Module2.pdf for general information for public

This blaster-training module was put together, under contract, with Federal funds
provided by the Office of Technology Transfer, Western Regional Office, Office of
Surface Mining, U.S. Department of the Interior, located in Denver, Colorado.
The module is an example of the technical assistance the Federal government
furnishes States to assist them in meeting the requirements of the Surface Mining
Control and Reclamation Act of 1977, upon which their State surface coal-mine
regulating programs are based. In particular, the module was requested and will be
used by the Sheridan District Office, Wyoming Department of Environmental Quality,
Land Quality Division.
A word of caution: please note that this module is not intended to stand alone,
nor is it a self-training type module. Rather, the information the module
provides MUST BE SUPPLEMENTED by information given by a certified blasting
instructor.
DISCLAIMER
The technologies described in the module are for information purposes only.
The mention herein, of the technologies, companies, or any brand names, does
not constitute endorsement by the U.S. Department of the Interior’s Office of
Surface Mining.

Initiation Systems
This module presents information pertaining to initiation
systems currently used in blasting operations at surface
coal mines.

The discussions of various initiation
systems that follow concentrate primarily
on common practice and safety.
Good results at any blasting operation
can be achieved only when the initiating
devices used to detonate explosive
charges are of the highest possible
quality, carefully chosen, and properly
used to meet the task at hand.
Unfortunately, initiating devices cannot
differentiate between energy supplied
purposely and energy supplied
accidentally.
For this reason, users of such devices
have the responsibility to maintain strict
control of them over the course of their
storage, transportation, and use.
Initiation Systems

Initiation devices have evolved into a variety of systems offering more flexibility and increased
safety over their earlier counterparts.
The use of non-electric systems eliminates the danger of premature detonation owing to radio-
frequency energy or stray electricity in areas where stray current is a concern.
Introduction
Modern, high-
energy blasting
machines are
designed to
provide a surplus
of firing energy
and reduce the
possibility of
misfires.

In order to choose the right initiation system for a blasting operation, certain considerations,
ensuring safe and effective blasts, must be taken into account.
The discussion of initiation systems that follows concentrates on common practice and the
various “tricks of the trade” that are associated with each individual system. It is highly
recommended that you confer with the manufacturer before finalizing your initiation program,
so that you have a full understanding of the individual system at your operation.
Introduction

As a general rule, before you choose an initiation system, you should familiarize
yourself with numerous site-specific factors at your operation. Consider the following
topics and use them with manufacturer recommendations to evaluate:
• Geology (rock properties and structure);
• Geometry (typical pattern dimensions);
• Vibration (recommended criteria, including regulations), in particular,
▪ Peak particle velocity and
▪ Frequency;
• Airblast (recommended criteria, including regulations);
• Fragmentation (with respect to blasting goals);
• Explosive performance (know your explosive!); and
• Borehole conditions (water, voids, weak walls, etc.).
Introduction

Introduction
An initiation system provides the initial energy required to detonate an explosive used for rock
blasting. Initiation systems require:
• An initial energy source,
• A distribution network to deliver the energy to each blasthole, and
• An in-hole component to initiate a detonator-sensitive explosive.
The systems are broadly classified as either
electric or non-electric and may contain various
combinations of cord and initiators either as
separate components or integrated.

Introduction: Initiators
Initiator is a term used in the explosive industry to describe any device that may be used to
start a detonation or a deflagration. There are four general classifications of initiators
currently being used in surface coal-mine blasting:
• Non-electric systems,
• Electric systems,
• Electronic systems, and
• Blasting-cap and safety-fuse systems.

Introduction: Detonators
Detonators are devices used to initiate high explosives.
A detonator is a complete explosive initiation device that includes the active part of the
assembly (usually enclosed in a metal shell) and the attached initiation signal transmitter
(for example, leg wires, a shock tube, or other signal-transmitting material).
Detonators are either instantaneous (no time-delay element), millisecond (ms) delay,
or long-period delay. Ms delays are commonly used for surface-mine blasting and are
manufactured with delay times up to 500 ms. Long-period delays are available for
periods up to several seconds.

Introduction: Types of Delays
Fuse
Base
charge
Primer
charge
Safety
fuse
(delay)
Shock-tube Wired
Igniter
Delay
module
Base
charge
Capacitor
Electronic delay
Primer
charge
Shock
tube
Anti-static
cup
Igniter
(bridge)
Delay
element(s)
Base
charge
Pyrotechnic delay
Primer
charge
Shock-tube Electric
Anti-static
cup

Choose a shock-tube initiation system for
operations with:
• Stray current hazards,
• Static-electricity hazards (including
wind, low humidity, plastic liners,
etc.),
• Small-diameter holes (resulting in
explosive densensitization,
• Sequential precision desired,
• Timing flexibility, and/or
• A need to reduce inventory.
Avoid using a shock-tube initiation system
for operations with extreme loading
conditions. Also, a mechanical or electrical
check is a MUST for matting shots and
burying shots undertaken using shock-tube
initiation.
Introduction: Shock-Tube Systems

• Dual-delay v. down-hole and surface
systems:
Assuming you decide to initiate your blast using a shock-tube system, you should take into
account several considerations:
• Loading conditions:
• Cord or shock tube downline
• Borehole size
• Type of shock tube
• Sleep times of shock tube
• Explosive’s sensitivity:
• Level of accuracy:
• Lot-to-lot
• Cord/shock tube
• Dead-pressing potential
• Level of reliability:
• Redundancy on surface
• Redundancy in the hole
Introduction: Shock-Tube Systems
• Pattern
• Flexibility
• Safety
• Level of precision:
• Common in-hole delay v.
variable in-hole delay
• Twin-path

Choose detonating cord for operations with:
• Extreme loading conditions
• Multiple priming requirements
Avoid using detonating cord in
small-diameter boreholes, where
explosive damage or disruption
might result. Also, a detonating
cord used with an explosive that is
too sensitive may trigger a
premature initiation. Detonating
cord can desensitize an explosive.
And, finally, because uncovered
detonating cord on the surface is
very loud when fired, it may not be
appropriate for use in a noise-
sensitive environment.
Introduction: Detonating Cord

