STDmNACE TflOL99-ENGL L999 .

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NACE Standard TM0199-99

Item No. 21236

THE CORROSION S O C I E T Y

Standard
Test Method

Standard Test Method for Measuring

Deposit Mass Loading (“Deposit Weight Density”)
Values for Boiler Tubes by the
Glass-Bead-BlastingTechnique
This NACE Internationalstandard represents a consensus of those individual members who have
reviewed this document, its scope, and provisions. Its acceptance does not in any respect
preclude anyone, whether he has adopted the standard or not, from manufacturing, marketing,

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purchasing, or using products, processes, or procedures not in conformance with this standard.
Nothing contained in this NACE Internationalstandard is to be construed as granting any right, by
implication or otherwise, to manufacture, sell, or use in connection with any method, apparatus,
or product covered by Letters Patent, or as indemnifying or protecting anyone against liability for
infringement of Letters Patent. This standard represents minimum requirements and should in no
way be interpreted as a restriction on the use of better procedures or materials. Neither is this
standard intended to apply in all cases relating to the subject. Unpredictable circumstances may
negate the usefulness of this standard in specific instances. NACE International assumes no
responsibility for the interpretation or use of this standard by other parties and accepts
responsibility for only those official NACE International interpretations issued by NACE
International in accordance with its governing procedures and policies which preclude the
issuance of interpretations by individual volunteers.

Users of this NACE International standard are responsible for reviewing appropriate health,
safety, environmental, and regulatory documents and for determining their applicability in relation
to this standard prior to its use. This NACE International standard may not necessarily address
all potential health and safety problems or environmental hazards associated with the use of
materials, equipment, and/or operations detailed or referred to within this standard. Users of this
NACE International standard are also responsible for establishing appropriate health, safety, and
environmental protection practices, in consultation with appropriate regulatory authorities if
necessary, to achieve compliance with any existing applicable regulatory requirements prior to the
use of this standard.

CAUTIONARY NOTICE: NACE International standards are subject to periodic review, and may
be revised or withdrawn at any time without prior notice. NACE International requires that action
be taken to reaffirm, revise, or withdraw this standard no later than five years from the date of
initial publication. The user is cautioned to obtain the latest edition. Purchasers of NACE
International standards may receive current information on all standards and other NACE
International publications by contacting the NACE International Membership Services
Department, P.O. Box 218340, Houston, Texas 77218-8340 (telephone +1 [281]228-6200).

Approved 1999-04-24
NACE International
P.O. Box 218340
Houston, Texas 77218-8340
+I (281)228-6200

ISBN 1-57590-082-3
O 1999, NACE International

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 STD-NACE TM0199-ENGL 1999 Ib1i52981 0502215 53" =
TM0199-99

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Foreword

This standard test method was developed to document the procedures used in determining
the amount of deposit accumulation on a boiler tube surface, commonly expressed as the
deposit-weight-density (DWD) value, via the glass-bead-blasting (GBB) technique. The GBB
technique for determining DWD values is suitable for removing a wide variety of boiler deposit
types, but it is especially useful when deposition is tightly adherent and would be difficult to
dislodge completely via other mechanical or chemical cleaning processes (as specified in Method
A and Method B of ASTM(') D 3483'). Typically, the GBB technique allows for complete deposit
removal in a very short time frame, without the risk of error induced by incomplete removal of
tightly adherent scale or excessive loss of the metal substrate during the cleaning process.2
This standard is for use specifically by those involved in providing technical assessments
concerning boiler cleanliness, such as university/corporate research laboratories, independent
researcWengineering consulting firms, or those in the chemical cleaning industry. This standard
is intended to be used to obtain accurate deposit-loading data, which may be pertinent to
establishing the necessity of chemically cleaning boiler systems to avoid boiler tube failure
incidents (such as those related to underdeposit corrosion and tube metal overheating), and to
track the rate of deposit growth over time.
This standard was prepared by NACE Work Group T-7H-6f, as assigned by the T-7H-6 Task
Group on Failure Analysis-Boiler Waterside, which is a component of Unit Committee T-7H,
Corrosion and Its Control in Steam-Generating Systems, and is published by NACE International
under the auspices of Group Committee T-7 on Corrosion by Waters.

