Blasting Operations

[ابوالحسنی محمد]

October 2009 24-1
Section 24
Blasting Operations
This section discusses blasting operations, with specific focus on the following

areas:

• General Requirements
• Radio and Electromagnetic Radiation
• Transporting Explosives
• Transporting Explosives Underground
• Storing Explosives
• Handling Explosives
• Loading Explosives and Blasting Agents
• Wiring operations
• Firing explosives
• Inspection following a blast
• Misfires
• Using safety fuses
• Using detonator cord
• Underwater blasting
24.1 General Requirements for Blasting Operations
In addition to the requirements of this section, the transportation, handling,
storage, and use of explosives are subject to provisions of ANSI A10.7 - Safety
Requirements for Transportation, Storage, Handling, and Use of Commercial
Explosives and Blasting Agents; 29 CFR 1910.109 - Explosives and Blasting
Agents; 29 CFR 1926, Subpart U - Blasting and the Use of Explosives (1926.900
to 1926.914); and 27 CFR Part 55 - Commerce in Explosives.
24.1.1 Competent Supervision. A blasting supervisor must be designated to
direct and supervise all blasting operations. This includes the transportation,
handling, storage, and use of explosives and blasting agents. The supervisor must
provide written records of past experience to the employer as evidence of
competency.
24.1.2 Qualifications.
a. Personnel. Employees who transport, store, handle, or use explosives
or blasting agents must be at least 21 years of age. They must be able to
give and understand written and verbal instructions.
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Health Standards
24-2 October 2009
b. Blasters. Blasters must be qualified through training, knowledge, and
experience in transporting, storing, handling, and using explosives, and
have a working knowledge of State and local laws and regulations which
pertain to explosives. Blasters must hold a Federal, State, or local license
or certificate, have proof of formal training attended within the last
5 years, or three recommendations from past employers or explosives
manufacturers testifying to the blaster’s knowledge and ability to perform
in a safe manner the type of blasting that will be required.
24.1.3 Blasting Plan. Submit a comprehensive blasting plan before the start of
blasting operations and have it approved. The blasting plan may be submitted as
part of the overall site safety plan, as required by the "Contractor Requirements"
section of these standards (for contract operations) or as a supplementary plan to a
Job Hazard Analysis. Explosives must not be transported onto the jobsite before
the plan has been approved. The plan must identify proposed methods and
procedures for conforming with referenced standards and regulations, and it must
include the following information:
• Method and equipment for transporting explosives and detonators
• Type and location of storage facilities
• Type and quantity of explosives and detonators
• Primer assembly procedure and location
• Employee training programs
• Provisions for protecting people, structures, and private and public
property
• Provisions for developing and distributing a daily blasting plan
covering hole diameter, spacing, loading, and delay patterns
• Provisions for disposal of explosives, blasting agents, and associated
materials
24.1.4 Security and Inventory. Secure and protect explosives from theft.
Maintain an accurate running inventory of all explosives stored at the jobsite.
Such records must be available. Promptly report any loss or theft to the
appropriate authorities.
24.1.5 Notifications. Notify the owners and operators of the facility and take all
necessary precautions for the safe control of the blasting operations before
beginning blasting operations in the immediate vicinity of buildings, public roads,
overhead powerlines, utility services, or similar facilities. At least 24 hours
before blasting in the vicinity of gas, electric, water, communications, or other
utilities is to begin, the blasting supervisor must notify appropriate utility
representatives.
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24.1.6 Smoking Restrictions. Prohibit smoking, firearms, matches, open flame
lamps, fire, heat-producing devices, and sparks in or near explosive storage sites
or in areas where explosives are handled, transported, or used.
24.1.7 Thunderstorms. Discontinue the handling or use of explosives during
the approach and progress of a thunderstorm. All employees must leave the
danger areas and seek a place of safety when these conditions are present. Install
an approved lightning warning device capable of detecting atmospheric
conditions that could produce lightning on the jobsite. Warning devices must be
acceptable to the COR or office head before installation.
24.1.8 Damage Control. Take precautions to minimize ground vibration,
airblast, and flyrock. Include a damage control section in the site blasting plan
that addresses these issues. Use blasting mats where flyrock damage is possible.