You might choose an electrical blasting
system if you are undertaking matting
shots or if your operation requires circuit
testing. However, these situations are
unlikely, and, currently, because of their
susceptibility to extraneous electrical
hazards, electrical blasting systems are
not recommended or acceptable for use in
Western coal-mine States. Specifically,
electrical circuits are vulnerable to stray
current potential, static hazards, and
radio-frequency hazards.
Instead, detonating cord, shock-tube
systems, or electronic systems are the
preferred safe means for initiating blasts
at surface coal mines in the West.
Electric detonators are used frequently in
surface coal mines to initiate detonating-
cord trunk lines. Accordingly, their safe
use will be discussed in this module.
Introduction: Electrical Blasting Systems

Choosing an electronic blast-initiation system is a large step for any surface coal mine. With
the possibilities of increased productivity improvements, increased security, design flexibility,
and system control also comes an increased level of product complexity. Each electronic
system requires a unique understanding of its standard-operation and hook-up procedures.
The advantages of an electronic blast-initiation system include its:
• Precision and accuracy,
• Blast-management capability, and
• Increased security.
The disadvantages of an electronic blast-
initiation system are that:
• It requires increased training,
• It is more complex, and
• It is more expensive.
Introduction: Electronic Systems

Non-Electric Systems
Typical non-electric systems used today consist of detonating cord, shock-tube
detonators, or a combination of the two. These systems are extremely popular in
Western coal mines and are sold by all the major explosive manufacturers in the
United States.
Non-electric initiation systems have safety advantages, principal among them an
immunity to stray electrical currents and radio frequencies. However, these
systems are susceptible to accidental initiation by a lightning strike. Non-electric
detonators contain sensitive ignition charges and base charges and can be
accidentally detonated by heat or impact.
Non-electric systems require an orderly hookup, and careful visual inspection is
necessary to verify the continuity of the system.

Non-Electric Systems
The Institute of Makers of Explosives’ (IME’s) recommendations with respect to non-electric
detonation systems are:
• ALWAYS use a detonating cord matched to the blasting methods and type of
explosive materials being used;
• NEVER make loops, kinks, or sharp angles in the cord, all of which might direct the
cord back toward the oncoming line of detonation;
• ALWAYS handle detonating cord as carefully as other explosive materials;
• NEVER damage detonating cord prior to firing;
• ALWAYS cut the detonating cord from the spool before loading the rest of the
explosive material;
• NEVER attach detonators for initiating a blast to detonating cord until the blast area
has been cleared and secured for the blast;
• ALWAYS make tight connections, following manufacturer's directions;
• NEVER use damaged detonating cord;
• ALWAYS attach detonators to detonating cord with tape or by means of a method
recommended by the manufacturer;
• ALWAYS point detonators toward the direction of detonation;
• ALWAYS attach detonators at least 6 inches from the cut end of the detonating
cord; and
• ALWAYS use a suitable booster to initiate wet detonating cord.

Detonating Cord
Detonating cord is round, flexible cord containing a core of pentaerythritol tetranitrate
(PETN) high explosive. The exterior sheathing is waterproof material surrounded by a
reinforcing textile/plastic wrapper.
The purpose of detonating
cord is to:
• Detonate other high
explosives with which it
comes in contact and
• Transmit a detonation
wave from one detonating
cord to another or to a non-
electric detonator.

Detonating Cord
Detonating cord is available for a wide range of core loads, and many variables must be
considered when determining the proper core-load detonating cord to use. These
variables include:
• The detonation
velocity of detonating
cord is 22,000 feet per
second;
• Core loads are
typically 2 to 400 grains
per foot; and
• There are 7,000
grains in 1 pound of
PETN.

Detonating Cord
A general rule when selecting detonating cord is to use the lowest cord load possible
consistent with conditions at hand.
Low cord loads will carry the same signal with much less air blast and disruption of the
explosive column. If the detonating cord is in contact with ANFO or ammonium nitrate-
based products, a lower core load will have less disruptive effects on the explosive
column and will result in greater blast efficiency.
When determining the core load to use at
your blasting operation, consider:
• What will initiate the cord?;
• What will the cord initiate?;
• The weather;
• The explosives used for the
main blasting charge;
• The use of detonator-sensitive
or nitroglycerin-based
explosives; and
• The diameter of the hole.

Detonating Cord
When selecting
downline detonating
cord, check with the
manufacturer of your
booster to determine
the minimum
recommended core-
load detonating cord for
reliable detonation. In
addition, check with
the manufacturer to
determine the correct
detonating cord for
your borehole
conditions.
Detonating cord can be used as downlines or trunklines. As downline,
detonating cord is used to initiate cord-sensitive boosters or ms-delay detonators.
From previous hole
To next hole
Downhole
Clip connector
Block connector
Detonating cord
downline
Short length in hole detonator

Detonating Cord
Initiating Detonating Cord
Even though modern detonators are very dependable, it is a good idea to use two
detonators at the point of initiation, especially when delay detonators are used for
surface initiation of multiple hole shots.
For maximum reliability, detonators should be attached to a short length of detonating
cord or pigtail, which in turn is tied into the system with a recommended knot just before
the blast. Most detonating cord is designed to be initiated with an electric detonator, a
non-electric detonator, or two cap-and-fuse assemblies.
Advantages of Using Detonating Cord
Detonating cord is easy to use, rugged, and insensitive; it is not susceptible to electric
hazards; and it is reasonably accurate.
Disadvantages of Using Detonating Cord
Detonating-cord misfires and cut-offs can occur from flyrock or sub-surface rock
shifting; downward initiation through the charge column can both cause low-order
deflagration and render the charge more dense, even to the point of “dead press;” and
detonating cord can disrupt stemming material.

Review Questions and Discussion
1. Identify the advantage(s) of initiating a blast using a totally non-electric shock-tube
system.
a. Such a system will not disturb the explosive column
b. Such a system is insensitive to lightning
c. Such a system is insensitive to static electricity
d. All of the above
2. The numbers identifying various sizes of detonating cord refer to the number of
grains of __ that are contained within a single linear __ of cord.
a. Cord; inch
b. Explosive; foot
c. Explosive; pound
d. Black powder; foot
3. True or false: detonating-cord downlines can decrease the efficiency of the blasting
agent the detonating cord is intended to set off?

Answers
1. d. correct.
2. b. is correct.
3. True. A detonating-cord downline does tend to
decrease the efficiency of the blasting agent the
detonating cord is intended to set off. This is
because, when detonating cord shoots, it can
burn and deadpress part of the explosive around
it, thereby destroying part of the explosive
column.

