AS 1141.11.2:2019 pdf download.Methods for sampling and testing aggregates Method 11.2: Particle size distribution for vision sizing systems.
5 Source reference sample
5.1 Initial preparation
The initial selection and preparation of a source reference sample shall be as follows:
(a) Recover sample(s) from quarry stock piles in accordance with AS 1141.3.1. NOTE A sample should be taken for each product for analysis by the VSS.
(b) Wash the sample(s) to remove all dust and all particles finer than 1.18 mm.
(c) Oven dry the sample to a constant mass at a temperature between 105 °C and 110 °C.
(d) Reduce the sample to the mass specified in Table 1, using a sample splitter or other suitable device and taking care to maintain the representative nature of the sample.
5.2 Calibration
5.2.1 General
Calibration of source reference samples shall be undertaken following any maintenance procedure, requiring replacement or realignment of any component of the optical system, or any change or upgrade to the system software package or every six months, whichever occurs first. A record of the calibration factors and the reported sizing analyses for each source reference sample shall be maintained as evidence of system stability. The system software shall maintain a record of times and authorization of changes to the VSS calibration factors. The calibration factors are stored in the system software. Secure systems should be established to ensure that the calibration factors can only be accessed and changed by authorized personnel.
5.2.2 Method
The calibration of a source reference sample shall be conducted as follows:
(a) Sieve the reference sample in accordance with AS 1141.11.1.
(b) Measure the reference sample using the VSS in accordance with the manufacturer’s instructions, using at least five runs.
NOTE Additional runs may be required until the software develops calibration factors that return a calculated particle size distribution comparable to the AS 1141.11.1 analysis.
(c) Collect and store the reference sample, avoiding loss of sample or sample contamination.
6 Test portion
6.1 General
The minimum mass of the test portion taken shall be related to the nominal size of the aggregate in accordance with Table 1. For an in-plant VSS, the sampling device shall deliver a test portion mass to the hopper, which equals or exceeds the applicable mass as defined in Table 1. The test portion should be of such a mass as to provide a similar number of particles to those contained in the source reference sample.
6.2 Mixtures of coarse and fine aggregates
Mixtures of coarse and fine aggregates shall be processed without separation of the coarse and fine material.
6.3 Preparation
For in-plant systems, test portions may be analysed without further preparation.
NOTE 1 Test portions of aggregates with a free moisture content of < 3 % may be measured in-line. For higher moisture values, in-line drying by infrared or the like may be necessary.
NOTE 2 The VSS method maybe limited if moisture in the test portion causes agglomeration of particles passing through the imaging station. If this occurs, action should be taken to reduce the agglomeration of the sample.
6.4 Washing
Test portions are not required to be washed.
7 Procedure
The test procedure shall be as follows:
(a) Insert a representative increment into the hopper, either manually (laboratory unit) or automatically (in-plant installation).
(b) Set up the VSS from the operators control panel (OCP) following the procedures detailed in the operational manual supplied by the manufacturer. Attention shall be paid to pre-set alarms and alerts, such as increment size and desired specification limits provided in the OCP screen, based upon the product characteristics and predetermined criteria. The system shall provide error messages, such as insufficient volume of material measured (sample too small) to alert the user to situations that would compromise the VSS calculations and subsequent results.
(c) When the test portion has been measured, make the data (raw and processed) available on the OCP screen and transfer to a data storage device, if required, where it can be subsequently distributed, reviewed and/or analysed.AS 1141.11.2 pdf download.