In NACE standards, the terms sha//, must, should, and may are used in accordance with the
definitinos of the terms in the NACE Publications Style Manual, 3rd.,ed., Paragraph 8.4.1.8. Shall
and must are used to state mandatory requirements. Should is used to state that which is
considered good and is recommended but is not absolutely mandatory. May is used to state that
which is considered optional.

(I) American Society for Testing and Materials (ASTM), 100 Barr Harbor Dr., West Conshohocken, PA 19428-2959.

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 TMO199-99

NACE International
Standard
Test Method

Standard Test Method for Measuring Deposit Mass Loading

(“Deposit Weight Density”) Values for Boiler Tubes by the
Glass-Bead-Blasting Tech n¡que
Contents

1. General..................................................................................................................... 1
2. Test Equipment and Apparatus ................................................................................. 1
3. Test Specimen Preparation....................................................................................... 2
4. Test Procedure ......................................................................................................... 2
5. Test Specimen Handling After Cleaning.................................................................... 3
6. Potential Interferences.............................................................................................. 4
References..................................................................................................................... 4
Appendix A-Sample DWD Report Calculation Sheet .................................................... 5

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TM0199-99

Section 1: General

1.1 This standard describes a simple test method that of the specific waterside scale formed on the heat transfer
employs GBB equipment to remove boiler waterside surface are key parameters that must be taken into
deposits on a piece of tubing removed from a represen- account in the process of making a decision to clean a
tative area of a boiler. The test specimens are cut from a boiler system to avoid tube failure. In addition, specific
sample tube, weighed before and after the cleaning boiler design, heat flux patterns, and operating conditions
process, and the amount of deposit per surface area is have significant influence on the amount of deposit
estimated by measuring the weight loss of the tube loading that can be sustained prior to the occurrence of
sample test piece after deposit removal via GBB and overheating and other deposit-relatedfailure processes.
dividing by the surface area of the test piece. The DWD
value that is obtained by this method is typically 1.3 Caution should be used in the interpretation of high
expressed in mgkm' or g/ft units, and is defined as the DWD values obtained from tubes subject to extreme
weight of the deposit per boiler tube surface area.(2) temperature conditions (beyond the oxidation limit of the
Currently, DWD values are commonly expressed in g/ft2 steel). This is because the DWD value produced may be
units. Procedures for test specimen processing, dimen- unusually high due to the presence of excessive mag-
sional analysis techniques, sources of potential interfer- netite scale via in situ oxidation. As such, deposit-loading
ences, and a sample DWD calculation worksheet are estimates of superheater tubes, reheater tubes, or water-
included. bearing tubes subject to excessive heat flux may actually
reflect the presence of heavy, in situ oxides rather than
1.2 Measurement of deposit accumulation obtained by transported and deposited water-formed scale constit-
this test method should not be the sole source of uents. No attempt to differentiate between water-formed
information used to decide on the necessity of chemically scale and in situ oxidation products is made; the overall
cleaning a boiler unit. Although producing an accurate deposit weight per surface area is estimated with this test
DWD value can be an important factor to aid in method. Other techniques (such as X-ray diffraction,
evaluating boiler cleanliness (and there are references in microchemical analysis of deposit layers, metallography,
the l i t e r a t ~ r e ~that
' ~ ' ~ utilize DWD data to assist in etc.) may be needed to ascertain the relative distribution
establishing chemical cleaning guidelines as a function of of deposit constituents and the influence of severe
boiler pressure), other details should be considered. For oxidation (excessive magnetite) on the DWD value.
example, the chemical composition and relative thickness

Section 2: Test Equipment and Apparatus

2.1 A commercial glass-bead-blasting cabinet shall be 2.5 A small flexible ruler or measuring tape with
used to perform this test. Various commercial units that gradations of 1.0 mm or 1/16 in. shall be used.
have a glass viewing window incorporated within an
enclosed blast cabinet are available. Typical operating 2.6 A point micrometer with a 0-to 25-mm (O-to 1.O-in.)
requirements are compressed air at 690 kPa (100 psig) range, 0.025-mm (0.001O-in.) increments, contact points
with a minimum 0.34 m3/min(12 ft3/min) flow rate. with 15" included angle, or similar, is optional. This type
of micrometer can be used during the test process to
2.2 Medium-size glass beads, 150- to 250-pm diameter estimate deposit thickness (via before/after-cleaning
range (60 to 100 mesh size) shall be used in the blast measurements), and on the cleaned specimens to
cabinet. estimate general corrosion loss and to assess pit depths.

