ASTM D3370-95a(1999)e1
(Practice)Standard Practices for Sampling Water from Closed Conduits
Standard Practices for Sampling Water from Closed Conduits
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:
Practice A- Grab Samples (Sections 9 to 17)
Practice B- Composite Samples (Sections 18 to 23)
Practice C- Continual Sampling (Sections 24 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 Note 5 and 13.4.
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e1
Designation:D 3370–95a (Reapproved 1999)
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.Anumber 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—Footnotes were editorially removed in June 1999.
1. Scope D3648 Practices for the Measurement of Radioactivity
D3694 Practices for Preparation of Sample Containers and
1.1 These practices cover the equipment and methods for
for Preservation of Organic Constituents
samplingwaterfromclosedconduitssuchasprocessstreamsat
D3856 Guide for Good Laboratory Practices in Laborato-
power stations for chemical, physical, microbiological, and
ries Engaged in Sampling and Analysis of Water
radiological analyses. It does not cover specialized equipment
D4453 PracticeforHandlingofUltra-PureWaterSamples
requiredforanduniquetoaspecifictestormethodofanalysis.
D4515 Practice for Estimation of Holding Time for Water
The following are included:
Samples Containing Organic Constituents
Sections
D4840 Guide for Sampling Chain-of-Custody Procedures
Practice A—Grab Samples 9 to 17
Practice B—Composite Samples 18 to 23
D4841 Practice for Estimation of Holding Time for Water
Practice C—Continual Sampling 24 to 29
Samples Containing Organic and Inorganic Constituents
1.2 For information on specialized sampling equipment, D5540 Practice for Flow Control and Temperature Control
tests or methods of analysis, reference should be made to
for On-Line Water Sampling and Analysis
volumes 11.01 and 11.02 of the Annual Book of ASTM
3. Terminology
Standards, relating to water.
1.3 This standard does not purport to address all of the 3.1 Definitions—For definitions used in these practices,
safety concerns, if any, associated with its use. It is the refer to Terminology D1129.
responsibility of the user of this standard to establish appro- 3.2 Definitions of Terms Specific to This Standard:
priate safety and health practices and determine the applica- 3.2.1 back pressure regulator—a device designed to main-
bilityofregulatorylimitationspriortouse.Forspecifichazards tain a constant pressure upstream of itself (variable or fixed
statements, see Note 5 and 13.4. back pressure regulators are available) to maintain constant
flow in analyzers in continual sampling.
2. Referenced Documents
3.2.2 composite sample—a series of grab samples inte-
2.1 ASTM Standards:
grated into a single sample or a sample collected at specific
A106 Specification for Seamless Carbon Steel Pipe for time intervals and integrated into a single sample. The goal of
High-Temperature Service
a composite sample is to characterize a process weighted
A 179/A179M Specification for Seamless Cold-Drawn
average in proportion to process parameters.
Low-Carbon Steel Heat-Exchanger and CondenserTubes 3.2.3 grab sample—a single sample from a process stream
A269 Specification for Seamless and Welded Austenitic
(flowing) or from a source of confined geometry (stagnant)
Stainless Steel Tubing for General Service withdrawn at a specific time. The goal of withdrawing a grab
A335/A335M Specification for Seamless Ferritic Alloy
sample is to obtain a small portion of the process stream or
Steel Pipe for High-Temperature Service confined geometry source in order to characterize the entire
D1066 Practice for Sampling Steam
system.
D1129 Terminology Relating to Water 3.2.4 headcup—amethodusedtoachieveconstantpressure
D1193 Specification for Reagent Water
(see back pressure regulator). It incorporates plumbing of the
sampletoaselectedheightabovetheinlettotheanalyzerinlet
line(s) to achieve the required inlet pressure for the analyzers.
Itisoccasionallyuseddownstreamofcolorimetricanalyzersto
These practicesareunderthe jurisdiction ofASTM CommitteeD-19 onWater,
and are the direct responsibility of Subcommittee D19.03on Sampling ofWater and
increase sample flow past the analyzer.The sample flows to an
Water-Formed Deposits, Surveillance of Water, and Flow Measurement of Water.
open cup with an overflow. This fixed head provides the
Current edition approved Sept. 10, 1995. Published November 1995. Originally
published as D3370–74T. Last previous edition D3370–95.
