A great many items we purchase have what is termed a "shelf life," more precisely described as the time that a commodity can be stored between the time of production or growth and the time of use or consumption. Some products improve with age (whiskey), but most deteriorate (fruits and vegetables).
It is necessary when you purchase a product to read the manufacturer's information or have good knowledge of the product from experience.
This same caution to the buyer or user applies to a consumer of explosives. All explosives produced in North America have a production date on their containers and in addition, usually give the shift and possibly the machine on which the product was produced.
The specification sheet on all explosives gives an indication of the sleep time of the product, but the shelf life is usually not advertised. Storage conditions can have a very drastic effect on shelf life and this is usually affected greatly by adverse temperature and humidity.
With the knowledge of shelf life and sleep time, the user can usually determine his options of types of explosives suitable for his requirements. In most cases, all of today's popular packaged products will fill the bill for today's seismic requirements without the necessity of requesting special formulations or packaging.
Just what are we asking of our seismic explosives today? To list them as I see it, we require:
- good rigid cartridge to withstand loading in rough holes
- cap well or recess for easy priming without the necessity of using a powder punch
- cartridge design with ease of coupling and attachment of drive point
- cap sensitive formulation without the need of a cap sensitive booster (primer)
- reasonable sleep time for normal depths
- velocity acceptable to the geophysicist
For seismic detonators we require:
- substantial metal shell with a plug waterproof to 30 metres
- flexible leg-wires to match our winter temperatures
- positive shunt system
- excellent resistance to stray electrical, static, radio frequency and other electrical sources
- traditional firing time characteristics
While these are not the only characteristics you may see written about various manufacturers' products, they are pretty well what we have come to expect over the years from local suppliers.
Maybe more the point is what would I like to see as specifications for seismic explosives.
My ideal seismic explosive would be:
- a cap sensitive composition with a shelf life of 2-5 years and sleep time of 6 months in water depths to 30 metres, that would de-sensitize positively in 612 months maximum
- a substantial plastic cartridge with a preformed capwell, easily couplable and receptive to drive points and wings.
- available in all popular less than 2 kg sizes
- a water sensitive section near the detonator that would allow water penetration in the 6-12 month sleep time.
My ideal seismic detonator would be as described earlier but with the addition of:
- an easily replaceable shunt.
- a shell that would allow water entry to de-sensitize the detonator in 6-12 months.
Most seismic is shot in under six months after drilling and loading. If it is not going to be shot in 6 months, then it is planned that way and special permission must be obtained. At the same time, plans can be made to use long sleep time products such as we regularly use today.
Why do I want the ideal explosives and detonators as described? For SAFETY reasons!
It is impossible to load the hundreds of thousands of seismic charges that our industry uses each year without having some that do not shoot for one reason or another.
Depending on where the work was done, there are good possibilities that future earth work for pipelines, road building or mining could uncover unexploded charges. If this happens, there is also the possibility of an incident causing bodily injury or death.
If a fatality did occur, it would be relatively easy to determine whose program the explosive was placed for. Legal liability in a case like this could probably be shared by everyone even remotely associated with the explosive, from manufacturer through to the client eventually paying for the program.
Development and use of the ideal seismic explosive and detonator as I have described would go a long way towards reducing or limiting the chance of liability.
This wish list of mine would, I hope, be shared by all of you reading this article. I would welcome your comments directly, by phoning me at 250-4627, by fax at 250-6948, or by letter to the Recorder.
In a future issue I will prepare a "wish list" for you the reader to fill out. You can tell me and I will certainly pass on to the explosive manufacturers what we as the industry's conscience, consider the safest, most practical product for our work.
'Til next time, at work or play LIVE SAFELY!