2.3 A dry-cutting band saw machine, portable band saw, 2.7 An instant-film copy camera, 35-mm or digital image
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or other appropriate dry-cutting device shall be used to camera, or other photographic system to record deposit
cut the test specimens from boiler tube sample segments. appearance and other features, is optional.

2.4 An analytical laboratory balance accurate within a 2.8 Engineering graph paper, utilized to estimate surface
minimum of 0.01 g in the range of 200-to 600-9 capacity area of the test specimen, is optional.
(or larger capacity) shall be used.

(*) 1 S/ff is equivalent to 1.O75 rng/crn2.

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Section 3: Test Specimen Preparation

3.1 Test Specimen 3.2.2 Inspect the internal surface to ensure that no
cutting debris or weld spatter (from torch cutting) is
3.1.1 The optimal length of tubing cut from the boiler present in the region to be tested. By visual
for evaluation is 0.6 to 0.9 m (2 to 3 ft), However, it inspection, select a region containing a represen-
is not uncommon to receive tube sectionskamples tative sample of the internal surface deposits
that are very short in length, or cut out in rectangular (typically a 7.6-cm [3.0-in.] length in the center of the
or circular shapes. Modification to the following tube sample). Avoid sampling at previously torch-cut
steps may be needed to determine the DWD value ends where contamination or deposit loss could have
occurred.

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for unusually shaped or undersized test pieces.
Comments should be added to the report (see
Appendix A) when unusual conditions are observed. 3.2.3 If necessary, clean the external surface of the
test specimen(@ by using the glass-bead blaster.
3.1.2 With this method, straight-bored cylindrical This step must be taken if loosely adherent external
tube samples from a boiler should be cut lengthwise scale is present on the tube sample and could
in half, and the deposit accumulation on each half possibly spall off in subsequent processing. During
should be measured individually on test specimens external scale cleaning, care must be taken to avoid
that are cut to approximately 7.6 cm (3.0 in.) in any inadvertent removal of internal deposit. This
length. This produces a standard test specimen with external cleaning step may be considered optional if
a surface area of about 60 to 65 cm2 (9.0 to 10.0 the external surface’s oxide layer is very thin and
in.*). Longer test specimens can be processed, but tightly adherent (¡.e., no risk of inadvertent deposit
this may be limited by the capacity of the analytical spalling of the external surface during handling of the
balance being used. Test specimens smaller than test specimen [see Paragraph 6.31). To avoid
7.6 cm (3.0 in.) long can be processed if necessary, sample mix-up, it is advisable to write the test
but the deposit-loading result may not be as specimen identification information on the external
representative if deposits are not homogeneous (see surface (or on the cut tube edges) immediately after
Paragraph 6.1). removing any external scale.

3.2 Test Specimen Preparation. The following procedure 3.2.4 With a dry-cutting saw, complete transverse
shall be used in test specimen preparation. cuts to produce a test specimen that is preferably 7.6
cm (3.0 in.) long in a representative region, then split
3.2.1 Visually inspect the length of tubing cut from the test specimen lengthwise to create two half-
the boiler to assess the nature of the internal deposit. pieces (hot-side/cold-side). After cutting, reinspect
For tubes exposed to a differential heat flux the surface for artifacts from the cutting process and
(waterwall, screen, etc.), identify the hot and cold carefully remove any debris and/or metal fines.
sides of the tube for test specimen removal from both Deburr rough-cut edges as necessary with a metal
sides, and locate areas of the heaviest deposit file. Using a felt-tip marker, paint pen, or vibratory
accumulation. In the case of tubes exposed to a engraver, identify the test specimens (¡.e., specimen
more uniform heat flux pattern around the tube number, hot, cold, etc.) by marking on the external
circumference (economizer, superheater, etc.), surface or the saw-cut end of the section.
removal of a test specimen from one side of the tube
may be adequate. If one side appears more heavily
deposited, it should be used for the test specimen.

