ASTM D1066-97(2001)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.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
An American National Standard
Designation:D1066–97 (Reapproved 2001)
Standard Practice for
Sampling Steam
This standard is issued under the fixed designation D 1066; 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.
1. Scope D 5540 PracticesforFlowControlandTemperatureControl
for On-Line Water Sampling and Analysis
1.1 This practice covers the sampling of saturated and
superheated steam. It is applicable to steam produced in fossil
3. Terminology
fired and nuclear boilers or by any other process means that is
3.1 Definitions:
at a pressure sufficiently above atmospheric to establish repre-
3.1.1 For definitions of terms used in this practice, refer to
sentative sample flow. It is also applicable to steam at lower
definitions given in Practice D 1129.
and subatmospheric pressures for which means must be pro-
3.2 Definitions of Terms Specific to This Standard:
vided to establish representative flow.
3.2.1 isokinetic sampling—a condition wherein the velocity
1.2 For information on specialized sampling equipment,
of the sample entering the port or ports of the sample nozzle(s)
tests or methods of analysis, reference should be made to the
is the same as the velocity in the stream being sampled.
Annual Book of ASTM Standards, Vols 11.01 and 11.02,
,
2 3 3.2.2 sample cooler—a small heat exchanger designed to
relating to water.
provide cooling/condensing of small process sampling streams
1.3 The values stated in either inch-pound units or SI units
of water or steam.
are to be regarded as standard. Within the text, the inch-pound
3.2.3 sampling—the withdrawal of a representative portion
units are shown in parentheses. The values stated in each
of the steam flowing in the boiler drum lead or pipeline by
system are not exact equivalents. Therefore, each system must
means of a sampling nozzle and the delivery of this portion of
be used independently of the other. Combining values from the
steam in a representative manner for analysis.
two systems may result in nonconformance with this specifi-
3.2.4 saturated steam—a vapor whose temperature corre-
cation.
sponds to the boiling water temperature at the particular
1.4 This standard does not purport to address all of the
existing pressure.
safety concerns, if any, associated with its use. It is the
3.2.5 superheated steam—a vapor whose temperature is
responsibility of the user of this standard to establish appro-
above the boiling water temperature at the particular existing
priate safety and health practices and determine the applica-
pressure.
bility of regulatory limitations prior to use.
4. Summary of Practice
2. Referenced Documents
4.1 This practice describes the apparatus, design concepts
2.1 ASTM Standards:
and procedures to be used in extracting and transporting
A 269 Specification for Seamless and Welded Austenitic
4 samples of saturated and superheated steam. Extraction nozzle
Stainless Steel Tubing for General Service
selection and application, line sizing, condensing requirements
A 335/A 335M Specification for Seamless Ferritic Alloy-
4 and optimization of flow rates are all described in detail.
Steel Pipe for High Temperature Service
3 Condensed steam samples should be handled in accordance
D 1129 Terminology Relating to Water
3 with Practices D 3370 and D 5540.
D 3370 Practices for Sampling Water in Closed Conduits
5. Significance and Use
5.1 It is essential to sample steam representatively in order
This practice is under the jurisdiction ofASTM Committee D19 on Water , and
is the direct responsibility of Subcommittee D19.03 on Sampling of Water and
to determine the amount of impurities, including moisture, in
Water-Formed Deposits, Surveillance of Water and Flow Measurement of Water
it. An accurate measure of the purity of steam provides
Samples.
information, which may be used to determine whether the
Current edition approved July 10, 1997. Published October 1997. Originally
published as D1066-49T. Last previous edition D1066-82 (1990). purity of the steam is within necessary limits to prevent
Annual Book of ASTM Standards, Vol 11.01.
damage or deterioration of subsequent equipment, such as
Annual Book of ASTM Standards, Vol 11.02.
turbines, etc. Impurities in the steam may be derived from
Annual Book of ASTM Standards, Vol 01.01.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D1066–97 (2001)
FIG. 1 Effect of Nono-Isokinetic Sampling
boiler water carryover, inefficient steam separators, natural salt decreasedandthecontaminantsdepositontheinnersurfacesof
solubility in the steam and other factors. the sample line (3). This condition has been found to be
prevalent only in regions of dry wall tube where the tempera-
6. Interferences
ture of the tube wall exceeds the saturation temperature of the
steam.
6.1 Saturated Steam— Sampling of steam presents difficult
extractionandtransportproblemsthataffecttherepresentative- 6.2.1 Interference also occurs when the transport tube tem-
perature is at or below the saturation temperature. The steam
ness of the sample.
