Blasting Through the Ages: The evolution of initiation systems

In previous articles of this series, we examined how drilling boreholes advanced from the early 1600s to modern day and how man created and reinvented explosives throughout history.

These great feats, however, would be meaningless without a safe, reliable method to detonate the explosives that break rock. In this article, we’ll briefly step through time and observe how miners of the past initiated blasts, as well as how initiation systems became safer and more reliable.

Looking back

The methods utilized for blasting with black powder in the 1600s are not well known, and few documents of the day readily address how explosives were initiated.

Still, those writing about blasting in the 1800s did recount the “old method” of initiating blasts. The old method involved filling either straw or a feather’s quill with black powder to prepare the initiation system. The main charge of black powder was then loaded into the borehole, and a pricker – a long, slender and typically metal rod – was inserted into the explosive charge.

The top of the borehole would then be filled with clay and pressed or tamped. After the entire hole was filled, the pricker would be gently removed. This would leave a hole through the tamping (stemming) zone. The straw initiator would then be pushed through the hole until it came in contact with the main charge with one tube in each borehole. The blaster would then light the tubes and get to cover in time for the blast to fire.

It’s easy to see how dangerous this process was and how even a moment of hesitation in lighting a hole would lead to either multiple holes not being lit, or the blaster still being in the area when the first holes detonated. One of the truly inventive parts of this system was that blasters knew how long it would take the black powder to burn in the different configurations, so they could crudely apply some timing between rows of holes using this system.

This entire system changed when William Bickford invented the safety fuse in 1831. This was not only safer, but easier to use and gave blasters more flexibility in timing the blast.

The safety fuse would be in direct contact with the black powder and cause it to ignite. The fuse was prepackaged with set burn rates, allowing for the calculation of the burn time based on the length.

In order to fire a blast, blasters would allow some fuse to hang out of each borehole. They would then tie strands together and light multiple groups of fuse at a time.

As early as 1833, drilling and blasting companies produced memos discussing the safety fuse and companywide adoption, along with the drastic reduction in misfires and blaster injuries and fatalities. While this was a new invention, the technology relied on the previous old method of filling a tube with powder that burned into the main charge, causing the main charge to catch fire.

Dynamite would not reliably detonate with just a safety fuse burning into it. Therefore, after dynamite was introduced, a new system of initiation was required to reliably detonate the mixture.

Key developments

The need, in turn, led Alfred Nobel to the invention of the blasting cap in 1863. This detonator used a small charge of mercury fulminate in a metal container, which would be placed into the dynamite. The cap then used the safety fuse, which was crimped or pressed on, at various lengths that blasters used to give it timing. The system produced a safe and reliable means of detonating dynamite, and the blasting cap took over the industry rapidly.

Benjamin Franklin invented the first electric blasting cap in 1750. He relied on two wires that were in contact with a small charge of black powder. When electricity was sent through the wires, they would cause the black powder to fire. This was not only the first recorded use of electricity to cause a black powder to fire, but also the first rudimentary blasting cap.

The world saw that explosives could be detonated with electricity, but it did not have the means to apply this in the field. That is, at least, until the latter part of the 1800s, when electric blasting machines were produced.

Many inventors from around the world claimed credit for the invention of electric blasting machines, but the first patent that is widely known is that of Henry Julius Smith – with the electric blasting cap in 1868, as well as the electric blasting machine in 1878.

This method of electric firing would go on to make vast improvements in reliability, safety and timing practices through the years. It was the dominant form of initiation around the world well into the 1970s.

In the 1960s, Per Anders Person and his group began looking into a new method of initiation: the nonelectric system. This was inherently different than the electrical system, utilizing hollow tubes that were filled with small amounts of HMX and aluminum – typically at a load of one-tenth of a grain per foot.

This method would allow a small dust explosion to travel through the tube and ignite the delay element of the blasting cap. This system is the most widely used in the world today and is typically called “nonel.”

Following the development of nonel tubing, the 1980s saw a tremendous amount of work on electronic caps, which utilize a computer chip and typically a capacitor system to fire. This allows for communication of a computer with the cap to ensure the wire is not damaged, reducing the cap scatter associated with pyrotechnic delays and increasing the flexibility of the blast timing.

Significant advancements in the systems took place in both electric and nonelectric initiation of the electronic blasting cap. The systems are employed around the world today.

Looking to the future

The future of explosive initiation will be filled with exciting innovations as engineers and scientists begin to unlock new levels of cap accuracy and flexibility.

As new products are developed and innovation takes place, expensive initiation systems will be reduced in pricing. This will lead to a widespread adoption of the electronic initiation system.

Today, groups are experimenting with wireless initiation systems using signals sent through the rock mass to initiate areas and keep blasters safe. In the distant future, innovations in initiation systems will advance to full wireless initiation to allow for autonomous drilling and loading of shots – with blasters controlling drill and load fleets from office spaces.

This will improve site efficiency and the cost of mining, allow for mining of orebodies that are not currently accessible to man, and increase the safety of operations.

Initiation system innovations will likely be the most important step for future autonomous blasting. Without simple-to-apply, wireless initiation systems, robotic loading systems would be extremely complex.

With these innovations and the removal of hooking up nonel or electronic tubing, simplified machines could load and prime holes for blasters without blasters having to be on the bench.

Anthony J. Konya is the vice president at Precision Blasting Services, consulting around the world in rock blasting and vibration from blasting. He is also the founder and CEO of Academy Blasting, an explosive engineering education company, and the host of AcademyBlasting.TV podcast.

---

About the Blasting Through the Ages series

The Blasting Through the Ages series is an initiative by Pit & Quarry and Academy Blasting to tell the story of the blasting world. The series will include four articles spanning four issues of the magazine, including:
Part 1. A Brief History of Drilling
Part 2. Explosive Advancement Through the Ages
Part 3. The Evolution of Initiation Systems
Part 4. Blasting: The Story of Breaking Rock