One of the most exciting and impactful technological developments in the explosives and mining industry today are electronic detonators, or electronic dets.
What are detonators?
Detonators are what makes blasts go. Each blast hole contains at least one detonator. This detonator is comprised of a blasting cap, small charge, at one end which is placed at the bottom of the hole. A length of plastic tubing then runs up to the top of the hole where there is a connecting head of some sort which connects that hole to the rest of the blast.
In the past, blasters have relied on non-electric detonators which upon their release also revolutionized the industry. Non-electric detonators contain aluminum powder in the tubing which burns at a fast rate. After the holes are drilled and loaded, the blaster takes these connecting heads on the non-electric detonators and connects them in a specific sequence. This is commonly referred to as “tying in” the shot, in order to “time the shot out”, meaning connect the holes in a sequence that will allow the best results possible from the blast.
These non-electric detonators are still commonly used today, however they have limitations. Due to the fact that these detonators burn, the rate of fire is not adjustable, and the aluminum powder only burns at one speed. This can be adjusted by the manufacturer but once the blaster has the product on the job site, the choices by which he can tie in the blast are limited. But not anymore.
Enter the electronic detonator.
Similar in appearance to the non-electric detonators, both have the same characteristics: blasting cap, tubing, and a connecting head. However, the electronic detonators have some mind-blowing capabilities. Each electronic detonator contains a computer chip. This allows the cap to be programmed and checked, even after it has been lowered down into the bottom of a hole and that hole loaded with product. Once all the holes are loaded, each electronic det is connected to a common wire ran all along the blast. This wire is then plugged into an electronic blasting machine where the blaster can then take control.
Electronic detonators have two important features.
The first feature is feedback. With non-electric detonators, once the hole is loaded and the caps hooked together, there is no way of knowing whether the tubing has been accidentally severed or some other underground issue that would cause the non-electric det not to fire. With the electronic detonator this is no longer the case. Once the wire is connected to the blasters box, the system will do a self-check to confirm all blasting caps are communicating properly and ready to fire. This is a great advantage for the blaster because issues can be solved before they arise. If a cap is not communicating properly, the blaster can adjust their plan and attempt to prevent a misfire or other safety hazard.
The second important feature of electronic detonators are the ability to program virtually any time to any detonator down to the millisecond (ms) with incredible accuracy. Since the non-electric cap relies on a material burning, it has a deviation of + or – about 3 ms. This means over the course of 100 holes, the timing of the 100th hole could be off by 300 ms. Obviously this would be an extreme case but when you are dealing with hole to hole or row to row times of 17, 25, or 42 ms, this 3 ms deviation is a big factor. With electronic detonators this is no longer an issue. This means that all of the holes will detonate exactly when they were designed to detonate, allowing for blast design to be taken to a new level of preciseness.
This preciseness allows for us to apply signature hole timing, which is using software to design blast timing using data from previous blasts. This minimizes the effect of vibration waves on a specific location or structure (think noise cancelling headphones). There are many other advantages to electronic detonators we can cover in later posts.
Much like how other professions demand tools that allow them more and more precise control, electronic detonators allow us to take blast design to the next level, and beyond.