influence of corrosive sulfur on the worldwide population of … · influence of corrosive sulfur...
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Influence of Corrosive Sulfur
on the Worldwide Population
of Power Transformers
ENDESA/CIGRE Conference
Santiago, Chile
August 12, 2009
Lance Lewand
Doble Engineering Company
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Introduction
• There is no one specific corrosive sulfur
compound that is responsible for all the
problems
• Possibly tens to hundreds of different
sulfur compounds in the oil
– some may be corrosive or become corrosive
– many more that are very stable given the use
of modern refining techniques
• The problem is real
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Topics of Discussion
• Evolution of the Corrosive Sulfur Phenomenon
• Impact on World Wide Electrical Industry
• Evolution of Corrosive Sulfur Detection
• Overview on Mitigation Techniques
• Analysis and worldwide experience on
passivation
• Experience in the Application of Standard Test
Methods
• Certification of Test Laboratories
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Evolution of the
Corrosive Sulfur
Phenomenon
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Historical Perspective
• Corrosive sulfur issues have existed since oil was
used in transformers (early 1900s)...problems with
elemental sulfur
• F.M. Clark of GE in the United States authored a
paper that effectively took ASTM D 130 for lubrication
oils and developed ASTM D 1275 for transformer oils
in the late 1940s because the problem was so
pronounced…issues with mercaptans, elemental
sulfur and sulfides
• The problem resurfaces every 2-3 decades
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Historical Perspective
• Sporadic reports from about 1960s through the 1980s
but not much published
• Doble found a US domestic oil to be corrosive in the
1995 Oil Survey
• Recent problems have occurred in the mid 1990s and
again since about 2001 - Doble paper in 2001
• 2004 - numerous failures of large power transformers
in various parts of the world caused additional
attention to the corrosive sulfur issue
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Historical Perspective
• 2005 - Doble initiates world wide collaborative
research study on corrosive sulfur with about 30
participating companies
• 2006 - Terna/Sea Marconi discover the presence of
DBDS in certain transformer oils - found to be
corrosive when breaks down
• 2007/2009 - Doble proves that higher local
temperatures from 200 to 400 C or higher can cause
degradation of stable sulfur species into corrosive
ones
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Historical Perspective
• 2008 - Doble and Mitsubishi (Japan) provide different
theories for how DBDS breaks down to form corrosive
sulfur that reacts with the copper.
– Doble: breakdown to form benzyl mercaptan, reacts with
copper, variation in mechanism between free breathing and
sealed transformers
– Mitsubishi: formation of copper/dibenzyl disulfide complex
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Impact on the
Worldwide
Electrical Industry
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World Wide Issue
• The corrosive sulfur problem is real - there is clear
evidence of corrosive sulfur being involved in
some failures
• Although a small percentage of the entire
population, the adverse economic impact has
been significant
• Mostly large power transformers (AC and HVDC)
and shunt reactors with paper-wrapped copper
conductors, also found in lower voltage
transformers and bushings down to 34 kV
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World Wide Issue
• 100+ large power transformer failures have occurred
worldwide since 2004, most in warmer climates,
some in cool climates - time at warm operating
temperatures important
• Unfortunately, Brazil has had a majority of the
failures due to its electrical transmission design that
requires the use of many shunt reactors
• Many corrosive sulfur failures have probably gone
undetected for lack of inspection at lower voltage
classes and lack of knowledge in 2004.
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• However, not all failures are from corrosive sulfur,
even when there is some evidence that corrosion
has occurred…must be investigated fully
• Design issues of transformer. Simon Ryder of Doble
UK provided paper at 2009 Doble Conference on
underlying design issues that cause areas of
localized overheating thus accelerating the corrosive
sulfur attack.
