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Hydrogen flux monitoring. A new tool for corrosion avoidance and management.
OPERA, LondonFrank Dean, Ion Science Ltd
28 November 2006Contact: [email protected]
Hydrogen flux through steel arises in various corrosion scenarios.
A new technology for measurement of hydrogen flux will be described.
Examples will be given of the technology’s benefits.
Finally, a mapping space illustrating the domains of various corrosion control methods and tools, including the flux monitor, will be offered to the seminar for additional discussion.
Introduction to Hydrogen Flux
• Hydrogen flux results from permeation of atomic hydrogen through the steel.
From 1 cm 2 steel surface
Volume V pL of H2 exiting surface each second from
= flux = V pL/ cm 2 / sNote 1 pL = 10-9 mL.
H HH HH HH HH HH HH HH-HH-HH-HH-H
Hydrogen atoms enter
and permeate steel
Hydrogen molecule in
air
Copyright � Ion Science 2006. All rights reserved.
Conditions required for flux measurement
Copyright � Ion Science 2006. All rights reserved.
Temperature, oC
(A) Hydrogen source (B) Permeable Steels
(C) Permeable coatings
0 to 120H2S, sour amine,
NH4HS / HCN and HF acid corrosion
<5% alloy (‘carbon’,
‘mild’)
Most, not zinc.
80 to 200 …plus severe acid corrosion eg acetic. < 10% alloy
Uncoated. Depending on temperature, alloy oxides
present a partial barrier to
permeation.
200 to 300All corrosion liberating
H, eg NAC < 13% alloy
300 to 400 All non-austenitic
400 to 500All steels
…plus PWHTbakeouts
…plus steel man’fr bakeouts
500 to 700 …plus hydrogen attack
Pump component showing naphthenic acid corrosion, encountered in refining of acid crude.T. Bazinger et al., http://www.ndt.net/article/wcndt2004/pdf/petrochemical_industry/604_batzinger.pdf
Flux accompanies corrosive wall loss…
An initiating crack in a 9-inch gas pipe responsible for two fatalities and temporary suspension of all German gas supplies, 1982. W.Bruckoff et.al., Corrosion ‘85, Paper 389, NACE conference series, Boston, Mass. 1985.
…and hydrogen damage
Flux measurements occur at different points of material use. Presently…
Hydrogen damage risk…Corrosive wall loss…
remove
Materials choice
Supply QA
Normal service
Decommission
Commission
Materials development
replace
PWHT
Corrosion control
Change in service
Materials choice
Supply QA
Normal service
Decommission
Commission
Materials development
Corrosion ocntrol
Change in service
remove
replace
PWHT
R&D, rare occasional routine, continuous
Flux measurement ‘markets’ are very different in character…
and hydrogen damage riskCorrosive wall loss
• broad, competitive
• public info limited by secrecy
• failure acceptable within limits
• accountable – cost of corrosion (plant integrity loss, production downtime, repairs) vs cost of feedstock and corrosion control
• specialised
• public info freely shared
• failure hardly ever acceptable
• risk of failure is so small andconsequence of failure so variant as to be unaccountable
How the Hydrosteel flux measurement works
pump
exhaust
Steel surface
Collector
Detector
Capillary
direction of air flow
...in a well defined flow of air F...
���� Flux J = F x c / A
Hydrogen captured from a well defined area, A...
...increasing the H2 in air concentration by c...
Copyright � Ion Science 2006. All rights reserved.
Hydrosteel is patented, manufactured, and marketed by Ion Science Ltd
Hydrosteel handheld flux monitor
Hydrosteel 6000 is a roaming hand held tool for spot flux measurement.
Used to identify corrosion hot spots and monitor unexpected corrosion episodes, as well as routine multi-point spot measurement surveys with AT-S probe.
Copyright � Ion Science 2006. All rights reserved.
Hydrosteel continuous flux monitor
Hydrosteel 7000 continuously monitors flux at fixed sites. Data is used to inform feedstock blending, process control, and corrosion control programs
analyser
Flux, background and temperature probe
sample conduit
15-24 V power supply
Copyright � Ion Science 2006. All rights reserved.
