ASTM D4418-00(2016)

Standard Practice for Receipt, Storage, and Handling of Fuels for Gas Turbines

SIGNIFICANCE AND USE
5.1 This practice provides the user of gas turbine fuel oils and the designer of gas turbine fuel systems with an appreciation of the effects of fuel contaminants and general methods of controlling such contaminants in gas turbine fuel systems.  
5.2 This practice is general in nature and should not be considered a substitute for any requirement imposed by warranty of the gas turbine manufacturer, or by federal, state, or local government regulations.  
5.3 Although it cannot replace a knowledge of local conditions or the use of good engineering and scientific judgment, this practice does provide guidance in development of individual fuel management systems for the gas turbine user.
SCOPE
1.1 This practice covers the receipt, storage, and handling of fuels for gas turbines, except for gas turbines used in aircraft. It is intended to provide guidance for the control of substances in a fuel that could cause deterioration of either the fuel system, or the gas turbine, or both.  
1.2 This practice provides no guidance for either the selection of a grade of fuel, a topic covered by Specification D2880, or for the safety aspects of the fuel and fuel systems. For example, this practice does not address the spacings of storage tanks, loading and unloading facilities, etc., and procedures for dealing with the flammability and toxic properties of the fuels.  
1.3 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.  
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

General Information

• Status: Historical
• Publication Date: 31-Mar-2016
• ICS: 75.160.20 - Liquid fuels
• Technical Committee: D02 - Petroleum Products, Liquid Fuels, and Lubricants
• Drafting Committee: D02.E0 - Burner, Diesel and Non-Aviation Gas Turbine Fuels

Relations

• Replaces: ASTM D4418-00(2011) - Standard Practice for Receipt, Storage, and Handling of Fuels for<br> Gas Turbines
• Effective Date: 01-Apr-2016
• Referred By: ASTM D6469-20 - Standard Guide for Microbial Contamination in Fuels and Fuel Systems
• Effective Date: 01-Apr-2016
• Referred By: ASTM D2880-23 - Standard Specification for Gas Turbine Fuel Oils
• Effective Date: 01-Apr-2016

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: D4418 − 00 (Reapproved 2016)
Standard Practice for
Receipt, Storage, and Handling of Fuels for Gas Turbines
This standard is issued under the fixed designation D4418; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope D6469 GuideforMicrobialContaminationinFuelsandFuel
Systems
1.1 Thispracticecoversthereceipt,storage,andhandlingof
fuels for gas turbines, except for gas turbines used in aircraft.
3. Terminology
It is intended to provide guidance for the control of substances
3.1 fuel entering the combustor(s)—this term is used to
inafuelthatcouldcausedeteriorationofeitherthefuelsystem,
designate the fuel that is actually burned in the gas turbine.
or the gas turbine, or both.
Fuel may actually be sampled at a point upstream from the
1.2 This practice provides no guidance for either the selec-
point of entry into the combustor(s), provided the sample is
tion of a grade of fuel, a topic covered by Specification D2880,
representative of the fuel actually entering the combustor(s).
or for the safety aspects of the fuel and fuel systems. For
3.2 fuel contaminants—in principle, are any fuel component
example, this practice does not address the spacings of storage
other than hydrocarbon oils. In the present context the con-
tanks, loading and unloading facilities, etc., and procedures for
taminants are foreign materials that make the fuel less suitable
dealing with the flammability and toxic properties of the fuels.
or even unsuitable for the intended use. The contaminants of
1.3 The values stated in SI units are to be regarded as the
primary interest are foreign materials introduced subsequent to
standard. The values given in parentheses are for information
the manufacture of specification quality fuel. Hence they are
only.
materials introduced in the distribution system (that is storage
1.4 This standard does not purport to address all of the tanks, pipelines, tank, trucks, barges, etc.), or in the user’s
storage and handling systems, or generated within these
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro- systems (rust generated in steel pipes and tanks by moist fuel,
etc.). Contaminants may be soluble or insoluble in the fuel.
priate safety and health practices and determine the applica-
bility of regulatory limitations prior to use.