6.1.1 Isokinetic sampling requires that the velocity of the loses superheat and dissolved contaminants deposit on the tube
wall. The sample is no longer representative. Superheated
fluid entering the sample nozzle port(s) is the same as the
velocity of the stream being sampled at the location of the steam samples shall be cooled or desuperheated in the sample
nozzle or immediately after extraction to ensure a representa-
sample nozzle. When the sample is not extracted isokinetically
the contaminants in the steam are not properly represented in tive sample. See 7.1.3.3 and 7.2.4.
the sample. The effects of non-isokinetic sampling are illus-
7. Materials and Apparatus
trated in Fig. 1 and can make the sample unrepresentative.
7.1 Extracting the Sample:
6.1.2 Traditionally, saturated steam samples with initial
7.1.1 Saturated Steam— Since saturated steam is normally
steam velocities above 11m/s (36f/s) were considered to
sampled as a two-phase fluid, made up of steam and small
provide adequate turbulent flow to ensure transport of most
droplets of water, isokinetic sampling shall be employed. Since
particulates and ionic components. More recent studies (1)(2)
steam velocities vary with boiler load it normally is not
find that because many sample lines are long and uninsulated,
practical to sample isokinetically throughout the load range.
steam samples are frequently fully condensed prior to reaching
Normally, the load of interest is full load or a guaranteed
thesamplestation.Partiallyorfullycondensedsamplesusually
overload. The sampling system shall be designed to provide
have a velocity too low to prevent excessive deposition and the
isokinetic sampling at this design load.
sample becomes nonrepresentative of the source. Detailed
7.1.1.1 At low velocities, the moisture in wet steam forms a
design of the sample line to control vapor and liquid velocity
film along the inside surface of the steam line that entrains
can minimize this interference but cooling of saturated steam
impurities(4).Table1showstheminimumsteamflowrequired
samples at the source is recommended to assure a representa-
for representative samples at various steam pressures.
tive sample. See Practice D 3370 for further information on
7.1.2 Superheated Steam—Superheated steam is usually
factors that affect liquid sample transport.
regarded as a single phase fluid. Unless particulates are being
6.2 Superheated Steam—Most contaminants can be dis-
measured, isokinetic sampling is not required. Most impurities
solved in superheated steam. However as steam pressure and
in superheated steam are present in vaporous form and are
temperature are reduced the solubility of many contaminants is
thoroughly mixed with the steam vapor. However, an oxide
layer forms on the steam side of superheater and reheater lines
and gets thicker with increased service. Since the physical
The boldface numbers given in parentheses refer to a list of references at the
end of this standard. properties of the oxide are different from the parent metal,
D1066–97 (2001)
TABLE 1 Minimum Saturated Steam Line Conditions at Point of
Sampling
Saturated Steam Pressure Minimum Steam Flow
psig (kPa) ft/s (m/s)
100 (690) 195 (59.6)
200 (1379) 141 (42.8)
300 (2068) 114 (34.8)
400 (2758) 95 (29.1)
500 (3447) 83 (25.3)
700 (4826) 70 (21.2)
1000 (6895) 54 (16.6)
1500 (10342) 36 (11.0)
2000 (13790) 26 (7.9)
2500 (17237) 18 (5.5)
2800 (19300) 13 (4.1)
FIG. 2 Single Port Nozzle
changing pressure and temperature cause the oxide layer to
information on port location, port sizing and internal passage
crack and exfoliate (3). The exfoliated material can retain
sizing for multi-port nozzles.
significant amounts of impurities, such as sodium, which can
7.1.3.3 Sampling Nozzles for Superheated Steam—The
be leached into the sample when the material contacts the
nozzles described for use with saturated steam can also be used
liquid phase of the sample (5) (6).
for superheated steam. However, isokinetic sampling is nor-
7.1.2.1 Because the dissolved contaminants in high pressure
mally not required for superheated steam unless particulates
superheated steam deposit on the inner surfaces of the nozzle
are measured.
and sample lines as the sample desuperheats, superheated
7.1.3.4 In order to minimize the deposition of contaminants
steam samples shall be rapidly desuperheated or condensed
from superheated steam several experts currently recommend
near the point of extraction. See 7.2.4.
