This standard is issued under the fixed designation B; the number 1 This test method is under the jurisdiction of ASTM Committee B08 on Metallic. ASTM B_机械/仪表_工程科技_专业资料。 Designation: B – 88 ( Reapproved ) Standard Test Method for Attribute Sampling. Purchase your copy of ASTM B – 88() as a PDF download or hard copy directly from the official BSI Shop. All BSI British Standards.
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ASTM B602 – 88(2016)
Historical Version s – view previous versions of standard. Through the selection of a sampling plan, the potential error is known and controlled.
This quantity may be a shipment from a supplier, articles that are ready for a subsequent manufacturing operation, or articles ready for shipment to a customer. Based on the results, a decision is made whether or not the lot conforms to the requirements.
The possibility exists that some of the uninspected articles are nonconforming. Therefore, basic to any sampling inspection plan is the willingness of the buyer to accept lots that contain some nonconforming articles. The number of nonconforming articles in accepted lots is controlled by the size of the sample and the criteria of acceptance that are placed on the sample.
Using the arithmetic mean of these values, the standard deviation of the process, and the factor k that is found in the Tables, a number is calculated see 9. If this number equals or exceeds the specified b62, the inspection lot conforms to the requirements. If it is less, the lot does not conform. If the standard deviation of the process is not known, the standard deviation of the sample is calculated and used.
There is always a risk that a random sample will not describe correctly the characteristics of the lot from which it is drawn, and that an unacceptable lot will be accepted or an acceptable lot will be rejected. The larger the b62, the smaller this risk but the larger the cost of inspection. Such lots will be accepted Note 1. If only a few articles in an inspection lot are nonconforming, the sample probably will indicate that the lot is acceptable; but there is a small probability that the sample will indicate that the lot is unacceptable.
The larger the proportion of nonconforming articles in an inspection lot, the more likely it will be that the sample will indicate that the lot is unacceptable. If every article in an inspection lot is nonconforming, a sample will always indicate that the lot is unacceptable. Throughout this method, it is assumed that no mistakes are made in sampling, measurement, and calculation. The AQL is the quality level that is considered to be acceptable.
The LQL is a quality level that is considered to be barely tolerable.
ASTM B – 88() Standard Test Method for Attribute Sampling of Metallic and Inorganic Coatings
A sampling plan is selected that has a high probability of accepting lots of AQL quality and of rejecting lots of LQL quality. An alternative is rectifying inspection in which rejected lots are screened and used.
They may be replaced with conforming articles.
When the incoming lots are of a good quality level, the average quality level of a series of lots will atm even better when the rejected lots are screened and resubmitted.
When incoming lots are of a poor quality level, the average quality of a series of accepted lots will again be good because many of the incoming lots will be rejected and upgraded. At intermediate quality levels of incoming lots, the average quality level of a series of accepted lots will again be improved, but it will not be improved as much as in either of the above cases; and there will be an intermediate quality level where the degree of improvement is the least.
It is the worst condition that can occur under rectifying inspection.
The tables give the AOQL for each plan. There is no AOQL for the plans used with destructive tests because destructive tests cannot be used to screen rejected lots.
The AOQLs atsm in the tables are strictly correct only when the sample is small with respect to the lot.
If this is not the case, the correct AOQL will be smaller than the tabulated value. The correct values are obtained by multiplying the tabulated values by the following equation: In plans of this type, several articles of product are drawn from a production lot.
A characteristic of the coating on the drawn articles is measured. The values obtained are used to estimate the number of articles in the lot that do not conform to a numerical limit, for example a b6002 thickness. The number is compared to a maximum allowable. It is also necessary that the variation of the characteristic from article to article in a production lot be normally distributed see Appendix X2.
Each article must be tested in the same way for example, coating thickness must b60 measured at the same location, see X2. If one or more of these conditions are not met, a variables plan cannot be used.
Instead, an attributes plan must be used. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. Referenced Documents purchase separately The documents listed below are referenced within the subject standard but are not provided as part of the standard.
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