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Original General Order 95 

 

Section VIII

 

Detailed Construction Requirements for Communication Lines
(Class C Circuits)

 

84.4    Clearances

 

Allowable variations in clearances due to temperature, loading, dead ending, etc., are given in Rules 37 and 38.

 

A.    Above Ground

 

The minimum vertical clearances shall be those specified in Rule 37, Table 1, with the following modifications:

 

(1)    Across Arid Or Mountainous Areas: The clearance of 15 feet specified in Table 1, Case 4, Column B may be reduced to not less than 13 feet over arid or mountainous areas which are not under cultivation and over which there is no likelihood of vehicular travel.

 

(2)    In Rural Districts: The clearance of Table 1, Case 4 Column B may be reduced to not less than 13 feet above ground along thoroughfares in rural districts where no part of the line overhangs any part of the thoroughfare one which is ordinarily traveled and where it is unlikely"tha1 the vehicles will be required to cross under the communication conductors.

 

(3)    Accessible To Pedestrians Only: Communication conductors of not more than 160 volts which transmit not more than 50 watts and communication cables having grounded metal sheaths may have a clearance above ground accessible to pedestrians only less than as specified in Table 1, Case 5, Column B (10 feet) but not less than 8 feet.

 

(4)    Fenced Railway Rights-Of-Way: Railway signals cables between line poles and signaling devices, which are entirely on fenced railway rights-of-way, and which are exposed to vehicular traffic but do not cross thoroughfares, may have clearances above ground less than as specified in Table 1, Column B, Case 4 (15 feet) but no less than 10 feet. Such cables which are entirely on fenced railway rights-of-way and which are in areas accessible to pedestrians only may have clearances above ground less than as specified in Table 1, Column B, Case 5 (10 feet) but not less than 7 feet.

 

B.    Above Railways And Trolley Lines

 

(1)    Which Transport Freight Cars: The clearance specified in Table 1, Case 1, Column B (25 feet) is based upon the maximum height of standard freight cars, 15 feet 1 inch between top of rail and top of running board. This clearance shall in no case be reduced more than 5% because of temperature and loading as specified in Rule 43.

 

(2)    Operated By Overhead Trolleys: The clearance specified in Table 1, Case 2, Column B (26 feet) is based upon a trolley pole throw of 26 feet, the usual maximum height of a free trolley pole above the rails or other traveled surfaces used by trolley cars or coaches. Where trolley lines have a maximum trolley throw at variance with 26 feet the specified clearance shall be increased or may be reduced accordingly except that in no case shall the clearance be less than 25 feet.  See Rule 87.4-B2 for the clearance of grounded cables and messengers.

 

Where railways operated by overhead trolleys transport freight cars, the clearance requirements of Rule 84.4-B1 also apply.

 

C.    Between Conductors: The minimum clearances shall be those specified in Rule 38, Table 2, (see also Rule 32.2-D) with the following modifications:

 

(1)    Open Wire

 

a)    On Related Line and Buck Arms: The clearance of 6 inches specified in Table 2, Case 14, Column C is not  required between conductors on line arm and related buck arm where the conductors supported by such arms do not cross.

 

b)    On Brackets Attached to Crossarms: Line conductors supported on brackets or extensions attached to cross- arms shall be maintained at, or outside of, the outer pin or dead-end positions on the crossarm with a radial separation not less than the minimum pin spacing specified in Table 2, Case 15 (3 inches) from any other line conductors supported by the same crossarm, except that not more than two conductors on the same side of pole on any crossarm may be sup- ported on brackets within the outer pin position and below conductors normally supported on pins on the crossarm provided that all conductors concerned do not carry more than 160 volts and the power transmitted does not exceed 50 watts and the vertical separation between conductors so supported on brackets and those attached on pins or dead ends on crossarms not supporting the bracket shall be not less than 12 inches. The vertical clearances specified in Table 2, Cases 1 to 14 shall be provided between the conductor on the bracket and the conductor level of any other conductors not supported on the crossarm to which the bracket is attached.

 

This rule shall not be held to apply to clearances between conductors of the same or similar circuits at or points of transposition.

