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WorksheetsExplosives and Blasting
Total questions: 93
Worksheet time: 9hrs 21mins
What is the only kind of explosive that may be used in a coal mine?
Non-permissible explosives.
Permissible explosives or other permissible blasting devices.
What is a permissible explosive?
One which has been approved by mine management.
One which has been passed certain tests conducted by the Bureau of Mines or MSHA.
One which has passed certain tests conducted by the KDMM.
For what purposes are permissible explosives designed?
For use in and around the mines.
For safe use in underground mines so as to prevent the emission of explosive mixtures in mine atmospheres.
For surface mines only.
What agency determines the permissibility of explosives?
The Kentucky Department of Mines and Minerals.
MSHA or, in the past, the U.S. Bureau of Mines.
What are the characteristics of the flame which determines the permissibility of an explosive?
A long flame of long duration.
A short flame of short duration.
A short flame of long duration.
What are the causes of deterioration of permissible explosives?
Moisture, improper storage, or age.
Permissible explosives will not deteriorate.
How must a permissible explosive be fired?
It can be fired with non-electric detonators of proper strength.
Only with electric detonators of proper strength.
What type of blasting unit must be used to fire permissible explosives?
A 6-volt DC battery.
A permissible shot-firing unit of adequate capacity to fire all caps.
What is the maximum charge of permissible explosives for a hole less than 6 feet in depth?
3 pounds
2 pounds
1-1/2 pounds
What is the maximum charge of permissible explosives for a hole 6 feet or more in depth?
3 pounds
2 pounds
1-1/2 pounds
How must explosives be stemmed?
They can be properly confined with any material.
They must be properly confined in a hole with incombustible stemming material of the following lengths: at least 24 inches long, or one-half the length of the hole if the hole is less than 4 feet.
What must be the condition of the place before permissible explosives are fired?
Methane content must be less than 2% and excessive coal dust should not be present.
Methane content must be less than 1% and excessive coal dust should not be present.
Methane content must be less than 1% and excessive coal dust can be present.
What may be the result of using permissible explosives in a non-permissible manner?
It will have no effect.
Ignition of methane/air/dust mixtures, misfires, blowouts, or premature ignitions.
What is the principal cause of explosive accidents when permissible explosives are used?
Carelessness or improper use.
Using the wrong brand of explosives.
What poisonous gases are liberated by explosives when fired?
Methane and carbon monoxide.
Carbon dioxide and nitric acid.
Carbon monoxide and oxides of nitrogen.
How shall explosives and detonators be transported into a mine?
They can be transported by hand only.
They shall be enclosed in non-conductive boxes and transported separately from firing devices.
They shall be enclosed in conductive boxes and transported separately from firing devices.
If explosive and detonators are to be hauled on the same trip, how shall they be kept in relation to each other?
They shall be separated by substantially fastened hardwood partitions, at least 6 inches thick.
They shall be separated by substantially fastened hardwood partitions, at least 4 inches thick, or by a construction providing equivalent safety protection.
How may explosives be hauled by electrically operated trips?
In open type cars or containers that are substantially well built and lined with non-conductive material.
In covered type cars or containers that are substantially well built and lined with non-conductive material.
What are the provisions related to carrying explosives on trips which transport workers?
Explosives can be carried on trips which carry workers.
Explosives are prohibited on trips which carry workers.
At what time interval should explosive trips precede or follow any other trip?
They should not be less than 5 minutes apart.
They should not be less than 10 minutes apart.
They should not be less than 15 minutes apart.
What supplies may not be hauled in the same trip with explosives?
Any material can be hauled in the same trip with explosives.
Oil, grease, or other highly flammable materials.
How may explosives and detonators be transported by belt conveyors?
They can be transported in open cases or in enclosed, insulated containers.
Only in the original, unopened case or in enclosed, insulated containers.
How shall explosives be stored?
Very carefully.
In cool, dry, well ventilated magazines.
It does not matter as long as they are stored underground.
In what condition should the area in or around magazines be maintained?
Rubbish or accumulations of combustible material should not be permitted in or within 50 feet of the magazines.
Rubbish or accumulations of combustible material should not be permitted in or within 25 feet of the magazines.
What quantity of explosives may be stored underground in magazines?
Not more than a 24 hour supply.
Not more than a 48 hour supply.
Not more than a 72 hour supply.
How should explosives be stored near the working faces?
They shall be stored in separate, closed containers and shall be in a location that is at least 25 feet from the face and out of the line of blasting.
They shall be stored in separate, closed containers and shall be in a location that is at least 50 feet from the face and out of the line of blasting.
How far from pipe lines, power lines, rails, or conveyors shall explosives and detonators be kept when stored near the working faces?
At least 10 feet.
At least 15 feet.
At least 20 feet.
What distance shall separate explosives and detonators when stored near working faces?
A distance of 5 feet.
A distance of at least 10 feet.
A distances of at least 15 feet.