• The amount of oil per kVA has significantly reduced
in newer designs then transformers of 30 years ago
World Wide Issue
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World Wide Issue
• Oils typically passed ASTM D 1275A and DIN
51353 but fail ASTM D 1275B
• Most units have several years of service, range
from under a year to 20 years old
• Generally no known advanced warning: No
generation of excessive amounts of combustible
gases - most often extremely localized
• Reacts with copper or silver conductors and can
form resistive film and overheating of contacts
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Copper Sulfide in Transformers
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Bushing Copper Sulfide
Bushing with
blackened conductor
Non-contaminated
bushing
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Evolution of
Corrosive Sulfur
Detection
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Corrosive Sulfur Detection
• 1953 - F.M. Clark of GE in the United States creates
ASTM D 1275 for the detection of corrosive sulfur in
transformer oils
• 1978 - ISO 5662 (same as ASTM D 1275)
• 1985 - DIN 51 353, German Method (100ºC for 18
hours using silver strip)
• 2001 - Doble introduced proposal to ASTM to change
the test temperature from 140 to 150 C - proposed
changed was not accepted.
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Historical Perspective
• In 2003, Doble introduced the Doble Modified D 1275
method which not only increased the temperature but
the duration as well (from 19 to 48 hours) and the use
of a sealed bottle - through collaboration with ABB -
US
• ASTM accepted the change in 2006 and it became
ASTM 1275B. D 1275 was renamed as D 1275A for
historical purposes
• late 2004 - Doble developed method for Passivator
detection
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Historical Perspective
• 2005 - ABB development of CCD test
• 2006 - Development of Siemens CCD Test
• 2006 - Development of Doble CCD Test
• 2006 - CIGRE Brazil Test Method for Corrosive
Sulfur. Similar to ASTM D 1275B but without the
sealed bottle - uses a flask
• 2007 - development of Doble Test Method for DBDS
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Historical Perspective
• 2006/2007 - Development of Covered Conductor
Deposition (CCD) IEC Test and low volume oil
corrosive sulfur test
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Corrosive Sulfur Tests, Oil
ASTM D1275A Doble CCD TestsASTM D1275B
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Results of D 1275B
Corrosive
Non-corrosive
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D 130 Color Scale
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Covered Conductor Deposition
• Cover Conductor Deposition Test (CCD) - first
proposed by ABB uses a insulating paper wrap
around a length of copper - all start with air-
saturated oil
• ABB uses a breathing environment, 4 days at 140 C
• Siemens uses a sealed environment, 3 days at 150 C
• Doble recommends using both sealed and breathing
environments and the Doble method uses commonly
found materials, 140 C for 4 days (or longer)– Sealed tubes miss some potential problems
– Sealed tubes sometimes show more pronounced deposits
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Example, 4 day CCD
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Deposition After 4-Day Test
Deleterious Deposit
• 400 times
magnification
• Paper fibers coated
with copper sulfide
• Can see bridges
between fibers
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Deposition After 4-Day Test
Deleterious Deposit
• 8000 times
magnification
• Close up of copper
sulfide growing out
from deposit mass
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Composition of Deposit After
4-Day Test
Element Weight Percent
Elemental analysis of deposit only
Copper 81.6
Sulfur 17.1
Calcium 1.4
Elemental analysis of wide area
Oxygen 32.3
Carbon 16.1
Copper 40.1
Sulfur 6.9
Calcium 0.6
