ASTM D2186-84(1999)e1
(Test Method)Standard Test Methods for Deposit-Forming Impurities in Steam
Standard Test Methods for Deposit-Forming Impurities in Steam
SCOPE
1.1 These test methods cover the determination of the amount of deposit-forming impurities in steam. Determinations are made on condensed steam samples in all test methods. Test Methods A, B, and C give a measure of the amount of total deposit-forming material present; Test Method D deals with special constituents that may be present. Special precautions and equipment, calculation procedures, and ranges of applicability are described. The following test methods are included: Sections Test Method A (Gravimetric or Evaporative) 6 to 12 Test Method B (Electrical Conductivity) 13 to 19 Test Method C (Sodium Tracer) 20 to 26 Test Method D (Silica and Metals) 27 to 30
1.2 Test Method A is applicable for determining total dissolved and suspended solids in concentrations normally not less than 0.1 mg/L (ppm). It is applicable only to long-time steady-state conditions and is not applicable for transients.
1.3 Test Method B will measure minimum impurity concentrations varying from 3 mg/L (ppm) down to at least 0.005 mg/L (ppm), depending on the means for removing dissolved gases from the steam condensate. The means for removing dissolved gases also affects the storage capacity of steam condensate in the system and, thus, affects the response of the system to transients.
1.4 Because of the high sensitivity of methods for measuring sodium in steam condensate, Test Method C provides the most sensitive measure of impurity content for samples in which sodium is an appreciable percentage of the impurities present. Concentrations as low as 0.6 [mu]g/L (ppb) can be detected by flame photometry and as low as 0.5 [mu]g/L (ppb) by sodium ion electrode. The apparatus can be designed with low volume, and, therefore, Test Method C is the most responsive to transient conditions.
1.5 Test Method D covers the determination of silica and metals in steam, which are not included in Test Methods B and C and are not individually determined using Test Method A.
1.6 This standard does not purport to address 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.
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An American National Standard
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Designation:D 2186–84 (Reapproved 1999)
Standard Test Methods for
Deposit-Forming Impurities in Steam
This standard is issued under the fixed designation D 2186; 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 (e) indicates an editorial change since the last revision or reapproval.
e NOTE—Footnotes were editorially removed in June 1999.
1. Scope 1.5 Test Method D covers the determination of silica and
metals in steam, which are not included in Test Methods B and
1.1 These test methods cover the determination of the
C and are not individually determined using Test Method A.
amountofdeposit-formingimpuritiesinsteam.Determinations
1.6 This standard does not purport to address the safety
are made on condensed steam samples in all test methods. Test
concerns, if any, associated with its use. It is the responsibility
Methods A, B, and C give a measure of the amount of total
of the user of this standard to establish appropriate safety and
deposit-forming material present; Test Method D deals with
health practices and determine the applicability of regulatory
special constituents that may be present. Special precautions
limitations prior to use.
and equipment, calculation procedures, and ranges of applica-
bility are described. The following test methods are included:
2. Referenced Documents
Sections
2.1 ASTM Standards:
Test Method A (Gravimetric or Evaporative) 6 to 12
Test Method B (Electrical Conductivity) 13 to 19
D 512 Test Methods for Chloride Ion in Water
Test Method C (Sodium Tracer) 20 to 26 2
D 515 Test Methods for Phosphorus in Water
Test Method D (Silica and Metals) 27 to 30
D 516 Test Method for Sulfate Ion in Water
1.2 Test Method A is applicable for determining total
D 857 Test Methods for Aluminum in Water
dissolved and suspended solids in concentrations normally not
D 859 Test Method for Silica in Water
less than 0.1 mg/L (ppm). It is applicable only to long-time
D 992 Test Method for Nitrate Ion in Water
steady-state conditions and is not applicable for transients.
D 1066 Practice for Sampling Steam
1.3 Test Method B will measure minimum impurity concen-
D 1068 Test Methods for Iron in Water
trations varying from 3 mg/L (ppm) down to at least 0.005
D 1125 Test Methods for Electrical Conductivity and Re-
mg/L (ppm), depending on the means for removing dissolved
sistivity of Water
gases from the steam condensate. The means for removing
D 1129 Terminology Relating to Water
dissolved gases also affects the storage capacity of steam
D 1339 Test Methods for Sulfite Ion in Water
condensate in the system and, thus, affects the response of the
D 1428 Test Methods for Sodium and Potassium in Water
system to transients.
and Water-Formed Deposits by Flame Photometry
1.4 Because of the high sensitivity of methods for measur- 2
D 1687 Test Methods for Chromium in Water
ing sodium in steam condensate, Test Method C provides the
D 1688 Test Methods for Copper in Water
most sensitive measure of impurity content for samples in 2
D 1886 Test Methods for Nickel in Water
which sodium is an appreciable percentage of the impurities
D 1888 Test Methods for Particulate and Dissolved Matter,
present. Concentrations as low as 0.6 µg/L (ppb) can be 2
Solids, or Residue in Water
detected by flame photometry and as low as 0.5 µg/L (ppb) by
D 2791 Test Method for Continuous Determination of So-
sodium ion electrode. The apparatus can be designed with low
dium in Water
volume, and, therefore, Test Method C is the most responsive
D 3082 Test Method for Boron in Water
to transient conditions.
