Chapter 21: Electronic Initiation Systems

Learning Objectives

• Describe the features, components, and benefits of electronic blast initiation systems (EBISs).
• Distinguish between electronic detonators and other types of detonators.
• Describe the safety features of electronic detonators.
• Discuss how delay timing is provided in electronic detonators, the range of delays available, and best practices for using those delays.
• Describe the types of accessories and tools used with electronic detonators.
• Explain the role of electronic blasting machines after testing is complete.
• Distinguish between software and firmware and what they do in electronic initiation systems.
• Describe requirements related to EBIS user training and certification.
• Identify general safety precautions for working with electronic initiation systems.

Overview

Electronic initiation systems, also known as electronic blast initiation systems or EBISs, are the most recent development in blast initiation technology.

Unlike electric initiation systems, EBISs contain detonators with programmable delay modules and capacitors. These features offer a higher level of protection from extraneous electricity (e.g., stray current). They also allow precise timing abilities. These abilities allow for improved blast results, such as better fragmentation, less vibration, and more control over air blast. However, communications within wired systems are critical and specific. Disruptions due to stray current, current leakage, or static electricity could result in garbled communications and commands.

Every electronic initiation system has a different design. Blasters need to complete an education and training program for each system they use.

Components

While the designs of electronic initiation systems vary widely, they have some components in common.

Electronic Detonators

An electronic detonator is an initiating device capable of detonating most high explosives. Most electronic detonators are wired, some use shock tube, and others are wireless.

Communication System

Most electronic initiation systems include a way for their parts to communicate, whether the systems are wired or wireless.

On-Bench Field Testing and Programming Equipment

The electronic bench testing unit (bench tester) can communicate with an individual detonator or a series of detonators.

Electronic Blasting Machine

An electronic blasting machine is required to fire the blast.

Electronic Detonators

Electronic detonators have an aluminum or copper alloy shell. Viewed from the outside, an electronic detonator may appear similar to an electric, safety fuse, or shock tube detonator. The main difference is in the internal design and construction.

In an electronic detonator, a circuit board and a microchip (or ASIC, an application-specific integrated circuit) provide delay timing. In conventional detonators, a pyrotechnic composition (a delay element that burns) provides delay timing.

In an electric detonator, the leg wires are directly connected to the ignition charge or bridgewire. This puts the detonator at risk of initiation from static, stray current, and/or radio frequency (RF) energy in the field.

In a wired electronic detonator, the wires are connected to a circuit board. This provides a level of separation where safety features are incorporated.

Safety Features

Electronic systems are at lower risk of premature detonation caused by static electricity and stray current. The lower risk is due to the communication, voltage, and frequency protocols used in these systems. Very specific commands at certain voltages and frequencies are needed to begin and sustain any communication with the detonator.

One of the main safety features is that the ignition charge is physically separated from the leg wires by the delay module and its safety structures. There are also several other design components that further increase the level of protection from extraneous electricity and the risk of premature initiation.

These safety features may include the following:

• Spark gaps (to discharge static charges)
• Input resistors (to handle high current inputs)
• Voltage-specific capacitors (for charging)
• Other electrical components necessary to provide safety during use

Despite these safety features, electronic detonators are not immune to premature detonation caused by high levels of electrical energy (e.g., a lightning strike).

Electronic detonators also provide a level of timing control and security from unauthorized use. The built-in logic circuits allow operators to control who can use the system through passcode protection.

Delays

Electronic detonators can provide delays of 1 to 30,000 milliseconds (30 seconds) in 1 ms intervals.

This allows precise blast-timing options that can be tailored to the rock characteristics of the blast location. This precision allows a lot of flexibility, but blasters need to adhere to the blast design. All blast-timing improvements are of no benefit unless an accurate drilling and blast layout is taken into account.

Shock Tube-Based Electronic Blast Initiation System Delays

The one exception to increased blast-timing flexibility is the use of a shock tube-based electronic blast initiation system. This type of system has predetermined delay timing built into it.

The advantages of shock tube-based EBISs are the similarity and wide understanding of how they work, as well as minimal training requirements.

One disadvantage is that these systems cannot be tested before firing. Another disadvantage is that the user is relying on the robustness of a familiar product type. In addition, timing accuracy can be compromised during use. That's because shock tube has inherent time incorporated into it as the reaction in the tube progresses along its length.

Accessories and Tools

Electronic detonators have various pieces of communication and control equipment. This hardware allows for the testing, addressing, programming, arming, and firing of the electronic circuit.

On-Bench Field Testing and Programming Equipment

The electronic bench testing unit (bench tester) can communicate with an individual detonator or a series of detonators. This communication provides the blaster with a large amount of information as well as the ability to set times for the detonators.

The bench tester may be called a scanner, logger, tagger, or programmer unit by different manufacturers. These units provide the blaster with circuit tests to ensure communication with the detonator. These tests detect the following:

• Broken wires
• Current leakage ranges
• Circuit board test protocols
• Fusehead existence

These units also allow programming of delay times and sequences of individual detonators. The methods, sequences, and types of communication vary between manufacturers.

Typically, these units can be used to test one or more detonators before, during, and after the blast-hole loading process. They can also provide blasters with the ability to do the following:

• Test the entire blast.
• Review individual detonator information.
• Check the number of detonators in a circuit.
• Check the full system integrity of a blast.