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Other Test Methods
for Sulfur and
Corrosive Sulfur
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Sulfur Tests, Oil
• ASTM D 130, Corrosive Sulfur in Petroleum Oils
• DIN 51 353, Corrosive Sulfur (Silver Strip)
• ASTM D 1275A, Corrosive Sulfur in Insulating Oil
• ISO 5662, Detection of Corrosive Sulfur
• ASTM D1275B, Corrosive Sulfur in Insulating Oil
• ASTM D 5623, Sulfur Speciation
• ASTM D 4294 (and similar tests), Total Sulfur in Oil
• ASTM D 3227, Mercaptans in Oil
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Sulfur Tests, Oil
• UOP 286/387 - Elemental Sulfur
• Doble Covered Conductor Deposition (CCD) Test,
Doble Test
• IEC 62535, Detection of Potentially Corrosive
Sulphur
• Doble Covered Conductor Deposition
(CCD+DT/Resistivity), Doble Test
• Dibenzyl disulfide (DBDS in Oil), Doble Test
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Sulfur Tests, Oil
• Tappi 406 - Reducible Sulfur in Paper and
Pressboard
• Tappi 444 - Silver Tarnishing by Paper and
Pressboard
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Overview on Mitigation
Techniques
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• Once deposition has occurred it CANNOT
BE REMOVED (at the present time)
• NOT ALL CORROSIVE SULFUR
CONTAMINATION IS THE SAME - each
case must be treated independently
• Prevent corrosion from occurring in the first
place
Mitigation Techniques
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Removal of Corrosive Sulfur:
DBDS
• Once Deposition Has Occurred, What can
be done?– Sparging/Vacuum
– Absorbents and adsorbents
– Drain and Flush
– Conversion Treatments
• Activated Copper
• Sodium Treatment (alkali processing)
– Not all corrosive sulfur compounds are removed
during these processes
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Sparging/Vacuum
0
20
40
60
80
100
120
140
160
Initial Cycle 1 Cycle 2 Cycle 3
Co
nc., m
g/k
g
Conc. (mg/kg)
Total % Removed
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Absorbents and Adsorbents
• Activated carbon
• Florisil (magnesium silicate)
• Fuller’s Earth (attapulgite clay)
• Molecular Sieve
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Procedure of Test
• Activated absorbent/adsorbent at 220 C for 4 hours
• Cooled is dessicator
• Prepared as slurry with oil at a ratio of 3 grams of
material to 100 mL of oil (=normal servicing ratio for
processing transformers, 0.25 pounds/gallon)
• Conducted 3 cycles to determine removal efficiency
• Oil sparged with nitrogen and sealed during
treatment cycle
• Treatment cycles were 15 minutes at 70 to 85 C and
a sample was taken for analysis after each cycle
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Activated Carbon
07.2 11.5
20.4
0
20
40
60
80
100
120
140
160
Initial Cycle 1 Cycle 2 Cycle 3
Co
nc., m
g/k
g
Conc. (mg/kg)
Total % Removed
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Fuller’s Earth/Clay
06.6
14.1 16.4
0
20
40
60
80
100
120
140
160
Initial Cycle 1 Cycle 2 Cycle 3
Co
nc
., m
g/k
g
Conc. (mg/kg)
Total % Removed
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Molecular Sieve
09.6
20.630.1
0
20
40
60
80
100
120
140
160
Initial Cycle 1 Cycle 2 Cycle 3
Co
nc.,
mg
/kg
Conc. (mg/kg)
Total % Removed
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Drain and Flush
• Removal of total volume of
transformer oil and dispose
• flush with 5-10% of volume and
drain and dispose of flush oil
• Let stand for 24 hours
• Refill with non-corrosive oil
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Drain and Flush
0
97.192.6
0
20
40
60
80
100
120
140
160
Initial Cycle 1 Retest
Co
nc., m
g/k
g
Conc. (mg/kg)
Total % Removed
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Dilution Effect on Corrosive Sulfur
Tests Bare Copper
Oil Combinations 150C
48 hrs
150C, 48 hrs
160C, 24 hrs
150C, 48 hrs
160C, 24 hrs
170C, 24 hrs
150C, 48 hrs
160C, 24 hrs
170C, 24 hrs
180C, 24 hrs
100% Corrosive Oil CORROSIVE