D 3370 Practices for Sampling Water from Closed Con-
duits
These test methods are under the jurisdiction of ASTM Committee D-19 on
Water and are the direct responsibility of Subcommittee D19.03 on Sampling of
Water and Water-Formed Deposits, and Surveillance of Water. Annual Book of ASTM Standards, Vol 11.01.
Current edition approved Oct. 26, 1984. Published January 1985. Originally Discontinued—See 1983 Annual Book of ASTM Standards, Vol 11.01.
published as D 2186 – 66. Last previous edition D 2186 – 79. Discontinued—See 1989 Annual Book of ASTM Standards, Vol 11.02.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
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D 2186–84 (1999)
3. Terminology TEST METHOD A—GRAVIMETRIC OR
EVAPORATIVE
3.1 Definitions—For definitions of terms used in these test
methods, refer to Terminology D 1129.
6. Scope
6.1 The gravimetric test method is recommended for appli-
4. Significance and Use
cations for which an average value of impurities over a period
4.1 Limiting the concentration of deposit-forming impuri-
of several days or weeks is desired. It is particularly useful for
ties in steam is of significance to protect both steam generators
samples in which a large percentage of the impurities are
and steam turbines from damage or degradation of perfor-
insoluble, do not contain sodium, or do not contribute appre-
mance, or both.
ciably to the electrical conductivity of the samples, because the
4.1.1 Steam entering superheaters and reheaters of steam
other methods are not satisfactory for these conditions. Ex-
generators always contains some impurities. If the concentra-
amples of such impurities are metals and metal oxides. It is not
tion of impurities is sufficiently low, the impurities are dis-
applicable when short-time trends are of interest or when
solved in superheated steam and are carried out of the steam
immediate results are desired. The test method is useful for the
generator. However, if the steam contains a sufficient amount
determination of concentrations of impurities of 0.25 mg/L
of any substance to exceed its solubility limit in steam, the
(ppm) or greater when a previously collected sample is used
substance is likely to form a deposit on the heat-transfer
and for impurities concentrations of 0.1 mg/L (ppm) or greater
surface. Because heat transfer in superheaters and reheaters in
when continuous sampling is used. Concentrations less than
fossil-fueled steam generators is controlled principally by the
0.1 mg/L (ppm) can be determined if a continuously flowing
low heat-transfer coefficient on the gas side, the formation of
sample is evaporated for an extremely long period of time.
steam-side deposits will have little effect on the overall
heat-transfer rate. However, steam-side deposits will increase
7. Summary of Test Method
the operating temperature of the heat-transfer surface. Such
7.1 This test method involves the evaporation of a quantity
temperature increases can lead to swelling and ultimately to
of steam condensate at a temperature below the boiling point
rupture of the tubing. Also, aggressive materials can concen-
and the weighing of the residue to determine the amount of
trate under solid deposits of porous materials, such as magne-
impurities in the sample. The evaporation process may be
tite (Fe O ), and can cause serious corrosion of the tubing.
3 4
carried out on a steam condensate sample previously collected,
4.1.2 As steam flows through turbines, its temperature and
or the sample may be taken continuously as the evaporation
pressure decrease rapidly. Because the ability of steam to
process is continued.
dissolve impurities decreases with decreasing temperature and
pressure, impurities in steam may exceed their solubility limit
8. Interferences
and form deposits on the turbine. Such deposits reduce steam
8.1 Possible interferences for this test method are described
flow area, particularly in the high-pressure portion of the
in Test Methods D 1888.
turbine where flow passages are small, and the roughness of
deposits and their effect on blade contours result in losses of
9. Apparatus
turbine efficiency. All of these effects lead to reduction of the
9.1 Apparatus shall be provided in accordance with the
plant maximum capacity, which appreciably reduces the finan-
applicable test method of Test Methods D 1888.
cial return on the capital investment in the power plant.
Furthermore, aggressive materials, such as sodium hydroxide
10. Procedure
(NaOH) and sodium chloride (NaCl), may condense and
deposit on turbine surfaces. Such deposits occasionally con-
10.1 Proceed in accordance withTest MethodAor B ofTest
tribute to failure due to cracking of highly stressed turbine Methods D 1888, as applicable.
blades and rotors. Repairs and outages are extremely costly.
11. Calculation
4.1.3 By monitoring the concentration of deposit-forming
impurities in steam, a power plant operator can take steps
11.1 Calculate the concentration of impurities in the sample
necessarytolimittheimpuritiestotolerableconcentrationsand
in accordance with Test Methods D 1888.
thus minimize or eliminate losses due to excessive deposits.