3.3 dissolved and free water—water may be present in the
fuel as dissolved water or as “free” (undissolved) water, or
2. Referenced Documents
both. The free water may be fresh or saline. Fresh water may
2.1 ASTM Standards:
enter the fuel from steam coils in storage tanks, from conden-
D1500 Test Method forASTM Color of Petroleum Products
sation out of moisture-laden air, or from leaking cooling coils.
(ASTM Color Scale)
Saline water can enter the fuel during transportation in barges
D1796 Test Method for Water and Sediment in Fuel Oils by
or tankers.
the Centrifuge Method (Laboratory Procedure)
3.4 particulate solids—may enter a fuel from the air (sus-
D2274 Test Method for Oxidation Stability of Distillate Fuel
pended dirt and aerosols) or from the distribution and storage
Oil (Accelerated Method)
systems (rust, corrosion products, gasket debris, and so forth).
D2276 Test Method for Particulate Contaminant in Aviation
3.5 metallic compounds—metals may be present as metallic
Fuel by Line Sampling
compounds in the fuel as a natural result of the composition of
D2880 Specification for Gas Turbine Fuel Oils
the crude oil and of the refining process. However, unless
D4057 Practice for Manual Sampling of Petroleum and
special precautions are taken, additional metallic compounds
Petroleum Products
can be acquired during distribution and storage.Acommercial
1 product pipeline may contain residues of lead-containing
This practice is under the jurisdiction of ASTM Committee D02 on Petroleum
Products, Liquid Fuels, and Lubricants and is the direct responsibility of Subcom- gasoline that would then be dissolved by the gas turbine fuel.
mittee D02.E0 on Burner, Diesel, Non-Aviation Gas Turbine, and Marine Fuels.
Tank trucks, railroad tankcars, barges, and tankers may be
Current edition approved April 1, 2016. Published May 2016. Originally
inadequately cleaned and contain residues of past cargos.
approved in 1984. Last previous edition approved in 2011 as D4418 – 00(2011).
Acidic components in saline water salts in the fuel may react
DOI: 10.1520/D4418-00R16.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
with distribution and storage equipment.
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
3.6 microbial slimes—may result when conditions are con-
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. ducive to the growth of microorganisms that are always
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D4418 − 00 (2016)
present.The presence of free water is essential to the growth of devices is a function of particulate levels and size distributions
many of these microorganisms that grow in tank water bottoms in the fuel. High levels of particulates can lead to short cycle
and feed on nutrients in the water or on the hydrocarbons. times in the operation of filters, filter/separators, centrifuges,
andelectrostaticpurifiers.Sincesuchseparationdevicesdonot
4. Summary of Practice
remove all the particulates, certain quantities will be present in
4.1 The body of this practice defines the contaminants
the down-stream fuel.
frequently found in turbine fuel oils and discusses the sources
6.1.3 Trace metals refer both to those metals present as
and significance of such contaminants.
metallic compounds in solution and to metals present in
particulates like rust.They are dissolved or suspended either in
4.2 Annex A1 is a guide for the receipt, storage, and
the fuel hydrocarbons or in free water present in the fuel. The
handling of distillate gas turbine fuels, Grades 1-GTand 2-GT,
significance of several individual trace metals with respect to
in accordance with Specification D2880.
hot corrosion is discussed in 6.1.4 through 6.1.5. Although
4.3 Annex A2 is a guide for the receipt, storage, and
lower levels of trace metals in a fuel will promote longer
handling of gas turbine fuels, Grades 3-GT and 4-GT, that
turbineservicefromacorrosionstandpoint,thespecificationof
contain residual components.
excessively low levels may limit the availability of the fuel or
4.4 Annex A3 is a guide for the selection and storage of materially increase its cost. Table 1 suggests levels of trace
fuels intended for long-term storage, when such fuels are metals that would probably yield satisfactory service.