100% Non-corrosive oil Non-corrosive Non-corrosive Non-corrosive Non-corrosive
50% Corrosive Oil
50% Non-corrosive Oil
Non-corrosive Non-corrosive Non-corrosive CORROSIVE
25% Corrosive Oil
75% Non-corrosive Oil
Non-corrosive Non-corrosive Non-corrosive CORROSIVE
10% Corrosive Oil
90% Non-corrosive Oil
Non-corrosive Non-corrosive Non-corrosive Non-corrosive
Doble has started testing mixtures in CCD tests. ABB - limited
data, mixture not effective in preventing deposits in CCD test
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Conversion/Destruction
Technologies
• Re-refining using liquid-liquid extraction, NMP
solvent (N-methyl-2-pyrrolidone)
• Sulfuric Acid treatment (must be OSHA
labelled)
• Activated Copper Treatment
• Nickel Catalyst
• Sodium Treatment
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Removal of Corrosive Sulfur
Compounds
• Percolating oil over activated copper
(>200 C), works for all corrosive sulfur
compounds
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Nickel Catalyst
0
16.923.5
30.1
0
20
40
60
80
100
120
140
160
Initial Cycle 1 Cycle 2 Cycle 3
Co
nc.,
mg
/kg
Conc. (mg/kg)
Total % Removed
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Sodium Treatment
0
84.7
98.9 99.8
0
20
40
60
80
100
120
140
Initial 5 minutes 10 minutes 15 minutes
Co
nc., m
g/k
g
Conc. (mg/kg)
Total % Removed
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Removal Technique Selection
• Drain and flush is being performed on in-
service transformers at the present time.
Utilities such as Terna have performed a
number of these
• The sodium treatment was explored
further as it is presently an available
commercial process that could easily be
scaled up from laboratory experiments
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Techniques not Explored
• Sea Marconi depolorization process -
chemically destroys the DBDS molecule
such as the sodium treatment but it is
proprietary so Doble did not have access to
how it works
• ABB removal process suggests the use of
commonly used oil processing technology
but no specifics were provided so Doble
could not duplicate in the laboratory.
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Passivation
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Metal Passivation
• The passivation process
– Binds the passivator molecule to the metal
surface so that same site cannot be occupied
(attacked) by a corrosive sulfur molecule.
– Passivator molecules should also bind with
free copper and silver particles present in the
bulk oil itself
– Other passivator products will bind to iron and
aluminum alloys
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What is a Metal Passivator?
• React with reactive metal surfaces and
dissolved metals in the oil and paper
– reduce rate of reaction with organic
compounds - suppressing catalytic effect
– reduce rate of reaction of corrosive materials
– corrosive sulfur species can actually be metal
passivators (dependent upon concentration)
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History of Passivators
• Used mainly in lubricating oil industries for
decades to avoid attack of metal surfaces
• Used in transformers as a means to mitigate
static electrification (mainly Japanese), late
1970s/early 1980s
• Used in Australia since the 1980s to provide
additional oxidation stability in transformers
• basically used for 3 different roles in transformers
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Transformer Use, 1st Role
• Suppress streaming electrification in large shell- form
transformers (addition of charge suppressant such as
BTA and alkylbenzene, works by being adsorbed to
copper surface and absorbed in paper and exhibits
excess electrons)
– Leda et. al., “Suppression of Static Electrification of Insulating Oil
for Large Power Transformers”, IEEE conference, 1986.
– Yasuda et. al., “Suppression of Static Electrification of Insulating
Oil for Large Power Transformers”, IEEE Transactions, 1982.
