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coal sampling Sampling Systems Used for Payment— Risks and Benefits Seven steps to improve an existing system BY CHUCK RENNER Full stream mechanical coal sampling is the method used to collect samples to be analyzed for shipment quality in most cases. From these samples quality adjustments specified in coal supply agreements between coal companies and buyers can be made. If a sample is not collected according to ASTM methodology, accepted practices and proper manufacturer recommended maintenance of sampling equipment, there is no chance to obtain a correct laboratory analysis. The basic unit of ASTM sample collection is the increment. Each increment (operation of the sampling cutter) is collected using guidelines recommended in the ASTM D7430–Standard Practice for Mechanical Sampling of Coal. This practice was first published in 2008. The purpose of this practice being published was to consolidate mechanical sampling guidelines and therefore provide one place in ASTM where information specific to mechanical sampling can be found. Coal supply agreements should reference this method for correct operation of mechanical samplers, auger samplers, total quality management of sampling systems and bias testing. The sequence of events to obtain a contractual analysis sample is as follows: • Loading: origin or destination sample collection; • Primary sampler: collection of the gross sample—each increment weighs from 30 lb to 1 ton; • Within system sample preparation begins: crusher—reduction of topsize; • Preparation continues: secondary sampler—division of sample mass; • Tertiary sampler: final sample; • Handling of final system sample: transfer to other container, subjecting the sample to possible sample loss and unaccounted for moisture loss or gain; • Division of sample: riffling; • Air drying of sample; • Division of the air dried sample: riffling; • Pulverizing to obtain the 60 mesh analysis sample; • Riffling and bottling for analysis; 40 www.coalage.com Table 1: Example Calculation of Cost of Negative Moisture Bias • Multiple units of analytical equipment: 1 gram per 10,000 tons (or more); and • Human input and reporting to database. Each step in this process is important. Multiple units of sampling, sample preparation and laboratory analysis are used. Several persons contact the sample from removal from the sampling system, sample handling, processing and analysis to go from 10,000 tons of coal (or more) to 1 gram (1/28 of an ounce) for analysis. A thorough quality assurance plan and audit plan must be in place to ensure that the process outlined above, going from 10,000 tons (or more) to 1 gram for analysis, is conducted correctly. It is also very important that the procedures are understood by site personnel to ensure consistent operation and sample handling. Training is needed on a regular basis. observed in systems operated by the most successful sampling system owners. Both the sampling system manufacturer and a testing company should be involved in the operation and correct maintenance of a sampling system. Hopefully the system owner will contact these professionals when issues arise instead of taking action that is not appropriate. Operators of sampling systems who don't have a comprehensive operating and maintenance program risk bias, availability issues and failure of audits by inspectors, which can show that the contractual sample is not taken correctly. When observers see issues it calls attention to the system operation and results in more frequent and detailed inspection and audit evaluation. Mechanical Sampling Financial Consequences of Bias— Contract Issues Some have characterized the modern sampling system as "automatic" sampling, particularly with the use of programmable logic controllers used to control the system operating parameters. Personnel who are charged with the task of maintenance of a sampling system understand that the systems are mechanical devices and require routine preventive maintenance (PM). To ensure that the system availability is as close to 100% as possible, a proactive PM program is What is the financial consequence of a finding of bias? The table above shows that an unresolved moisture bias can mean significant financial liability. The contractual sampling system was tested for bias. The bias test resulted in a 0.19% moisture bias which was not subsequently resolved. When the bias test results were given to the utility, a determination of a financial liability was calculated and submitted to the coal company for reimbursement over the 1 million ton contract (See Table 1). May 2013