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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.

    Battery boxes:

    Must be adequately ventilated.

    Each wire or cable leaving a battery box on storage battery operated equipment shall have:

    Short-circuit protection in an explosion-proof enclosure.

    What should be provided in the bottom of each battery box?

    Drainage holes.

    The purpose of hose conduit is to:

    Provide for mechanical protection.

    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 meet the requirements of Schedule 2G, all conduit hose on equipment:

    Must be flame-resistant.

    The minimum thickness of hose conduit allowed is:

    3/16 inch.

    Conduit hose must be marked flame resistant:

    Every three feet.

    Conduit hose is used for:

    The mechanical protection of a cable.

    Conductors must have current-carrying capacities that meet:

    ICEA standards

    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.

    A cable reel is required on self-propelled equipment that travels at a speed exceeding:

    2.5 mph

    What is the maximum tramming speed permitted for a continuous miner?

    2.5 MPH.

    Any underground machine traveling faster than how many MPH must be equipped with a cable reel?

    2.5 MPH

    What is the minimum distance that a 1/2-inch bolt can extend into the threaded portion of the hole on a permissible enclosure?

    1/2 inch.

    An electric motor that is a power source for a permissible mining machine:

    Must be explosion-proof

    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 type of packing glands should be locked?

    All glands

    What is the maximum radial clearance that should be allowed when installing a typical plug for spare lead entrance holes?

    .003 inch.

    To check a plane flange joint you would use what size feeler gauge?

    0.005 inch.

    Since certain electrical components almost always spark when in operation, they:

    Must be placed in explosion-proof enclosures before they are considered "permissible."

    A permissible box must withstand an explosion pressure of:

    150 psi.

    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.

    The maximum clearance between the lid and the box of a step-flange joint is:

    0.006 inch.

    How far should a 1/2-inch bolt extend into the threaded portion of the hole?

    At least 1/2 inch.

    If the cover of the permissible compartment has a step shape, it is:

    A step flange joint.

    All unused holes in permissible compartments must be:

    Closed with specially designed fittings or plugs.

    If there are damaged threads on a screw-type cover:

    The cover must be replaced.

    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.

    Inspection covers or screw type joints must be:

    Threaded in snug and locked in place.

    What is the minimum thread engagement of bolts for an enclosure which is greater than 124 inches?

    3/8 inch.

    End bells on motors and reset switches are typical examples of:

    Step flange joints.

    Most end bells on explosion-proof motors should be checked with a feeler gauge.

    .007 inch.

    To check a step flange joint you should use what size feeler gauge?

    0.007 inch.

    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:

    .004 inch.

    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 allowed to be under a permissible bolt?

    Lock washers.

    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?

    1/2 inch.

    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?

    1/8 inch.

    Breathers or pressure-relief devices are installed on an explosion-proof enclosure to:

    Relieve pressure, ventilate, or drain.

    Permissible compartments are designed to be:

    Explosion proof.

    What is the minimum distance from the interior of an enclosure to the edge of a bolt hole (more than 124 cubic inches)?

    7/16 inch.

    A plane flange joint has a maximum clearance between the box and the lid of:

    0.004 inch.

    The packing material in a stuffing box is compressed tightly against the cable by:

    Tightening the packing gland nut.

    A flat metal to metal joint is a:

    Plane Flange Joint.

    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.

    A screw type joint cannot be used if:

    The threads are damaged.

    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.

    All bolts in a permissible enclosure must have:

    Lock washer.

    The maximum clearance of a plane flange joint allowed for permissibility is:

    0.004 inch.

    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:

    1/8 inch.

    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?

    .004 inch.

    Insulated wires should pass through metal walls of electric compartments only through:

    Insulated bushings.

    What size feeler gauge should be used to check plane flange joints?

    .005 inch.

    A .007-inch feeler gauge is used by an inspector to check:

    Step flange joints.

    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:

    3/16 inch.

    Packing material used in stuffing boxes should be:

    An approved packing material.

    Cast or welded enclosures should be designed to withstand a minimum internal pressure of:

    150 PSI.

    What is the maximum-sized opening permitted for a plane flange joint?

    .004 inch.

    How thick must lenses for headlights be?

    1/2 inch.

    What is the maximum-sized spacing permitted for bolts securing enclosure covers with joints all in one plane?

    6 inches.

    A .005-inch feeler gauge is used to check:

    Plane flange joints.

    What size feeler gauge should be used to check end bells on most motors?

    .007 inch.

    The minimum clearance between the shoulder of the nut and the top of a stuffing box in a properly packed, standard packing gland is:

    1/8 inch.

    The minimum amount of packing that should be in a packing gland along a conductor is:

    1/2 inch.

    Before electric face equipment is deemed permissible, the equipment must meet the:

    Specifications set forth by the Secretary.

    All electric equipment used in return air outby the last open crosscut:

    Must be permissible.

    The maintenance required to keep equipment in permissible condition is the responsibility of the:

    Mine operator.

    Permissibility is required for electrical equipment and components:

    Inby the last open crosscut and in return air.

    Permissible electric face equipment is defined as:

    Equipment which has been tested and approved.

    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?

    2 feet.

    Cable grips or insulated clamps shall be provided on:

    Portable trailing cables.

    When mounting ground wires:

    Always use terminals or clamps.

    All trailing cables and drop cables must have:

    A restraining clamp in permissible condition.

    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:

    25 amps

    The frame to ground potential of any off-track machine must not exceed:

    40 volts.

    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:


    What is the most violent explosive percent of methane?


    "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.

    What is the explosive range of methane?

    5% to 15%.

    The maximum speed of travel of a machine receiving power from a trailing cable.

    6 MPH.

    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.

    The number of temporary splices permitted in a single length of trailing cable is:


    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?

    6 mph.

    The minimum-sized trailing cable permitted for direct current powered mobile haulage units is:

    No.4 AWG

    The maximum length permitted for trailing cables (4/0 and larger) is:

    1,000 feet.

    When a trailing cable is used to power an underground mining machine, that machine must not move faster than:

    6 mph.

    What is the minimum-sized trailing cable permitted for AC-powered mobile haulage units?

    No.6 AWG.

    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.

    In most cases, the length of a portable cable should not exceed:

    500 feet.

    Trailing cables must be marked:


    A No. 6 AWG trailing cable should be no longer than:

    550 feet

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