Annual Book of ASTM Standards, Vol 01.01.
3 4
Annual Book of ASTM Standards, Vol 11.01. Annual Book of ASTM Standards, Vol 11.02.
Copyright © ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959, United States.
D 3370
constant pressure, assuming inlet flow to the head cup exceeds prevent an artificial degree of accuracy from being assigned to
outlet flow to the grab sample and analyzers. the data derived from tests on the sample.
5.4 The samples shall be of sufficient volume and shall be
NOTE 1—Contemporary designs of back pressure regulators provide
taken frequently enough to permit reproducibility of testing
excellentsensitivitytopressurechangeandhavelimitedtheneedforhead
requisiteforthedesiredobjective,asrequiredbythemethodof
cups and the concurrent space and maintenance problems as well as
sample contamination potential. analysis to be used.
5.5 Laboratories or facilities conducting water sampling
3.2.5 pressure reducer—a device designed to reduce pres-
should be in compliance with Guide D3856.
sure, and therefore control flow, of sample to a pressure level
where it can be regulated easily. This device shall be located
6. Interferences
downstream of the cooled sample where cooling is required.
6.1 Ifchemicalsareinjectedorotherstreamsareintroduced
3.2.6 sample cooler—a small heat exchanger designed to
into the medium to be sampled, the sample collection point
provideprimaryorsecondarycooling,orboth,ofsmallprocess
should be placed far enough downstream to ensure a com-
sampling streams of water or steam.
pletelymixedsample.Assumingturbulentflow(forexample,a
3.2.7 time response—the time required for the system to
Reynolds number of at least 4000), locating the sample
reach 63.2% of the total change between the state of initial
collection point an equivalent length of 25 diameters down-
equilibriuminresponsetoastepchangeintroducedattheinput
streamofthechemicalinjectionpointisconsideredacceptable.
to the system.
An equivalent length of 50 diameters is recommended for
3.2.8 variable rod in tube orifice—a type of pressure re-
laminar flow.
ducer for high pressure samples that uses a retractable tapered
6.2 The sampling of high-purity water requires special
rod inside a reamed tube to provide a variable orifice for
consideration.Contactwithanymaterialotherthantheoriginal
pressure reduction that is parallel with the sample flow. This
container subjects the sample to possible contamination or
eliminates wear of the orifice and provides variable pressure
alteration. This includes contact with air. Additional require-
reduction and flow.
ments are given in Practice D4453.
4. Summary of Practices
7. Materials andApparatus
4.1 These practices include three procedures for sample
7.1 Sample Lines:
collection. The first is for the collection of a grab sample of
7.1.1 General—Samplelinesshouldbedesignedsothatthe
water at a specific site representing conditions only at the time
sampleisrepresentativeofthesource.Theyshallbeasshortas
of sampling. Grab sampling is the only procedure suitable for
feasible and of the smallest practicable bore to facilitate
bacteriological analysis and some radiological test procedures.
flushing, minimize conditioning requirements, reduce lag time
4.2 The second practice is for collection of a composite
and changes in sample composition, and provide adequate
sample at a specific site, portions of which are collected at
velocityandturbulence.Thelinesshallhavesufficientstrength
varied time intervals.Alternatively, the composite may consist
to prevent structural failure. The designer is responsible for
of portions collected at various sites or a combination of both
ensuring that applicable structural integrity requirements are
site and time variables.
met. Small tubing is vulnerable to mechanical damage and
4.3 The third practice provides a continuously flowing
should be protected.
sample from one or more sampling sites, suitable for on-line
7.1.1.1 Traps and pockets in which solids might settle shall
analyzers or for collecting grab samples from a continuously
be avoided, since they may be partially emptied with changes
flowing sample stream.