 

c)    Attached Directly to Poles: On poles which carry for no crossarms, open wire conductors which are attached to the sides of poles by means of hooks, knob port or brackets may be placed in any position within the 3 feet next below the topmost conductor on the pole.  The vertical separation between conductor support on the same side of pole in this space of 3 feet shall be not less than 6 inches. Below this point (3 feet below the topmost conductor) conductors shall be attached to one side of pole only, not more than 6 conductors shall be so attached, and the vertical separation between these conductors shall be not less than 12 inches.

 

On poles which carry communication crossarms only one pair of open wire conductors may be attached to opposite sides of the pole by means of hooks, knob or brackets, at a point not less than 2 feet below the lowest level of conductors supported on crossarm.  Below this point (2 feet below conductors on crossarm) other conductors which are attached to surface of pole shall be attached to one side of pole only, not more than six conductors shall be so attached, and their vertical separation shall be not less than 12 inches.

 

Branch or tap lines and service drops from conductors attached to poles may be similarly attached to the face or back of a pole, but not both.

 

(2)    Duplex, Triplex, And Cables: Insulated single conductors (rubber insulated), duplex, triplex, and paired conductors are considered as cables (see definition, Rule 20.3) and the clearances for such conductors are specified in Rule 87.4.

 

D.    From Poles And Crossarms

 

Table 1, Case 8, Column B specifies a minimum clearance of 15 inches from center line of pole which is applicable to communication conductors including cables and service drops. Modifications of this basic 15-inch clearance are specified in Rule 37 and by the following provisions where conductors are not on poles jointly used for supporting supply conductors excepting supply service drop clearance attachments (see Rules 54.8-C2 and 54.8-C3).

 

The clearance of 3 inches specified in Table 1, Case 9, Column B is not intended to apply to communication conductors.

 

(1)    Conductors Supported On Crossarms: The 15-inch minimum clearance from center line of pole specified for communication conductors supported on crossarms may be reduced under the following conditions:

 

For open wire toll and other open wire line conductors not used for exchange or local distribution, a clearance of not less than 9 inches from center line of pole may be used;

 

For open wire exchange or local distribution conductors which were originally installed as toll line conductors, a clearance of not less than 9 inches may be used provided such exchange conductors do not carry more than 160 volts and 50 watts and a clearance of not less than 15 inches from center line of pole shall be obtained when appreciable reconstruction of such lines is undertaken;

 

For open wire and local exchange and local distribution conductors in rural districts, the conductor clearance from center line of pole maybe not less than 9 inches provide voltage of such conductors is not more than 160 volts, power transmitted does not exceed 50 watts, the clearance of not less than 9 inches shall apply only to conductors supported on a crossarm in the pole top position and no conductors are supported below such crossarms except supply service drops of clearance crossarms. This provision for lines in rural districts is intended to permit the use of a related buck arm, in which the climbing space shall conform to the requirements of Rule 84.7-B ;

 

Cables or messengers may be attached to opposite sides of pole and have clearances less than 15 inches from center line of pole where placed 2 feet or more below the level of the lowest communication conductors supported on crossarms;

 

Cables or messengers may have clearances less than 15 inches from center line of pole where placed between crossarms or less than 2 feet below the level of the lowest commumcation conductor supported on crossarms provided, for climbing space purposes, such cables are placed on one side of pole only and any conductor (supported by a crossarm and on the opposite side of pole) which is within 36 inches vertical may from the level of the cable or messenger is not less than 24 inches (if an exchange conductor) or 18 inch (if a toll conductor) horizontally from the vertical plane of such cable or messenger. (See App. G, 84.)

 

(2)    Conductors Not Supported On Crossarms: Communication conductors which are not supported on crossarms may be attached to poles by means of hooks, knob r be or brackets and thus are not required to be any specified distance from center line of poles provided the clearance between conductors complies with the requirements Rule 84.4-C1c. The minimum clearance of such conductors from the surface of poles shall be such that suitable insulation is maintained.