Use modern blasting seismographs and methods to measure ground vibrations and
air blast levels at designated structures or locations. Unless otherwise specified,
control the blasting so that ground vibrations and airblast levels do not exceed the
following:
Ground Vibration Limits1
Type of Structure2
Peak Particle Velocity (inches per second)
At Low Frequency3
(<40 Hertz)
At High Frequency
(>40 Hertz)
Modern homes, drywall
interiors 0.75 2.0
Older homes, plaster on
wood lath construction for
interior walls
0.5 2.0
Reference: Siskind, D.E., M.S. Stagg, J.W. Kopp, and C.H. Dowding, “Structure Response and
Damage Produced by Ground Vibration from Surface Mine Blasting.” U.S. Department of the
Interior, Bureau of Mines, Report of Investigations RI 8507, 1980.
1The graph in Appendix B of the above reference may be used in lieu of the limits listed in this
table.
2For precarious structures not listed in the table, use the limits for older homes; for all other
structures not listed in the table, use the limits listed for modern homes.
3All spectral peaks within 50 percent amplitude of the predominant frequency must be analyzed.
Airblast Limits
Instrumentation Air Blast (decibels)
0.1 hertz high-pass system 134
2 hertz high-pass system 133
5 or 6 hertz high-pass system 129
C-slow (for events not exceeding 2 seconds’ duration) 105
Reference: Siskind, D.E., V.J. Stachura, M.S. Stagg, and J.W. Kopp, “Structure Response
and Damage Produced by Airblast from Surface Mining,” U.S. Department of the Interior, Bureau of
Mines, Report of Investigations RI 8485, 1980.
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Health Standards
24-4 October 2009
24.1.9 Warning Signs. Post warning signs at access points to blasting areas.
24.1.10 Destruction of Explosives. Deteriorated or damaged explosives,
blasting agents, blasting supplies are prohibited. Destroy and remove these and
all excess explosives from the site in accordance with the specific written
instructions of the manufacturer.
24.1.11 Empty Explosive Containers. Destroy empty boxes and combustible
packing materials which have contained explosives in accordance with the
manufacturer’s disposal procedures. If disposal is through burning, all personnel
must remain at least 100 feet from the burning site once the material has been
ignited and until no visible flames or smoke have been detected for 1 hour.
24.1.12 Fire. If a fire begins that involves explosives, or where the danger of the
fire contacting explosives is imminent, do not fight the fire. All personnel must
seek safe shelter; guard the fire area to prevent intruders.
24.2 Radio and Electromagnetic Radiation
Take adequate precautions to prevent accidental discharge of electric blasting
caps from current induced by radar, radio transmitters, powerlines, and similar
sources of electromagnetic radiation.
24.2.1 Mobile Radio Transmitters. Mobile radio transmitters or cellular
telephones within 100 feet of electric blasting caps or delays not in their original
containers are prohibited unless de-energized and effectively locked.
Post warning signs at least 36 by 42 inches in size, stating BLASTING ZONE—
TURN OFF 2-WAY RADIOS AND CELLULAR TELEPHONES, on all public
roads within 1,000 feet of blasting operations, using electronic detonators.
24.2.2 Non-electric Firing Systems. If it is not possible to observe the safe
clearance distances from radio frequency (RF) transmitter stations, as set forth in
Institute of Makers of Explosives (IME) publication 20, "Safety Guide for the
Prevention of Radio Frequency Radiation Hazards in the Use Of Electric Blasting
Caps," use nonelectric firing systems to blast. Electrical detonators must not be
stored or used within the IME-specified distances of a transmitter station.
24.3 Requirements for Transporting Explosives
Transporting explosives by air, water, or on public highways must comply with
the provisions of US Department of Transportation Regulations contained in
46 CFR 146-149 - Water Carriers; 49 CFR 171-177 Subchapter C - Hazardous
Materials Transportation; and 49 CFR 390-397, "Motor Carriers."