– Professor Markus Zahn and Darrell Schlicker in a report to the MIT
president, 1995-1996, BTA used to lower the flow electrification in
transformer oil
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Transformer Use, 2nd Role
• Reduction of Oxidation of the Oil;
– Malchiore and Mills, Sun Oil Company, IEEE
publication 1967; suggest the use of metal
deactivator to reduce oxidation by reducing the
catalytic effect of copper
– Krishnamoorthy et. al., IEEE publication, 1992:
suggest there is a synergistic effect between
antioxidants and metal deactivators to reduce
oxidation of oil. Also suggest the process does
not work as well with just the metal deactivator
and works better at lower temperatures
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Transformer Use, Third Role
• Suppress Corrosive Sulfur Attacks by
use of Passivator in the 2003-2004 time
frame suggested by the following:
– CIBA now BASF
– Certain Transformer Manufacturers
– Certain Oil Refiners
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Passivator Types - Examples
• Nitrogen Based
– Benzimidazole
– Benzothiazole
– Benzotriazole (BTA)
– Irgamet 30 and 39
– Cobratec 122 and 911S
– Certain amines
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Passivator Types - Examples
• Sulfur Based or mixtures (used mainly in
the lubrication industry)
– Cuvan 484 and 826
– Rokon
– Vanlube 601 and 691
– 2,5-dimercapto-1,3,4-thiadiazole
– Amoco-150
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Passivation by Corrosive
Sulfur
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Passivation in Transformers
• First and foremost it is a chemical bond
• Chemi-sorption process
• Adsorption - adhesion of a chemical species
onto the surface of particles - does not enter the
bulk phase
Copper
Oxide
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Passivation in Transformers
• Bonding is 90 to 99% effective on clean
copper surfaces in oils where corrosive
sulfur does not already exist
• Passivator will not bond to sites already
taken up by corrosive sulfur species as the
bonding between sulfur and copper is very
strong
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In Transformers, How Does it Work
• Action is to preferentially bond with the copper
surface to “passivate” it or cause the copper from
reacting with the sulfur and organic compounds
• benzotriazole/ derivatives bonding to copper
through nitrogen lone pair orbitals
• hydrogen bonding to the copper oxide film
• Forms a Cu-BTA polymer through strong charge
transfer interactions between BTA molecules
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Attack by Corrosive Sulfur
SS
S
S
SS
S
SS
S
S
S
SS
S
S
Cu
Cu
Cu
Cu
Cu
Cu
Initiation of the formation of copper sulfide in the
presence of corrosive sulfur
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Passivation by BTA (derivatives)
• Highly ordered
• Newest studies indicate that the BTA
molecules are standing upright
• 3 forms of bonding
– hydrogen bonding between BTA and oxide layer
– BTA bonding to Cu through nitrogen lone pair orbitals
– BTA to BTA bonding through charge transfer
interactions
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Passivation of Cu Surface
Most research indicates that a single monolayer is
formed, some indicate 2 or 3 molecules thick at most
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Passivation Process
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Recommended Usage
• Current recommended usage:– BTA: 20-20 mg/kg (ppm)
– Irgamet 39: 100 mg/kg (ppm)
– Irgamet 30: 10-50 mg/kg (ppm)
• i.e.: 7.5 pounds (3.4 kg) of Irgamet 39 in
10,000 gallons (33,636 kg) of oil
• lab tests have shown that about 10-30%
of the passivator goes to the paper
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Mixing
• Mixing directly in transformer (not
recommended)
• Removing some transformer oil into drum,
mixing in the liquid passivator and then
pumping back into the unit
• Manufacturers are providing techniques to
best perform addition, can be done on-line
• Passivator is susceptible to removal by
vacuum processing, Fullers’ Earth, etc.
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Analysis and Worldwide
Experience on
Passivation
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Experience on Passivator Use
• Good technique to stop corrosive sulfur from
continuing where the bare copper/silver metal is
not already contaminated
• Doble recommends its use until a long term
solution is determined
• Contaminated surfaces with copper sulfide
cannot be passivated
• Opinions are mixed concerning long term
effectiveness of passivator
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Experience on Passivator Use
• Movement of Passivator to paper is good as it
protects the paper from the formation of copper
sulfide and binds to the copper and silver ions
already residing in the paper.
• TERNA has shown, in a earlier study in Brazil
2006/2007, that they still had failures in reactors that
were passivated compared to those with the oil
changed out.