11.2 Dissolved matter and total matter are usually of great-
est interest in the determination of impurities in steam. The
5. Sampling
determination of fixed solids after ignition at some temperature
greater than 103°C (217°F) may be of more significance than
5.1 Collect the samples in accordance with Practice D 1066
the measurement taken at 103°C, depending on the type of
and Practices D 3370 as applicable.
solids in the sample and the maximum temperature to which
5.2 The concentrations of sodium and silica in steam
the steam is to be heated in the application.
samples are usually well below 1 mg/L (ppm). Because these
materials exist in relative abundance in normal plant and
12. Precision and Bias
laboratory environments, even in atmospheric dust, extreme
caution must be used when collecting and handling samples to 12.1 The precision of the analytical results is given in Test
avoid contamination. The use of a continuously flowing Methods D 1888. Because of the uncertainties involved in
sample, which eliminates the need for collecting, handling, and sampling steam, it is not possible to state the overall precision
storing individual samples, is preferred. of this test method.
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D 2186–84 (1999)
TEST METHOD B—ELECTRICAL CONDUCTIVITY degassing the sample before its electrical conductivity is
measured. Because mechanical degassing is not completely
13. Scope
effective, the amount of residual gases must be determined and
the measured conductivity value must be corrected for their
13.1 Ion-Exchange Degasser—An ion-exchange degasser
effect. Although mechanical degassers may still be used to a
consistsofanion-exchangeresinthatexchangeshydrogenions
limited extent, they are no longer available commercially. The
for all cations in the sample, thereby eliminating all basic
use of mechanical degassers should be considered obsolete.
dissolved gases, including volatile amines. By converting
14.3 Basic dissolved gases, many of which are not effec-
mineral salts to their acid forms, it also increases the specific
tively removed by mechanical degassing, are converted to
conductance of the impurities. As a result, the linear relation-
water by an ion-exchange degasser.The ion-exchange degasser
ship between conductivity and impurity content is extended to
also converts mineral salts to their acid form by exchanging
a much lower level, depending on the carbon dioxide content.
hydrogen ions for the metallic cations. Since the specific
The test method is very useful for measuring low concentra-
conductance of the acid form is roughly three times that of the
tions of impurities, such as condenser cooling water leakage, in
steam condensate, and it is especially useful, for indicating original mineral salts at 25°C (77°F), the sensitivity of mea-
surementisincreased.Iftheconductancemeasurementismade
small or intermittent changes in impurity content from some
at the atmospheric boiling point (approximately 100°C
normal value. The test method is not satisfactory for the
(212°F)), the specific conductances of the ions are increased
determination of impurities in steam condensate samples that
and the sensitivity of measurement is improved still further.
contain acidic gases, such as carbon dioxide, large percentages
of insoluble matter, or substances that ionize weakly. The
15. Interferences
sensitivity and accuracy of the method are decreased for
15.1 Residual gases remaining in steam condensate samples
samples in which hydroxides represent an appreciable percent-
age of the impurities, because hydroxides, which contribute to after mechanical degassing constitute interference with the
conductivity measurement. The concentrations of these gases
the formation of deposits, are converted to water by the
ion-exchange resin. This characteristic is particularly signifi- remaining in the samples shall be determined, and appropriate
corrections shall be subtracted from the measured conductivity
cant when steam is generated at sufficiently high pressure to
cause appreciable vaporization of sodium hydroxide from the values.
boiler water.
16. Apparatus
13.2 MechanicalandIon-ExchangeDegasser—Bycombin-
ing mechanical and ion-exchange degassing of steam or 16.1 Apparatus shall be provided in accordance with Test
condensed steam, or both, effective elimination of both acidic Methods D 1125.
and basic dissolved gases is attained. This arrangement has the 16.2 Ion-Exchange Degasser—The ion exchange column
same advantages and limitations as the ion-exchange degasser shall consist preferably of sulfonated styrenedivinyl-benzene
alone, except that it will remove acidic gases, and the greater resin in a container of plastic or other corrosion-resistant
sensitivity afforded by measuring the conductance at atmo- material. A column of approximately 38-mm (1.5-in.) internal
spheric boiling water temperature extends the linear relation- diameter and 305 mm (12 in.) in length, containing about 272
ship between conductivity and the ionized impurity content g (0.6 lb) of resin, is satisfactory for most applications. Woven
down to about at least 0.005 mg/L (ppm). Although the plastic fabric or similar corrosion-resistant material is required
relationship becomes somewhat nonlinear, the conductance is at each end of the column to retain the resin and to permit the
sensitive to concentration changes down to at least 0.005 mg/L condensate sample to enter and leave the column.An example
(ppm). of an ion-exchange column, equipped with a conductivity cell,
flowmeter, and thermometer, is shown in Fig. 1.
14. Summary of Test Method
14.1 Because the concentrations of impurities in steam
condensate are usually very low, most impurities are assumed
to be completely dissolved and completely ionized. Therefore,
the electrical
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