distillate fuels. 6.1.4 Ash is the noncombustible material in an oil. Ash
forming materials may be present in fuel oil in two forms: (1)
4.5 Annex A4 is a guide for gas turbine users who are
solid particles, and (2) oil- or water-soluble metallic com-
considering the use of fuels from alternative non-petroleum
pounds. The solid particles are for the most part the same
sources.
material that is designated as sediment in the water and
5. Significance and Use
sediment test. Depending on their size, these particles can
contributetowearinthefuelsystemandtopluggingofthefuel
5.1 This practice provides the user of gas turbine fuel oils
filterandthefuelnozzle.Thesolublemetalliccompoundshave
and the designer of gas turbine fuel systems with an apprecia-
little or no effect on wear or plugging, but they can contain
tion of the effects of fuel contaminants and general methods of
elements that produce turbine corrosion and deposits as de-
controlling such contaminants in gas turbine fuel systems.
scribed in 6.1.5.
5.2 This practice is general in nature and should not be
6.1.5 Vanadium and Lead—Fuel contaminants might in-
considered a substitute for any requirement imposed by war-
clude soluble compounds such as vanadium porphyrins, me-
ranty of the gas turbine manufacturer, or by federal, state, or
tallic soaps, or tetraethyl lead that cannot be removed from the
local government regulations.
fuel at the gas-turbine site.
5.3 Although it cannot replace a knowledge of local condi-
6.1.5.1 Vanadium can form low melting compounds such as
tions or the use of good engineering and scientific judgment,
vanadium pentoxide which melts at 691 °C (1275 °F), and
this practice does provide guidance in development of indi- causes severe corrosive attack on all of the high-temperature
vidual fuel management systems for the gas turbine user.
alloys used for gas-turbine blades. If there is sufficient magne-
sium in the fuel, it will combine with the vanadium to form
6. Significance of Contaminants
compounds with higher melting points and thus reduce the
6.1 Contamination levels in the fuel entering the combus-
corrosion rate to an acceptable level. The resulting ash will
tor(s) must be low for improved turbine life. Low contamina-
form deposits in the turbine and will require appropriate
tion levels in the fuel in the turbine’s in-plant fuel system are
cleaning procedures.
required to minimize corrosion and operating problems. Pro-
6.1.5.2 When vanadium is present in more than trace
viding fuel of adequate cleanliness to the gas turbine combus-
amounts either in excess of 0.5 ppm or a level recommended
tor(s) may require special actions by the user. These actions
by the turbine manufacturer, it is necessary to maintain a
mightincludespecialtransportationarrangementswiththefuel
weight ratio of magnesium to vanadium in the fuel of not less
supplier, particular care in on-site fuel storage and quality
than 3.0 in order to control corrosion.
control procedures, and establishment of on-site cleanup pro-
6.1.5.3 An upper limit of 3.5 is suggested since larger ratios
cedures.Eachofthefourclassesofcontaminantsdefinedin3.2
will lead to unnecessarily high rates of ash deposition. In most
has its own significance to system operation.
6.1.1 Water will cause corrosion of tanks, piping, flow
TABLE 1 Trace Metal Limits of Fuel Entering Turbine
dividers, and pumps. Corrosion or corrosion products in
Combustor(s)
close-tolerance devices, such as flow dividers, may cause
Trace Metal Limits by Weight, max, ppm
plugging and may stop flow to the turbines. Free water is
Designation
Sodium plus
Vanadium Calcium Lead
potentially corrosive in sulfur-containing fuels, it may be
Potassium
particularly corrosive. Free water may contain dissolved salts
No. 0-GT 0.5 0.5 0.5 0.5
that may be corrosive, and may encourage microbiological No. 1-GT 0.5 0.5 0.5 0.5
No. 2-GT 0.5 0.5 0.5 0.5
growth.