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
practicaltodetermineandunderstandinterrelationshipssothat
required to reach and maintain equilibrium.Although limited, other work
results obtained at a minimum number of points may be used has also noted effects of sorption of dissolved species within tube wall
deposits.Velocitiesnear1.8m/s(6f/s)seemtooptimizethesefactors,but,
to characterize the system.
other velocities can provide acceptable results. Sample velocity should be
5.3 Samples collected from a single point in a system are
considered as a key design issue along with type of sample, lag time,
alwaysrecognizedasbeingnon-representativetosomedegree.
pressuredrop,neworexistingsamplelines,etc.whendeterminingsample
Forthisreason,totalrepresentativenessofsamplescannotbea
prerequisite to the selection of a sampling point.The degree of
representativeness of the sample shall be assessed and the
Theboldfacenumbersinparenthesesrefertothelistofreferencesattheendof
assessment made a part of the permanent record. This will this standard.
D 3370
flow rates. Maintaining the selected velocity is necessary to achieve
7.2.4 Pressure Regulators—Since most on-line analyzers
sample representivity.
are flow sensitive, as well as temperature sensitive, the flow
rate in the branch circuits shall also be controlled to ensure
7.1.2 Materials—The material from which the sample lines
repeatable analytical results.This is achieved by establishing a
are made shall conform to the requirements of the applicable
constant pressure zone where the sample line feeds the
specifications as follows:
analyzer branch lines. See Practice D5540 for additional
ASTM Designation
Pipe (seamless carbon steel for high-temperature Specification A 106
information. Because of the relationship of pressure and flow,
service)
a zone of constant pressure will ensure that each analyzer fed
Pipe (seamless ferritic alloy-steel for high-temperature Specification A 335
service) from this zone gets a constant flow rate independent of actions
Tubing (seamless carbon-steel for high-temperature Specification A 179
takenintheotherbranchlineswhilemaintainingconstantflow
service)
in the main sample line. Maintaining constant flow is also
Tubing (seamless or welded alloy-steel for high- Specification A 269
temperature service) essential in regularly monitored grab samples. Two methods
Tubing, Plastic (polyethylene), or equivalent
areavailabletoachievethisconstantpressurezoneinconjunc-
non-leaching inert materials
tion with the upstream pressure reducer: ( 1) back pressure
Carbonsteelpipeortubingmaybesatisfactoryforsampling
regulator (fixed or variable) or ( 2) head cup. Using a
lines where levels of contaminants in the sample are high, or
forepressure regulator without a back pressure regulator or
sampleconstituentsrequireit.Forsamplinghigh-puritywaters
head cup is not recommended. A forepressure regulator alone
or corrosive waters, the sampling lines shall be made of
will not provide a constant sample line flow. Flow changes in
stainless steel that is at least as corrosion resistant as 18%
the branch lines below the regulator result in the forepressure
chromium, 8% nickel steel (AISI 304 or 316 austenitic
regulator closing or opening to maintain the analyzer inlet
stainless steels are commonly used (6).
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
7.2.4.1 Use of a back pressure regulator is the preferred
through the tubing and cause an analytical bias. The selection of the
method to achieve the constant pressure zone. Total sample
sample line material should be based on the parameters of interest.
flow is established using the primary pressure reducer with all
7.2 Valves and Fittings:
flowgoingthroughthebackpressureregulatingvalvetodrain,
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.Branchlinestoeachanalyzer
AISI 316 austenitic stainless steel is commonly used. Pressure
are connected to this fixed pressure zone. When flow is
and temperature ratings should be selected based on the
initiated to an analyzer, the back pressure regulator will close
specific service of the valve/fitting.
slightly to maintain the pressure at the regulator inlet. Simi-
7.2.2 Isolation Valves— At least one shut off valve (com-
larly, when flow to an analyzer is shut off, the regulator will
monly referred to as a root valve) shall be placed immediately
open to accommodate the increased flow. Since the pressure at
after the point from which the sample is withdrawn so that the
the branch connections to the other analyzers is maintained
samplelinemaybeisolatedwhendesired.For
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