Detonating Cord
When attaching the detonator, be sure that its loaded tip is pointed in the direction
you want the detonating cord to detonate (initiation can only be ensured in the
direction the detonator is pointing). If you are using an electric detonator, wrap the
cord and detonator securely together with electrician’s tape at the desired point of
initiation, at least 8 inches from the cut end of the cord.
If you are using a non-electric lead-in line, place the detonating cord pigtail in the
bunch block parallel to the detonator, wrap the detonating cord around the bottom
of the bunch block, back in the bunch block parallel to the detonator, and snap the
lid firmly closed.
To use a cap-and-fuse assembly, place the detonators of the two assemblies side
by side and attach them securely to the detonating cord. Tie a pigtail assembly to
the detonating cord downline at the intended point of initiation using one of the
recommended knot connections.
A recommended practice is to end-prime a wet detonating cord. Detonating cords
are much less sensitive when they are wet. A straight length of cord will continue to
detonate reliably, wet or dry. Side priming is not reliable for wet cord.
The only recommended methods of wet-end initiation are end priming with a No. 8
strength (or higher) detonator or using a high-velocity booster such as a cast
booster or an 80-percent gelatin dynamite.

Detonating Cord
One downline is usually adequate for small-, medium-, or large-diameter holes. However, two
downlines are recommended in deep, large-diameter blastholes loaded with multiple boosters
that are separated by blasting agents or other non-detonator-sensitive explosives. In addition,
two downlines are recommended when blastholes are decked. To help prevent cut-offs when
using multiple downlines, keep them separated in the borehole and free of slack.
Detonating cord should be spliced together with a conventional square knot.
DO NOT SPLICE DOWNLINES.
Splices are never recommended in
the downlines inside a borehole,
because failures can result from:
• The damaging of the splice
during loading or stemming
operations,
• Penetration of water through
the exposed cord ends, or
• Cracks in the cord’s
covering around the knot.

Detonating Cord
As a trunkline, detonating cord is used to initiate surface-delay units such as ms-
delay connector detonators, trunkline delays, and downlines.
When selecting trunkline detonating
cord:
• Check with the
manufacturer to determine
what core load detonating
cord will initiate surface
connections and
recommended knots and
• Determine the correct
trunkline detonating cord
to use with your surface
delays for a delayed
pattern.
The manufacturer will recommend a
core load and proper hook-up
methods.

Detonating Cord
Knots, Connections, and Layouts
Detonating cord is easy to connect for a blast. Most detonating cords will transmit a detonation
reaction between sections spliced or joined together securely and tightly with the proper knots.
Proper knots will reliably initiate most cords used in surface-mining applications. (The exception
here would be that some light-grain cords may not initiate reliably through knots or splices.
Consult the manufacturer of your detonating cord when splicing or connecting unusually large- or
small-grain detonating cord.)
When connecting detonating cord sections together:
• Make sure the cut ends are free of water, oil, or other contaminants. Place all
connections or detonators at least 12 inches (0.3 meters) from the exposed (cut) end to
be sure of positive initiation. This includes all knots, ms-connector blocks, and
short-lead detonators.
• Make sure all the connections are at right angles. Avoid sharp angles, which can
cause the cord to cut itself off. Angle cut-off failures are caused when detonating cord
branchlines or downlines slant back at an acute angle toward the main detonating cord
trunkline. Explosive energy or fragments can sever a branchline or downline before the
detonation wave reaches it through the knotted connection.
• Do not kink, bend, scrape, or leave slack in the detonating-cord trunklines or
borehole downlines or uplines. The extra line extending out of the hole allows for
slumping and is not confined as slack.

Detonating Cord
Knots, Connections, and Layouts—continued
• Make all detonating cord knots tight and in contact so they cannot work
loose. Loose knots may fail to transmit the detonation wave. Avoid having knots in
any downline cord.
• Make sure every borehole has (1) two paths by which the detonation can
reach it and (2) cross-ties between the trunklines at regular intervals frequent
enough to provide positive detonation of the trunkline. Cross-ties should be
placed more frequently when the spacing and burden are small. Cross-ties are
recommended insurance against trunkline cut-offs from ground movement or flying
debris from holes that fire earlier in the shot’s sequence.
• Always cut off the excess cord or “tails” after tying in to prevent the initiation
signal from crossing over the trunkline and cutting it off.
• Always keep the shot pattern as clear as possible of debris, boxes, box liners,
explosives, etc., so that the trunkline layout is readily visible, distinctive, and
neat.
• When several detonating cord downlines, uplines, or trunklines are used,
make sure they do not cross over each other.

Detonating Cord
Knots, Connections, and Layouts—continued
• In locations that are close to residential or commercial sites, the noise from
detonating cord trunkline may cause complaints. This can be solved in a
number of ways, including:
• Eliminating the trunkline and initiate each downline at the surface with an
electric or non-electric detonator,
• Initiating a detonating cord upline from the bottom of a hole with an electric
or non-electric detonator, or
• Covering the trunkline with at least 12 inches of fine drill cuttings or dirt.

Detonating Cord
Right-Angle Connections
Connections between (1) downlines or uplines and a detonating cord trunkline, (2) cross-ties
between trunklines, or (3) other right-angle hookups should be made with a double-wrap half-
hitch (sometimes called a double-wrap clove-hitch).
The most satisfactory connection between a stiff detonating-cord downline and a flexible
trunkline is made by clove-hitching the trunkline around the downline or using a plastic
detonating-cord connector.
If there is no slumping or subsidence of the charge, the single-wrap clove-hitch is sufficient;
however, single-wrap clove-hitches can be pulled out by slumping charges. This is prevented by
clove-hitching the trunkline over a loop in the downline (instead of the single cord) and tucking
the loose end through the loop at the top.

Detonating Cord
Instantaneous and Surface-Delay Systems
Instantaneous firing may still be done where vibration
or airblast problems are not a concern. However,
most blasts using detonating cord are delayed either
on the surface or in the borehole by means of ms-
delay techniques.
Surface-delay initiation, used without in-hole delays,
is more vulnerable to failures or partial failures from
ground movement than is surface-delay initiation
used with instantaneous methods or in-hole delays.
The most common ways of surface-delaying a blast
with detonating cord are:
• Using ms-delay connectors in the
detonating-cord trunkline,
• Using ms-delay electric or non-electric
detonators attached to the cord downline,
and
• Using surface shock-tube delay detonators.

