Alert no. 112 | 13 June 2023 | Version

Formation of Tetra-Amine Copper Nitrate (TACN) on copper fittings located on Mobile Processing Unit (MPU)

What happened?

During a routine inspection by the Explosives Inspectorate the formation of Tetra-Amine Copper Nitrate (TACN) was identified on a brass padlock and copper fittings located on an explosive Mobile Processing Unit (MPU).

How did it happen?

Lack of knowledge and awareness of the potential for the formation of TACN on copper fittings exposed to ammonium nitrate.

Key issues

TACN is an impact sensitive explosive compound formed when reactive metals such as zinc, copper or its alloys (brass) are exposed to an aqueous solution of ammonium nitrate.

The impact required to initiate TACN is reported to be equivalent to dropping a 2 kg weight from a height of approximately 20 cm.

Persons working on equipment contaminated with TACN can be exposed to the potential for a small, localised explosion caused by impact or heat to the TACN affected areas.

Recommendations

Operators who store, transport, use and manufacture ammonium nitrate should:

• replace reactive metal fittings on MPU with non-reactive materials wherever possible.
• replace all reactive metals in ammonium nitrate and emulsion storage and handling facilities with non-reactive materials (e.g., stainless steel, aluminium, or plastic where climatically suitable).
• ensure engineering standards include the above recommendations.
• review workshop procedures to ensure that they highlight the hazards associated with the use of reactive metals on vehicles and storage areas exposed to ammonium nitrate.
• train employees including maintenance workers to identify TACN.
• refer to explosive’s technical advice on cleaning methods to remove possible TACN compound.
• never use impact or hot-work tools on an item known or suspected to contain TACN.
• regularly wash down areas exposed to ammonium nitrate spillages or dust.

References and further information

• Resources Safety & Health Queensland -Safety Alert #3 – Decontamination of explosives equipment prior to maintenance
• The Australian Industry and Safety Group (AEISG) code of practice for mobile processing units (MPU)
• Department of Industry NSW - Safety Bulletin -Exposure to copper or copper alloys to ammonium nitrate – TACN formation