GB/T 25709-2010Autogenous and semi-autogenous mills (English PDF)
自磨机和半自磨机
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Issued by
General Administration of Quality Supervision, Inspection and Quarantine; Standardization Administration of the PRC
Level / Type
National · Recommended
Issue date
December 23, 2010
Implementation date
July 1, 2011
Scope
GB/T 25709-2010 is the English-translated version of 自磨机和半自磨机.
China's national standard for autogenous and semi-autogenous grinding mills. It specifies the types and basic parameters, the technical requirements, the test methods, the inspection rules and the marking, packaging, transport and storage of AG and SAG mills.
An autogenous mill grinds the ore with itself. Instead of a charge of steel balls, the mill is fed with run-of-mine rock and the large lumps act as the grinding media, breaking the smaller ones as the shell rotates; a semi-autogenous mill adds a modest ball charge to supplement them where the ore does not provide enough competent lumps.
The attraction is what it removes from the flowsheet.
A conventional circuit crushes in stages - primary, secondary, tertiary - before grinding, and each stage is a building full of crushers, screens and conveyors; an AG or SAG mill takes primary crusher product directly and replaces all of that, which is why these mills became the standard for large new concentrators.
They are also the largest rotating machines in the industry, over ten metres in diameter, drawing many megawatts through gearless or girth gear drives.
The difficulty is that the grinding media are the feed, so the mill's performance depends on the ore: a change in the hardness or the size distribution of what is mined changes the throughput directly, and a mill can overload with material it cannot break or run empty of media if the ore is too soft.
That is why the load, the power draw and the charge are monitored continuously and why the standard specifies the mill in terms of the shell, liners, discharge grates, drive and bearings as a system, together with the parameters that let a mill be sized against an ore. Issued on 23 December 2010 and in force since 1 July 2011.
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Document preview — GB/T 25709-2010
National Standard of the People's Republic of China
- ICS
- 73.120
- Classification
- D 94
Issued by: General Administration of Quality Supervision, Inspection and Quarantine; Standardization Administration of the PRC
Contents
- 1 Scope
- 2 Normative references
- 3 Terms and definitions
- 4 Types and basic parameters
- 5 Technical requirements
- 6 Test methods
- 7 Inspection rules
- 8 Marking, packaging, transport and storage
1 Scope
This standard specifies the types and basic parameters, the technical requirements, the test methods, the inspection rules and the marking, packaging, transport and storage of autogenous and semi-autogenous mills.
The ore grinds itself
Instead of steel balls, the mill is fed run-of-mine rock and the large lumps act as the grinding media, breaking the smaller ones as the shell turns.
A semi-autogenous mill adds a modest ball charge where the ore does not supply enough competent lumps.
And it deletes three buildings
A conventional circuit crushes in primary, secondary and tertiary stages before grinding, each a building of crushers, screens and conveyors.
An AG or SAG mill takes primary crusher product directly and replaces all of it - which is why it became the standard for large new concentrators.
The largest rotating machines in the industry
Over ten metres in diameter, drawing many megawatts through gearless or girth gear drives.
But the media are the feed
So performance depends on the ore: a change in hardness or size distribution changes throughput directly.
The mill can overload with material it cannot break, or run short of media if the ore is too soft - which is why load, power draw and charge are monitored continuously rather than set once.
......
This preview omits tables, figures, formulas and parts of the technical clauses. The complete document — 15 pages — is available in the English PDF.
Referenced standards
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