Detonating Cord
Instantaneous and Surface-Delay Systems: Ms-Connectors
Ms-connectors allow an easy method of firing detonating-cord blasts by short-interval delays on the
surface. These connectors come in a variety of delay intervals and are tied into a trunkline between
the boreholes or between groups of boreholes to sequence the blast.
The rule of thumb is to allow 1 foot (0.3 meters) between holes for each ms of delay and
always to locate ms-connectors either midway between holes or closer to the hole being
delayed.
connected to the first detonating cord in the sequence. The shock tube transfers the detonation
between the boreholes to the delay detonator at the other end of the tube, which is connected to
the next detonating cord downline.
Although both the delay element and a high-explosive base
charge are enclosed within a plastic block in an ms-connector,
the connector should be protected from abusive shock, heat,
impact, or friction (ms-connectors have an impact sensitivity
equivalent to that of regular delay detonators). Be sure to clear
unnecessary personnel and equipment from the shot area
before ms-connectors are tied in.
Non-electric shock-tube detonators can be used in surface
operations to reduce noise levels where the use of electric
detonators is not an option. The J hook on the shock tube is

Detonating Cord
Firing Surface-Delay Systems
Trunklines should be initiated with electric or non-
electric detonators to maintain optimum control of
the instant of firing. Use two detonators if the cord
is wet.
The detonators are attached side by side along the
detonating cord with the exploding ends pointing in
the direction that the detonating cord will fire.
Securely fasten the detonators with tape to ensure
direct contact with the detonating cord. Care
should be taken to prevent the end of the
detonating cord from becoming wet where the
detonators will be attached. A booster must be
used if the core is wet and cannot be cut back to a
dry core.
A recommended precaution is to first attach the
detonators to a length of detonating cord about 18
inches long; such a cord is sometimes called a
“pigtail.” The pigtail can be placed several feet
away from the main detonating cord until after
unnecessary personnel have been cleared from the
blast area and just before the scheduled blast time.
For hookup, the pigtail can be tied onto the main
trunkline by means of a square knot.
Click on the image above to play
a clip showing detonation
initiated by a coal-shot cord.

1. Which, if any, of the cord sizes in this list will consistently initiate primers?
a. 4.5-grain
b. 7.5-grain
c. 40-grain
d. 50-grain
e. None of the above
f. All of the above
2. True or false: detonating cord on the surface of the ground can produce significant
air blast?
3. What type of knot should be used to connect a detonating-cord downline to a
detonating-cord trunkline?
a. Half-hitch or clove-hitch
b. Square knot
c. Overhand knot
d. Fisherman’s knot

Answers
1. c. and d. are correct.
2. True.
3. a. is correct.

Shock-Tube Systems
Shock-tube systems use a small detonation in an almost empty plastic tube to transmit the
initiation signal at approximately 6,500 to 7,000 feet/second (1,980 to 2,130 meters/second)
throughout the blast pattern.
The plastic shock tube is composed of one or more layers of plastic, which are designed to
enhance the tensile strength and abrasive resistance of the tubing. The inside of the shock
tube is made of Surlyn™, which binds the thin interior coating of explosive dust (HMX and
aluminum) to itself. A shock-tube system is highly insensitive to initiation by heat or impact
and requires an intense, high-impulse shock to initiate the reaction.
Hand-held mechanical devices that use a shot-shell primer activated by a firing pin are
frequently used, as well as devices that use a piezoelectric crystal to generate energy.

Shock-Tube Systems
Safety Considerations
The tubing in a shock-tube system remains intact after
activation, unlike detonating cord, which is consumed in
detonation. Shock-tubing may rupture during its initiation, and
it is never advisable to hold the tubing in the hand during the
initiation process.
Owing to the wide variety of shock-tube systems available, it is
essential that the blaster (1) be knowledgeable about the
system he or she is using and (2) follow the manufacturer’s
recommendations. Components from different types of
systems should never be mixed in a single blast, unless
specifically approved by the manufacturers.
Care must be exercised during the hook-up procedures.
Omitting a charge or failing to make a connection will result in
a misfire. Many surface-delay components produce a metal
and plastic shrapnel when detonated. Most systems
recommend covering the connections with dirt or drill cuttings
to confine the shrapnel.
Vehicles such as bulk trucks must not drive over the tubing,
connectors, or any surface components. No tools should be
used to pry on any component containing a detonator, nor
should any tool be used to open, close, fasten, or clean out
any connector containing a detonator or detonating device.

Shock-Tube Systems
Many shock-tube system configurations are available from most explosive manufacturers. Ms
trunkline delay assemblies are used for surface blasting. Many varieties of shock-tube delay
detonators are available with a delay unit attached to one end of the tubing. Such a
configuration can be used to generate individual-hole delays in a modified-series hookup.
Detonator timing includes the burn time of the shock tube.
Hole-to-hole and row-to-row timing can be introduced by using a combination of surface and in-
hole units or a combination of dual-delay detonators with both an in-hole delay and a surface
delay on the same unit.

Shock-Tube Systems
Shock-Tube Lead-in Line Detonators
A shock-tube lead-in line detonator allows for initiation of non-electric patterns from a safe
distance. Factory assembled, spooled units with a detonator typically come in lengths of 75 to
1,000 feet (25 to 300 meters) or longer.
Ms and Long-Period Shock-Tube Detonators
Ms and long-period shock-tube detonators are used as in-hole detonating units or as delay units
between holes in a row or rows in a blast. NEVER cut factory-assembled shock-tube detonators
to attempt a splice or a surface connection.

Shock-Tube Systems
Shock-Tube Downlines with Shock-Tube Trunkline Delay Units
Shock-tube downlines can be used with surface trunkline delay units. Shock-tube surface-delay
trunkline units use a plastic connector attached to a non-electric detonator with ms-delay timing.
To make the connection, crimp the detonator to a factory-assembled shock-tube of a certain length
and charge all boreholes with the desired delay. To connect the boreholes, place the shock-tube
downline and the shock-tube trunkline to the next hole in the plastic connector block or bunch
block on the surface trunkline delay unit.
Close the hinged flap on the surface delay block, making sure that the tubes extend straight from
the plastic block for at least 6 inches before they turn in any direction. Cover the connections with
dirt or stemming material to reduce the possibility of shrapnel cut-offs.