Hydrosteel Probes
LT-R Probe: for >3.5 in diameter, <130 oC steel Range: 10 to 22,000 pL/cm2/s
AT-S Probe: Permanently fixed.
For >3.5 in diameter, <130 oC steel.
Range: 1 to 3,500 pL/cm2/s
Most accurate probe
HT-S Probe: Permanently fixed.
For >3.5 in diameter, <130 oC steel.
Range: 10 to 22,000 pL/cm2/s
Copyright � Ion Science 2006. All rights reserved.
HT-R Probe: for >3.5 in diameter, <500 oC steel Range: 10 to 22,000 pL/cm2/s
Hydrosteel technology attributesResponse:
Accurate
Rapid response
Rapid cleadown
Low drift
Wide dynamic range
Reproducible
Environmental:
Selective
Condensation resistant
Dust resistant
EM noise proof
Temperature tolerant
Corrosion resistant
Test site suitablity:
Non-invasive
Steel geometry tolerant
Steel temperature tolerant
Safety:
Intrinsically safe
Non-toxic
Non-hazardous
ISO 9001:2002 manufacture
Readily calibrated vs traceable standardUseability:
Easy to use
Serviceable
No consumables
Long term measurement capability
…but is the data useful?!
Flux and other corrosion monitors compared
Tool Location Non-intrusive? Corrosion rate information____________________________________________________________
Linear Polarisation (LPR), fixed � inferred, (real time) Electrical Resistance (ER)
Weight loss coupons: fixed � direct (historic)
Ultrasonic thickness movable � direct (historic)(UT) measurement
Field Signature Monitoring fixed � inferred (weekly)(FSM)
Flux: movable or fixed � inferred sour, HF, high T only(near real time)
During low temperature corrosion, flux measurement also provides an indication
of hydrogen damage risk (HIC). Copyright � Ion Science 2006. All rights reserved.
Crude oil
DESALTING
ATMOSPHERIC DISTILLATION
GAS SEPAR-ATION
GAS PLANT POLYMERIZATION
ALKYLATION GASOLINE (NAHTHA)
SWEETENING TREATING
and PROCESSING
DISTILLATE SWEETENING
TREATING and
PROCESSING
RESIDUAL TREATING
and PROCESSING
HYDRO TREATING,
PROCESSING
CATALYTIC REFORMING
HYDR0DE-SULFURIZATION
HYDR0DE-SULFURIZATION
CATALYTIC CRACKING
COKING VISBREAKING
SOLVENT DEWAXINGSOLVENT
EXTRACTION
HYDROTREATING
SOLVENT DEASPHALTING
VACUUM DISTILLATION
CATALYTIC ISOMERIZATION
CATALYTIC HYDROCRACKING
GreasesLubricants
Waxes
Residual fuel oils
Diesel fuel oils
Distillate fuel oils
SolventsKerosene
Jet fuels
Solvents
Automotive gasoline
Aviation gasoline
LPG
Fuel gasesPolymerizat
ion feed
Alkylation feed
GreasesLubricants
Atmospheric tower residue
Cat cracked residual oils
Hvy vacuum distillate
HDS mid distillate
SR mid distillate
SR Kerosene
HDS hvy naphtha
Reformate
iso-naphtha
Polymerization naphtha
n-butane
alkylate
LT SR naphtha
Lt hydrocracked naphtha
Hvy cat cracked distilliate
Lt catcracked naphtha
Lt cat cracked distilliate
Thermally cracked residue
Vacuum residue
Lt thermal cracked distillate
Raffinate
Asphalt
Hvy vacuum distillate
Lt vacuum distillate
SR Gas oil
SR middle distillate
SR Kerosene
Heavy SR naphtha
Light SR distillate
Light crude oil distillate
souramm. bisulf
HF NAC/sulfidic
amine
Schematic of sites of frequent corrosion induced flux indications in a refinery
An HF acid alkylation unit can provide a refinery with a very profitable revenue stream, converting C4 gases to ‘high octane’ petrol.
