Overview
ISO 12742:2020 - "Copper, lead and zinc sulfide concentrates - Determination of transportable moisture limits - Flow-table method" defines a laboratory procedure to determine the Transportable Moisture Limit (TML) of sulfide concentrates that can liquefy during transport. The standard covers copper, lead and zinc sulfide concentrates within specific metal mass-fraction ranges and for TML values between 3 % and 28 % (mass fraction). It updates earlier editions and aligns TML determination with sampling, moisture measurement and testing best practice.
Key topics and technical requirements
- Scope and applicability
- Applies to concentrates containing: lead 10–80 %, zinc 10–65 %, copper 10–55 % (mass fractions).
- Applicable TML range: 3 % to 28 %.
- Principle
- Moisture is adjusted by adding water, the sample is formed into a cone in a mould, placed on a flow table, and subjected to repeated drops. The flow moisture point is the moisture content at which the sample shows plastic deformation (flow).
- TML = 90 % of the flow moisture point.
- Apparatus and environment
- Requires a specified flow table and frame, mould, tamper (30 mm tamper head specified), calibrated balances (sensitivity related to sample mass), mixing bowl, measuring cylinder/burette, drying oven (105 °C ± 5 °C), and airtight containers.
- Laboratory conditions must minimize temperature, humidity and airflow changes to prevent moisture gain/loss.
- Sampling and sample preparation
- Laboratory sample minimum mass: 12 kg (taken per ISO 12743 sampling procedures).
- Nine test portions prepared (including a ≥2 kg portion for moisture-as-received).
- Partial drying procedures are included if a received sample exceeds the TML.
- Test procedures and validation
- Bracket method and graphical method (for validation) are described to identify the flow moisture point.
- Moisture determination follows ISO 10251 guidance for drying/mass loss on drying.
- Safety
- Warning that hazardous materials and equipment may be involved; users must follow appropriate health and safety and regulatory requirements.
Practical applications and users
- Ensures safe maritime and land transport of sulfide concentrates by assessing liquefaction risk.
- Primary users:
- Mining companies and concentrators (quality control and cargo certification)
- Accredited testing laboratories and metallurgical laboratories
- Ports, ship operators and freight forwarders (cargo acceptance and stowage)
- Regulatory bodies and compliance auditors referencing IMSBC Code requirements
- Typical uses: periodic TML updates (commonly every six months), pre-shipment testing, incident investigation and transport risk mitigation.
Related standards and references
- ISO 12743 - Sampling procedures for metal and moisture content (referenced)
- ISO 10251 - Determination of mass loss on drying for concentrates (referenced)
- IMSBC Code (International Maritime Organization) - related guidance for safe carriage of bulk sulfide concentrates
Keywords: ISO 12742:2020, transportable moisture limit, TML, flow-table method, copper concentrates, lead concentrates, zinc concentrates, sulfide concentrates, moisture determination, cargo liquefaction, IMSBC Code.