• Timing of passivation is very important as some
metal surfaces may be too corroded for passivation
to be effective
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Experience on Passivator Use
• Test oil by ASTM D 1275B or CCD test to determine if
it is corrosive
• If corrosive, then test for DBDS– if no DBDS is present, add passivator (means some other
corrosive sulfur compound is present)
– if DBDS is present >100 ppm, add passivator
– if DBDS is present >35 ppm, add passivator and determine
best course for future
– If DBDS is <35 ppm then much of it probably had degraded
to form corrosive sulfur species which has or will attack the
copper/silver. Passivation may not supply much protection
in this case but may slow the process down
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Experience on Passivator Use
• Must monitor the level of passivator over the life of
transformer and keep it above 25 ppm (mg/kg)
• Continue to perform on annual or semi-annual basis
– ASTM D 1275B
– CCD Test
– DBDS Test
– Passivator concentration
• Most passivators will not cause changes in routine
analytical tests performed such as DGA or oil quality
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Experience on Passivator Use
• However, on occasion, some stray gassing and
some high oil power factor values have been
encountered
• Utility must be prepared to add passivator to the
equipment several times over the life of the
equipment
• Use electrical tests to determine how far corrosive
sulfur has progressed
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Experiments in the Doble Lab
• Doble has performed a lot of testing and
continues to do so as part of a
collaborative study on corrosive sulfur
• Passivator tested does work at lower
temperatures
– for example, oils in which passivator has been added
in both air and nitrogen environments have been aged
at 80 C since February 28, 2005 (>1000 days)
– Refer to the results on the next slide
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Passivator Testing at 110 C
GOS=Oil with good oxidation stability (PFVO)
POS=Oil with poor oxidation stability (PFVO)
Corroded = copper from failed transformer, pieces
used for testing were at 3A tarnish level
Cu Type Atmosphere Oil Type Time to Heavy Corrosion
Clean nitrogen GOS >185 days, still ongoing
Corroded nitrogen GOS >185 days, still ongoing
Clean air GOS 45 days
Corroded air GOS 32 days
Clean nitrogen POS >185 days, still ongoing
Corroded nitrogen POS >185 days, still ongoing
Clean air POS 43 days
Corroded air POS 30 days
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Passivator at 110 C
The air aged samples
are not only darker
but also cloudy even
though the water
content is very low
The N2 aged samples
are bright and clear
and none of the
copper has tarnished
to failure
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Interaction between Passivator and
oxygen at 110 C
Testing performed at
150 C. It seems that
there is a reaction with
the passivator and air
that causes a flocculent
to form. The same
flocculent seems to be
forming in the 110 C
aged samples in air.
(only when air and
passivator is present so
far)
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What is the Flocculent?
• Conducted SEM/EDX and FT-IR analysis of
the material filtered from the oil
• Seems to be an oxidized version of Irgamet
39 with some degree of copper and sulfur
present (copper/sulfur hydrocarbon
complex)
• Doble attempted various tests to determine
if the material was conductive or not.
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What is the Flocculent?
• Electrical tests on the material filtered out
of the oil did not indicate any adverse
electrical properties.
• The filtered oil however did increase in
dielectric strength, 10 to 29 kV (D 1816)
and the power factor of the oil was
reduced significantly at 25 C from 0.6% to
0.04%
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Passivator Reduction Over Time, 110 C
0
20
40
60
80
100
120
0 5 10 15 20 25 30
Elapsed Time, Days
mg
/kg
GOS, N2, Clean
GOS, N2, Corroded
GOS, Air, Clean
GOS, Air, Corroded
POS, N2, Clean
POS, N2, Corroded
POS, Air, Clean
POS, Air, Corroded
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Cu-BTA Polymer Collapse
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Observations during 80, 110 and
150 C Testing
• There was a reduction in passivator no matter the
temperature, atmosphere in the aging vessel or type
of copper (clean, slightly corroded-3A)
• Could not be determined how much of the passivator
was adhering to the copper at the higher
temperatures or degraded.
