hydrogen flux monitoring. a new tool for corrosion …...hydrogen flux monitoring. a new tool for...

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


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...


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.


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


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


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- ]


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


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


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.


• 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.


• 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


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


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


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.


0


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 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:


... set up heat treatment circuitry...


... bake out at 300 degrees Centigrade whilst monitoring hydrogen at circumferential sites…


A

H

G

FE

D

C

B

... and fit a new plate.


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


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


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

hydrogen flux monitoring. a new tool for corrosion …...hydrogen flux monitoring. a new tool for...

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