Subchapter M. AERIAL PASSENGER TRAMWAYS

§ 7.411. Scope.

 In addition to detailed requirements provided for the principal categories of this Subchapter, the following stipulations apply to each category of this subchapter:

   (1)  For purposes of design, the average passenger shall be considered as having a weight of 170 pounds.

   (2)  If a designer or manufacturer of equipment wishes to use materials not covered by the code or which may be developed in the future, it is intended that full information be submitted to the committee. The design details, materials and construction features shall provide safety factors equivalent to those specified in this Subchapter.

   (3)  It is assumed in all cases that tramways will run in a straight line, in plan, between the terminals. Proposals involving lines with angles require special consideration by the authority having jurisdiction unless this subchapter is amended to include such designs.

   (4)  Provision shall be made to render first aid in the event persons are injured on the tramway. This shall include provision for transporting an injured person off the mountain.

   (5)  Good housekeeping shall prevail at all times.

 (a)  Before any tramway is placed in operation it shall be subjected to thorough inspection and tests to confirm that it meets the requirements of the approved plans and specifications in every respect. This shall include but not necessarily be limited to all of the following:

   (1)  A final check for tightness of all structural connections.

   (2)  A final check of the lubrication of all moving parts.

   (3)  Open gearing shall be checked for alignment and clearances.

   (4)  All bearings, couplings, and shafting shall be checked for alignment and fit.

   (5)  Belting shall be checked for proper tightness.

   (6)  A final check of position of counterweights and bull wheel carriages, and for freedom of movement of such carriages.

   (7)  Under the most adverse static loadings, track cables and hauling ropes shall be checked for sag.

   (8)  Track cable saddles and hauling rope line sheave units shall be checked for alignment in the planes of their respective cables or ropes.

   (9)  Hauling rope shall be checked for alignment at entrance to the bull wheels.

   (10)  Thorough operating tests shall be made under full loading and partial loadings which provide the most unfavorable conditions, and include an operational check of motive power, acceleration, deceleration, all brakes, all pushbutton stops, all automatic stops and limit switches, all communication devices, and the like.

 (b)  The tests shall include at least one full day of continous operation for the purpose of checking for the overheating of moving parts, excessive vibration or deflection of any mechanical or structural components, free movement of counterweights, and the like.

 (a)  Routine. A schedule for systematic maintenance shall be developed and set down in writing for all installations subject to the provisions of this Subchapter. Such schedule should be based on a maintenance manual which shall be provided by the designer of the tramway. The manual shall include the type of lubricant and frequency of lubrication of each element involving moving parts. It shall stipulate that parts showing excessive wear shall be replaced immediately and, if possible, establish yardsticks to define excessive wear. It shall include a schedule for checking and tightening all bolts especially on rope attachments. The maintenance schedule shall establish a specific period of time which will represent one complete cycle of maintenance operations, including all component parts, assigning a time within such cycle for the maintenance work on each component. The schedule shall include a daily check of all normal operating brakes, all communications, and all stopping devices, both manual and automatic. A daily check shall also be made to assure that the counterweight sheaves are free to turn. Also included shall be periodic checks of all emergency brakes. A signed complete log or diary shall be kept of the actual execution of maintenance work recorded daily. Such log shall not only state that the component is given attention on that day, but also the condition of the component if it shows any signs of deterioration, and also the replacement of any components. It shall also contain a daily record of the position of all counterweights and bull wheel carriages.

 (b)  Special inspections. Each tramway shall be inspected at least once each year by a specialist acceptable to the authority having jurisdiction.

 (c)  Special requirements for cables. Ropes and cables in all installations subject to the provisions of this Subchapter shall conform to the following:

   (1)  Track cables. All end connections and areas near saddles shall be inspected at established intervals of time for broken wires and worn spots. At longer intervals, the whole length shall be inspected. Such intervals shall not be longer than those recommended by the track cable manufacturer.

   (2)  Hauling ropes. The general condition of hauling ropes, including those of cable links for monorail lifts, and also including splices, shall be noted each day by the observation of one complete cycle under normal operating conditions. At established intervals, the whole length of rope shall be examined for conditions such as broken wires, worn spots, pitting, lubrication, and the like. Fixed grips shall be moved and the rope inspected at least once every 2 years, but not at longer periods than recommended by the tramway designer. For purposes of maintaining orderly and useful records, it is suggested that they be moved uniform distances and always in the same direction. Each time a fixed grip is moved, the rope which has been under and near the grip shall be examined for deterioration, and records should be made which will make it possible at any time during the life of the rope to locate the spots where grips have previously been located. On the link-type hauling ropes of monorail lifts with swaged button-end fittings, links should be removed at random and proof-tested for safety factor and signs of corrosion annually or more often as required.

   (3)  Counterweight and other ropes and cables. Counterweight and other ropes and cables are subject, when applicable, to the provisions specified for track cables and hauling ropes in paragraphs (1) and (2).

