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The maximum surface temperature of all components on machines approved under Schedule 2G is:
150 degrees Centigrade.
All mobile equipment that is powered by a trailing cable and travels in excess of 2.5 mph must be provided with:
A cable reel.
The "dead-man" type switch on a hand-held tool functions by:
Closing with hand pressure and opening if pressure is released.
Each wire or cable leaving a battery box on storage battery operated equipment shall have:
Short-circuit protection in an explosion-proof enclosure.
Battery box covers:
Must be lined with a flame-resistant insulating material preferably bonded to the inside of the cover.
Battery-box covers must meet all of the following requirements, EXCEPT:
Be made of a non-sparking material.
How should hose conduit be marked to indicate it is flame-resistant?
Flame-resistant USBM - Not exceeding 3 feet.
To protect the trailing cable from being run over by mobile equipment,all self-propelled equipment:
Which moves faster than 2.5 mph must be equipped with cable reels.
Any underground machine traveling faster than how many MPH must be equipped with a cable reel?
What is the minimum distance that a 1/2-inch bolt can extend into the threaded portion of the hole on a permissible enclosure?
Control panels and electrical motors are equipped with access openings and inspection covers:
So maintenance personnel can more readily check for damaged or worn parts.
When a bolt with a diameter larger than 3/8-inch is used, thread engagement should be:
Equal to or greater than the diameter of the bolt.
What is the maximum radial clearance that should be allowed when installing a typical plug for spare lead entrance holes?
Since certain electrical components almost always spark when in operation, they:
Must be placed in explosion-proof enclosures before they are considered "permissible."
If the threads are stripped out of the cover of an explosion-proof box, which of the following methods is NOT accepted method of repair?
Drill hole through and use bolt nut.
Each bolt, stud or screw used to fasten a cover to an explosion-proof enclosure must be provided with a:
Lock washer to help hold it in position.
A permissible joint that is made of a large screw with five or six threads is called a:
Screw type joint.
All unused holes in permissible compartments must be:
Closed with specially designed fittings or plugs.
When a bolt hole in an explosion-proof enclosure is stripped out, it:
Is no longer considered permissible
Lenses for headlights used on mining machines must be constructed of glass or other suitable material with physical characteristics:
1/2-inch thick tempered glass.
What is the minimum thread engagement of bolts for an enclosure which is greater than 124 inches?
If the threads in the bolt holes of a permissible enclosure are stripped out, which of the following is NOT an acceptable means of repair?
Drill a hole through and use a nut and bolt.
Plane flange joints on explosion-proof enclosures cannot exceed a separation distance of:
The primary purpose of a breather on explosion-proof compartments is:
To allow harmful gases that cause corrosion to escape.
The use of bolts with more than one lock washer in a control panel box is considered:
An improper assembly.
Which of the following is NOT a requirement of cables between machine components?
They must be less than 6 feet in length.
What is the minimum distance a 1/2-inch bolt can extend into the threaded portion of the hole of a permissible enclosure?
Electrical components that normally arc during operation:
Must be properly enclosed to be considered permissible.
What minimum clearance must be maintained between the packing gland nut and the stuffing box?
Breathers or pressure-relief devices are installed on an explosion-proof enclosure to:
Relieve pressure, ventilate, or drain.
What is the minimum distance from the interior of an enclosure to the edge of a bolt hole (more than 124 cubic inches)?
The packing material in a stuffing box is compressed tightly against the cable by:
Tightening the packing gland nut.
Stuffing boxes are drilled into the walls of the explosion-proof enclosures in such a way that:
There's space for packing material to be placed around the cable.
Because of the electrical wiring inside headlights, the lens rings:
Should be mechanically tight and sealed or padlocked.
Plane flange joints and step flange joints are the types of joints formed:
When two pieces of metal come together.
When a bolt hole in an explosion-proof enclosure is stripped out, and re-tapping it to the next larger size:
7/16 of an inch of metal from the interior of the enclosure to the closest edge of the hole must be maintained.
When a standard packing gland is properly packed, the minimum clearance permitted between the shoulder of the packing nut and the top of the stuffing box is:
What is the minimum size of asbestos packing material allowed?
A 3/16-inch diameter if round and 3/16 x 3/16-inch if square.
What is the maximum-sized clearance of a plane flange joint on a shuttle car allowed by law?
Insulated wires should pass through metal walls of electric compartments only through:
Permissible electrical equipment is equipment which:
Is similar in all respects to that which has been approved by the USBM.
When 1/4-inch packing is used in a stuffing box, the maximum allowable diametrical clearance between the cable and the holes in the stuffing box and the packing nut is:
What is the maximum-sized spacing permitted for bolts securing enclosure covers with joints all in one plane?
The minimum clearance between the shoulder of the nut and the top of a stuffing box in a properly packed, standard packing gland is:
Before electric face equipment is deemed permissible, the equipment must meet the:
Specifications set forth by the Secretary.
The maintenance required to keep equipment in permissible condition is the responsibility of the:
Permissibility is required for electrical equipment and components:
Inby the last open crosscut and in return air.
Headlights used on permissible mining machines to provide illumination in the direction of travel:
Must be permissible.
What is the minimum distance from combustible material that unattended enclosed motors, rectifiers, and transformers may be placed?
The primary function of a strain clamp is to:
Transfer most of the strain from the trailing cable to the frame of the equipment it feeds.
In low-and medium-voltage, three-phase AC systems, the maximum ground-fault tripping current should not exceed:
A tool or switch that is held in an operator's hand or supported against an operator's body will NOT be approved if the nameplate rating on the tool or switch exceeds:
300 volts DC or AC.
The term "intrinsically safe circuits" refers to circuits that:
Do spark but will not ignite a methane-air mixture
Tools or switches held in the operators hand or supported against his body:
Cannot have a nameplate voltage rating of more than 300 volts.
Material that will burn when held in a flame but will cease burning when the flame is removed is defined as:
"Flame-resistant," as applied to trailing cables and conduit hose, means:
Cables and hose will burn when held in a flame, but will cease burning when removed from flame.
The maximum operating temperature of the external surface of a machine is:
150 Centigrade or 302 Fahrenheit.
Which of the following is a requirement of a temporary splice?
It must be mechanically strong and well-insulated.
Which of the following is NOT a requirement of a permanent splice?
It must be more than 25 feet from the machine (except cable reel).
Which of the following is a requirement of a permanent splice?
It must be mechanically strong with adequate conductivity.
Which of the following is NOT a requirement of a temporary splice made in a trailing cable?
It must be vulcanized.
What is the maximum allowable speed of travel of a machine that receives power through a trailing cable?
The minimum-sized trailing cable permitted for direct current powered mobile haulage units is:
When a trailing cable is used to power an underground mining machine, that machine must not move faster than:
If trailing cables are run over by mobile face equipment:
Arcing or sparking could result which, in turn, could set off an explosion or cause a fire.
Flame resistant as applied to trailing cables and hose conduit means:
It will burn when held in a flame but will cease when the flame is removed.
All trailing cables used to conduct electrical energy to face equipment shall conform to the following EXCEPT:
Have at least 3 power wires and one ground wire.