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coal sampling continued companies, the following were observations from three cases: 1. The upstream cutter edge of a primary cross-belt cutter became bent due to repeated contact with the coal flow on a loadout conveyor. The cutter opening was reduced from 6 in. to 2.8 in. When the smaller final sample mass was noticed by site personnel, the secondary sample timer interval was reduced to "get more sample" versus conducting an inspection and repairing or replacing the cutter. (See Figure 1) • It is likely in this case, the reduced cutter opening rejects coarse particles. Coarse particles are typically the lower ash, higher Btu particles. This situation likely causes a bias toward higher ash and lower Btu, hurting the system operator of the mining company and causing lost opportunity to collect premiums and may cause a penalty or suspension due to lower than contracted quality. 2. In the case of two loadout inspections on behalf of utilities, observations were made regarding the final sample containers not being airtight or protected and resulting in the potential for unaccounted for moisture loss and a likely bias. • In Figure 2, the final sample falls into the "milk can" container, is unprotected and open to contamination and moisture loss. • In Figure 3, the final sample bag was found open after the first half of the train was loaded. Site personnel seemed to be Table 2: Barge Unloading Two-stage Sampling System 42 www.coalage.com unaware of the possible problem with leaving the bag standing open. More training is needed. 3. An inspection of a sampling system and related processes was made on behalf of a utility. An observation was made that the system's bias test was conducted differently from the routine sample handling method. The recent bias test report was reviewed. The secondary sampler of this two-stage system has the capability to deliver the increments to two final sample containers located on opposite sides, A and B of the secondary sample belt feeder. During the bias test, the A and B sample was combined for analysis. The routine operational procedure of the system was to take one side—the A sample for the "in-house" analysis and the other side—the B sample was sent to the independent laboratory for the utility's analysis. If the two sides are to be used independently, the system operating parameters must be set to provide the minimum number of increments per ASTM for each side and the system must be tested during the bias test to verify that this practice, i.e., each side is "unbiased." Regulatory Authority & Quality Assurance When testing a belt scale or a batch weighing system there is a regulatory authority that certifies the operation of the weighing system. With mechanical sampling, the authority is the language in the coal supply agreement. Coal supply agreements have some specificity as to sampling using the phrase "according to ASTM" to describe issues related to sampling and operation of a mechanical sample. A bias test, extraction table, sampling ratio charting, review of operational and maintenance procedures and other parameters may be cited in the agreement. Many agreements may not cite the new ASTM sampling practice, D7430. Specific analysis methods may or may not be specified. More specificity in coal supply agreements is recommended to ensure that the preferred quality assurance parameters will not be ignored. The process to ensure the correct sample is collected and analyzed is not solely to use a bias test as the ultimate authority. The bias test is only part of the process. After the bias test, what happens in the intervening period between bias tests? A program of sampling system quality assurance can provide confidence to the contract parties to ensure that a good faith effort is made. An agreed upon program can outline processes for contract samples to be collected in the proper manner and the processes from sample collection to laboratory analysis be known i.e., no surprises. A competent program contains the following elements: • An initial commissioning or system improvement program for the mechanical sampler such as the Seven Step program, which includes inspection, sampling ratio charting and bias testing. • Preventive maintenance—ensuring the mechanical stability of the sampling system improves system availability. • Written procedures—documentation demonstrates a proactive way to ensure that the program is known to all personnel involved and the contractual partner. • Sampling may be conducted at origin and destination. For the sampling processes that are not contractual to have a competent challenge, similar quality assurance practices must be used. Ignoring quality assurance because a system is not the contractual sampling system can take away the opportunity to challenge the contractual sample. • Periodic inspection, including evaluation using an extraction table. • Sample crusher product sieve analysis. Seven Step Program for System Improvement or Commissioning It is risky to "jump into" a bias test as soon as the first system is operational. The plan below is a measured action plan to ensure successful system startup and improvement of an existing system. • Inspect the system while in service and while taken out of service. Include inspections of the pneumatic, hydraulic, and electric drive components, cutters, chute work, crusher components and PLC function. Measure all cutter speeds, cutter operating intervals and sample flow rates. Prepare a detailed description of all mechanical problems found. • Fix the mechanical problems found during the inspection. • Prepare a sample extraction table describing how the sampling system is now operating. Make the corrections to the sampling parameters necessary to eliminate bias. This is critical. Prepare a corrected sample extraction table which includes the design sampling ratio. May 2013