Shock-Tube Systems
Shock-Tube In-Hole Delays with Detonating-Cord
Trunklines
Under this application, the boreholes are charged with
the desired delays for the application and the main
explosive charge is introduced. Then, the detonating-
cord trunkline and the surface connectors are placed as
needed for the blast. The detonating cord snaps onto
the shock-tube in-hole unit via a J-connector. This
connection replaces the knot a detonating-cord downline
would have employed. The shock-tube must remain
perpendicular to the detonating-cord trunkline.
Shock-Tube In-hole Delays with Detonating-Cord
Downlines
Short-lead units are the most common type of in-hole
delay used with detonating-cord downline. Typical short-
lead units have 30 inches (76 centimeters) or more of
shock-tube crimped to a delay detonator. The other end
of the tube is looped to facilitate tying it to the detonating-
cord downline.
Short-lead units ensure bottom-hole initiation and have
the added advantage of downhole delays. They may
also be used to make sliding primers for double priming
and/or decking applications. In this instance, the shock-
tube is in contact with the detonating cord in the slider
well of the cast-booster.

Shock-Tube Systems
Detonating-Cord Downlines with Shock-Tube
Trunklines
When detonating-cord downlines are used with
short-lead units, it is sometimes necessary to
initiate detonating cord on the surface with
shock-tube trunkline delays. Shock-tube is
noiseless and allows for the design of many easy
surface-delay patterns.
One end of a trunkline delay has a J-connector;
J-connectors allow fast and easy connection to a
detonating cord. The other end contains the
bunch-block connection into which the
detonating-cord downline is inserted. The end of
the detonating cord should be knotted so the
cord does not pull away from the bunch block.
The trunkline unit going to the next borehole or row is connected to the downline via the J-connector
(make sure that adequate distance is maintained between the J-connector and the outgoing trunkline
delay unit).
The detonating cord should extend straight from the bunch block. Trunkline delays should be covered
with drill cuttings to prevent shrapnel cut-offs.
Shock-tube and detonating cord should never be placed in the same bunch block. The different
propagation velocities of shock-tube and detonating cord will cause the shock-tube to cut off.

Shock-Tube Systems
Dual-Delay Detonators
The newest type of shock-tube detonator is
rapidly replacing other shock-tube systems
in many surface applications, especially
where detonating cord is not used. Dual-
delay detonators combine non-electric in-
hole and surface initiation in one product.
The in-hole detonator is a standard ms- or
long-period-delay detonator, and the
surface end contains a low-strength ms-
delay initiator. The surface delay is housed
in a plastic block clip that can be clipped to
the shock-tube of the next hole in the blast
pattern. All holes are loaded with the same
in-hole delay detonators, and the surface
units will also have the same delay. The
desired timing is acquired by tying the
holes together in the sequence that is
needed for detonation. Rows can be tied
together using a trunkline delay with bunch
blocks or surface connectors.

1. True or false: connections between blastholes using surface-delay detonators should
not be made until immediately prior to clearing the blastsite?
2. The detonation velocity of a Nonel™ flash tube (which is a brand-name shock tube) is:
a. 18,000 feet/second
b. 1,800 feet/second
c. 6,500 feet/second
d. 65,000 feet/second
3. A shock-tube and a detonating-cord initiation system should NEVER be tied in
together using this type of surface connection:
a. Square knot
b. J-hook
c. Bunch block
d. All of the above
4. True or false: a Nonel™ delay connector, which itself incorporates a detonator, must
be stored with other detonators?

Answers
1. False. The blastsite should be cleared before initiating any
tie-in of the pattern.
2. c. is correct.
3. a. is correct.
4. True.

Electric Systems
leg wires
rubber plug
bridge wire
delay element
primary charge
base charge
ignition charge
Typical electric systems used today consist of electric
detonators connected in series, in parallel, or in a
combination of the two.
The use of initiation systems that employ all-electric
detonators is becoming very rare in surface coal
mines and will not be covered in depth in this module.
This drop-off is use is largely owing to the
vulnerability electric detonators have to stray current
and radio frequencies.
The selection of the type of circuit to use with an
electric-detonation system will depend upon the
number of detonators to be fired and the type of
operation. A simple series circuit is used on small
blasts, consisting of less than 50 electric detonators.
A series-in-parallel circuit is used when a large
number of detonators is involved.
In almost every application, capacitor-discharge
blasting machines offer the safest, most dependable,
and most economical source of electrical energy for
blasting.

Electric Systems
Step-by-Step Field Procedures
The step-by-step procedures for checking a blasting circuit in
the field are:
• Determine the type of blast, the number of detonators to be fired, the type of leg
wires, the type of detonators, the length and gauge of the leading wire, and the
connecting wires (if they are used);
• Calculate the equivalent number of 2.0-ohm copper-wire detonators that will be
used in the blast, and determine the number of (1) balanced series and (2)
detonators per series;
• Make certain the connecting wire in an individual series does not cause an
imbalance in resistance that exceeds 10 percent;
• Calculate the resistance of the lead line and compare it to the acceptable limits;
and
• Check the circuit with a blaster’s multimeter to determine the resistance.
Four Principals
Successful electrical blasting depends upon four general principles:
• Proper selection and layout of the blasting circuit,
• Adequate energy source compatible with the type of
blasting circuit selected,
• Recognition and elimination of all electrical hazards,
and
• Circuit balancing, good electrical connections, and
careful circuit testing.

Electric Systems
leg wires
rubber plug
bridge wire
delay element
primary charge
base charge
ignition charge
Some of the components of an electric-blasting system are:
• An electric detonator, which is a metal shell containing a
high-explosive base charge designed to initiate other
explosives;
• Leg wires, which are insulated solid copper, iron, or
copper-clad iron wires that protrude from electric
detonators, allowing them to be connected to a blasting
circuit;
• A lead line, which is an insulated copper wire (gauge 10
to 14) used to connect detonators to the blasting machine;
• Connecting wires, which are expendable insulated
copper wires (gauge 16 to 20) used to connect (1)
boreholes or (2) individual series to the lead line;
• A blasting machine, which is a capacitor-discharge
machine capable of delivering the necessary current to
detonate a series of electric detonators; and
• Some means to test circuits (a blaster’s multimeter, a
blasting ohmmeter, or a blasting galvanometer all can be
used to test blasting circuits for continuity and resistance).
The blasting circuit in an electric-blasting system consists of electric detonators that are wired by
connecting wires to the lead or firing line, which in turn is connected to the blasting machine.