• Reduction of the passivator at 80 C was slower than
at 110 and 150 C
• Reduction of passivator at 110 and 150 C was
actually quite similar in time
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Observations during 80, 110 and
150 C Testing
• Passivator in oils sparged in air was reduced at a rate
quicker then those sparged in nitrogen (at the same
temperature)
• Less oxidatively (POS) stable oils exhibit a much
quicker reduction in passivator than more oxidatively
stable oils even though both oils contained no added
DBP or DBPC.
• Other experiments have confirmed that POS oils
show a much quicker time to corrosive sulfur attack.
However, it does not seem to be a function of the
actual oxidation inhibitor content.
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Prevention
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Prevention - Good Specifications
• Oil - the new tests that are being developed for
detecting corrosive sulfur will help with prevention
– Change in Standard and Specifications needed
– Testing to be more rigorous (Stop it before it starts)
– Multiple tests on oil/paper will be required to look at all
aspects
• Electrical tests to be developed for testing
transformers
• Electric apparatus should have good thermal
performance and electrical characteristics with
adequate margins
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Prevention - Good Specifications
• Oil - the new tests that are being developed for
detecting corrosive sulfur will help with prevention
– Change in Standard and Specifications needed
– Testing to be more rigorous (Stop it before it starts)
– Multiple tests on oil/paper will be required to look at all
aspects
• Electrical tests to be developed for testing
transformers
• Electric apparatus should have good thermal
performance and electrical characteristics with
adequate margins
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Experience on the
Application of Standard
Test Methods
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Standard Test Methods
• Must be followed exactly, any deviations will
give you abnormal results
• Not all laboratories have the experience to run
the test
• Thus laboratories that provide research into
corrosive sulfur issues along with routine testing
have a better understanding of what the
different analysis entails and can interpret the
results better
• For example:
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Comments on the D 1275B Test
• There are reportedly discrepancies
between laboratories when testing the
same samples
– One lab reports: Corrosive, 4A or 4B
– Another lab reports: Non-corrosive, 1B
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Requirements of 1275B Test
• The requirements of the test are very
specific:
– Promptly place the prepared copper strip in a
clean 250 mL bottle to which has been added
220 mL of the oil to be tested.
– Bubble nitrogen through the oil in the bottle by
means of a 1/16 inch inner diameter glass or
stainless steel tube connected to the reduction or
needle valve of the cylinder (rubber connections
must be sulfur-free) for 5 minutes at a rate of
0.5 L/minute.
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Requirements of 1275B Test
– Quickly screw in the PFTE plug equipped
with fluoro-elastomer o-ring.
– Place the bottle in the oven at 150 C. After
15 minutes of heating at 150C, partially
unscrew the PFTE plug to release the
pressure and then screw it back down.
Remove the bottle after heating for 48 h 20
minutes at 150 2 C. Allow to cool.
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The Differences
Sealed
BottleFlask
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A Closer Look
Bottle Used That is
Totally Sealed
150 2 C, 48 h 20 min
Flask that allows Air
Ingress
150 5 C, 48 h 20 min
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Even Closer Look, 4b Vs 1b
Bottle Used That is
Totally Sealed, 4b
150 2 C, 48 h 20 min
Flask that allows Air
Ingress, 1b
150 5 C, 48 h 20 min
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Current Specifications
• Passivators would be considered an additive
• ASTM D 3487 - does not allow the use of
additives other than DBP and DBPC
• IEC 60296 - only allows the use of additives only
if agreed upon
• Australian AS1767.1 - allows the use of additives
if agreed upon
• Doble TOPS - does not allow the use of additives
other than DBP and DBPC
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Certification of Test
Laboratories
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Certification of Test Labs
• There is no official certification of test labs that
perform corrosive sulfur testing
• Labs can be certified such as ISO 9000:2008 or
17025 but that is not always a good indication
that the analysis is being performed correctly.
• Choose a laboratory that is will recognized at
providing good quality results and has been
involved with the corrosive sulfur issues