSCRIPT
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5/20/2018 Presentation for API 934F
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API 934F Task Group
Procedure to Calculate the
Minimum Pressurization Temperature (MPT) for Heavy
Wall Vessels in High Temperature High Pressure
Hydrogen Service - 2Cr-1Mo
Presentation at API 934F Task Group Meeting,
September 18, 2012, New Orleans, LA
Jim McLaughlin
Consultant
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Basis for Calculating the MPT of Heavy Wall Vessels in
High Temperature High Pressure Hydrogen Service
Fast Fracture Considerations
Low energy brittle fracture promoted by temper embrittlement effects
Older reactor vessels (fabricated before circa 1980) without compositional
controls to limit impurity levels, such as P, Sn, Sb and As
Newer reactor vessels (fabricated after circa 1980) with compositional
controls to limit impurity levels, such as P, Sn, Sb and As
Effect of hydrogen on fast fracturenew consideration
Slow Stable Crack Growth Considerations
Hydrogen embrittlement controls slow stable crack growth
Recent research at UVa shows that hydrogen embrittlement effects
rapidly disappear at a threshold temperature above which noembrittlement occurs
Hydrogen embrittlement effects also function of impurity levels
MPT determined by limiting temperature consideration due to fastfracture and slow stable crack growth considerations
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Fast Fracture Considerations - Temper Embrittlement Guidance
Fast fracture addressed in same manner as in Part 3 of API579, paragraph3.4.3.1, Pressure Vessels, Method A
Need to establish starting temperature for entering Figure 3.7 to establish theMinimum Allowable Temperature (MAT) as a function of the applied stress ratiofollows same temperature reduction curves as in Section VIII, Divisions 1 and 2 of
the ASME Code.
Use an estimate of the 40 ft-lb transition temperature in the temper embrittled
condition as the starting temperature
Use 250F (121C) for older reactor vessels (fabricated before circa 1980)without compositional controls to limit impurity levels, such as P, Sn, Sb and As
Use 300F (149C) for older reactor vessels without compositional controls and
made from plate with long seam made with single ESW pass
Use 150F (65C) for newer reactor vessels (fabricated after circa 1980) with
compositional controls to limit impurity levels, such as P, Sn, Sb and As
For reactor vessels with step cool requirements, use the maximum calculated orallowed temperature after the step cooling heat treatment with a 3.0 multiplier
factor
When is temper embrittlement a consideration?
Suggesting that temper embrittlement be considered only when the maximum
expected operating temperature (normally the end of run temperature) for the
reactor vessel is 700F (371C) or higher
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Effect of Hydrogen on Fast Fracture New Consideration
Effect of hydrogen on fast fracture at low temperaturesArcelorMittal data
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Effect of Hydrogen on Fast Fracture New Consideration
Hydrogen has significant effect on fast fracture at low temperatures
summary of ArcelorMittal data on 2Cr-1Mo with a very low FATT of-80C (-112F)
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5/20/2018 Presentation for API 934F
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Effect of Hydrogen on Fast Fracture New Consideration
Test conducted on 2Cr-1Mo with high impurity levels as prepared by Kobe Steelshows that the effect of hydrogen on fast fracture at higher temperatures decreases
As the temperature approaches 150F (65C), the fracture toughness approaches 100MPam even when soluble hydrogen levels are 3 ppm, highest expected level inrefining hydroprocessing service.
Conclusion: Effect of hydrogen on fast fracture insignificant above 150F (65C)
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5/20/2018 Presentation for API 934F
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Effect of Hydrogen on Fast Fracture New Consideration
Combining results on the effects of hydrogen on fast fracture at low temperature
per the ArcelorMittal testing, with the results of the Kobe tests at higher
temperatures, the following curve can be used to define the shift in the fracturetoughness transition temperature that results from the effect of hydrogen on fast
fracture
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Slow Stable Crack Growth Considerations
Hydrogen embrittlement controls slow stable crack growth considerations
Hydrogen embrittlement effects as determined by a slow strain rate risingload test show that the effects disappear once the temperature reaches athreshold temperature above which hydrogen embrittlement effects areinsignificant.
Above threshold temperature reactor pressure limited to the full design
pressureBelow threshold temperature reactor pressure limited to 30% of the full design
pressure
Testing performed at UVa and data available from other sources are usedto develop curves for the hydrogen embrittlement threshold temperature
as a function of the bulk hydrogen level in the steel and the concentration
of hydrogen that can accumulate in the plastic zone a head of a crack.
Curves were developed for 2Cr-1Mo steel with high impurity levels and low
impurity levels.