 

(3)    Colinear, Conflicting Or Crossing Lines (See Rule 32.3): Where two communication lines are colinear or otherwise in conflict or where a pole of one line is interset in another line at crossings, the clearances of Rule 32.3 and Table 1, Case 8, Column B may be modified as follows:

 

In applying any of the provisions of this Rule 84.4-D3 an unobstructed climbing space on each pole concerned shall be maintained with horizontal dimensions of not less than 30 inches square for conductors carrying more than 160 volts and 50 watts, and not less than 18 inches in width and 30 inches in depth for conductors carrying lower voltage and power.

 

a)    Where Clearance Arms Are Used: Where clearance arms are used, on poles which support only Communication conductors, to support the conductors, to support the conductors of a coliener or conflicting communication line the clearance of such conductors from the center line of pole shall be not less than 15 inches for conductors carrying more than 160 volts and 50 watts and shall be not less than 9 inches for conductors carrying lower voltage and power.

 

b)    Where Clearance Arms Are Not Used: Communication conductors which in passing another communication pole unattached would be less than 15 inches from the center line of pole or less than 5 inches from the surface of pole shall be attached to the pole in accordance with the provisions of Rules 84.4-C1c and 84.4-D2.

 

(4)    Conductors Passing Supply Poles And Unattached Thereto: The center line clearance between poles supporting supply conductors and any communication conductors which pass such poles unattached shall be not less than 22 inches (1 times the clearance specified in Table 1, Case 8), except where the supply pole is within 10 feet of the pole on which the communication conductors are supported. Where poles of the two lines are less than 10 feet apart, clearances not less than as specified in Table 1, Case 8, shall be maintained.

 

(5)    Center Line Clearance At Angles In Lines And At Transpositions: The clearance of 15 inches from center line of pole specified in Table 1, Case 8, Column B (and the reduced clearance of 9 inches permitted by Rules 84.4-D1 and 84.4-D3a) may be reduced at angles in lines and at transposition supports; provided that at angles in lines the reductions of the 30 inch and 18 inch widths of climbing spaces shall not exceed the reduction specified in Rule 84.7-A1, and further provided that the 30 and 18 inch widths of climbing space shall not be reduced at transposition supports (see App. G, Fig. 34).

 

E.    Above Or Beside Buildings, Bridges And Other Similar Structures

 

Conductors (including cables) shall be so arranged as to hamper and endanger firemen and workmen as little as possible in the performance of their duties. The basic clearances of conductors from buildings are specified in Table 1, Cases 6 and 7. The requirements of Table 1, Case 7, also apply at fire escapes, exits, windows, etc., at which human contact may be expected.

 

Communication cables are not required to be any specified distance from the sides of buildings, but they shall be installed so that they do not interfere with the free us of fire escapes, exits, etc.

 

The vertical clearance of communication conductor (including cables) above buildings as specified in Table 1, Case 6, may be reduced to not less than 2 feet under the following conditions:

 

Over roofs of 3/8 pitch (37 degrees from the horizontal) or greater,

 

Over roofs where the conductor does not overhang the building by more than 6 feet.

 

See Rule 84.8-C4 for service drop clearance requirements

 

F.    Under Or Through Bridges, Viaducts or Similar Structures

 

Open wire communication conductors which cross under or through bridges, viaducts, or similar structures shall be maintained at clearances above ground and walkways a two specified in Table 1, Cases 1 to 6; at a radial clearance from unprotected conductors of other classifications not less than as specified in Table 2, Case 3; at clearance from walls and the underside of such structures as specified in Table 1, Case 7 except where it is not practicable to obtain the 3-foot clearance therein specified this clearances may be reduced to not less than 6 inches where the voltage does not exceed 160 volts; or where supported on the walls or underside of such structures, at clearances as specified in Table 1, Case 9 with supports at least every 50 feet.

 

In lieu of the above requirements, conductors which cross under or through bridges, viaducts, or similar structure shall be enclosed in metal sheaths, run in metal conduits in or be placed in ring construction on a messenger.

 

G.    From Guys And Messengers (see Table 2, Cases 18 and 19,. Column C; also Rules 86.4-C and 87.4)