Electric Systems
In any blasting operation, the blasting machine should be directly under the control of the
blaster in charge. It should be kept locked while not in use with the key in the blaster’s
possession.
The lead (firing) line should not be laid out until the blast
circuit is completely wired and all unnecessary personnel
have been cleared to a safe location. After the lead line is
laid out, it should be tested with a blaster’s multimeter for
continuity.
Always inspect the lead line for cuts and abrasions to the
insulation BEFORE every blast.
The lead line must be shunted at the blasting machine
before connecting the other end to the blasting circuit.
NEVER connect an unshunted lead line to the blasting
circuit.
After the final connections have been made, the resistance
of the entire circuit should be tested once again and the
readings should match the calculated resistance. If proper
readings are not obtained, reshunt the lead line before
returning to the blast area to locate and correct the
problem. DO NOT allow the bare ends of the circuit or the
lead line to come in contact with the ground or with any
metallic object.

Electric Systems
Testing Blasting Circuits
A blaster’s multimeter, blasting ohmmeter, or blasting
galvanometer can be used to test blasting circuits for continuity
and resistance.
Individual detonators should be tested before making the primer
and then again before stemming is placed in the borehole. Each
circuit should be tested prior to hooking up the lead line. The
circuit plus the lead line should be tested prior to firing the shot.
NEVER USE ANY TEST INSTRUMENTS NOT SPECIFICALLY
DESIGNED FOR BLASTING CIRCUITS. The reason for this is
that most standard electrician’s AC-DC voltmeters and VAO
meters are capable of supplying sufficient current to detonate an
electric detonator; accordingly, they should never be used near
blasting circuits.
Before using the test instrument, make certain the needle can be
adjusted to “zero” when the terminals are shunted. Digital meters
should read “zero” in the display. Replace the batteries with the
same type of battery specified by the manufacturer for use in the
blasting instrument. NEVER change batteries in the presence of
electric detonators.

Electric Systems
Current and Extraneous Electricity
Sufficient current must be delivered within ms’s, to a large number of detonators simultaneously,
in order to successfully detonate the blasting circuit.
The accepted “safe” level of extraneous electricity for electrical blasting is derived from the
current required to detonate the most sensitive commercial electric detonators plus a safety
factor. The minimum firing current for electric detonators currently manufactured in the United
States is approximately 0.25 amps.
The IME has established the maximum “safe” current permitted to flow through an electric
detonator without hazard of initiation as one-fifth of the minimum firing current, or 0.05 amps,
which provides a current safety factor of five.
ELECTRIC BLASTING MUST NOT BE CONDUCTED IN AREAS WHERE EXTRANEOUS
CURRENTS GREATER THAN 0.05 AMPS EXIST.
Click on the image to the left to
view a chart describing sources of
extraneous electricity.

1. When the switch on a blasting machine is thrown, the __ is closed, or completed, and
the detonators wired to it __.
a. Circuit; detonate
b. Loop; misfire
c. Shunt; are checked
2. In an electric detonator, the leg wires are connected to lead wires, which in turn are
connected to an electrical blasting __.
a. Tester
b. Multimeter
c. Machine
3. What instrument is used to measure resistance in a blasting circuit?
a. Ohmmeter
b. Battery charger
c. Blaster’s galvanometer
d. Blaster’s multimeter
4. Why aren’t electric detonators used much at surface coal mines in Wyoming?
a. Because of danger posed to them by overhead powerlines in the State
b. Because of cellular-phone use in the State
c. Because of lightening storms in the State
d. Because of snow in the State

Review Questions and Discussion—continued
5. Lightning, static electricity, and radio-frequency energy are forms of __ that are very
hazardous to any electric-blasting enterprise.
a. Flyrock
b. Extraneous electricity
c. Airblast
d. Blasting waves
6. True or false: a flashlight battery could detonate an electric blasting cap?
7. In an electrical-blasting system, primers are detonated by:
a. Detonators set off by electrical charges
b. Detonating cord
c. Heat generated by the fuel oil or other chemical in the blasting agent
d. All of the above
8. A single electric detonator may detonate when:
a. No voltage flows through the wires
b. A current of 0.25 amps flows through the wires
c. The leg wires are joined
d. b. and c. above

Answers
1. a. is correct.
2. c. is correct.
3. d. is correct.
4. a., c., and d. are correct.
5. b. is correct.
6. True.
7. a. is correct.
8. b. is correct.

Electronic Systems
Electronic-initiation systems are the latest trend in modern surface-mine blasting. These
systems are numerous, and many of the larger explosive manufacturers have developed their
own systems.
Unlike electric and non-electric systems, electronic
blasting machines and accessories are designed
specifically for each manufacturer.
Tie-in protocol and connectors are very specific to
each manufacturer’s system, and each user must
become familiar with the specific detonators,
operational limits, applications, and guidelines for his
or her system.

Electronic Systems
Simple systems use factory-programmed electronic detonators that are initiated from shock tubes
in the same way that ordinary shock tubes detonate. Each of these electronic detonators contains
a piezoceramic device and a timing oscillator.
Some electronic systems are very complex and require custom blasting machines or computers to
fire their detonators. Such detonators are field programmable and offer increased flexibility in
operations that do a variety of blasting.

Electronic Systems
Blast-Management Capability
Electronic systems offer many computer-
aided capabilities that are unavailable for
electric and non-electric systems.
Electronic systems offer automatic safety
checks for short circuits and non-
connected firing lines, as well as systems
checks for missing and extra detonators.
They also map one-to-one among
blasting plans stored in the blasting
machine, and each detonator is checked
online before firing.
Detonators can be programmed
individually, or the entire blast plan can
be programmed using a data card.
Security Level
The blasting machines used in electronic blasting systems will not activate unless the blaster
unlocks the unit with either a key, a pass code, or both. Most electronic detonators are
unable to be detonated with a conventional blasting machine.

Electronic Systems
Factory-Programmed Systems and Field-Programmed Systems
Factory-programmed systems have “fixed” delay periods, and holes to be shot with such
systems are loaded in the same manner as are standard electric or shock-tube systems.
Some manufacturers of factory-programmed systems include surface connectors for
efficient tie-in or to maintain electrical polarity.
Click on the image above to play a clip showing the
operation of a field-programmable detonator.
Field-programmed systems,
on the other hand, are
programmed on the bench.
There are no fixed delay times
associated with these
detonators. In addition, most
field-programmed systems have
an electronic memory that
allows them to be programmed
either prior to loading or any
time prior to firing by a direct
communication between the
blasting machine and the
detonator.

