ASTM D3370-95a(2003)e1
(Practice)Standard Practices for Sampling Water from Closed Conduits
Standard Practices for Sampling Water from Closed Conduits
SIGNIFICANCE AND USE
The goal of sampling is to obtain for analysis a portion of the main body of water that is representative. The most critical factors necessary to achieve this are points of sampling, and materials selection, system design, time of sampling, frequency of sampling, and proper procedures to maintain the integrity of the sample prior to analysis.
Homogeneity of the process to be sampled is frequently lacking, necessitating multiple-point sampling. If it is impractical to utilize a most-representative sampling point, it may be practical to determine and understand interrelationships so that results obtained at a minimum number of points may be used to characterize the system.
Samples collected from a single point in a system are always recognized as being non-representative to some degree. For this reason, total representativeness of samples cannot be a prerequisite to the selection of a sampling point. The degree of representativeness of the sample shall be assessed and the assessment made a part of the permanent record. This will prevent an artificial degree of accuracy from being assigned to the data derived from tests on the sample.
The samples shall be of sufficient volume and shall be taken frequently enough to permit reproducibility of testing requisite for the desired objective, as required by the method of analysis to be used.
Laboratories or facilities conducting water sampling should be in compliance with Guide D 3856.
SCOPE
1.1 These practices cover the equipment and methods for sampling water from closed conduits such as process streams at power stations for chemical, physical, microbiological, and radiological analyses. It does not cover specialized equipment required for and unique to a specific test or method of analysis. The following are included: SectionsPractice A-Grab Samples9 to 17Practice B-Composite Samples18 to 23Practice C-Continual Sampling24 to 29
1.2 For information on specialized sampling equipment, tests or methods of analysis, reference should be made to volumes 11.01 and 11.02 of the Annual Book of ASTM Standards, relating to water.
1.3 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. For specific hazards statements, see 8.3 and 13.4.
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Standards Content (Sample)
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Designation:D 3370–95a (Reapproved 2003)
Standard Practices for
Sampling Water from Closed Conduits
This standard is issued under the fixed designation D 3370; 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.
This standard has been approved for use by agencies of the Department of Defense.
e NOTE—Warning notes were editorially moved into the standard text in January 2004.
1. Scope D 1066 Practice for Sampling Steam
D 1129 Terminology Relating to Water
1.1 These practices cover the equipment and methods for
D 1193 Specification for Reagent Water
samplingwaterfromclosedconduitssuchasprocessstreamsat
D 3648 Practices for the Measurement of Radioactivity
power stations for chemical, physical, microbiological, and
D 3694 Practices for Preparation of Sample Containers and
radiological analyses. It does not cover specialized equipment
for Preservation of Organic Constituents
required for and unique to a specific test or method of analysis.
D 3856 Guide for Good Laboratory Practices in Laborato-
The following are included:
ries Engaged in Sampling and Analysis of Water
Sections
D 4453 Practice for Handling of Ultra-Pure Water Samples
Practice A—Grab Samples 9 to 17
Practice B—Composite Samples 18 to 23
D 4515 Practice for Estimation of Holding Time for Water
Practice C—Continual Sampling 24 to 29
Samples Containing Organic Constituents
1.2 For information on specialized sampling equipment,
D 4840 Guide for Sampling Chain-of-Custody Procedures
tests or methods of analysis, reference should be made to D 4841 Practice for Estimation of Holding Time for Water
volumes 11.01 and 11.02 of the Annual Book of ASTM
Samples Containing Organic and Inorganic Constituents
Standards, relating to water. D 5540 Practice for Flow Control and Temperature Control
1.3 This standard does not purport to address all of the
for On-Line Water Sampling and Analysis
safety concerns, if any, associated with its use. It is the
3. Terminology
responsibility of the user of this standard to establish appro-
priate safety and health practices and determine the applica- 3.1 Definitions—For definitions used in these practices,
bilityofregulatorylimitationspriortouse.Forspecifichazards refer to Terminology D 1129.
statements, see 8.3 and 13.4. 3.2 Definitions of Terms Specific to This Standard:
3.2.1 back pressure regulator—a device designed to main-
2. Referenced Documents
tain a constant pressure upstream of itself (variable or fixed
2.1 ASTM Standards: back pressure regulators are available) to maintain constant
A 106/A 106M Specification for Seamless Carbon Steel
flow in analyzers in continual sampling.
Pipe for High-Temperature Service 3.2.2 composite sample—a series of grab samples inte-
A 179/A179M Specification for Seamless Cold-Drawn
grated into a single sample or a sample collected at specific
Low-Carbon Steel Heat-Exchanger and Condenser Tubes
time intervals and integrated into a single sample. The goal of
A 269 Specification for Seamless and Welded Austenitic a composite sample is to characterize a process weighted
Stainless Steel Tubing for General Service
average in proportion to process parameters.