Section 4: Test Procedure

4.1 It is optional, but often very useful, to photograph the [see Paragraph 4.41) will provide the “before-cleaning”
internal surface in an area exhibiting deposits data for the test specimens.
representative of the test specimen using an appropriate
photographic system. 4.3 All measurement data (¡.e., weight, lengths,
thicknesses, and depths) should be recorded on a
4.2 The test specimen shall be weighed on an analytical standardized laboratory calculation data sheet (see
balance with a minimum accuracy of 0.01 g. The weight Appendix A).
measurements (and optional micrometer measurements

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TMOI 99-99

4.4 It is optional, but sometimes very useful, to obtain an pressure setting is 550 kPa (80 psig), and the usual
estimate of the waterside deposit thickness. To obtain duration of blasting is about 30 seconds with an
this value, the combined thickness of the tube wall and appropriately sized gun nozzle tip and sufficient air flow
waterside deposit prior to cleaning should be carefully volume. In any event, the surface should be blast
measured using a point micrometer, after external cleaned until it is judged to be completely free of deposit
surface deposit removal has been achieved. Three or and any adherent magnetite layer (down to a shiny metal
more locations on the cleaned external surface where the condition). Assuming optimal equipment settings, blast
thickness readings were obtained should be marked and times exceeding one minute are not typical at these
recorded. Three data points are normally sufficient. prescribed operating conditions, and should not be
These marked sites should be remeasured after cleaning necessary. Tests on clean carbon steel coupons or
to obtain approximate deposit thickness values. cleaned tube specimens are recommended to evaluate
the potential risk (if any) of excessively long blast times
4.5 The internal surface of the test specimens can now (see Paragraph 6.5).
be cleaned using the glass-bead blaster. A typical

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Section 5: Test Specimen Handling After Cleaning

5.1 Following cleaning, the test specimens shall be trimmed to fit the irregular shape, the approximate
reweighed to the nearest 0.01 g, and the tube wall surface area of the region cleaned can be estimated
remeasured at the marked sites for thickness to provide by comparing the weight of the paper pattern to the
the “after-cleaning” measurements. known weight of a sheet of paper that has a specific
square area. The size can thus be determined by
5.2 The surface area of each test specimen shall then be proportional analysis.
measured. If the specimen shape is regular (Le., a
standard test specimen) a flexible ruler will suffice. 5.3 Determinationof the DWD value
Measurements should be within the nearest 1.0 mm or
1/16 in. For a standard, regular-shaped test sample, the 5.3.1 Subtracting the “after-cleaning” data from the
longitudinal dimension should simply be multiplied by the “before-cleaning” data will provide the weight loss
actual circumferential length of the cut test specimen to (¡.e., the deposit weight) and thickness of the internal
yield the total internal surface test area (for a $andard deposit that was removed.
sample size, this is typically around 60 to 65 cm (9.0 to
10.0 in.’). 5.3.2 A DWD value can be determined by dividing
the weight of the internal deposit by the surface area.
5.2.1 If the surface dimensions of the test specimens The overall expression to determine the DWD value
are irregular, engineering graph paper or a paper- shall be calculated using Equation (1) or (2):
pattern technique can be used. If a paper sheet is

initial weight (mg)- final weight (mg)

DWD (mg/cm2 )= (11
area (cm’ )

initial weight ( g ) - jhal weight ( g )

DWD(g/ft2)=
area (in.’ ) x ( I fi’ / I 4 4 in.’ )

Note: DWD (g/ft2) = DWD (mg/cm2)x 0.929.

5.4 The DWD value should be reported to the nearest 5.6 It is optional, but sometimes useful, to employ a pin-
integer value, unless higher precision is required. type micrometer to measure pit depths or the extent of
other corrosion loss on the cleaned test specimen.
5.5. It is optional, but often desirable, to photograph the
internal surface after cleaning in a representative area of 5.7 The cleaned test specimens may be sprayed with
the test specimen using an appropriate photographic clear acrylic paint to avoid flash rusting after evaluation.
system. A fume hood should be used as necessary to avoid
overspray and odor.