24.3.1 Vehicles. Vehicles used to transport explosives must conform to the
following requirements:
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October 2009 24-5
a. They must be in good repair, with all electrical wiring completely
protected and securely fastened to prevent short circuits.
b. They must have tight floors. Cover any exposed spark-producing metal
with wood or other nonsparking material to prevent contact with
containers of explosives.
c. Do not load them beyond rated capacity, and secure the explosives to
prevent shifting or dislodgment.
d. Transport explosive materials in open-bodied motor vehicles only if
they have been loaded into a portable magazine that is securely fastened to
the truck bed. Never transport explosive materials in open-bodied motor
vehicles that depend on a fire-resistant tarpaulin cover for protection.
e. Mark vehicles transporting explosives with reflectorized signs on both
sides and the front and rear with "EXPLOSIVES" in red letters. Make
letters at least 4 inches high on a white background or placarded in
accordance with 49 CFR Part 172, Subpart F - "Placarding."
f. Equip them with two or more fire extinguishers with a rating of at least
2-A:40-B:C.
g. Inspect them daily before use to ensure that the vehicle is in proper
condition for safe transportation. The inspection must determine that fire
extinguishers are charged and ready; electric wiring is protected and
fastened to prevent short circuiting; chassis, motor, pan, and underbody
are reasonably clean and free of oil and grease; fuel tanks and lines are
secure and have no leaks; tires are in serviceable condition with proper
inflation; and lights, brakes, horns, wipers, etc., are functioning properly.
24.3.2 Vehicle Operators. Motor vehicle operators transporting explosives must
be at least 21 years old and be properly licensed drivers. Drivers must be
physically fit, careful, capable, and reliable. Drivers must not be unlawful users
of, or addicted to, alcohol, narcotics, or dangerous drugs. Drivers must be
familiar with applicable local, State, and Federal laws and regulations governing
the transportation of explosive materials. Transportation on Federal highways or
other public roads requires a commercial driver's license.
24.3.3 Caps and Detonators. Do not transport blasting caps and detonators with
other explosives unless the blasting caps or detonators are in a closed metal
storage container that has at least a 2-inch wood lining. Such containers must be
at least 2 feet away from other explosives.
24.3.4 Flammable Materials. Do not transport spark-producing tools, carbides,
oil, matches, firearms, acids, storage batteries, oxidizing or corrosive compounds,
or flammable materials with explosives.
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24-6 October 2009
24.3.5 Parking. Attend vehicles containing explosives at all times. Do not park
loaded vehicles, even if attended, near any bridge, tunnel, or other structure that
may be occupied or locations where people may congregate or assemble.
24.3.6 Fueling. Do not refuel vehicles while they are carrying explosives.
24.3.7 Smoking Restrictions. Employees who transport, handle, or use
explosives must not smoke or carry on their persons or in the vehicle matches,
lighters, firearms, ammunition, or flame-producing devices of any description.
24.3.8 Riders. Permit only the authorized driver and helper to ride on trucks
transporting explosives or detonators.
24.4 Requirements for Transporting Explosives Underground
In addition to the requirements set forth in the previous subsection,
"Requirements for Transporting Explosives," the provisions of this subsection
apply to underground transportation of explosives.
24.4.1 Hoists. Notify the hoist operator before transporting explosives or
blasting agents in a shaft conveyance. Do not permit any person to ride a hoist or
shaft conveyance transporting explosives or blasting agents. Do not transport
detonators while transporting explosives.
24.4.2 Powder Cars and Trucks. Convey explosives and blasting agents only
in specifically built or equipped insulated powder cars or truck-mounted
containers approved by the State entity having jurisdiction. Mark powder cars
with reflectorized signs on both ends and sides with "EXPLOSIVES" in letters at
least 4 inches high against a sharply contrasting background at all times that there
are explosives in the car. Cover or remove the signs when no explosives are
present. Do not transport explosives or blasting agents on a locomotive; at least
two car lengths must separate the locomotive from the powder car. Pull (do not
push) powder cars.
24.4.3 Common Transport of Detonators and Explosive Materials.
Physically separate compartments for transporting both detonators and explosive
materials in the same conveyance or car by at least 24 inches or by a solid
partition at least 6 inches thick. Do not transport detonators and other explosive
materials together in any shaft-conveyance.
24.4.4 Transportation of Personnel and Explosives. No personnel, other than
the transport operator, helper, and the individuals handling the explosives may
ride transports carrying explosives.
24.4.5 Truck Transportation. Trucks transporting explosives underground
must meet other applicable provisions of these standards and have their electrical
systems checked weekly to detect possible electrical hazards. A written record of
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October 2009 24-7
such inspections must be maintained. Auxiliary lights on truck beds powered by
the truck's electrical system are prohibited. Do not store explosives in trucks.