A 335/A335M Specification for Seamless Ferritic Alloy 3.2.3 grab sample—a single sample from a process stream
Steel Pipe for High-Temperature Service
(flowing) or from a source of confined geometry (stagnant)
withdrawn at a specific time. The goal of withdrawing a grab
sample is to obtain a small portion of the process stream or
These practices are under the jurisdiction ofASTM Committee D19 on Water,
confined geometry source in order to characterize the entire
and are the direct responsibility of Subcommittee D19.03 on Sampling ofWater and
system.
Water-Formed Deposits, Analysis of Water for Power Generation and Process Use,
On-Line Water Analysis, and Surveillance of Water. 3.2.4 head cup—amethodusedtoachieveconstantpressure
Current edition approved Sept. 10, 1995. Published November 1995. Originally
(see back pressure regulator). It incorporates plumbing of the
approved in 1974. Last previous edition approved in 1995 as D 3370 – 95a.
sample to a selected height above the inlet to the analyzer inlet
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
line(s) to achieve the required inlet pressure for the analyzers.
contact ASTM Customer Service at service@astm.org. 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.
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D 3370–95a (2003)
It is occasionally used downstream of colorimetric analyzers to For this reason, total representativeness of samples cannot be a
increase sample flow past the analyzer. The sample flows to an prerequisite to the selection of a sampling point. The degree of
open cup with an overflow. This fixed head provides the representativeness of the sample shall be assessed and the
constant pressure, assuming inlet flow to the head cup exceeds assessment made a part of the permanent record. This will
outlet flow to the grab sample and analyzers. prevent an artificial degree of accuracy from being assigned to
the data derived from tests on the sample.
NOTE 1—Contemporary designs of back pressure regulators provide
5.4 The samples shall be of sufficient volume and shall be
excellent sensitivity to pressure change and have limited the need for head
taken frequently enough to permit reproducibility of testing
cups and the concurrent space and maintenance problems as well as
requisiteforthedesiredobjective,asrequiredbythemethodof
sample contamination potential.
analysis to be used.
3.2.5 pressure reducer—a device designed to reduce pres-
5.5 Laboratories or facilities conducting water sampling
sure, and therefore control flow, of sample to a pressure level
should be in compliance with Guide D 3856.
where it can be regulated easily. This device shall be located
downstream of the cooled sample where cooling is required.
6. Interferences
3.2.6 sample cooler—a small heat exchanger designed to
6.1 If chemicals are injected or other streams are introduced
provideprimaryorsecondarycooling,orboth,ofsmallprocess
into the medium to be sampled, the sample collection point
sampling streams of water or steam.
should be placed far enough downstream to ensure a com-
3.2.7 time response—the time required for the system to
pletely mixed sample.Assuming turbulent flow (for example, a
reach 63.2 % of the total change between the state of initial
Reynolds number of at least 4000), locating the sample
equilibriuminresponsetoastepchangeintroducedattheinput
collection point an equivalent length of 25 diameters down-
to the system.
streamofthechemicalinjectionpointisconsideredacceptable.
3.2.8 variable rod in tube orifice—a type of pressure re-
An equivalent length of 50 diameters is recommended for
ducer for high pressure samples that uses a retractable tapered
laminar flow.
rod inside a reamed tube to provide a variable orifice for
6.2 The sampling of high-purity water requires special
pressure reduction that is parallel with the sample flow. This
consideration.Contactwithanymaterialotherthantheoriginal
eliminates wear of the orifice and provides variable pressure
container subjects the sample to possible contamination or
reduction and flow.
alteration. This includes contact with air. Additional require-
ments are given in Practice D 4453.
4. Summary of Practices
4.1 These practices include three procedures for sample
7. Materials and Apparatus
collection. The first is for the collection of a grab sample of
7.1 Sample Lines:
water at a specific site representing conditions only at the time
7.1.1 General—Sample lines should be designed so that the
of sampling. Grab sampling is the only procedure suitable for
sampleisrepresentativeofthesource.Theyshallbeasshortas
bacteriological analysis and some radiological test procedures.
feasible and of the smallest practicable bore to facilitate
4.2 The second practice is for collection of a composite
flushing, minimize conditioning requirements, reduce lag time
sample at a specific site, portions of which are collected at
and changes in sample composition, and provide adequate
varied time intervals.Alternatively, the composite may consist
velocity and turbulence.The lines shall have sufficient strength
of portions collected at various sites or a combination of both
to prevent structural failure. The designer is responsible for
site and time variables.
ensuring that applicable structural integrity requirements are
4.3 The third practice provides a continuously flowing
met. Small tubing is vulnerable to mechanical damage and
sample from one or more sampling sites, suitable for on-line
should be protected.
analyzers or for collecting grab samples from a continuously
7.1.1.1 Traps and pockets in which solids might settle shall
flowing sample stream.
be avoided, since they may be partially emptied with changes
in flow conditions and may result in sample contamination.