injecting condensed and cooled sample directly into the super-
7.1.3 Sampling Nozzles— Stratification of suspended solids
heated steam sampling nozzle (1). Due to concern for induced
in horizontal steam pipes can influence the composition of the
thermal stresses, few power plants have installed nozzles with
steam samples. To minimize the effects of stratification it is
integral condensate injection. An acceptable alternative is to
recommended that steam sampling nozzles be located in long
condense the sample immediately after extraction. See 7.2.4
vertical pipes. To ensure that all water droplets are carried in
for sample line and condensing design criteria.
the flow stream, downward flow is preferred. Nozzles which
7.1.3.5 Materials and Installation—Sampling nozzles shall
must be located in a horizontal pipe should be near the top of
be adequately supported and shall be designed to prevent
the pipe (1). Sampling nozzles can be either of a single port or
failure due to flow-induced vibration, thermal stress cycling
multiport configuration as specified or recommended by the
andotherpossiblecauses.NozzlesaremostoftenmadeofAISI
boiler manufacturer or design engineer.
316 (7) or other austenitic stainless steel or alloy 600 (1)(6).
7.1.3.1 Single Port Nozzles—A single port nozzle which is
Weld joints used for dissimilar metals are subject to high
positioned at a known distance from the inner surface can also
thermal stresses due to different coefficients of thermal expan-
be used when it is at a location where a predictable velocity
sion. Care should be used in weld rod selection and inspection
gradient exists. Normally this would be at a location where
of all dissimilar metal weld joints.
fully developed turbulent flow exists which enables the deter-
7.1.3.6 Sample ports shall be drilled cleanly, using the
mination of velocity at any location in the steam line. Single
standard drill size nearest to the calculated port diameter. The
port nozzles are most frequently located at a distance from the
port inlet ends shall not be chamfered or rounded, and the
pipe wall where the actual velocity equals the average velocity,
outlet ends shall be free of burrs. The smallest recommended
typically 0.2 R of the pipe (1)(6). Fig. 2 depicts this typical
port diameter is 3.18 mm ( ⁄8) in. Port diameters of less than
single port nozzle. This type of single port nozzle can be easy
2.38 mm ( ⁄32) in. are subject to plugging and shall not be used.
to install and provides good results at a reasonable cost. Fig. 3
Total port area shall be determined to maintain isokinetic
shows another single port nozzle used to sample saturated
sampling in the nozzle port(s) at the desired sampling rate and
steam in superheater supply tubes.
design steam load.
7.1.3.2 Multi-Port Nozzles—Multi-port nozzles which
7.1.3.7 At least one shut off valve (commonly referred to as
sample at various locations across the pipe cross section can
a root valve) shall be placed immediately after the point from
also be used. These nozzles may be used only at locations
which the sample is withdrawn so that the sample line may be
where the velocity profile across the pipe can be determined
isolated. In high pressure applications two root valves are often
(1). Ports shall be located so that each port samples from an
used. The valve(s) selected should be rated for the pressure/
equal fraction of the cross-sectional area of the pipe being
temperature of the sample source.
sampled. Since the steam velocity varies across the pipe
7.2 Transporting the Sample:
section, each port diameter must be sized to result in isokinetic
sampling with the proper fraction of sample collected from 7.2.1 General—Sample lines should be designed so that the
each port. Table 2 and Fig. 4, Fig. 5, and Fig. 6 detail sample remains representative of the source. See 6.1 and 7.1.1.
D1066–97 (2001)
NOTE 1—Sampling nozzle shall be centered on superheater supply tube.
FIG. 3 Steam Sampling Nozzle, Single-Port Type
TABLE 2 Calculations for Steam Sampling Nozzles for Lines 6 in. (152 mm) and Larger, Equal Size Ports, Unequally Spaced
Nominal pipe size ________ in. ________ cm
D = Pipe OD ________ in. ________ cm
o
D = Pipe ID ________ in. ________ cm
T = Pipe wall thickness ________ in. ________ cm
N = Total number of ports ________
Radii of port circles:
r =(D /2) 1/N ________ in. ________ cm
=
1 1
r =(D /2) 3/N ________ in. ________ cm
=
2 1
r =(D /2) =5/N ________ in. ________ cm
3 1
F = Flow rate of fluid through pipe ________ lb/h ________ m/s
f = Flow rate of total sample extracted ________ lb/h ________ m/s
2 2
A = Traverse area of pipe = 0.7854 D ________ in. ________ cm
2 2
a = Total port area = Af/F ________ in ________ cm
A
________ in. ________ cm
d = Diameter of ports = =a/0.7854N
Use ____ drill Use ____ drill
________ in. ________ cm
b = Diameter of nozzle bore = =3a/1.
...