When shall explosives and detonators be removed from their containers?
After arriving at the face area.
As needed.
Immediately before use at the working face.
In what manner should explosives and blasting caps in a mine be kept?
They must be kept closed at all times.
Open for inspection at all times.
What type of blasting units must be used to fire permissible explosives?
Six volt DC batteries.
A permissible shot-firing unit of adequate capacity to fire all caps.
By whom shall shots be charged and fired?
A certified miner.
The mine superintendent.
By certified shotfirers designated by the mine foreman.
How is an electric blasting cap protected from stray electric current?
By means of a shunt.
It cannot be protected from stray electric current.
How is a shunt made?
It is made by short-circuiting the ends of the leg wires.
It is made by keeping the ends of the leg wires loose.
How should a shunt on leg wires be maintained until it is removed?
It should be short circuited or shunted at the end near the face or until ready to attach to the blasting unit.
It should be short circuited or shunted at the battery until ready to attach to the blasting unit.
How should the shotfiring cable be handled between the charge and firing station?
It should be staggered as to length, ends kept well separated and attached to the detonator leg wires, and unreeled from the charge toward the "firing station".
It should be staggered as to length, ends kept well separated when attached to the detonator leg wires, and unreeled from the firing station to the charge.
What are 2 dangers of electric fires?
There are no dangers when using electric detonators.
The current may be applied before all workers have reached a safe place or stray electric currents may cause premature detonation.
When should the blasting cap be placed in the explosives?
It can be done before the holes are drilled in order to save time.
Not until the holes are ready to be charged.
Where should the blasting cap be placed when a borehole is charged?
It shall be placed in the borehole last, pointing outward, and the rest of the charge shall be pushed in a continuous train to the back of the borehole.
The blasting cap, or primer shall be placed in the borehole first, pointing outward, and the rest of the charge shall be pushed in a continuous train to the back of the borehole to prevent cuttings from getting between the cartridges.
The blasting cap can be placed in the middle of the charge.
What is the primer used to fire a charged hole?
It is a blasting cap inserted into the stemming.
An explosives cartridge with a blasting cap inserted.
How should the blasting cap be inserted in a primer?
The blasting cap can be inserted in the primer and shall be at a depth of at least 3/4 of an inch.
In making a primer, a powder punch of non-sparking material shall be used. The hole in the cartridge shall be at least 1/2 inch deeper than the length of the detonator used. Rolling the end of the cartridge is prohibited.
What is meant by the term "multiple blasting"?
Detonating only one hole at a time.
Detonating more than one hole at a time.
What are disadvantages of multiple blasting?
There are no disadvantages to multiple blasting.
One or more of the shots may fail to detonate due to faulty wiring or defective detonators. Failed shots are usually covered by loose coal from the other shots and are undetected until dug into by machines or by hand.
How must the leg wires be connected when using delay detonators?
In a parallel circuit.
In a series circuit.
May instantaneous, regular or zero-delay detonators be fired in the same circuit as delayed detonators?
Yes.
No.
What is the minimum delay interval between adjacent rows of shots when using delay detonators?
Fifty milliseconds.
25 milliseconds.
100 milliseconds.
What must be done before a misfire is removed when using delay detonators?
The failed shot must be tested with a volt meter.
The failed shot must be tested with a galvanometer.
Do a shotfirer and drill operator for solid blasting have to be certified?
No.
Yes.
Should mudcaps (adobes) or other non-permissible, unconfined shots be fired underground?
Yes.
No.
What is the purpose of cutting the coal prior to blasting?
To provide an additional free face or faces to assist the action of the explosive and lesson the danger of blown-out shots.
It serves no purpose in cutting the coal prior to blasting.
Must a coal mine have a permit to shoot from the solid?
No, it is not necessary.
Yes.
What procedure should coal mine operators follow in order to engage in shooting coal from the solid?
They must carefully train their workers.
They should submit an application for a permit to the commissioner of the Department of Mines and Minerals on a form prescribed by the DMM.
What is the danger of blasting off the solid?
There are no dangers associated with solid blasting.
Ignition of explosive mixtures of gas and coal dust by blown-out shots.
What is the minimum burden that all blasting charges shall have?
12 inches in all direction, if the height of the seam permits.
18 inches in all direction, if the height of the seam permits.
At least 24 inches.
What is the limit of drilling blast holes in relation to cut depth?
Blast holes must be drilled beyond the depth of the cut.
Blast holes shall not be drilled beyond the depth of the cut.
What is the remedy for holes that are drilled deeper than the cut?
Nothing is required since only one or two holes may be drilled deeper than the cut.
The holes must be stemmed with incombustible material to the depth of the cut.
Why should holes not be drilled deeper than the depth of the machine cut?
They may result in a blown-out shot and will not be as effective.
The coal may not be broken up as well as needed.
How does the shot-firer know if holes are drilled to the correct depth?
He would not know if holes are drilled to the correct depth.