Inherently Safe Design

Bench testers are designed to be "inherently safe" devices. Inherently safe designs require that all electronic testing and communication are always done at voltage and current levels that are below the levels needed to charge and fire a detonator. By design, the tester does not have the capability to produce or deliver enough energy to fire a blast or a single detonator. This design feature makes electronic detonators nearly impossible to fire accidentally.

Today's testing and programming equipment is also designed with methods of securing the communication. Passcodes and protocols ensure that only qualified and properly trained personnel use the equipment.

Importing Blast Designs

Some EBISs have the ability to import a blast design created by a computer. This includes predetermined timing as well as the order of hookup. Importing a design relieves blasters of managing the input of timing but requires them to adhere to a predetermined plan to completion. When necessary, the blaster does have the option to make adjustments.

Electronic Blasting Machines

After successful testing of all electronic detonators, a blasting machine is required to fire the blast.

Most electronic blasting machines offer the ability to successfully program and fire several thousand electronic detonators in a single operation. In addition, electronic blasting machines can synchronize and fire remotes and repeaters. This allows the blaster to be up to several kilometres away from a blast site.

A specific blasting machine must be used with each manufacturer's system. Blasting machines have unique design features and communication protocols. These features and protocols help ensure safe and reliable system-level tests, programming, charging, and firing of the shot. Only fully qualified and trained personnel should use these systems.

Electronic blasting machines provide the following:

• Password protection and/or a physical key or other device to prevent accidental firing
• Programming capability
• The energy levels needed to charge the detonators in a circuit and send a fire command

How They Differ from Other Field Equipment

The charging capability of electronic blasting machines sets these units apart from all other field equipment for electronic detonators. These blasting machines are not considered inherently safe devices. For this reason, blasters are required to clear the blast area of personnel, vehicles, and equipment before hooking up the circuit to the firing device or blast controller.

In general, electronic blasting machines have the same ability as bench testers to test electronic detonators. They also have the ability to test and program the entire system or all units within a blast. However, a blasting machine accomplishes this at a higher voltage than any bench tester. For this reason, a blasting machine should only be connected to an electronic detonator blast with the intention of programming and firing that blast.

Full-scale testing is made possible by the blasting machine's ability to communicate at a higher energy level. The extra energy helps ensure reliable communication as well as charging of all firing circuits. In general, two-way communication is needed for full system testing as well as full charging of each detonator's communication and/or firing capacitors. This allows for reliable performance of the manufacturer's system-wide tests before the final charge and fire commands are sent.

Software and Firmware

Blasters can use laptop computers to create and analyze blast designs for electronic initiation systems.

The blast design software typically allows the blaster to do the following:

• Visualize the blast.
• Ensure efficient blast performance.
• Download the design directly into the EBIS control equipment.

Bench testers and blasting machines use firmware that acts as the operating system for the detonators and other parts of the EBIS. The firmware helps ensure communication, reliability, and safety.

User Training and Certification

Each manufacturer's EBIS is unique, and none of the parts or technologies can be interchanged between systems. For example, each EBIS requires a specific blasting machine designed by the manufacturer of that system. Users need to be fully trained and certified by the manufacturer in order to operate these systems.

Each system can vary considerably in design, function, complexity, and capability. To ensure safety and reliability on the worksite, every user needs to understand all of the features of the system they will use.

General Safety Precautions

• Follow the manufacturer's instructions, especially hookup procedures and safety precautions.
• Do not use electronic initiation systems outside the manufacturer's specified operational temperatures.
• Do not use equipment or electronic detonators that appear to be damaged or poorly maintained.
• Do not mix electronic detonators of different types in the same blast, even if they are made by the same manufacturer.
• Use the wires, connectors, and coupling devices specified by the manufacturer.
• Keep exposed wires from contacting the ground or other conductors.
• Keep wire ends, connectors, and fittings clean and free from dirt or contamination prior to connection.
• Protect electronic detonator wires, connectors, coupling devices, shock tube, and other components from mechanical abuse and damage.
• Do not load blast holes near power lines unless the firing lines and detonator wires are anchored or are too short to reach the power lines.
• Use extreme care when programming delay times in the field to ensure correct blast designs. Incorrect programming can result in misfires, flying material, excessive air blast, and vibration.
• Keep detonator leads, coupling devices, and connectors protected until ready to test or fire the blast.
• Follow the manufacturer's recommended practices to protect electronic detonators from electromagnetic, RF, or other electrical interference sources.
• Do not use test equipment and blasting machines designed for electric detonators with electronic detonators.
• Do not use blasting machines, testers, or instruments with electronic detonators that are not specifically designed for the system.
• Verify the electronic initiation system's integrity before firing the blast.
• Do not hold an electronic detonator while it is being programmed.
• Ensure the blaster has control over the blast site throughout the programming, system charging, firing, and detonation of the blast.
• Clear the blast site of personnel, vehicles, and equipment before hooking up the circuit to the firing device or blast controller.
• Fire electronic detonators using the equipment and procedures recommended by the manufacturer.
• Follow the manufacturer's instructions when aborting a blast. Then follow the manufacturer's recommended wait time before returning to the blast site.
• If the manufacturer's specific instructions for aborting the blast were not followed, wait a minimum of 30 minutes before returning to the blast site after aborting the blast.
• Do not allow the battery terminals of an electronic device to be exposed to the electrical wire leads of an electric detonator.
• Do not handle or use electronic detonators during an electrical storm. Evacuate workers from the blast site to a safe location.