HF acid corrosion provides a ‘perfect’ flux measurement scenario; corrosion and flux output are often continuousand extensive - correlation can be close.
Process control of corrosion by flux monitoring (1)
HF corrosion chemistry
Fe + 2HF (anhydrous) => 2H + FeF2 passivating
FeF2 + 4H2O (damp) => FeF2 .4H2O passivating
FeF2 .4H2O + 4H2O (in < 65% HF*) = FeF2 .8H2O soluble in HF!
FeF2 .4H2O (>60 oC) => FeF2 + 4H2O dehydrates and shrinks, losing passivity
FeF2.4H2O + Fe + 3HF (damp, O2) => H + FeF2. FeF3. 4H2O shrinks, losing passivity
FeF2. FeF3. 4H2O + 3HF (damp, O2) => H + FeF3. 3H2O non-passivating
FeF3. 3H2O + xHF (excess) => FeF4- or FeF6
3- solubilised
FeF2.4H2O + ¼ O2 (moist, HF free) => FeOOH + 2HF + 2½ H2OHF liberated moves towards steel
*Note 2% H2O in HF condenses (78 oC) => 36% H2O in condensate.
H [surface] ↔ H [in Fe] flux entry[Actual cathodic reaction in aqueous environment is considered to be HF2
- + e -> H(in Fe) + 2F- ]
Copyright � Ion Science 2006. All rights reserved.
Flux
×th
ickn
ess
/ pl/c
m/s
Horizontal test series BB’
0
100
200
300
0 5 10 15 20Distance from East end of vessel / feet
AA' CC'
Vertical test series
0
50
100
150
200
250
300
0 2 4 6 8 10 12Distance from base / feet
CC'
AA'
DD'
EE'
HF acid corrosion of a vessel.
• … and lower corrosion where liquid exposure is low…
• or quiescent.
• Spot flux maps indicate higher corrosion in regions of liquid movement
Vessel temperature 35 oC.
Frank Dean, Corrosion 2002 Coference, NACE, Paper 02344
336
332
312
348471
332
2”14”
45
18
12
6
569
12
6
605
Overhead column
Exchanger
By pass
250
358
363
12
6
HFA acid corrosion of a pipe
• Very similar flux values observed where process flow is uniform,
• higher at sites of erosion-corrosion,
• and lower where stagnant.
Illustration: F.W.H.Dean, P.A.Nutty, M.Carroll, Corrosion 2001, NACE, Paper 01636.Otherwise Copyright � Ion Science 2004. All rights reserved.
Flux (pL/cm2/s) indicated
Frank Dean, Corrosion 2002 Coference, NACE, Paper 02344
0
100
200
300
400
500
600
700
5/1/2000 8/2/2000Date
Flux
x th
ickn
ess
/ pl/c
m/s
T86, P4123, Depropanizer FeedBottom Exch. to DepropanizerT89, "
T91, "
T92, E117, Depropanizer OverheadCondensorT99, "
5 sites avg, F107, Acid Settler lowersectionT123, P4087, Acid Settler to pumps
T163, E107D, Acid Cooler, vessel
T164, "
T172, F145, Recontactor, boot
T173, "
T178, F145, Recontactor, vessel
T179, "
T180, "
T192, "
35 days
• In this example of fifteen sites in an HF unit, the two sites at which flux increased were located on steel in the same service (acidcooling).
Co-trending of hydrogen flux
Copyright � Ion Science 2006. All rights reserved.
0
50
100
150
200
250
300
0.0 0.2 0.4 0.6 0.8 1.0 1.2mm/yr
Flux
x th
ickn
ess
/ arb
itra
ry u
nits
Average flux x thickness reading vs average historic metal loss for a number of vessels in HFA service.
• Correlation of flux with corrosion rate must consider corrosion variability over time.
Correlating corrosion rate with flux measurements
Copyright � Ion Science 2006. All rights reserved.
0
50
100
150
200
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
Days elapsed
Flux
/ pl
/sqc
m/s
Continuous monitoring hydrogen flux from HF alylation unit site to ensure corrosion does not exceed a certain threshold.