Electronic Systems
Factory-Programmed, Fixed Delay-Period
Systems
A typical* factory-programmed, fixed delay-
period electronic system features:
• Typically, two wires;
• Electric tie-in principles;
• Coded security;
• Multiple delay periods;
• A blast machine; and
• Sequential capability.
________________
*As we have noted, there are several
different electronic systems on the market today,
and many of the larger explosive manufacturers
have developed their own systems, each of them
slightly different from the next. Hence, this and
the descriptions on the following pages
summarize only what might be considered a
“typical” example of the subtype of system to
which they pertain, not any system in particular.

Electronic Systems
Factory-Programmed, Shock-Tube-Initiated Systems
A typical factory-programmed, shock-tube-initiated
electronic system features:
• Shock-tube leads;
• Energy transition;
• Electronic delay; and
• Standard tie-ins.
17ms 17ms 17ms

Electronic Systems
Field-Programmed, Variable-Delay-Period
Systems
A typical field-programmed, variable-delay-period
electronic system features:
• Two or more wires;
• Digital/coded security;
• 1-ms interval delays;
• Blast-machine programming;
• Hand-held programmers; and
• Blast-design software options.

Electronic Systems
In–Hole, Fixed-Delay-Interval Control Systems
A typical in-hole, fixed-delay-interval control
system features:
• 5-wire ribbon wire;
• A blast machine and controllers;
• Series tie-in;
• Plug-in connectors;
• 32-second in-hole delay; and
• Pre-programmed surface controllers.

Electronic Systems
Passively Programmed, Field-Programmed
Systems
A typical passively programmed, field-
programmed system features:
• Two wires;
• A blast machine, a computer, and
scanners;
• Network tie-in;
• Plug-in connectors; and
• A bar-code reader that is sequenced
and programmed.

Electronic Systems
Precise timing control is the main advantage of electronic detonators. Detonator firing errors are
on the order of microseconds, as distinguished from the ms errors associated with pyrotechnic-
delay detonators. Electronic detonators use circuit boards and programmable application-
specific integrated circuit (ASIC) processors
to add very precise delays that are more reliable
than traditional pyrotechnic delays.
Click the black screen above to see a test
example of the accurate timing effects of
electronic detonators, which, unlike 8-ms
pyrotechnic delays, fire simultaneously.
CIRCUIT BOARD:
logic capacitor
ASIC processor
firing capacitor
fuse head
detonating wire
CIRCUIT BOARD:
logic capacitor
ASIC processor
firing capacitor
fuse head
detonating wire
Electronic
detonator.
leg wires
rubber plug
bridge wire
delay element
primary charge
base charge
ignition charge
Electric
detonator.

Electronic Systems
IME “always” recommendations with respect to electronic detonation systems are:
• ALWAYS follow manufacturer’s warning and instructions, especially hook-up procedures and safety
precautions;
• ALWAYS fire electronic detonators with the equipment and procedures recommended by the manufacturer;
• ALWAYS verify the integrity of the detonator system prior to initiation of a blast;
• ALWAYS follow the manufacturer’s instructions when aborting a blast (wait a minimum of 30 minutes before
returning to a blastsite after aborting a blast, unless the manufacturer provides other specific instructions);
• ALWAYS keep detonator leads, coupling devices, and connectors protected until ready to test or fire the
blast;
• ALWAYS keep wire ends, connectors, and fittings clean and free from dirt or contamination prior to
connection;
• ALWAYS follow manufacturer’s recommended practices to protect electronic detonators from
electromagnetic, radio-frequency, or other electrical interference sources;
• ALWAYS protect electronic detonator wires, connectors, coupling devices, and shock-tube or other
components from mechanical abuse and damage;
• ALWAYS ensure that the blaster in charge has control over the blastsite throughout the programming,
system charging, firing, and detonation of the blast; and
• ALWAYS use extreme care when programming delay times in the field, to ensure correct blast designs;
incorrect programming can result in misfires, flyrock, excessive airblast, and vibration.

Electronic Systems
Likewise, IME “never” recommendations with respect to electronic detonation systems are:
• NEVER mix electronic detonators and electric detonators in the same blast, even if they are made by
the same manufacturer, unless such use is approved by the manufacturer;
• NEVER mix electronic detonators of different types and/or versions in the same blast, even if they are
made by the same manufacturer, unless such use is approved by the manufacturer;
• NEVER mix or use electronic detonators
and equipment made by different
manufacturers;
• NEVER use test equipment and blasting
machines designed for electric detonators
with electronic detonators;
• NEVER use equipment or electronic
detonators that appear to be damaged or
poorly maintained; and
• NEVER attempt to use blasting
machines, testers, or instruments with
electronic detonators that are not
specifically designed for the particular
electronic-detonation system you are using.

Electronic Systems
In addition, IME recommends that you:
• NEVER attempt to cut and splice leads unless specifically recommended by the manufacturer;
• NEVER make final hook-up to the firing device or blast controller until all personnel are clear of the
blast area;
• NEVER load boreholes in open work areas near electric powerlines unless the firing lines and
detonator wires are anchored or are too short to reach the powerlines;
• NEVER handle or use electronic
detonators during the approach and
progress of an electrical storm (personnel
must be withdrawn from the blast area to a
safe location under such conditions);
• NEVER use electronic detonator systems
outside the manufacturer’s specified
operational temperature and pressure
ranges;
• NEVER test or program an electronic
detonator in a booster, cartridge, or other
explosive component (primer assembly)
before it has been deployed in the borehole
or otherwise loaded for final use; and
• NEVER hold an electronic detonator
while it is being tested or programmed.
Click the image above to play a video
clip showing an electronic-detonation
system in use.

1. Some electronic blasting systems are very complex and require either custom blasting
machines or __ to fire their detonators.
a. CD blasting machines
b. Guns
c. Loggers
d. Computers
2. Factory-programmed detonators are available for some electronic blasting systems,
whereas other systems use smart detonators that can be programmed on the:
a. Shelf
b. Bench
c. Truck
d. All of the above
3. True or false: field-programmed detonators usually have fixed delay times?
4. Pyrotechnic delays typically show timing ranges of ± 5 milliseconds. Electronic-delay
timing ranges have been tested to ± 1:
a. Nanosecond
b. Millisecond
c. Macrosecond
d. Microsecond
5. True or false: incorrect detonator programming can result in misfires, flyrock,
excessive airblast, and vibration?

