Safety Jack

A very contentious issue over the years has been the balance between safety and efficiency. Therefore I feel this is as good a forum for the issue as any.

First I’d like to make an analogy. A gun barrel, particularly a shotgun, has round projectiles in it. I know, many years ago when proper shot was not always available, all sorts of projectiles were loaded in to gun barrels to fend off the enemy, or bring down whatever quarry was intended. The main reason for the projectiles being round was so that there was no (or less) chance of the projectiles binding on each other and impeding the opportunity of the shot getting out of the barrel or getting bound up with each other.

OK Jack, how in heavens name does this passion for shotgun sport have anything in common with your job which is to contain the energy in a borehole in order to give you a good clean sharp signal when you fire 2 kg at 18 m?

A lot of money is expended in getting that charge to depth in some areas and frequently heliportable operations make the costs just that much greater.

A great deal of time and expertise has gone into the art of breaking rock. We as explorationists don’t want to break rock, just get good energy return. However the similarity in both ventures is very close. The miner and the quarry man or contractor want to move overburden in the most efficient manner. We want to contain the energy in as small a point as possible with the least amount of energy loss.

Over the years many studies amounting to untold thousands of dollars have been conducted by just as many companies to come up with a very simple answer. I subscribe to the Journal of Explosives Engineers published by the International Society of Explosives Engineering to which I have belonged for several years. During this time, many papers have been written on the correct bore-hole size to stemming size, type and collar (height of stemming). A recent issue of the Journal of Explosives Engineering introduced a new Questions & Answers column edited by Stan Lippincott, a forty year man in the explosives industry. The introduction of this column by Paul Kunze, Chairman of the International SEE Technical Committee, caught my eye and was the briefest description of a point I have been trying to make to some people in the seismic industry for years.

I reprint the Question & Answer in full for your benefit with my comments. Q “There are several different kinds of material that have been used for stemming blastholes: dry sand, damp sand, pea gravel, drill cuttings, crushed rock, clay, etc. Assuming you have these choices, which is the most effective?”

A One company’s studies ranked stemming materials in this order, from the least efficient to the most efficient: air, water, wet drill cuttings, wet sand, paper cartridge of rock dust, clay dummies, wet crushed stone, dry drill cuttings, dry sand, dry crusher run stone, dry screened stone. We believe 1/4" - 3/8" clean dry crushed stone is best. On the subject of stemming, this company conducted a stemming test using schedule 40 steel pipe. Three sections of pipe were loaded half full with explosives. One was not stemmed, one was half stemmed and the third was fully stemmed. All three were shot and the difference was dramatic. The unstemmed pipe was partially ruptured in the area holding the explosives, the half stemmed pipe was split open to a greater degree, but the fully stemmed pipe was peeled back like a banana. Just another good argument for using the right stemming, and enough of it, to contain the explosive gasses as much as possible while not adversely affecting top breakage. The points I would like those in charge of making these decisions to make note of are:

1. Use 1/4" - 3/8" crushed rock, never pit run or round stone.

2. Use adequate stemming so that none of it has an opportunity to move up the bore-hole.

I reprint this portion with the permission of Joyce Linson, managing editor of the Journal of Explosives Engineers and thank her and her contributors for the information provided.

Even when shooting a well stemmed bore-hole, the seismic shooter should always maintain a minimum of 30 m from the hole, (as should his helper); should always keep trees, a vehicle or other obstacle between him and the bore-hole; and of course always have, and use, proper eye, ear and head protection.

I would certainly be remiss if I did not again take issue with both those that choose to take pictures of workers in seismic and those that choose to print the pictures to please assure that seismic workers wherever they may be in the world are all entitled to the same basic safety items we take for granted, such as a hard hat. Even the ones that are being worn look as though they were just issued and sure are lovely and clean. (Clean mud in Bolivia?)

’Til next time, at work or leisure - Live Safely!

Editors’ Note

Our apologies to Jack and other safety conscious readers relative to the missing hard hat on the Bolivia cover photo. Unfortunately, that is the reality of life in some places. Hopefully Jack’s message will help to influence the industry to change its safety awareness internationally as well as domestically.

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