Copyright � Ion Science 2006. All rights reserved.
• Acidic crudes are increasingly used by refiners. They contain carboxylic acids known as ‘naphthenic acid’ which corrode steel, within and immediately downstream of distillation equipment.
• It is very desirable to measure this corrosion so as to optimise feedstock blending, process control and inhibitor treatment. The cost of corrosion and its control is offset against the gain from using lower price feedstock.
• In 2002, a flux probe was marketed by Ion Science, with datashowing that the probe indicated flux due to active corrosion at high temperatures.
Process control of corrosion by flux monitoring (2)
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
14-Oct-02 21-Oct-02 28-Oct-02 04-Nov-02 11-Nov-02
Hyd
roge
n ac
tivity
/ ba
r
0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
0.16
0.18
TAN
Position 1
Position 2
Position 3
Position 4
Position 5
Position 6
Position 7
Position 8
Position 9
Total crude fraction / %
Throughput / 10000 T/day
TAN
existing H2S / g/kg
Example 1: spot flux measurements during a corrosion episode due to change in a refinery crude slate TAN at nine disparate sites.
A.M.Etheridge, E.B.McDonald, D.G.Serate, F.Dean, Corrosion 2004, NACE, Paper 04477.
0
100
200
300
400
500
600
Aug-01 Jan-02 Aug-02 Jan-03 Aug-03 Jan-04 Jul-04Date
Flux
/ pl
.cm
-2.s
-1
1
1
4
2
3
3,125,64
57
7
8,9 8,13 910,11
TAN of crude slate
increasedInhibitor
introducedInternal inspection reveals
minimal corrosion
Example 2: Four spot flux measurement surveys carried out over a three year period. Indicated site locations approximate due to re-
cladding.
Copyright � Ion Science 2006. All rights reserved.
• Refinery process streams, and natural gas and gas oil reserves often contain high partial pressures of H2S, sour gas, which causes corrosion as well as presenting a hydrogen damage risk.
• This can be addressed by using HIC resistant steels, but a stream may turn more sour during its service life, it may be very sour, or the cost of quality steel be may prohibitive. Then, inhibitors are injected into the stream to mitigate corrosion.
• Flux measurements may offer confirmation of effective inhibitor usage.
Ensuring effective inhibitor usage.
Example 1: methane reactor subject to sour corrosion
0
50
100
150
200
250
18/12/05 28/12/05 7/1/06 17/1/06 27/1/06 6/2/06 16/2/06 26/2/06
Date
H2
flux
[pL/
cm² s
]
Start of inhibitor dosing
Copyright � Ion Science 2006. All rights reserved.
SOUR CO2 GAS GATHERING LINE
0
2
4
6
8
10
12
Jan-05 Feb-05 Mar-05 Apr-05 Jun-05 Jul-05 Aug-05 Sep-05
Inhi
bito
r, p
pm o
r E
R p
robe
rea
ding
0
10
20
30
40
50
LPR
mils
/yea
r, o
r flu
x, p
L/cm
2 /s
LPR corr. rate, mils/yr
INHIBITOR
ER
Flux, pL/cm2/s
Copyright � Ion Science 2006. All rights reserved.
Example 2: A gas gathering line containing sour gas.
• Sour gas, contained in gas and oil gas wells, and released and concentrated in gas-oil separation plants and refinery units is liable to corrode mild steel, with concommitant hydrogen injection into steel. The hydrogen activity so generated can be over a million bar molecular hydrogen equivalent.
• Flux measurements, together with steel wall thickness and temperature, can be used to determine hydrogen activity.
• HIC risk is largely eliminated by following standards for materials choice, and using coatings and inhibitors.
• Flux measurements offer confirmation of effective HIC testing, and occasionally, diagnosis of HIC inducing scenarios.