24.4.6 Transporting Explosives to the Face or the Loading Area. Take only
the quantity of explosives or blasting agents estimated necessary for the blast to
the face or loading area. Take explosives or blasting agents to the loading area
only after the drilling has been completed and the holes are ready to be loaded.
Remove surplus explosives and blasting agents from the area before wiring up the
blast.
24.4.7 Makeups. Make up primers and delays at the face or loading area, unless
a primer-makeup plan is submitted and approved.
24.5 Explosives Storage
24.5.1 Requirement. Store explosives and related materials in approved
magazines and in accordance with the applicable provisions of the Bureau of
Alcohol, Tobacco, and Firearms as set forth in 27 CFR 55, "Commerce in
Explosives." Magazines must be bulletproof, rodent-resistant, weather-resistant,
ventilated, and constructed to the standards of the Bureau of Alcohol, Tobacco,
and Firearms, or the Institute of Makers of Explosives.
24.5.2 Magazine Location. Locate explosives magazines in accordance with the
State and local laws. The COR or office head must approve the proposed sites
before location or construction. Consider contractor and Government offices,
shops, etc., to be inhabited buildings when determining magazine locations,
quantities, and safe distances.
24.5.3 Notifications. Notify local authorities, such as law enforcement agencies
and fire departments, of the type, planned quantity, and storage location on the
site before bringing explosives onto a site for storage.
24.5.4 Detonators. Do not store blasting caps, electric blasting caps, detonating
primers, and primed cartridges in the same magazine as other explosives or
blasting agents. Locate detonator magazines at least 100 feet from magazines
containing other explosives or blasting agents, if unbarricaded, and at least 50 feet
away, if barricaded.
24.5.5 Combustible Materials. Do not permit smoking or open flame within
100 feet of storage magazines. Remove vegetation and combustible material
within 25 feet of all magazines.
24.5.6 Security. Securely lock magazines at all times except to inspect or move
explosives. Maintain an inventory of all storage and withdrawal of explosives.
Inspect magazines storing explosives at least every 7 days to ensure that there has
been no unauthorized entry or removal of explosives.
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24-8 October 2009
24.5.7 Posting. Post areas around magazines with "EXPLOSIVES" signs. Place
the signs so that a bullet passing through the sign will not strike a magazine.
24.5.8 Storage. Store explosives in their original containers. Store containers of
explosives with the top side up as designated on the container. Use the oldest
stock of explosives first.
24.5.9 Maintenance. Promptly remove debris and combustible material from
magazines. When magazine floors become stained with explosives, clean them in
accordance with the explosive manufacturer’s instructions.
24.5.10 Transfer In and Out. Provide for the safe transfer of explosives in and
out of magazines, including providing ramps or walkways, as necessary.
24.5.11 Storage Underground. Do not permanently store explosives
underground. Temporary storage must comply with the following requirements:
a. Powder Cars. Restrict temporary storage to limited supplies stored in
specially designed powder cars located at least 1,000 feet from the face or
blasting area. Do not permit transformers, storage of flammable materials,
welding, open flame, smoking, and other ignition sources within 100 feet
of the powder car.
b. Posting and Lighting. Designate the storage area or siding by a red
light visible in all directions, and post both ends of the powder car with a
luminous sign, stating "EXPLOSIVES - NO SMOKING, FLAME, OR
WELDING WITHIN 100 FEET."
c. Protection. Locate or barricade the powder car to protect it from
damage. Design siding or car-passes, when used for temporary storage, to
protect the powder car from accidental entry by other cars and to prevent
accidental entry of the powder car to the main line. The protective devices
installed are subject to approval of both the employer and the State entity
having jurisdiction.
24.6 Requirements for Handling Explosives
24.6.1 Handling Explosives. Handle explosives carefully. Do not drop, throw,
or slide them. Carry detonators, primers, and other explosives in separate
containers when transporting them manually. When they are not in their original
containers, place them in a suitable nonmetallic container for manual
transportation.
24.6.2 Removal from Containers. Remove explosives from their original
containers only as needed for immediate use. Use only nonsparking tools or
devices to open such containers. Dispose of empty containers and packing in
accordance with the manufacturer's recommendations, or promptly burn them in
an approved location.
