The Ideal Seismic Explosive Possible or Not?
It was interesting receiving the information from the query in the March issue of the Recorder. I particularly enjoyed those that I spoke to personally. There was a lot of thought and background that went into the statements made by some respondents.
As a reminder, here are the questions we posed:
- What do you consider the ideal velocity in metres per second?
- What velocity range would you accept as the highest m.p.s. and the lowest m.p.s.?
- What is the ideal cartridge weight in kilograms?
- What multiples of cartridge weight would you regularly use?
- What is the smallest cartridge weight you would normally use in single hole work?
- What do you consider an ideal outside diameter of a cartridge in millimetres?
- Do you have a preference of cartridge composition, plastic, paper, other material?
- Do you prefer: (a) a cap-booster priming system? (b) a cap sensitive formulation?
- Do you agree with pre-formed cap wells?
- Do you agree with the concept of limited sensitivity life of loaded explosives?
- If no to the above, do you agree that liability for subsequential damage or injury due to digging into an unexploded charge may be shared by all associated parties?
- If designing a limited sensitivity sleep time explosive, what would you consider as a (a) minimum life sensitivity? (b) maximum life sensitivity?
- Cutting of explosive cartridges to make smaller charges is not only hazardous but actually in contravention of existing legislation. Do you believe the saving in cost is worth the possible risk of detonation when being cut?
- Shallow patterns with very light charges have greater potential for future contact with unexploded charges than deeper charges. (a) Would you recommend a shorter detonator/cartridge sleeptime for this type of use? (b) What length of time - maximum, minimum?
- Did the article by R. Goodhart on pole shooting give you more confidence in it as a viable seismic source?
- Would you be inclined to use the pole system more than in the past?
- Do you have any other recommendations or requests of the explosives manufacturers?
Let's look at the averaged results and I'll have some comments to add.
- The ideal velocity average is 7170 metres per second, higher than I would have expected. Many people were in favour of the velocity of pentolite.
- Velocity range acceptable turned out to be a low of 5370 m.p.s. to a high of 6870 m.p.s. Strange that the high did not agree with the ideal.
- Ideal cartridge weight averaged 1.3 kg which actually was made up of 66% 1 kg and 33% 2 kg.
- Half of the respondents would usually only use single cartridge charges and the other half two cartridge charges. Some respondents made specific note that these multiples vary greatly with heliportable work.
- The smallest cartridge weight usually used averages 0.9 kg, but the smallest stated size was 150 gr. I don't think this question gave us a usable result.
- 90% favoured a 50 mm cartridge diameter and 10% favoured a 60 mm diameter.
- 87.5% favoured plastic cartridges and 12.5% favoured paper.
- All respondents favoured a cap sensitive formulation over a combination capbooster formulation.
- Everyone agrees with pre-formed capwells.
- Everyone agreed with the concept of limited life sensitivity of loaded explosives.
- In keeping with the answer to the above, all agreed on shared liability for damages which may occur upon digging into unexploded charges.
- The average minimum life sensitivity for loaded explosives was 3.3 months with a maximum life of 9.3 months.
- Nobody believed that explosive cartridges should be cut in the field. The response to this and question 9 regarding preformed cap-wells does not bode well for the manufacturers of brass accessory powder punches and powder knives. I personally have never been in favour of cutting explosives in the field. This unanimous response pleases me greatly.
- Shallow patterns with small charges have greater potential for future contact with unexploded charges and 87.5% of the respondents recommended a shorter sleep time for these charges. The recommended minimum was 2.4 months and maximum 5.3 months (less than the averages for conventional depth charges).
- 20% of those who read Goodhart's article on pole shooting had more confidence in the system and 80% did not.
- As with the above, the same percentages apply, 80% would not use the pole system of seismic source.
- Suggested improvements for the Explosive Manufacturers to consider:
- Make a positive shunting system that is not easily removable but is able to be reshunted easily,
- design a cartridge to protect leg wires,
- design a cartridge to accept detonating cord without the need to punch the cartridge,
- good cap-well design in mid cartridge,
- universal cartridge design to eliminate confusion or to correct use by drillers, give better instruction to drillers and blasters,
- design a detonator not susceptible to initiation by static electricity,
- explosive industry to be "honest", advise the seismic industry of problems they are having that we may encounter and be aware of,
- bright high visibility packaging,
- the ideal detonator that will not have leg wire but be detonated remotely.
The answers to question 17 were very good and deserve some consideration. My comments are:
- This type of shunting system is in limited use, to my knowledge. I have heard of the product being introduced to the field but the drillers did not know how to use the system. The re-shunting feature was not described to the driller and the drillers either threw it away and twisted the wires or left it in the insulation and twisted the wires also. Neither way was of any help to the shooter, as the design was intended.
- Some cartridges have leg-wire protection built into the design, but the drillers must be trained on their correct use.
- As with the leg-wire design, some cartridges will accept detonating cord quite well, but training must go along with a good design.
- I'm not aware of a cap-well being built into a cartridge at a mid-point any more. I designed one that was in use during the 1970's, but I don't think that was carried on. The person suggesting this modification was concerned that detonators placed at the extreme ends of the cartridge were at risk of being damaged by leg wires being broken, or to the extreme of undue pressure in loading causing a detonation due to impact, which is a very likely situation.
- I've never before heard of a universal cartridge design and I'm not sure it could ever happen. We're all told by each manufacturer that they have the best "mouse trap". It could happen I suppose, if the maker of the best "mouse trap" made it available to the other manufacturers, for a suitable fee of course.
- Manufacturers now claim their detonators are "static proof".
- More than one person is concerned about the "honesty" of the manufacturers/distributors. It would be good if they were up-front and said, "We're having a problem and some product may have slipped by our QC - Please look out for a mis-shapen whatsit on our gizmo" or, "Our packager lost a finger in a machine malfunction, and until he learns another way to count to ten, we may have shortages in your product count". It's amazing that with the type of packaging and generally low quantities of units that we still have overages and shortages in cartridges and detonators.
- Several people requested bright, high visibility cartridges, cartons, and legwires. When we have shortages, a lot of hours may be spent looking for a white detonator carton in the winter with snow falling. Some manufacturers still use a "camouflage brown" color of paper on their economy line paper cartridges. Then there is the other manufacturer who makes the same product with a readily visible yellow. I realize that everyone wants a product that is "distinctively ours". I think it's time that we include with our designs a product that is best for the circumstance, not just different.
- The surprise suggestion I've saved for last!
A wireless detonator.
Oh it will never work!
Remember the wireless radio (What's that!)
I don't think its so far fetched. Think of all the benefits from not having leg wires.
- stocking one size only
- far less bulk, very small magazines needed
- very easy priming procedures
- no more broken lead wires - no misfires.
I discussed the wireless detonator with the person who suggested it and he thought it was a good idea but hardly attainable. I hadn't had any time to think about it myself but defended the industry by saying that the best thing is to give them a tough job to do. They usually can. There's an enormous amount of talent in their R&D departments.
I'd put my money on a "remote wireless seismic detonator" being available by 1997 if our explosives manufacturers put their minds to it soon.
The next step in pursuing this topic will be to advise the Safety Committee of the C.A.G.C. of the findings. This committee will discuss the topic, hopefully come to unanimity on the Ideal Seismic Explosive, present it to the C.A.G.C. membership for acceptance and approval, then forward it to the explosive manufacturers for action.
We won't have results overnight, but let's be optimistic about obtaining improvement.
'Til next time, at work or play, please have a safe and enjoyable summer and LIVE SAFELY!