HIC damage - prevention
Hydrogen Permeation Experiment Without CRA Metalspray Coating
0
200
400
600
800
1000
1200
0 24 48 72 96 120 144 168 192 216 240 264 288 312 336 360
Time in Hours
Hyd
roge
n Fl
uxpl
/sqc
m/s
Plate A No HIC Detected Plate B HIC Detected
• The flux through a steel which suffers hydrogen induced cracking (HIC) is not significantly different from a steel which is HIC resistant• Activity of hydrogen at flux entry face calculated at 1.7 106 bar.
S.J.Mishael, F.W.H.Dean, C.M.Fowler, Corrosion 2004, NACE, Paper 04476.
Measurements verifying severe hydrogen cracking environment
16 mm plates simultaneously exposed to NACE A solution saturated with 1 bar H2S at 22 oC
Hydrogen Permeation Experiment With CRA Metalspray Coating
0
200
400
600
800
1000
1200
1400
0 24 48 72 96 120 144 168 192 216 240 264 288 312 336 360
Time in Hours
Hyd
roge
n Fl
uxpl
/sqc
m/s
Plate B HIC Detected Plate B No HIC Detected
purge with N2
Two 16 mm HIC susceptbile plates simultaneously exposed to NACE A solution saturated with 1 bar H2S at 22 oC, one metallised plate, the other not.
Measurements verifying effectiveness of corrosion barrier
S.J.Mishael, F.W.H.Dean, C.M.Fowler, Corrosion 2004, NACE, Paper 04476.
Plate B metallised, no HIC detected
0
10
20
30
40
50
60
70
80
90
9 12 15 18 21 24 27 30 33 36 39 42 45
Time / hr
See
lege
nd
4
5
6
7
8
9
10
11
12
13
14
Flas
h D
rum
Pre
ssur
e co
ntro
l val
ve
Flux / pl/sqcm/sModelled flux profileFlash Drum Level Control ValveFlash Drum Pressure Control Valve
model H entry activity a0 = 78
(am)
a0
Amine Flash drum (70 0C).
Short term flux incidents endure for the time of the incident, plus time required for H diffusivity through steel, depending on steel emperature and thickness. . Modelling enables time of onset of corrsion to be identified.
Flux associated with an episodic hydrogen blistering scenario
Copyright � Ion Science 2006. All rights reserved.
Rich amine line.
425 375
550
875 625 900
12 in
O
Abt 20 ft downstream, 50 to 70
Cross section -View from South
Anti foam inlet, ½ in
View from North
Gas to flare outlet, ¾ in.
Inhibitor inlet, ½ in North
600 700
635 11400
500
565 995
1075 1085
2020 2350
1105 445
835
1105 540
435
Abt 20 ft downstream, 100 to 200
Monitor flux at convenient location just downstream of cause of flux.
Flux associated with an episodic hydrogen blistering scenario
0
Copyright � Ion Science 2006. All rights reserved.
0
500
1000
1500
12 24 36 48 60
Time elapsed / hr. 0, 24, 48… = midnight
Flux
pl/s
qcm
/sm
odel
mea
sure
0
200
400
600
80012 24 36 48 60
Mod
eled
hyd
roge
n ac
tivity
a
0
Rich amine line (70 0C).
400,000 bar
7 am
•Identifying a corrosion problem
Flux associated with an episodic hydrogen blistering scenario
• Flux measurements identified source of original blistering and a newly discovered corrosion even to be oxygen entrainment from inhibor line.
Illustration F.W.H.Dean, Corrosion 2002, NACE, Paper 02344.
Steel equipment subject to hydrogen charging during service may contain trapped hydrogen which, although at benign concentrations (~ 1 ppm), if not out-gased by heat treatment, is concentrated in the heat affected zone of a weld (~ 5-10 ppm), sufficiently on cooling of the weld to cause stress oriented hydrogen induced cracking.
Hydrogen bakeout monitoring to prevent hydrogen in weld damage
• Assurance hydrogen level is safe for welding• Prospect for reducing production downtime• Research into necessity of bake-outs
A vessel dome in HF service had sustained hydrogen damage. Areas of blistering and delamination are indicated, together with cut away perimeter.
Arrow shows direction of recent lamination growth...