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October 2009 24-9
24.7 Loading Explosives and Blasting Agents
24.7.1 Planning. Plan and schedule excavation so that drilling and loading
operations will not conflict. Do not permit loading within 50 feet of drilling
operations. Do not permit any activity, other than that which is required for
loading holes, within 50 feet of loaded holes or holes that have the explosives in
place, ready to load. A qualified blaster must supervise loading operations.
24.7.2 Drilling. Do not drill in an area already blasted until examining
remaining "bootlegs" (holes that do not detonate full depth) for unexploded
charges, as well as the total area, to make sure no unexploded charges remain. Do
not insert drills, picks, or bars into bootlegs, even if examination fails to disclose
explosives.
24.7.3 Loading Areas. Make boreholes ready for loading, and remove
equipment and tools not used for loading from the area before delivering the
explosives to the site. Isolate the loading areas with appropriate signs or
temporary barricades to prohibit access by unauthorized people. While the bare
holes are being loaded with explosives, exclude all personnel, other than those
involved in the loading of boreholes, from the blast site.
24.7.4 Boreholes. Make boreholes large enough to permit loading of cartridges
and explosives without forcing. Prime, load, tamp, and fire as promptly as
possible with a minimum of exposure to personnel.
24.7.5 Tamping. Tamp only with wooden or plastic tamping poles without
exposed metal parts. Nonsparking metal connectors on jointed poles are
permissible. Seat cartridges by even, steady pressure, and do not tamp primers.
24.7.6 Priming. Follow the manufacturer's recommendations in priming
cartridges. Make primers up only at the loading area and in quantities limited to
the number required for a single round of blasting.
24.7.7 Stemming. Stem all blastholes in open work with noncombustible
material to the collar or to a point that will confine the charge.
24.7.8 Extraneous Electricity. Prohibit electric conductors, electric equipment,
and all sources of ignition in or adjacent to the loading area. Remove lights
50 feet from the face before starting to load in tunnels and shafts. If stray currents
are suspected, thoroughly check out the area with suitable instruments. If stray
currents cannot be eliminated, use nonelectrical detonators, delays, and caps.
24.7.9 Shunts. Do not remove the manufacturer's shunt from the cap leg wires
until you complete loading and connect the cap into the blasting circuit.
24.7.10 Sprung Holes. Do not chamber (spring) boreholes.
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24.7.11 Blasting Mats. Where blasting may expose personnel or property to
injury or damage from flying material, cover the charges with blasting mats.
Carefully protect the blasting circuits, and do not permit the circuits to contact
steel mats.
24.7.12 Loading and Shooting. Do not leave loaded holes unattended or
unprotected. If possible, fire all holes loaded on a shift during that same shift. If
it is necessary to delay firing because of an emergency, isolate the area and post
watchpersons to prevent entry to the area. Conduct aboveground blasting
operations between sunup and sundown.
24.7.13 Pneumatic Loading Systems. Conduct the hazards from static
electricity and stray currents associated with pneumatically loading boreholes
with blasting agents, take the following precautions:
a. Use only approved pneumatic loaders.
b. Effectively ground and bond the entire system, including placers,
valves, and loading hose. Ground at the face in tunnels and shafts. Do not
use piping and rails to ground the system.
c. Following installation of the ground, check the ground with an
approved meter to ensure that the resistance is within safe limits.
d. Use loading hoses of an approved, nonsparking, semiconductive
material designed to maintain static electricity within safe limits.
24.7.14 Underground Use of Blasting Agents. Before using blasting agents
underground, a powder technician representing the explosive manufacturer or
supplier must inspect the proposed method of loading and the loading equipment.
Submit written evidence of such inspection and approval of the systems.
24.8 Wiring Operations
24.8.1 Firing Devices. Use an electric blasting machine to fire blasts using
electronic detonators. Do not fire blasts by connection to any other electrical
system. Fire blasts using nonelectric detonators with a blasting machine or
starting device prescribed by the detonator manufacturer. Do not use cap and fuse
firing underground or in the excavation of shafts. Do not use electric blasting
caps within 500 feet of energized high-voltage lines or facilities.