No. 3-GT 0.5 0.5 0.5 0.5
6.1.2 Particulate solids may shorten the life of fuel system
No. 4-GT (Consult turbine manufacturers)
components. Life of fuel pumps and of various close-tolerance
D4418 − 00 (2016)
cases, the required magnesium-to-vanadium ratio will be tions where the fuel is moved by sea transport, the sodium-
obtained by additions of magnesium-containing compounds to plus-potassium level should be checked prior to use to ensure
thefueloil.Thespecialrequirementscoveringtheadditionand that the oil has not become contaminated with sea salt. For gas
type of magnesium-containing additive, or equivalent, shall be turbines operating at turbine inlet gas temperatures below
specified by mutual agreement between the various interested
650 °C(1200 °F),thecorrosionduetosodiumcompoundsisof
parties. The additive will vary depending on the application, minor importance and can be further reduced by silicon-base
but it is always essential that there is a fine and uniform
additives. A high sodium content is even beneficial in these
dispersionoftheadditiveinthefuelatthepointofcombustion. turbines because it increases the water-solubility of the depos-
6.1.5.4 For gas turbines operating at turbine-inlet gas tem-
its and thereby increases the ease with which gas turbines can
peratures below 650 °C (1200 °F), the corrosion of the high- be water-washed to obtain recovery of the operating perfor-
temperature alloys is of minor importance, and the use of a
mance.
silicon-base additive will further reduce the corrosion rate by
6.1.6.3 Calcium—Calcium is not harmful from a corrosion
absorption and dilution of the vanadium compounds.
standpoint: in fact, it serves to inhibit the corrosive action of
6.1.5.5 Leadcancausecorrosion,andinadditionitcanspoil
vanadium. However, calcium can lead to hard-bonded deposits
the beneficial inhibiting effect of magnesium additives on
thatarenotself-spallingwhenthegasturbineisshutdown,and
vanadium corrosion. Since lead is only rarely found in signifi-
are not readily removed by water washing of the turbine. The
cant quantities in crude oils, its appearance in the fuel oil is
fuel-washing systems, used at some gas turbine installations to
primarily the result of contamination during processing or
reduce the sodium and potassium level, will also significantly
transportation.
lower the calcium content of fuel oil.
6.1.6 Sodium, Potassium, and Calcium—Fuel contaminants
6.1.7 Microbial Slimes—Microbial slimes caused by micro-
might also include fuel-insoluble materials such as water, salt,
organisms can plug filters and other close-tolerance openings.
or dirt, potential sources of sodium, potassium, and calcium.
Someorganismscancausecorrosionaswellasproduceslimes.
Thesearenormallyremovedatthegas-turbinesite,unlesssuch
Under anaerobic conditions, hydrogen sulfide, which may
contaminants are extremely finely divided.
cause corrosion, can be generated by biological action. Bio-
6.1.6.1 Sodium and Potassium can combine with vanadium
cides are available for controlling the growth of
to form eutectics that melt at temperatures as low as 566 °C
microorganisms, but their effect on trace metal levels and other
(1050 °F) and can combine with sulfur in the fuel to yield
fuel properties should be considered. Since water is required
sulfates with melting points in the operating range of the gas
for the growth of the microorganisms, one way of controlling
turbine. These compounds produce severe corrosion, and for
their growth is to eliminate the presence of water through
turbines operating at gas inlet temperatures above 650 °C
tank-stripping operations or other separation techniques. Refer
(1200 °F), additives are not yet in general use that control such
to Guide D6469 for a more complete discussion.
corrosion.
6.1.6.2 Accordingly, the sodium-
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: D4418 − 00 (Reapproved 2011) D4418 − 00 (Reapproved 2016)
Standard Practice for
Receipt, Storage, and Handling of Fuels for
Gas Turbines
This standard is issued under the fixed designation D4418; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope
1.1 This practice covers the receipt, storage, and handling of fuels for gas turbines, except for gas turbines used in aircraft. It
is intended to provide guidance for the control of substances in a fuel that could cause deterioration of either the fuel system, or
the gas turbine, or both.
