IS sieve (IS sieve)

An IS sieve is a test sieve manufactured to the dimensions and mesh specifications laid down by the Bureau of Indian Standards (BIS) in the IS 460 series. Test sieves are designated by their aperture size (e.g. the 850-micron IS sieve), and using standardised sieves ensures that particle-size measurements are consistent and comparable across laboratories and across the country.

In the effluent discharge standards, the IS sieve appears in a specific requirement for suspended solids discharged to inland surface water: in addition to the 100 mg/L mass limit, the standard requires that the particles should pass the 850-micron IS sieve — i.e. there should be no coarse particles larger than 850 microns. This guards against discharging gritty, coarse solids that would settle and accumulate in the receiving water even if the total mass is within limits.

For recyclers, the IS sieve is relevant in two ways. First, as part of the effluent suspended-solids compliance — particularly for plastic washing and other solids-laden streams, the treated effluent must not carry coarse particles above 850 microns. Second, and more broadly, IS sieves are standard tools for particle-size analysis throughout recycling operations: grading shredded and granulated material, checking the size distribution of plastic flakes, granules, char, granulated rubber, and any size-classified product, and verifying screen and shredder performance.

The practical relevance is that the IS sieve is the standardised reference for any particle-size specification a recycler deals with — both the regulatory 850-micron effluent requirement and the routine product-grading and quality-control sieving of recycled materials. Specifying sizes by IS sieve designation (rather than approximate descriptions) ensures consistency with customers, labs and regulators. For a recycler producing size-graded flake, granule or char products, IS-sieve-based grading is the standard language of particle-size quality.