Over deze norm
NEN-ISO 16742 sets out the basic methods for sampling fine iron ore of nominal top size <1 mm that is mixed with water to form a slurry. At very high ratios of fine solids to water when the material assumes a soft plastic form (about 80% solids depending on the particle size distribution of the solids), the mixture is correctly termed a paste. Sampling of pastes is not covered in this International Standard. The procedures described in this International Standard apply to sampling of iron ore that is transported in moving streams as a slurry. These streams may fall freely or be confined in pipes, launders, chutes, spirals or similar channels. Sampling of slurries in pressurised pipes is not covered in this International Standard. The slurry stream can only be sampled satisfactorily at a transfer point prior to the pressurised pipe at the end of the pipe when the slurry is no longer under pressure. In addition, sampling of slurries in stationary situations, such as a settled or even a well-stirred slurry in a tank, holding vessel or dam, is not recommended and is not covered in this International Standard. This International Standard describes procedures that are designed to provide samples representative of the slurry solids and particle size distribution of the slurry under examination. After filtration of the slurry sample, damp samples of the contained solids in the slurry are available for drying (if required) and measurement of one or more characteristics in an unbiased manner and with a known degree of precision. The characteristics are measured by chemical analysis, physical testing or both. The sampling methods described are applicable to slurries that require inspection to verify compliance with product specifications, determination of the value of a characteristic as a basis for settlement between trading partners or estimation of a set of average characteristics and variances that describe a system or procedure. Provided flow rates are not too high, the reference method against which other sampling procedures are compared is one where the entire stream is diverted into a vessel for a specified time or volume interval, ensuring that all parts of the stream are diverted into the vessel for the same period of time. This method corresponds to the stopped-belt method described in ISO 3082. Reference increments shall be taken as close as possible to increments taken using the sampling procedure under evaluation.