ASTM D6792 Standard Practice for Quality System in Petroleum Products and Lubricants Testing Laboratories
1. Scope
1.1 This practice covers the establishment and maintenance of the essentials of a quality system in laboratories engaged in the analysis of petroleum products and lubricants. It is designed to be used in conjunction with Practice D6299.

NOTE 1 - This practice is based on the quality management concepts and principles advocated in ANSI/ISO/ASQ Q9000 standards, ISO/IEC 17025, ASQ Manual, and ASTM standards such as D3244, D4182, D4621, D6299, D6300, E29, E177, E456, E548, E882, E994, E1301, E1323, STP 15D, and STP 1209.

1.2 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory requirements prior to use.

2. Referenced Documents
2.1 ASTM Standards:
D3244 Practice for Utilization of Test Data to Determine Conformance with Specifications
D4182 Practice for Evaluation of Laboratories Using ASTM Procedures in the Sampling and Analysis of Coal and Coke (Withdrawn 2010)
D4621 Guide for Quality Management in an Organization That Samples or Tests Coal and Coke (Withdrawn 2010)
D6299 Practice for Applying Statistical Quality Assurance and Control Charting Techniques to Evaluate Analytical Measurement System Performance
D6300 Practice for Determination of Precision and Bias Data for Use in Test Methods for Petroleum Products and Lubricants
D6617 Practice for Laboratory Bias Detection Using Single Test Result from Standard Material
D7372 Guide for Analysis and Interpretation of Proficiency Test Program Results
E29 Practice for Using Significant Digits in Test Data to Determine Conformance with Specifications
E177 Practice for Use of the Terms Precision and Bias in ASTM Test Methods
E456 Terminology Relating to Quality and Statistics
E548 Guide for General Criteria Used for Evaluating Laboratory Competence (Withdrawn 2002)
E882 Guide for Accountability and Quality Control in the Chemical Analysis Laboratory
E994 Guide for Calibration and Testing Laboratory Accreditation Systems General Requirements for Operation and Recognition (Withdrawn 2003)
E1301 Guide for Proficiency Testing by Interlaboratory Comparisons (Withdrawn 2012)
E1323 Guide for Evaluating Laboratory Measurement Practices and the Statistical Analysis of the Resulting Data

2.2 ISO Standards:
ISO Guide 30 Terms and Definitions Used in Connection with Reference Materials
ISO/IEC 17025 General Requirements for the Competence of Testing and Calibration Laboratories
ISO 4259 Petroleum Products - Determination and Application of Precision Data in Relation to Methods of Test ANSI/ISO/ASQ Q9000 Quality Management System Standards

3. Terminology
3.1 Definitions:
3.1.1 accepted reference value, ARV, n - a value that serves as an agreed upon reference for comparison, and which is derived as: (1) a theoretical or established value, based on scientific principles, (2) an assigned value, based on experimental work of some national or international organization such as the U.S. National Institute of Standards and Technology (NIST), or (3) a consensus value, based on collaborative experimental work under the auspices of a scientific or engineering group.

3.1.2 accuracy, n - the closeness of agreement between a test result and an accepted reference value.

3.1.3 audit, n - a systematic examination of a laboratory's quality system procedure and related activities by an internal or external team to determine whether these procedures or activities are implemented according to the documented system.

3.1.4 bias, n - the difference between the population mean of the test results and an accepted reference value.

3.1.5 calibration standard, n - a material with a certified value for a relevant property, issued by or traceable to a national organization such as NIST, and whose properties are known with sufficient accuracy to permit its use to evaluate the same property of another sample.

3.1.6 certified reference material, CRM, n - a reference material one or more of whose property values are certified by a technically valid procedure, accompanied by a traceable certificate or other documentation which is issued by a certifying body.

3.1.7 measurand, n - the measurable quantity subject to measurement.

3.1.8 outlier, n - a result far enough in magnitude from other results so as to be considered not a part of the set.

3.1.9 precision, n - the closeness of agreement between test results obtained under prescribed conditions.

3.1.10 proficiency testing, n - determination of a laboratory's testing capability by evaluating its test results in interlaboratory exchange testing or crosscheck programs.
3.1.10.1 Discussion - One example is the ASTM D02 committee's proficiency testing programs in a wide variety of petroleum products and lubricants, many of which may involve more than a hundred laboratories.

3.1.11 quality assurance (QA), n - a system of activities, the purpose of which is to provide to the producer and user of a product, measurement, or service the assurance that it meets the defined standards of quality with a stated level of confidence.
3.1.11.1 Discussion - Quality assurance includes quality planning and quality control.

3.1.12 quality control (QC), n - a planned system of activities whose purpose is to provide a level of quality that meets the needs of users; also the uses of such a system.

3.1.13 quality control sample (QC sample), n - for use in quality assurance program to determine and monitor the precision and stability of a measurement system; a stable and homogenous material having physical or chemical properties, or both, similar to those of typical samples tested by the analytical measurement system. The material is properly stored to ensure sample integrity, and is available in sufficient quantity for repeated long-term testing.

3.1.14 reference material (RM), n - a material with accepted reference value(s), accompanied by an uncertainty at a stated level of confidence for desired properties, which may be used for calibration or quality control purposes in the laboratory.
3.1.14.1 Discussion - Sometimes these may be prepared "in-house" provided the reference values are established using accepted standard procedures.

3.1.15 repeatability, n - the quantitative expression of the random error associated with a single operator in a given laboratory obtaining repetitive results with the same apparatus under constant operating conditions on identical test material. It is defined as the difference between two such results at the 95 % confidence level.

3.1.16 reproducibility, n - a quantitative expression of the random error associated with different operators using different apparatus, and so forth, each obtaining a single result on an identical test sample when applying the same method. It is then defined as the 95 % confidence limit for the difference between two such single and independent results.

3.1.17 site precision (R'), n - the value below which the absolute difference between two individual test results obtained under site precision conditions may be expected to occur with a probability of approximately 0.95 (95 %). It is defined as 2.77 times the standard deviation of results obtained under site precision conditions.

3.1.18 site precision conditions, n - conditions under which test results are obtained by one or more operators in a single site location practicing the same test method on a single measurement system using test specimens taken at random from the same sample of material over an extended period of time spanning at least a 15 day interval.

3.1.19 traceability, n - property of the result of a measurement or the value of a standard whereby it can be related to stated references, usually national or international standards, through an unbroken chain of comparisons all having stated uncertainties.

3.2 Definitions of Terms Specific to This Standard:
3.2.1 precision ratio (PR), n - an estimate of relative magnitude of repeatability and reproducibility. The PR for a given standard test method can provide information on the relative significance between variation caused by different operators and laboratories compared to a single operator in a laboratory performing the standard test method.

3.2.2 test performance index (TPI), n - an approximate measure of a laboratory's testing capability, defined as the ratio of test method reproducibility to site precision.

3.3 Acronyms:
3.3.1 NIST - National Institute of Standards and Technology (formerly called National Bureau of Standards), Gaithersburg, MD.

4. Significance and Use
4.1 A petroleum products and lubricants testing laboratory plays a crucial role in product quality management and customer satisfaction. It is essential for a laboratory to provide quality data. This document provides guidance for establishing and maintaining a quality system in a laboratory.