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TM0199-99

Section 6: Potential Interferences

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6.1 Test Specimen Size: With the GBB method, However, if the oxide layer on the external surface is very
excellent data repeatability can be achieved regardless of thin and tightly adherent (Le., little-to-no risk of external
test sample size. However, there are circumstances in deposit interference), cleaning the external surface may
which a too-small test specimen may provide a potential not be strictly necessary as a procedural step.
interference in determining a representative DWD value.
Specifically, if the deposit being removed from the boiler 6.4 Glass Bead Condition: The glass beads in the bead-
tube is not homogeneous (Le., thick, uneven deposits that blast unit should be in good condition with minimal
may tend to spall off when the tube test specimen is cut contamination. Scheduling routine dumping and
out), processing of small test specimens (less than the replacement of the glass bead charge at a specific time
7.6-cm [3.0-in.] standard test length) should be avoided. interval (¡.e., once every 30 days) should avoid
In addition, slight measurement errors that are inherently accumulation of scale (which could act as a more
a problem with processing of small test specimens can aggressive abrasive than the glass beads), and/or
be easily avoided by processing a larger, standard-size excessive breakdown of glass beads into fine dust.
test specimen. Simple visual inspection of the glass beads should
provide sufficient indication of whether the charge has
6.2 Contamination of Test Surfaces: Another potential become contaminated or has reduced cleaning
interference is the presence of surface contaminants such effectiveness due to excessive breakdown (via long-
as weld spatter, abrasive cut-off wheel residue, or oils duration use).
that could influence the test specimen weight and
condition during its removal from the boiler (as discussed 6.5 Tenacious Scale: During a typical cleaning cycle,
in Paragraph 3.2.2). Thus, torch-cut ends, etc., should most adherent boiler tube deposits can be removed in
be avoided during selection of a representative region for less than 30 seconds with optimal equipment perform-
cutting out the test specimen. ance and settings. In this time frame, loss of the metal
substrate is relatively insignificant (around 0.20 mglcm‘,
6.3 External Scale: To avoid interference with external which is negligible).6 However, long-duration blasting
scale, the tube outer surface should be cleaned as with glass beads to “dislodge” tenacious scale (silica-
described in Paragraph 3.2.3. Failure to do so may result based scale, thick metal oxides formed via tube
in an erroneous DWD value because external scale could overheating, etc.) is not recommended because of the
spall off the external surface during sample handling after risk of excessive metal substrate loss. For tubes with
the initial weight has been recorded, which would such tenacious scale, ASTM D 3483, Method A (bending
contribute to the weight-loss calculation. scraping method) is preferable, or ASTM D 3483, Method
B (acid solvent method) may be also be considered.

References

1. ASTM D 3483 (latest revision), “Standard Test 4. J,G, Singer, ed., Combustion: Fossil Power, A
Methods for Accumulated Deposition in a Steam Reference Book on Fuel Burning and Steam Generation,
Generator Tube” (West Conshohocken, PA: ASTM). 4th ed. (Windsor, CT: Combustion Engineering Inc.,
ABB, 1991), p. 18.
2. M.J. Esmacher, J.M. Jevec, T.M. Laronge, K.A.
Selby, D.A. Shifler, “Evaluation of Boiler Tube Deposit 5. Babcock & Wilcox Plant Service Bulletin PSB-44-3M-
Weight Density Methodology,” CORROSION/97, paper N-6/91, Chemical Cleaning Guide, June 1991.
no. 454 (Houston, TX: NACE, 1997).
6. M. Esmacher, “Deposit Weight Density Methodology
3. EPRI TR-10241, “Guidelines for Chemical Cleaning for Industrial Boilers, “ Materials Performance 28, 1
of Fossil-Fueled Steam Generating Equipment” (Palo A (January 1988): pp. 74-78.
lot, CA: Electric Power Research Institute [EPRI], June
1993).

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TMO199-99

Appendix A

Sample DWD Report Calculation Sheet

Lab Number

(Optional)
DeDosiWall Thickness Measurements
Area 1 Area 2 Area 3
Weiciht:
Before Cleaning: Before Cleaning

After Cleaning:
Deposit
Test Sample Weight Loss: Thickness:

Tube Measurements

Longitudinal Axis (L):

CircumferentialAxis (C):

Calculated Area (L x C):

DWD(mg/cm2) = weight loss (mg) - mg/cm2

area (cm2)
or

D W D ( g / f t 2 )= weight loss ( g ) - g&t2

area ( i n . 2 ) x ( l f t 2/144 in.’)

[ ] See attached Comments (if applicable)

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