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Hydrogen Embrittlement Threshold Temperature
(High Impurity 2Cr-1Mo)
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Hydrogen Embrittlement Threshold Temperature
(Low Impurity 2Cr-1Mo)
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Suggested Hydrogen Embrittlement Threshold Temperature
Curves for Use in MPT Assessment
Each curve represents a constant ratio of the bulk hydrogen concentration
in the steel versus the concentration at a distance of 470m from thecrack tip.
For the purposes of an assessment 3 different levels of hydrogenconcentration at the crack tip are defined. Each of these levels represent
different stress intensity levelsthe higher the stress intensity the greater
the hydrogen concentration at the crack tip
Nominal hydrogen concentration (C470m/Cbulk= 1)This is the level that wouldbe expected with a crack similar to the crack that existed in the compact
tension sample used for testing for hydrogen embrittlement
Conservative hydrogen concentration (C470m/Cbulk= 1.54)This is the level
that would be expected with a crack that has a higher stress intensity than thecrack in the compact test specimen.
Non-conservative hydrogen concentration (C470m/Cbulk= 0.5)This is the levelthat would be expected with a crack that has a lower stress intensity than the
crack in the compact test specimen.
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Hydrogen Embrittlement Threshold Temperature
(High Impurity 2Cr-1Mo)
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Hydrogen Embrittlement Threshold Temperature
(Low Impurity 2Cr-1Mo)
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MPT Assessment of Typical Hydroprocessing Reactors
MPT assessment for 2 typical reactor vessels
Fast fracture considerationsBoth reactors screened base materials
and welding consumables with a step cooling procedure
For this assessment the starting temperature for fast fracture curve aftertemper embrittlement effects are accounted for is 75F
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MPT Assessment of Typical Hydroprocessing Reactors
Effect of hydrogen on fast fracture
First need to determine the bulk hydrogen level in thereactor wall
The following assumptions are made for this calculation Calculation is made at the maximum expected operating
temperature and hydrogen partial pressure using the latestdiffusivity and solubility data from Kobe Steel
Assume that the cladding is cracked so that there is no benefitfrom the stainless steel cladding in reducing hydrogensolubility in the steel
No benefit calculated for outgassing during reactor shutdown
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5/20/2018 Presentation for API 934F
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MPT Assessment of Typical Hydroprocessing Reactors
Effect of hydrogen on fast fracture
Reactor 1 Fast Fracture Starting Point Temperature 75F + 31F = 106F
Reactor 2 Fast Fracture Starting Point Temperature 75F + 25F = 100F
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MPT Assessment of Typical Hydroprocessing Reactors
Slow Stable Crack Growth Hydrogen Embrittlement Effects
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MPT Assessment of Typical Hydroprocessing Reactors
Slow Stable Crack Growth Considerations Control Over Entire
Temperature Range for MPT Assessment
Reactor 1
Reactor 2
Low Impurity 2Cr-1Mo
Does Not
Meet MPTGuidance
Meets MPTGuidance
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MPT Assessment of Typical Hydroprocessing Reactors
(Old Reactors without Compositional Controls)
MPT assessment for 2 typical reactor vessels
Fast fracture considerationsBoth reactors were fabricated prior to
1980 and did not have any compositional controls to maintain low impuritylevels
For this assessment the starting temperature for fast fracture curve aftertemper embrittlement effects are accounted for is 250F
Since the starting temperature for the fast fracture curve is above 150F,there will be no additional temperature added to the starting temperature
to account for the effect of hydrogen on fast fracture
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MPT Assessment of Typical Hydroprocessing Reactors
Slow Stable Crack Growth Hydrogen Embrittlement Effects
High Impurity 2Cr-1Mo
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MPT Assessment of Typical Hydroprocessing Reactors
Fast Fracture Controls at Higher Temperatures and Slow Stable Crack
Growth Controls at Lower Temperatures
High Impurity 2Cr-1Mo
Does NotMeet MPTGuidance
Meets MPTGuidance
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5/20/2018 Presentation for API 934F
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Additional Work Needed on MPT Assessment Procedure
Improved understanding of the 3 curves being suggested for the hydrogenembrittlement threshold temperature as a function of bulk hydrogen levels
What are typical crack sizes/geometries indicated for each of these curves in areactor vessel
Ted Anderson will discuss further
Assumptions included in the MPT procedureAre they too conservative?
Assuming that a crack compromises the stainless steel claddingUsing the dissolved hydrogen level at the maximum expected metal
temperature and hydrogen partial pressure level without any reduction provided
for out gassing during shutdown
3 curves being suggested for the hydrogen embrittlement threshold
temperature
Use of rising load test results to define hydrogen embrittlement effects
Need to conduct testing on 2Cr-1Mo-V material
Hydrogen embrittlement effort
Effects of hydrogen on fast fracture