1.2 This practice provides no guidance for either the selection of a grade of fuel, a topic covered by Specification D2880, or
for the safety aspects of the fuel and fuel systems. For example, this practice does not address the spacings of storage tanks, loading
and unloading facilities, etc., and procedures for dealing with the flammability and toxic properties of the fuels.
1.3 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory
limitations prior to use.
2. Referenced Documents
2.1 ASTM Standards:
D1500 Test Method for ASTM Color of Petroleum Products (ASTM Color Scale)
D1796 Test Method for Water and Sediment in Fuel Oils by the Centrifuge Method (Laboratory Procedure)
D2274 Test Method for Oxidation Stability of Distillate Fuel Oil (Accelerated Method)
D2276 Test Method for Particulate Contaminant in Aviation Fuel by Line Sampling
D2880 Specification for Gas Turbine Fuel Oils
D4057 Practice for Manual Sampling of Petroleum and Petroleum Products
D6469 Guide for Microbial Contamination in Fuels and Fuel Systems
3. Terminology
3.1 fuel entering the combustor(s)—this term is used to designate the fuel that is actually burned in the gas turbine. Fuel may
actually be sampled at a point upstream from the point of entry into the combustor(s), provided the sample is representative of the
fuel actually entering the combustor(s).
3.2 fuel contaminants—in principle, are any fuel component other than hydrocarbon oils. In the present context the
contaminants are foreign materials that make the fuel less suitable or even unsuitable for the intended use. The contaminants of
primary interest are foreign materials introduced subsequent to the manufacture of specification quality fuel. Hence they are
materials introduced in the distribution system (that is storage tanks, pipelines, tank, trucks, barges, etc.), or in the user’s storage
and handling systems, or generated within these systems (rust generated in steel pipes and tanks by moist fuel, etc.). Contaminants
may be soluble or insoluble in the fuel.
3.3 dissolved and free water—water may be present in the fuel as dissolved water or as “free” (undissolved) water, or both. The
free water may be fresh or saline. Fresh water may enter the fuel from steam coils in storage tanks, from condensation out of
moisture-laden air, or from leaking cooling coils. Saline water can enter the fuel during transportation in barges or tankers.
This practice is under the jurisdiction of ASTM Committee D02 on Petroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility of Subcommittee
D02.E0 on Burner, Diesel, Non-Aviation Gas Turbine, and Marine Fuels.
Current edition approved Oct. 1, 2011April 1, 2016. Published October 2011May 2016. Originally approved in 1984. Last previous edition approved in 20062011 as
D4418 – 00(2006).(2011). DOI: 10.1520/D4418-00R11.10.1520/D4418-00R16.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D4418 − 00 (2016)
3.4 particulate solids—may enter a fuel from the air (suspended dirt and aerosols) or from the distribution and storage systems
(rust, corrosion products, gasket debris, and so forth).
3.5 metallic compounds—metals may be present as metallic compounds in the fuel as a natural result of the composition of the
crude oil and of the refining process. However, unless special precautions are taken, additional metallic compounds can be acquired
during distribution and storage. A commercial product pipeline may contain residues of lead-containing gasoline that would then
be dissolved by the gas turbine fuel. Tank trucks, railroad tankcars, barges, and tankers may be inadequately cleaned and contain
residues of past cargos. Acidic components in saline water salts in the fuel may react with distribution and storage equipment.
3.6 microbial slimes—may result when conditions are conducive to the growth of microorganisms that are always present. The
presence of free water is essential to the growth of many of these microorganisms that grow in tank water bottoms and feed on
nutrients in the water or on the hydrocarbons.
4. Summary of Practice
4.1 The body of this practice defines the contaminants frequently found in turbine fuel oils and discusses the sources and
significance of such contaminants.
4.2 Annex A1 is a guide for the receipt, storage, and handling of distillate gas turbine fuels, Grades 1-GT and 2-GT, in
accordance with Specification D2880.
