Wincoal A
Circulation
- Coal Mine Owners
- Coal Mine Managers
- Coal Mine Unions
- Inspectors
- Exchem and Orica
Safety Circular - Wincoal A
Dear Sir
Background
Recently a batch of Wincoal A Group P5 permitted mining explosive, submitted by Exchem for its two-yearly check test at the Health and Safety Laboratory's Buxton Testing Gallery, failed to meet the incendivity requirements set out in the HSE's Testing Memorandum TM2. Some of the 26 test shots in the first series of Group P5 tests caused flammable gas mixtures to ignite, so it failed to meet the test criteria of zero failures. Exchem submitted a second sample from a different batch for retesting and that also failed to meet the incendivity requirements, again causing some ignitions. As a consequence of this Exchem decided to withdraw all supplies of Wincoal A from the market pending further testing. Because of this HSE considers it unnecessary to withdraw the current approval for Wincoal A as a Group P5 permitted explosive.
There is no other Group P5 explosive approved, and no ready supply of an approved Group P3 explosive (such as Aquespex). This is already causing serious difficulties for mines that rely on firing explosives in coal.
Whilst the check tests proved that this batch of Wincoal A did not meet the incendivity requirements for a Group P5 explosive, they indicated that it would have passed by a comfortable margin the less stringent tests for a Group P3 explosive. This in turn indicates that it is no less safe to use than an approved Group 3 explosive, provided it is used in circumstances applicable to that group. It would however take several weeks for the Health and Safety Executive to approve this batch of Wincoal A as a P3 explosive, exacerbating the difficulties that mines are already experiencing.
Because the Mines Inspectorate considers that it is no less safe to use explosives from the failed batch of Wincoal A Group P5 explosive in circumstances applicable to Group P3 explosives, we have decided to issue a temporary exemption from certain of the provisions of Regulation 5(1) of The Coal and Other Safety Lamp Mines (Explosives) Regulations 1993.
The Exemption
The exemption has the effect of permitting the use of Wincoal A as a non-approved Group P3 explosive.
The main practical issues centre around using as a Group P3 explosive an explosive wrapped and packaged as a Group P5 explosive and the exemption requires managers to take further steps to control the use of such explosives and to ensure that it is used as a P3.
The exemption requires managers to make sure that such explosives are stored separately from other explosives, to ensure that the check sheet placed in each container of explosives includes an instruction to shotfirers that it is only to be used in circumstances applicable to Group P3 permitted explosives, and to ensure that shotfirers receive sufficient training to make them aware that use of such explosives is restricted to those conditions applicable to Group P3 permitted explosives.
The exemption is time limited as the Inspectorate expects the manufacturing and supply difficulties to have been overcome in that time.
Other Matters
Although not included in the exemption, managers are reminded of a further requirement of Regulation 9(2)(a) for those who issue containers of explosives to ensure that explosives are not mixed.
As, in places other than cross-measures drifts, Group P3 explosives can only be used with instantaneous detonators, managers may also consider imposing additional controls on the issue of detonators for use with the non-approved explosive.
The Mines Inspectorate will carry out sample compliance checks during the exemption period.
Yours faithfully
S P WingHM Principal District Inspector of Mines