Designation: D2961 − 11

Standard Test Method forSingle-Stage Total Moisture Less than 15 % in CoalReduced to 2.36-mm (No. 8 Sieve) Topsize 1

This standard is issued under the fixed designation D2961; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (´) indicates an editorial change since the last revision or reapproval.

1. Scope

1.1 This test method covers a single-stage procedure for thedetermination of total moisture less than 15 % in coal reducedto 2.36- mm (No. 8 sieve) topsize. This test method is fordetermination of total moisture only. Materials subjected to thistest shall not be used in the determination of other testparameters. It is recognized that the conditions of the test canincrease the potential for significant oxidation effects on somecoals. If the oxidation potential is of concern, the use of thissingle-stage method shall involve prior agreement between theparties involved. This test method shall not be construed as thereferee standard test method for total moisture. For refereepurposes, users of this test method are referred to Test MethodD3302 for moisture determination methods which are not assusceptible to oxidation effects.

1.2 Statistical analysis of data from several sources indi-cates that at a 95% confidence level, there is statistically nosignificant difference between the mean value of the resultsobtained by D2961 and D3302 (that is, no bias is detectedbetween the two methods at the 95% confidence level) formoisture levels between 1.4% and 15.8%. These two testmethods were not compared in this study for some ranks ofcoal including lignite and anthracite. (See 10.2.)

1.3 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.

1.4 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.

2. Referenced Documents

2.1 ASTM Standards:2

D121 Terminology of Coal and CokeD2013 Practice for Preparing Coal Samples for AnalysisD3302 Test Method for Total Moisture in Coal

3. Terminology

3.1 Definitions—For additional definitions of terms used inthis test method, refer to Terminology D121.

4. Summary of Test Method

4.1 Moisture is determined by establishing the weight lossof the coal sample by drying in an oven with forced-aircirculation.

5. Significance and Use

5.1 The measurement of total moisture is required to deter-mine whether coal meets commercial or environmentalspecifications, or both. Within the limitations prescribed in thescope, this test method describes a procedure for determinationof total moisture that requires less time than the proceduresdescribed in Test Method D3302.

6. Apparatus

6.1 Drying Pans, noncorrodible, stable at the temperatureused, and of such size that the sample can be spread to a depthof not more than 25 mm (1 in.).

6.1.1 The pan size may be varied to suit the size of thesample and the oven. The height of the sides shall be no morethan 40 mm (11⁄2 in.) so that air is not restricted in passing overthe coal.

6.2 Drying Oven, forced air-type capable of maintaining atemperature of 107 6 3°C and constructed to provide for a

1 This test method is under the jurisdiction of ASTM Committee D05 on Coaland Coke and is the direct responsibility of Subcommittee D05.21 on Methods ofAnalysis.

Current edition approved Nov. 1, 2011. Published December 2011. Originallyapproved in 1971. Last previous edition approved in 2007 as D2961 – 02(2007).DOI: 10.1520/D2961-11.

2 For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at service@astm.org. For Annual Book of ASTMStandards volume information, refer to the standard’s Document Summary page onthe ASTM website.

Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States

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continuous air flow to all parts of the oven. Air changes shallbe at the rate of two to four volumes per minute.

7. Sampling

7.1 The sample shall be prepared to 2.36 mm (No. 8)according to Test Method D2013. Divide from the 2.36-mm(No. 8) sieve size subsample (Test Method D2013) a portionnot less than 125 g.

7.2 That portion of the sample used for the moisturedetermination shall have a minimum weight of 125 g.

8. Procedure

8.1 Weigh the empty drying pan. Record the mass in gramsas W1. Transfer the sample from the sample container to thedrying pan. Distribute the sample uniformly over the pan. Donot exceed a depth of 25 mm (1 in.). Place the empty samplecontainer in the drying pan. Weigh the drying pan, coal sample,and empty sample container. Record the mass in grams as W3.

8.2 Place the pan, sample, and empty sample container inthe oven at a temperature of 107 6 3°C. Maintain the air flowto provide continuous introduction of air while ensuring thatfine particles are not elutriated. Dry for 11⁄2 h, remove from theoven, and weigh immediately. Record the mass.

8.3 Return to the oven for an additional 1⁄2 h, remove, andweigh. Record the mass. Repeat the drying at 1⁄2-h intervalsuntil the change in mass for the 1⁄2-h period is less than 0.05 %of the original mass of the coal sample.

Change in mass % 5

S Loss in mass during the12

hour intervalD *100

~Original sample mass!

(1)

8.4 Remove any residual coal from the dried sample con-tainer and weigh the empty container. Record the mass as W2.

NOTE 1—If the moisture determination is to be made in the immediatevicinity of sample preparation, the sample need not be placed in acontainer, but can be weighed directly in a tared drying pan.

9. Calculation

9.1 Calculate the moisture content of the sample as follows:

M 5 @~W3 2 W4!/~W3 2 W1 2 W2!# 3 100 (2)

where:M = total moisture in the coal as analyzed, %,W1 = weight of empty pan,W2 = weight of empty sample container,W3 = weight of coal plus pan plus sample container wet, andW4 = weight of coal plus pan plus sample container after

drying.

10. Precision and Bias

10.1 The precision of this test method for the determinationof Single-Stage Total Moisture in coal are shown in Table 1.

10.1.1 Repeatability Limit (r)—the value below which theabsolute difference between two test results of separate andconsecutive test determinations, carried out on the samesample in the same laboratory by the same operator using thesame apparatus on samples taken at random from a singlequantity of homogeneous material, may be expected to occurwith a probability of approximately 95%.

10.1.2 Reproducibility Limit (R)—the value below whichthe absolute difference between two test results carried out indifferent laboratories using samples taken at random from asingle quantity of material that is as homogeneous as possible,may be expected to occur with a probability of approximately95%.

10.2 Bias—Bias of this test method has not beendetermined.3

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TABLE 1 Concentrations Range and Limits for Repeatability andReproducibility for Single-Stage Total Moisture

Repeatability Limit Reproducibility Limitr R

0.30% 0.50%

D2961 − 11

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