By carefully measuring the depth of the cut and holes.
How shall a hole be prepared before loading the charge?
It must be drilled only.
It shall be scrapped as clean as possible.
What may be the result of a charge that is separated by unremoved drill cuttings?
Nothing will result.
Incomplete explosion and possible burning of the unexploded charge.
How many types or brands of explosives may be used in the same hole?
Only 2.
Only 1.
How shall explosives be confined in a drill hole?
They shall be confined with combustible stemming material only.
They shall be confined with incombustible stemming material.
What is proper stemming material?
Coal dust or any available material.
Incombustible material such as sand, clay, rock dust or special devices such as water dummies.
What is the effect of incombustible stemming upon the flame of an explosive blast?
The length and duration of the flame are increased.
The length and duration of the flame are decreased.
What is the danger of improper stemming?
The coal will not be shot efficiently.
The danger of a blown-out shot.
What type of tool should be used for tamping?
Only metallic tamping bars should be used for charging and tamping bore holes.
Only non-metallic tamping bars shall be used for charging and tamping bore holes.
What kind of tamping tools are prohibited?
Wood or plastic tamping bars.
Metal or metal-clad tamping bars.
May electrical equipment be operated in the face area while blast holes are being charged?
Yes.
No.
How soon after charging shall holes be fired?
Within 30 minutes.
Promptly.
What may be the cause of premature detonation of a shot?
Improper stemming.
Stray electric currents.
Overcharging the hole.
What creates the force when an explosive is fired?
The sudden expansion of the gases liberated.
The sudden expansion of the coal that's being blasted.
What is required before shots may be fired in a working place?
The place shall be properly examined for the presence of carbon dioxide.
The place shall be properly examined for the presence of methane.
What is considered a dangerous percentage of methane when permissible explosives are to be fired?
Methane content of 2% or more.
Methane content of 1% or more.
In what direction is the maximum force of an explosive exerted?
The force is exerted unequally in all directions.
The force is exerted equally in all direction; however, it takes the direction of least resistance.
How should warnings be given when shots are about to be fired?
By distinctly shouting "fire" two times after miners have withdrawn from the area where the blasting will occur.
By distinctly shouting "fire" three times after miners have withdrawn from the area where the blasting will occur.
What should persons do when warned that shots are to be fired?
Nothing is required.
They should withdraw immediately and proceed to a safe place.
Where should persons be when shots are fired?
Around a corner of a pillar and out of the line of fire.
At least 50 feet from the face area.
When should the shotfirer make the connection to the blasting cable?
As soon as he's ready.
When all persons are out of the line of fire.
What shall be done before work is resumed after blasting?
Nothing is required.
The roof shall be examined and the working place shall be checked for gases and made safe.
What is the first thing to do when a misfire has occured?
Disconnect the wires from the blasting unit and short-circuit them at that location.
Disconnect the wires from the face area and short-circuit them at that location.
How long shall any person wait after a misfire before going back in the place?
At least 10 minutes.
At least 15 minutes.
At least 5 minutes.
How shall a misfire be removed?
By firing a separate charge at least 3 feet away from, and parallel to, the misfired charge.
By firing a separate charge at least 2 feet away from, and parallel to, the misfired charge or by washing the stemming and the charge from the borehole with water, or by inserting and firing a new primer after the stemming has been washed out.
How can misfires be prevented?
They can never be prevented.
By careful selection of explosives and firing devices and correct loading and firing of the charge.
Who shall be designated to fire shots?
Any experienced certified miner.
Only a certified shotfirer.
Anyone designated by the certified mine foreman.
What precaution must be taken when using permissible explosives in a mine?
A test for gas shall be made before each shot or groups of shots is fired.
A test for gas shall be made before and after firing each shot or groups of shots.
What other work may be done while shots are being charged?
Cleanup work may be done with a scoop.
No other work shall be permitted in the danger zone except emergency work necessary to safeguard the employees.
What type of tools may be used for opening explosive cases or boxes and inserting holes in the individual sticks of explosives?
Metallic tools may be used.
Only non-sparking tools may be used for this type of work.
When may the shunt be removed from the detonator leg-wire?
Not until the shot-firer is ready to connect to the firing cable.
The shunt can be removed after the explosives are removed from the packages.
May shots be fired by any other means than a permissible unit?
Yes.
No, except when all personnel are outside the mine.
What safety measure must be strictly observed before shots are fired in any working place?
The workers may be warned at the beginning of each shift.
Ample warning must be given and care taken to ascertain that all persons are in the clear, including persons working the adjoining vicinity, before shots are fired.
What is the danger of under-charging or over-charging a shot or shots?
The shots will not go off.
Blown-out shots.
Why is rapid firing of shots considered dangerous?
Gas and dust liberated from the first shots may be ignited by the succeeding ones.
There are no dangers when rapid firing is performed.
What device should be used to check the continuity of a circuit before blasting?
A volt meter.
A galvanometer.