5. Significance and Use
Sample tubing shall be shaped so that sharp bends, dips, and
5.1 The goal of sampling is to obtain for analysis a portion
low points are avoided, thus preventing particulates from
of the main body of water that is representative. The most
collecting.Expansionloopsorothermeansshallbeprovidedto
criticalfactorsnecessarytoachievethisarepointsofsampling,
prevent undue buckling and bending when large temperature
and materials selection, system design, time of sampling,
changes occur. Such buckling and bending may damage the
frequency of sampling, and proper procedures to maintain the
lines and allied equipment. Routing shall be planned to protect
integrity of the sample prior to analysis.
sample lines from exposure to extreme temperatures.
5.2 Homogeneity of the process to be sampled is frequently
NOTE 2—Studies (1–5) on particle transport in sampling lines have
lacking, necessitating multiple-point sampling. If it is imprac-
indicated that sample velocity rate and stability are important factors in
tical to utilize a most-representative sampling point, it may be
determining deposition and erosion rates on sample tube walls and time
practical to determine and understand interrelationships so that
required to reach and maintain equilibrium.Although limited, other work
results obtained at a minimum number of points may be used
to characterize the system.
5.3 Samples collected from a single point in a system are
The boldface numbers in parentheses refer to the list of references at the end of
always recognized as being non-representative to some degree. this standard.
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D 3370–95a (2003)
has also noted effects of sorption of dissolved species within tube wall
recommended for large pressure reductions because of suscep-
deposits.Velocitiesnear1.8m/s(6f/s)seemtooptimizethesefactors,but,
tibility to erosion, plugging, and wire drawing of the stem or
other velocities can provide acceptable results. Sample velocity should be
seat.
considered as a key design issue along with type of sample, lag time,
7.2.3.2 For samples less than 500 psig (3447 kPa), the
pressuredrop,neworexistingsamplelines,etc.whendeterminingsample
pressure reducer shall be a needle valve or forepressure
flow rates. Maintaining the selected velocity is necessary to achieve
sample representivity. regulator.Aneedle valve is preferred since it will not hunt with
small pressure variations.
7.1.2 Materials—The material from which the sample lines
7.2.4 Pressure Regulators—Since most on-line analyzers
are made shall conform to the requirements of the applicable
are flow sensitive, as well as temperature sensitive, the flow
specifications as follows:
rate in the branch circuits shall also be controlled to ensure
repeatable analytical results. This is achieved by establishing a
ASTM Designation
constant pressure zone where the sample line feeds the
Pipe (seamless carbon steel for high-temperature Specification A 106
service) analyzer branch lines. See Practice D 5540 for additional
Pipe (seamless ferritic alloy-steel for high-temperature Specification A 335
information. Because of the relationship of pressure and flow,
service)
a zone of constant pressure will ensure that each analyzer fed
Tubing (seamless carbon-steel for high-temperature Specification A 179
service) from this zone gets a constant flow rate independent of actions
Tubing (seamless or welded alloy-steel for high- Specification A 269
taken in the other branch lines while maintaining constant flow
temperature service)
in the main sample line. Maintaining constant flow is also
Tubing, Plastic (polyethylene), or equivalent
non-leaching inert materials
essential in regularly monitored grab samples. Two methods
are available to achieve this constant pressure zone in conjunc-
Carbon steel pipe or tubing may be satisfactory for sampling
tion with the upstream pressure reducer: ( 1) back pressure
lines where levels of contaminants in the sample are high, or
regulator (fixed or variable) or ( 2) head cup. Using a
sample constituents require it. For sampling high-purity waters
forepressure regulator without a back pressure regulator or
or corrosive waters, the sampling lines shall be made of
head cup is not recommended. A forepressure regulator alone
stainless steel that is at least as corrosion resistant as 18 %
will not provide a constant sample line flow. Flow changes in
chromium, 8 % nickel steel (AISI 304 or 316 austenitic
the branch lines below the regulator result in the forepressure
stainless steels are commonly used (6).
regulator closing or opening to maintain the analyzer inlet
pressure thereby changing the main sample line flow and
NOTE 3—Plastic tubing should be avoided where low values of dis-
disrupting the representivity of the sample from its source.
solved oxygen are to be measured since atmospheric gases may diffuse
through the tubing and cause an analytical bias. The selection of the
7.2.4.1 Use of a back pressure regulator is the preferred
sample line material should be based on the parameters of interest.
method to achieve the constant pressure zone. Total sample
flow is established using the primary pressure reducer with all
7.2 Valves and Fittings:
flow going through the back pressure regulating valve to drain,
7.2.1 Materials—Valveandfittingmaterialsshouldbecom-
recovery, or for grab sample. The regulating valve establishes
patible with the sample and the sample line material selected.
afixedpressureatthevalveinlet.Bra
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