Oooops forgot your question... My understanding is... Primary...

Oooops forgot your question... My understanding is... Primary screening - with crusher at height, can expect some larger ore (say 10-30+mm) to pass through. So may have a first screen relatively large sieve size (say 10mm, depends on ore properties) which collects and ejects to mini stckpile, which is then reloaded into the crusher for another pass. Secondary screening - just next screen finer size. DFS talk about P100 6.3 (100% passing a 6.3mm sieve size, is easily measurable for quality control, contract specification and payment, etc). So any ore larger than 6.3mm in size is captured and ejected for another pass through crusher. Tertiary screening - maybe smaller or finer ore size by decreasing screen size, again rejects resent to the crusher. OR can be more specific in obtaining ore size. The LFP feedstock desired size is 0.5mm. So two screens, say one 0.6mm and the other 0.5mm will enable ore captured on 0.6mm screen ejected back into the process line after the 0.5mm screen, any ore captured on 0.5mm screen ejected into the LFP process train, and finer ore through both stays in the process line. Screen sizes are arbitary based on ore characteristics, and surface area on how much throughput you want. Desirable to step down screen sizes gradually to avoid larger ore from blocking holes and overloading loosing throughput. Hope this is what you were after?