Separation Distances for Ammonium Nitrate Blasting Intermediates

In Great Britain the HSE prescribe Separation Distances for ANBI  (UN3375). These distances are found in an Annex to a Guidance Document for those persons wishing to Manufacture or Store ANBI. The tables of separation for protected places on and off site are structured in such a way that any quantity exceeding 1 ton and not exceeding 10 tons attracts the same separation distances. I have a scenario where a site requires to store 10 tons of ANBI but is hampered by internal separation distances. If the scenario involved only conventional 1.1 explosives the matter would be resolved by placing 2 x 5 ton stores the requisite distance apart. The ANBI tables do not allow for this.

My question is: Can any member advise on a Technical Justification for reducing Separation Distances for ANBI or provide a documented precedent that would assist?

2 answers

  1. Answered by Professsor G C Sen

    Sorry, I have no experience on this field.

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  2. Answered by Malc Ingry

    The separation distances for >1 tonne up to =10tonnes of ANBI quoted in Appendix are
    Cat 1 0m
    Cat 2 83m
    Cat 3 208m
    Cat 4 355m
    Changing 1 x 10 tonne tank to 2 x 5 tonne tanks
    The 5 tonne tanks would count as separate if they were more than 10m apart. However, as you say, the 5 tonne is in the same band as 10 tonne so splitting it doesn’t gain you anything

    The 0m covered by cat 1 includes
    • protected places of Class A (as defined in Schedule 5 to ER2014);
    • protected places of Class B;
    • protected places of Class C which are capable of being closed to traffic, where appropriate, and which can be evacuated within 45 minutes of a fire starting on the ANBI site;
    • protected places of Class D used as industrial premises which are capable of being evacuated within 45 minutes of a fire starting on the ANBI site; and
    • isolated dwellings where arrangements are in place for their evacuation within 45 minutes of a fire starting on the ANBI site.
    The 83 m covered by cat 2 includes
    • protected places of Class C that are not capable of being closed to traffic, where appropriate, and which cannot be evacuated within 45 minutes of a fire starting on site; and
    • protected places of Class D other than:
    o those which are capable of being evacuated within 45 minutes; and
    o those which house a vulnerable population.

    The above are generally external distances

    For internal distances use para 125

    125 ANBI storage tanks and ammonium nitrate stores should be separated from other buildings or stocks of flammable materials on or off the site by either:
    • a fire-resisting barrier; or
    • a fire-break separation distance of 10 m.
    If you felt that’s too advantageous. Then the normal internal distances to ordinary buildings in the explosive regs are Class F. These distances are half of class D. So if you can evacuate the building in 45 minutes, it’s 0m (so 10m or a fire-resisting barrier), if you can’t evacuate in 45 mins it’s ½ x 83m = 42m . (note if more than 20 people in the building it becomes full class D distance, also if the people in the building aren’t directly involved with the bulk ANBI, the full class D distance would apply rather than the half distance)
    The distance from a magazine on site depends on the quantity of explosive in the magazine and whether it’s mounded, see table 2 of the guidance.
    Other dangerous goods.
    Separation from flammables in Para 125;
    Separation of ANBI from Ammonium nitrate Appendix 2 para 2 says the fire break distance of 10m
    Separation of ANBI from other bulk DG. Not so specific. In the explosive regs it’s Class D, so we could consider the 0m/83 m options depending on evacuation time, but I’d always have a minimum of 10m or a fire resistant barrier

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