4.3 Annex A2 is a guide for the receipt, storage, and handling of gas turbine fuels, Grades 3-GT and 4-GT, that contain residual
components.
4.4 Annex A3 is a guide for the selection and storage of fuels intended for long-term storage, when such fuels are distillate fuels.
4.5 Annex A4 is a guide for gas turbine users who are considering the use of fuels from alternative non-petroleum sources.
5. Significance and Use
5.1 This practice provides the user of gas turbine fuel oils and the designer of gas turbine fuel systems with an appreciation of
the effects of fuel contaminants and general methods of controlling such contaminants in gas turbine fuel systems.
5.2 This practice is general in nature and should not be considered a substitute for any requirement imposed by warranty of the
gas turbine manufacturer, or by federal, state, or local government regulations.
5.3 Although it cannot replace a knowledge of local conditions or the use of good engineering and scientific judgment, this
practice does provide guidance in development of individual fuel management systems for the gas turbine user.
6. Significance of Contaminants
6.1 Contamination levels in the fuel entering the combustor(s) must be low for improved turbine life. Low contamination levels
in the fuel in the turbine’s in-plant fuel system are required to minimize corrosion and operating problems. Providing fuel of
adequate cleanliness to the gas turbine combustor(s) may require special actions by the user. These actions might include special
transportation arrangements with the fuel supplier, particular care in on-site fuel storage and quality control procedures, and
establishment of on-site cleanup procedures. Each of the four classes of contaminants defined in 3.2 has its own significance to
system operation.
6.1.1 Waterwill Water will cause corrosion of tanks, piping, flow dividers, and pumps. Corrosion or corrosion products in
close-tolerance devices, such as flow dividers, may cause plugging and may stop flow to the turbines. Free water is potentially
corrosive in sulfur-containing fuels, it may be particularly corrosive. Free water may contain dissolved salts that may be corrosive,
and may encourage microbiological growth.
6.1.2 Particulate solidsmay solids may shorten the life of fuel system components. Life of fuel pumps and of various
close-tolerance devices is a function of particulate levels and size distributions in the fuel. High levels of particulates can lead to
short cycle times in the operation of filters, filter/separators, centrifuges, and electrostatic purifiers. Since such separation devices
do not remove all the particulates, certain quantities will be present in the down-stream fuel.
6.1.3 Trace metalsrefer metals refer both to those metals present as metallic compounds in solution and to metals present in
particulates like rust. They are dissolved or suspended either in the fuel hydrocarbons or in free water present in the fuel. The
significance of several individual trace metals with respect to hot corrosion is discussed in 6.1.4 through 6.1.5. Although lower
levels of trace metals in a fuel will promote longer turbine service from a corrosion standpoint, the specification of excessively
low levels may limit the availability of the fuel or materially increase its cost. Table 1 suggests levels of trace metals that would
probably yield satisfactory service.
6.1.4 Ashis Ash is the noncombustible material in an oil. Ashforming Ash forming materials may be present in fuel oil in two
forms: (1) solid particles, and (2) oil- or water-soluble metallic compounds. The solid particles are for the most part the same
material that is designated as sediment in the water and sediment test. Depending on their size, these particles can contribute to
wear in the fuel system and to plugging of the fuel filter and the fuel nozzle. The soluble metallic compounds have little or no effect
on wear or plugging, but they can contain elements that produce turbine corrosion and deposits as described in 6.1.5.
D4418 − 00 (2016)
TABLE 1 Trace Metal Limits of Fuel Entering Turbine
Combustor(s)
Trace Metal Limits by Weight, max, ppm
Designation
Sodium plus
Vanadium Calcium Lead
Potassium
No. 0-GT 0.5 0.5 0.5 0.5
No. 1-GT 0.5 0.5 0.5 0.5
No. 2-GT 0.5 0.5 0.5 0.5
No. 3-GT 0.5 0.5 0.5 0.5
No. 4-GT (Consult turbine manufacturers)
6.1.5 Vanadium and Lead—Fuel contaminants might include soluble compounds such as vanadium porphyrins, metallic soaps,
or tetraethyl lead that cannot be removed from the fuel at the gas-turbine site.