Answers
1. d. is correct.
2. b. is correct.
3. False.
4. d. is correct.
5. True.

Cap-and-Fuse Systems
A cap-and-fuse system, also called a fuse-detonator system, consists of blasting caps and
fuse detonators that are crimped to a length of safety fuse.
In a safety-fuse system, the fuse is typically ignited with either a hot-wire fuse lighter, a pull-
wire fuse lighter, or an igniter cord and igniter-cord connectors.
Cap-and-fuse systems should be used only by supervised, trained, experienced, and skilled
blasters who are completely familiar with the use of explosives on a day-to-day basis.
In addition, cap-and-fuse blasting should only be used where a long delay time between the
detonating of individual holes will not create a problem.

A safety fuse is a medium through which flame is continuously
conveyed at a relatively uniform speed to initiate the heat-sensitive
charge in an ordinary blasting cap. Cap-and-fuse assemblies are
able to fire single charges or multiple charges designed to initiate in
rotation.
Charges that must be shot instantaneously, as in pre-shear
(perimeter control, presplitting, etc.) work, or those that require
short delay intervals cannot use a safety-fuse initiation method,
because blast timing with a fuse is not sufficiently precise.
IME recommendations with respect to cap-and-fuse detonation
systems are:
• ALWAYS handle a fuse carefully to avoid damaging the
covering;
• In cold weather, ALWAYS warm the fuse slightly before
using it, to avoid cracking the waterproofing;
• ALWAYS know the burning speed of a safety fuse
(burning speed can be determined by conducting a test burn
of the fuse in use, to make sure you have time to reach
safety after lighting it);
• NEVER use lengths of safety fuse less than 3 feet; and
• NEVER insert anything but a fuse into the open end of a
detonator.

In addition, IME recommends that you:
• ALWAYS cut 1 or 2 inches off a fuse, to ensure a dry end (cut the fuse squarely across with
the proper tool designed for this purpose; DO NOT use a knife);
• ALWAYS seat the fuse lightly against the detonator charge and avoid twisting after it is in
place;
• ALWAYS ensure that the detonator is securely crimped to the fuse;
• ALWAYS use a waterproof crimp or waterproof the fuse-to-detonator joint in wet work;
• ALWAYS use cap crimpers to crimp the detonator to the safety fuse;
• NEVER twist the fuse inside the detonator;
• NEVER use a knife or teeth for crimping;
• NEVER use an open-fuse detonator for a booster;
• NEVER cut a fuse until you are ready to insert it into the detonator;
• NEVER crimp detonators by any means except a cap crimper designed for the purpose;
and
• NEVER attempt to remove a detonator from the fuse to which it is crimped.

The steps for assembling a fuse detonator and a safety fuse are:
Step 1.—Wait until you are ready to insert the fuse into the fuse detonator before
cutting it.
Step 2.—Cut off 1 or 2 inches of the fuse to ensure a dry end.
Step 3.—Measure the correct length of the fuse from the roll, and cut squarely
across with a fuse cutter designed for this purpose. Do not use a knife.
Step 4.—Visually inspect the inside of the detonator for foreign material or moisture;
if the detonator is wet or if foreign matter cannot be removed by pouring,
do not use the detonator. Instead, dispose of it in an approved manner.
Step 5.—Put the safety fuse gently against the powder charge.
Step 6.—Crimp the end of the fuse detonator where the fuse enters, using a cap
crimper.

The crimp is an indentation on the cap
shell that joins the cap and fuse
together. Crimps should be tight
enough both to hold the cap securely in
place and to provide a watertight seal.
If the crimp is loose, the fuse may pull
away from the cap charge or out of the
cap, allowing moisture to come in
contact with the ignition powder.
All crimps must be made near—not
more than 3/8 inch (9.5 millimeters)
from—the open end of a cap shell.
Crimping more than 3/8 inch (9.5
millimeters) from the open end of the
shell can prematurely initiate the cap.
NEVER ATTEMPT TO CRIMP THE
CAP WITH THE FUSE CUTTER, AS
THE CAP MAY DETONATE.

Recommended steps for lighting a safety fuse are:
Step 1.—Make sure you can reach a safe location after lighting, with sufficient time
before initiation.
Step 2.—Place sufficient stemming over the explosive material to protect it from
fuse-generated heat and sparks.
Step 3.—Have a partner before lighting the fuse. One person should light the fuse,
and the other should time and monitor the burn.
Step 4.—Light the safety fuse using a specially designed lighter: a single-fuse
ignition requires a hot-wire lighter, a pull-wire lighter, or thermalite
connectors; a multiple-fuse ignition requires an igniter cord with
thermalite connectors.
Igniter cord. Igniter-cord
connectors.

With respect to cap-and-fuse systems, remember that:
• The fuse burns at its core, not at its cover;
• You should have two persons present when lighting the fuse;
• The explosive charge must in place before the fuse is lit; and
• If the charge does not detonate or you do not hear the
detonation at the calculated time, you should not return to the
blast area for at least 1 hour.

1. __ is a permissible means of lighting a safety fuse.
a. A cigarette lighter
b. A hot-wire lighter
c. Matches
d. All of the above
2. When a safety fuse or blasting caps appear to have misfired, persons shall not
enter the blast area for __ minutes.
a. 20
b. 30
c. 45
d. 60
3. Which of the following are sources of extraneous electricity?
a. Lightning storms
b. Stray AC current
c. Radio frequency
d. All of the above

Review Questions and Discussion—continued
4. Why would you choose a shock tube over a detonating cord to detonate your
blast?
a. Airblast concerns
b. Storage concerns
c. The desire for greater control over timing
d. All of the above
5. In locations that are close to residential or commercial sites, the noise that a
detonating-cord trunkline generates during a blast may cause complaints.
Which, if any, of the following approaches might be used to address this
prospective problem?
a. Eliminate the trunkline by replacing it with either an electric, a flash-tube,
or an electronic detonator
b. Initiate a detonating cord upline, from the bottom of the hole, using either
an electric or a non-electric detonator
c. Cover the trunkline with at least 12 inches of fine drill cuttings or dirt
d. Any of the above

Answers
1. b. is correct.
2. d. is correct.
3. d. is correct.
4. d. is correct.
5. a. is correct.

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