24.8.2 Wiring Procedure. Do not remove the manufacturer's shunt from the cap
leg wires until the cap has been connected to the leadlines or to another cap in
preparation for the assembly of two or more caps into a single series. When firing
two or more series of caps as a series-parallel system, make sure that the caps in
each series are the same in number (quantity, not delay periods), and test each
series separately with an approved blasting galvanometer to: (1) ensure that the
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October 2009 24-11
series is complete, and (2) ensure that each series has the same resistance and that
the resistance is close to the calculated resistance for the series. If the first
reading indicates an incomplete circuit, locate the fault and correct it. If the
second reading indicates a higher or lower resistance than calculated, correct the
situation before final hookup and firing.
24.8.3 Electric Caps and Delays. All caps and delays in a shot must be made by
the same manufacturer, and the number in a circuit must not exceed the capacity
of the blasting machine or power source.
24.8.4 Galvanometer Testing. Make the following tests with an approved
blasting galvanometer during all wiring operations:
(1) Test the circuit, including all caps, before connecting it to the firing
line.
(2) Check the firing line before connecting it to the blasting machine or
power source.
24.8.5 Firing Lines. Firing lines must be of sufficient current-carrying capacity
but not smaller than No. 14 gauge solid copper wire or equivalent. Do not
connect the firing line to the blasting machine or power source until you have
completed and tested the wiring and cleared the blast area. Do not ground a
power circuit used for firing electric blasting caps.
24.8.6 Connecting and Lead Wires. Connecting and lead wires must be
insulated single solid wires of sufficient current-carrying capacity.
24.8.7 Power Circuit. When using a power circuit for firing, lock the firing
switch in the "OFF" (open) position at all times, except when firing. Design the
power circuit so that the firing lines to the cap circuit are automatically shortcircuited
when the switch is in the "OFF" position. Entrust the keys to the firing
switch only to the blaster. In underground operations, the firing circuit must have
a "lightning" gap of at least 5 feet, located between the firing switch and the
source of power. Bridge the gap with a flexible jumper cord just before firing the
blast.
24.9 Firing
24.9.1 Preparation. Before connecting the firing line to the power source, notify
all personnel in the danger area of the blast and remove them to a safe area. Make
satisfactory arrangements for evacuating the danger area and ensuring that no one
enters the area before the blast.
24.9.2 Responsibility. The blaster must be in charge of the blasting machine or
firing switch, and must connect the firing line to the firing device. The blaster
must make all connections from the cap circuit back to the firing device, and the
firing line must remain shorted until connected to the firing device immediately
before firing.
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24-12 October 2009
24.9.3 Blasting Signal. Sound the following blasting signal on a clearly audible
whistle, horn, or siren before each surface or underground blast:
• Blasting warning: A 1-minute series of long blasts 5 minutes before
the blast signal
• Blast signal: A series of short blasts 1-minute before the shot
• All clear: A prolonged blast following inspection of the blast area
24.9.4 Posting Blasting Signals. Post blasting signals at all access points, and
before each shot, post competent flagpersons at all access points to the danger
area.
24.9.5 Disconnecting. Immediately following the blast, disconnect the firing
line from the firing power source or blasting machine and shunt it. Lock firing
switches open.
24.10 Inspections Following a Blast
24.10.1 All Blasts. Before the all-clear signal, the blaster must thoroughly
inspect to determine if all charges have fired. The blaster must carefully check
wires and search for unexploded charges.
24.10.2 Underground. In addition to the previously listed requirements, check
and test the heading for adequate ventilation and safe concentrations of dusts,
toxic vapors, and gases. Also, before permitting personnel in the heading, scale
the face and make it safe.
24.10.3 All-Clear Signal. Sound the all-clear signal only after satisfactorily
completing the inspection.
24.11 Requirements Regarding Misfires
If you suspect or find a misfire, keep all personnel, except the blaster and
employees necessary to handle the misfire, out of the danger area. Prohibit all
work in the danger area except that necessary to remove the misfire hazard. If a
misfire occurs while using cap and fuse, all personnel must remain at a safe
distance from the charge for at least 1 hour. If other electric or nonelectric
initiating methods are used, the blasting supervisor may reduce the waiting period
to 30 minutes.
