ASTM D4621 Standard Guide for Quality Management in an Organization That Samples or Tests Coal and Coke
16. Quality Control Practices
16.1 To the greatest extent possible, personnel who actually perform the work are involved in the quality control process.
16.2 The laboratory generates current estimates of process capabilities for test methods. Such estimates include results from interlaboratory test programs, from process capability programs (Appendix X1) and from measurement of variability attributable to sample preparation and testing (13.5 and Practice D2013). These uncertainties are consistent with the accuracy required by the user(s), and are consistent with any standard test methods relevant to the tests. Measurement uncertainties are communicated to clients upon request.
16.2.1 Repeatability capability is established for each test method, using appropriate statistical procedures on data from replicate analyses of control material or test samples (see Appendix X1).
16.2.2 Reproducibility capability is determined through participation in one or more interlaboratory proficiency test programs (16.3).
16.2.3 Repeatability and reproducibility statistics are routinely updated and readily available (see Practice E 177 and Guide E 1323 for guidance).
16.3 Interlaboratory Proficiency Tests - The laboratory participates in at least one interlaboratory comparison or proficiency testing program (sometimes referred to as a "round-robin" program) that is relevant to the test methods performed (Practice E 177).
16.3.1 An SOP exists that defines who is responsible for managing participation, and how the participation is conducted and administered.
16.3.2 Data from proficiency testing programs are preserved and are summarized in statistical form or on control charts, or both. The SOP defines a procedure for routinely examining data for evidence of any persistent deviations from proficiency test averages which could indicate a bias (Note 13).
NOTE 13 - Ascertaining that the laboratory's results are within some arbitrary range of the proficiency test mean value on a month-to-month basis is not a satisfactory use of proficiency test data because it does not lead to the detection of any persistent biases.
16.3.3 Written policies define statistically based levels of nonconformance ("control limits") at which action needs to be taken to modify or recalibrate a procedure based on performance in the proficiency test program. Responsibilities and procedures for taking action are explicitly defined, and a record is maintained of actions that are taken.
16.4 Control of Quality - The laboratory routinely ensures that every test method is in control and applies statistical techniques or control charts to interpret and communicate results from such control testing in a timely fashion.
16.4.1 Calibration verification is one part of the quality control process (Section 14).
16.4.2 Test methods are verified by routinely analyzing or testing one or more quality control materials (Appendix X2).
16.4.3 The procedures for using samples of control materials are specified in the SOP for the test method or in a more general "quality control SOP", or both.
16.4.4 Quality control measurements are performed on a timely basis to detect out-of-control situations before considerable effort is wasted in improper sample testing. When a prolonged series of measurements (sequential analyses) is made, for example specific energy or instrumental sulfur analyses, the laboratory verifies that the test method is in-control at intervals throughout the series of tests. If a number of samples are processed simultaneously (for example, a batch of crucibles are placed in a furnace at the same time for determining ash contents), the laboratory verifies that the process is in control by including a sample of a control material within the batch.
16.4.5 Data from control materials are preserved in a log or file and are summarized in statistical or control chart form using the simplest, most direct presentation for easy comprehension. Generally, control chart procedures are preferred (Appendix X3), because they provide, at a glance, information about the control history of a process. Statistical or control chart summaries are updated as soon as possible to provide timely information about the state of control.
16.5 Out-of-Control Conditions - Specific, statistically based criteria for recognizing out-of-control conditions, including numerical control limits that require action when exceeded are established for each test method. See Appendix X3 and Guide E 1323 for guidance on recognizing out-of-control situations.
16.5.1 Explicit instructions define what actions are to be taken when control sample data exceed control limits (Appendix X3).
16.5.2 Analysts or other technical personnel are required to notify a designated individual (for example, a supervisor or manager) when an out-of-control excursion is detected. The authorized individual decides whether the analyst can analyze and correct the problem or if additional persons need to become involved.
16.5.3 Only specified individuals have authority to modify equipment or procedures to achieve an acceptable level of control. This policy is strictly enforced to prevent casual tampering with or modification of equipment and procedures. Whenever a procedure or equipment is modified, the appropriate SOP or equipment log is immediately changed.
16.5.4 Written procedures are followed to verify that any modification does accomplish the objective, and that the process is under control.
16.5.5 After a process has been brought under control, specific steps are taken to prevent recurrence of the nonconformance.
16.5.6 A quality discrepancy record documents each excursion beyond control limits and the corrective actions taken to bring it under control. Responsibility for generating a quality discrepancy record is well defined.
16.6 The quality manager or a designee who is familiar with the quality assurance process but who does not participate in the quality control activities periodically monitors the status of the quality control system and data. The quality manager prepares a report documenting the performance to assure the staff and clients that the testing procedures are performing within expected limits.
16.7 Whenever a new test method is adopted, or new piece of equipment is placed in service or a change in the character of samples is observed, the quality control procedures are reviewed to determine if they are still appropriate.
16.8 Any changes to the quality control system are documented in appropriate manuals and SOPs.