Sites for hydrogenbakeoutmonitoring.All located outside zone of detected delamination.
C.N.Brown, M.J.Carroll, F.W.H.Dean, J.H.Harrison, A.Kettle, Corrosion 2004, NACE, Paper 04478.
E
G
A
Cblister boundary
delamination boundary
cutaway boundary
It was decided to remove the affected steel:
C.N.Brown, M.J.Carroll, F.W.H.Dean, J.H.Harrison, A.Kettle, Corrosion 2004, NACE, Paper 04478.
... set up heat treatment circuitry...
C.N.Brown, M.J.Carroll, F.W.H.Dean, J.H.Harrison, A.Kettle, Corrosion 2004, NACE, Paper 04478.
... bake out at 300 degrees Centigrade whilst monitoring hydrogen at circumferential sites…
C.N.Brown, M.J.Carroll, F.W.H.Dean, J.H.Harrison, A.Kettle, Corrosion 2004, NACE, Paper 04478.
A
H
G
FE
D
C
B
... and fit a new plate.
C.N.Brown, M.J.Carroll, F.W.H.Dean, J.H.Harrison, A.Kettle, Corrosion 2004, NACE, Paper 04478.
0
5,000
10,000
15,000
20,000
13:00 14:00 15:00 16:00 17:00 18:00 19:00 20:00Time / hr:min
Flux
/ pl
/sqc
m/s
0
50
100
150
200
250
300
350
Bak
eout
tem
p. /
deg
C
A' (mon.)
B (mon.)
B
C
D
E
F
G
H
H (mon.)
B', D',E',F',G', H'H
1,000
C.N.Brown, M.J.Carroll, F.W.H.Dean, J.H.Harrison, A.Kettle, Corrosion 2004, NACE, Paper 04478.
Flux measurements during bakeout.
Outgased concentrations are obtained by summing area under each site flux profile
F E
D
C
BA
H
G3.00 ppm.cm:= 1.2 ppm from 2.5 cm depth. cf1 ppm weld
threshold!
Direction of lamination growth
C.N.Brown, M.J.Carroll, F.W.H.Dean, J.H.Harrison, A.Kettle, Corrosion 2004, NACE, Paper 04478.C.N.Brown, M.J.Carroll, F.W.H.Dean, J.H.Harrison, A.Kettle, Corrosion 2004, NACE, Paper 04478.
The domain of monitoring corrosion and corrosivityA field is proposed which maps the domain of techniques with their applications
Pre
dict
ive
scop
e
Copyright � Ion Science 2006. All rights reserved.
Locale ResolutionBroad,
genericNarrow, specific
year
sho
urs
d
ays
mon
ths
Wt.
loss
cou
pons
ER
LPR Fe
edst
ock
anal
ysis
UT
Spo
t Fl
uxP
EC
, FS
M
Pro
cess
st
ream
an
alys
is
Maintenance planning
Lab
sim
ulat
ion
Corrosion control
Process optimisation
Feedstock optimisation
Monitoring techniques: UT = ultrasonic thickness LPR = linear polarisation resistance ER = Electric resistance PEC = pulsed eddy current FSM =field signature monitor.
Placements of techniques are approximate
Corrosion avoidance
HIC risk avoidance
Act
ive
HIC
Note:
- Basic strategem is to avoid first, then control and monitor.
- HIC avoidance and flux monitoring are at diametric ends of the field.
- UT is perfect fit for maintenance planning. Flux tool best for process/feedstock optimisation where analysis/predictive tools are not fully comprehensive.
SummaryField worthy flux measurements provided by a new tool, Hydrosteel, offer access to a new zone on the corrosion monitoring map, specifically in regards to sour, HF and high temperature (>100 deg C) corrosive service of steel.
The tool is very effective in identifying episodes of location and time variant corrosivity, so as to inform process optimisation and corrosion control.
The tool has also proven excellent in the monitoring of hydrogen during pre-weld hydrogen bakeouts, and in the identification of HIC risk atcritical sites.
Other applications are on-going.
Thank you for your interest