24.11.1 Refiring. Refiring is the desired method of clearing misfires. The
following actions are mandatory:
a. For electrically fired blasts in which broken wires or faulty connections
caused the misfire, make repairs, reconnect the firing line, and attempt to
fire the charge.
b. For misfires originally initiated by detonating cord or nonelectrical
detonators, the blaster must inspect lines coming out of the holes, and if
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October 2009 24-13
they appear to be intact, the blaster can reconnect them and attempt to
detonate the misfired holes.
c. In blastholes where leg wires are discontinuous or leads or detonating
cord cut off, there may still be explosives in the hole that can be reprimed
and fired. Remove any stemming in the hole. Float stemming out with
water. Place a new primer in the hole and attempt to fire the charge.
24.11.2 Removal of Explosives. This procedure must be the last resort. Perform
it only when refiring has failed or when refiring would present a hazard. Remove
explosives by washing them out with water, or, if the misfire is underwater, blow
them out with air.
24.11.3 Work Restrictions. Do not permit drilling, digging, or picking until:
(1) you have detonated all missed holes or removed the explosive, and (2) the
blaster has approved the resumption of work.
24.12 Requirements for Using Safety Fuses
Use safety fuses only where sources of extraneous electricity make the use of
electric caps dangerous. Do not use damaged fuse or fuse with sharp kinks.
24.12.1 Capping. Before capping a safety fuse, cut a short length from the end
to ensure a fresh-cut end in each blasting cap.
24.12.3 Crimper. Use cap crimpers of approved design for attaching blasting
caps to safety fuse.
24.12.4 Length of Fuse. The minimum length of safety fuse must be as required
by State law, but it must not be less than 30 inches. Provide the blaster sufficient
time to permit the blaster to reach a place of safety.
24.12.5 Multiple Cap and Fuse Use. At least two blasters must be present when
multiple cap fuse blasting is done by hand lighting methods. Each blaster must
light no more than 12 fuses when using hand-lighting devices.
24.12.6 Mudcapping. Do not use cap and fuse to fire mudcap charges unless
you separate the charges sufficiently to prevent one charge from dislodging other
shots in the blast.
24.13 Use of Detonating Cord
24.13.1 Care in Use. Use only detonating cord consistent with the type and
physical condition of the borehole, stemming, and the type of explosive.
Consider and handle detonating cord in the same manner as other explosives.
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Health Standards
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24.13.2 Installation. Cut the line of detonating cord extending out of a borehole
or from a charge from the supply spool before loading the remainder of the hole
or placing additional charges. All runs must be free of loops, sharp kinks, or
angles that take the cord back toward the oncoming line of detonation.
24.13.3 Connections. Detonating cord connections must be competent and
positive and in accordance with approved and recommended methods. Make
knot-type or other cord-to-cord connections only with detonating cord in which
the explosive core is dry. Inspect connections before firing.
24.13.4 Use of Delays. When using detonating cord millisecond-delay
connectors or short-interval-delay electric blasting caps with detonating cord,
follow the manufacturer's recommendations.
24.13.5 Connecting Blasting Caps. When connecting blasting caps to
detonating cord, tape or otherwise attach the cap securely along the side or the
end of the cord, with the end of the cap containing the explosive pointed in the
direction in which the detonation is to proceed.
24.13.6 Detonators. Do not bring detonators for firing the trunkline to the
loading area, and do not attach the detonating cord until everything else is in
readiness for the blast.
24.14 Underwater Blasting
24.14.1 Supervision. A competent blaster must conduct all blasting operations.
Do not fire any blast without that person’s approval.
24.14.2 Loading Tubes. Do not use loading tubes and casings of dissimilar
metals for electric or other stray-current-affected detonators or explosives. When
tubes are necessary, load these electrically affected devices through nonsparking
loading tubes.
24.14.3 Detonators. For underwater blasting operations, use only water-resistant
blasting caps and detonating cord or other detonators and/or firing systems and
methods approved by the manufacturer.
24.14.4 Marking Charges. When placing more than one charge underwater,
attach a float device to an element of each charge so that it will be released by the
firing. Handle misfires using precautions and procedures in this section.
24.14.5 Blast Warning. In addition to the standard audible blast warning,
display blasting flags.
24.14.6 Boats in Area. Do not fire blasts while any vessel underway is within
1,500 feet of the blasting area. Notify those onboard vessels moored or anchored
within 1,500 feet before the blast is fired.
Section 24—Blasting Operations
October 2009 24-15
24.14.7 Swimming and Diving. Do not fire blasts when swimmers or divers are
in the vicinity and exposed to injury from the blast.