6.1.5.1 Vanadiumcan Vanadium can form low melting compounds such as vanadium pentoxide which melts at 691°C
(1275°F),691 °C (1275 °F), and causes severe corrosive attack on all of the high-temperature alloys used for gas-turbine blades.
If there is sufficient magnesium in the fuel, it will combine with the vanadium to form compounds with higher melting points and
thus reduce the corrosion rate to an acceptable level. The resulting ash will form deposits in the turbine and will require appropriate
cleaning procedures.
6.1.5.2 When vanadium is present in more than trace amounts either in excess of 0.5 ppm 0.5 ppm or a level recommended by
the turbine manufacturer, it is necessary to maintain a weight ratio of magnesium to vanadium in the fuel of not less than 3.0 in
order to control corrosion.
6.1.5.3 An upper limit of 3.5 is suggested since larger ratios will lead to unnecessarily high rates of ash deposition. In most
cases, the required magnesium-to-vanadium ratio will be obtained by additions of magnesium-containing compounds to the fuel
oil. The special requirements covering the addition and type of magnesium-containing additive, or equivalent, shall be specified
by mutual agreement between the various interested parties. The additive will vary depending on the application, but it is always
essential that there is a fine and uniform dispersion of the additive in the fuel at the point of combustion.
6.1.5.4 For gas turbines operating at turbine-inlet gas temperatures below 650°C (1200°F),650 °C (1200 °F), the corrosion of
the high-temperature alloys is of minor importance, and the use of a silicon-base additive will further reduce the corrosion rate by
absorption and dilution of the vanadium compounds.
6.1.5.5 Leadcan Lead can cause corrosion, and in addition it can spoil the beneficial inhibiting effect of magnesium additives
on vanadium corrosion. Since lead is only rarely found in significant quantities in crude oils, its appearance in the fuel oil is
primarily the result of contamination during processing or transportation.
6.1.6 Sodium, Potassium, and Calcium—Fuel contaminants might also include fuel-insoluble materials such as water, salt, or
dirt, potential sources of sodium, potassium, and calcium. These are normally removed at the gas-turbine site, unless such
contaminants are extremely finely divided.
6.1.6.1 Sodium and Potassium can combine with vanadium to form eutectics that melt at temperatures as low as 566°C
(1050°F)566 °C (1050 °F) and can combine with sulfur in the fuel to yield sulfates with melting points in the operating range of
the gas turbine. These compounds produce severe corrosion, and for turbines operating at gas inlet temperatures above 650°C
(1200°F),650 °C (1200 °F), additives are not yet in general use that control such corrosion.
6.1.6.2 Accordingly, the sodium-plus-potassium level must be limited, but each element is measured separately. Some gas
turbine installations incorporate systems for washing oil with water to reduce the sodium-plus-potassium level. In installations
where the fuel is moved by sea transport, the sodium-plus-potassium level should be checked prior to use to ensure that the oil
has not become contaminated with sea salt. For gas turbines operating at turbine inlet gas temperatures below 650°C
(1200°F),650 °C (1200 °F), the corrosion due to sodium compounds is of minor importance and can be further reduced by
silicon-base additives. A high sodium content is even beneficial in these turbines because it increases the water-solubility of the
deposits and thereby increases the ease with which gas turbines can be water-washed to obtain recovery of the operating
performance.
6.1.6.3 Calcium—Calcium is not harmful from a corrosion standpoint: in fact, it serves to inhibit the corrosive action of
vanadium. However, calcium can lead to hard-bonded deposits that are not self-spalling when the gas turbine is shut down, and
are not readily removed by water washing of the turbine. The fuel-washing systems, used at some gas turbine
...