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SOP No. 33
Standard Operating Procedure for
Calibration of Weight Carts
 
  1. Introduction
    1. This Standard Operation Procedure (SOP) describes the procedure to be followed for the calibration of weight carts used to test livestock and vehicle scales.
    2. Prerequisites
      1. Facility. Verify that the laboratory facilities meet the following minimum conditions to meet the expected uncertainty possible with this procedure.

        Table 1. Environmental Conditions
        Echelon
        Temperature
        Relative Humidity (percent)
        III
        18 ° C to 25 ° C, maximum change 1.0 ° C/h
        40 to 60 ± 10

      2. Balance/scale. Verify that the balance, scale, or load cell is in good operating condition with sufficiently small process standard deviation as verified by a valid control chart or preliminary experiments to ascertain its performance quality.
        1. If a scale or load cell is used for the calibration that is not a permanent piece of equipment in the calibration laboratory, appropriate verification and repeatability statistics must be obtained prior to a calibration to determine suitability and acceptability for calibration. Records must be maintained of this verification. Minimum verification includes an increasing and decreasing load test to at least the capacity of the weight cart, a shift test, a sensitivity test at the test load, and evaluation of the repeatability based on a minimum of 7 repeated weighings (following the same SOP to be used to test the weight cart).
        2. The expanded uncertainty (k=2) must be less than one-third of the applicable tolerance and should be evaluated prior to calibration.
      3. Standards. Ensure the availability of suitable working standards or recently calibrated (and unused) field standards in quantities up to the capacity of the weight cart(s) that will be calibrated. All standards must have known conventional mass values.
      4. Staff. Verify that the operator is experienced in precision weighing techniques and has had specific training in SOP 8, SOP 4, SOP 29, and GMP 10. Safety precaution: weight carts should always be calibrated with at least two people present.


Weight Carts Home | SOP 33 Home | Section 1 | Section 2 | Section 3 & 4 | Section 5 | Section 6 & 7 | Section 8 | Section 9 & 10 |
Appendix A | Inspection Checklist | Appendix B



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Date created: May 21, 2002
Last updated: October 1, 2002

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