   (4)  All ropes and cables. Lubrication shall be carried out in accordance with the recommendations of the designer of the tramway. Retirement of rope from service shall occur on the basis of the general condition and history of the rope and its predecessors as indicated by the inspection reports. Consideration shall be given to the condition of the splices, the deterioration or corrosion, the surface wear and the number of broken wires in the worst rope lay.

 (a)  Requirements regarding the marshalling of passengers for smooth and safe loading and unloading without interference are subject to a clear plan of operations. Once such a plan is established by management, succeeding steps shall include the training of attendants and the formulation of a layout of gates and fences.

 (b)  When wind conditions reach such a point as to make continued operation hazardous to passengers or equipment, the tramway shall be shut down.

   This section cited in 34 Pa. Code §  7.453 (relating to operation).

SINGLE AND DOUBLE REVERSIBLE AERIAL TRAMWAYS

§ 7.421. Definitions.

 The following words and terms, when used in this section and § §  7.422—7.432 (relating to single and double reversible aerial tramways), shall have the following meanings, unless the context clearly indicates otherwise:

   Bicable tramway—A tramway which incorporates standing tracks, usually made of wire cable on which the carriers ride.

   Double reversible tramway—A tramway in which two cars or two lines of cars oscillate back and forth between the terminals on two separate paths of travel.

   Monocable tramway—A tramway which does not incorporate standing tracks on which the carriers ride. The carriers are instead supported as well as propelled by the hauling or traction wire rope.

   Single reversible tramway—A tramway in which a single car or line of cars moves back and forth between the terminals on a single path of travel.

 The provisions of § §  7.421—7.432 (relating to single and double reversible aerial tramways) apply to that class of aerial tramways in which the carriers reciprocate between the terminals, particularly those referred to as single reversible (‘‘to and fro’’) tramways and double reversible (‘‘jigback’’) tramways. Such tramways may be either monocable or bicable.

 (a)  In selecting the location and alignment of tramways, consideration shall be given to the following:

   (1)  Electric power lines.

   (2)  Railways.

   (3)  Highways.

   (4)  Structures.

   (5)  Rock and earth slides, cave-ins, washouts, and the like.

   (6)  Avalanches of snow.

   (7)  Wind action.

   (8)  Icing.

   (9)  Ski slopes and trails.

   (10)  Rivers and gullies.

   (11)  Buried installations, including pipelines.

 (b)  Location with respect to such conditions shall meet the requirements of the authority having jurisdiction. Generally, tramways shall not be in the immediate proximity of, nor cross over or under the items described in paragraphs (1)—(4), except when permitted and approved by the authority having jurisdiction.

 The clearing shall be wide enough to prevent interference with the tramway by the adjacent vegetation. Such clearings shall be protected, if necessary, to avoid washouts which might endanger the tramway or its foundations. Dead trees shall be cleared out far enough back from the line to avoid their falling on the tramway.

 (a)  Towers shall be located to conform to the profile of the terrain and designed to provide clearance of the cabins and ropes from all obstructions and ski or hiking trails. Under the most adverse loading conditions, a minimum space of 5 feet shall exist between the lower edge of the cabin or ropes and the terrain or other possible obstacles, including snow pack. Whenever the space is less than 15 feet, a protective fence shall be erected to divert all surface transportation or persons from possible collision.

 (b)  On monocable tramways, the tower arrangement shall be such that the hauling rope may not depart from a group of tower rollers should the tension in the hauling rope become twice its most unfavorable design value at that point. If a factor of less than two is used, adequate retaining rollers, properly placed, shall be provided. Where the rope load is normally upward, that is, where ‘‘hold-down’’ or ‘‘depression’’ rollers are used for normal operating conditions, the rope shall not leave the group of rollers under a condition in which twice the normal concentrated design load passes the tower while the rope is under normal design tension.

 (c)  On bicable tramways, the tower arrangement shall be such that the track cable under the most adverse operating conditions has a positive break over angle at the saddle. If angles of less than one degree are unavoidable, provision shall be made to keep the track cable in the saddle. Such provisions shall not interfere with any track cable in the saddle nor with any track cable brake operation.

 (d)  Towers shall be so located as to minimize the surge of the line under operating conditions. Local wind conditions shall be taken into consideration. Towers and ropes shall be so arranged as to prevent the collision of passing cabins in the event of lateral swinging due to winds.

 (e)  At passing places, the distances between the two cabins swung ten degrees inward from the vertical should be at least 2 feet, 6 inches. In no case shall this distance be less than 0.5% of the span length.

 (f)  Towers containing provision for change in height of rope and cable supports shall not be used.

 (a)  Capacity. The design capacity of each cabin shall be posted in a conspicuous place in that cabin and at each loading platform.

 (b)  Speed. Maximum car speeds shall be as follows:

   (1)  Bicable tramways using track cable brakes on the carriage shall not exceed 1,500 feet per minute.

   (2)  Bicable tramways using two or more traction ropes and not using track cable brakes shall not exceed 2,000 feet per minute.

   (3)  Monocable tramways shall not exceed 800 feet per minute across tower rollers, and 2,000 feet per minute in clear spans.

   (4)  On bicable or monocable tramways, cabins entering terminals shall not exceed 300 feet per minute.

   (5)  On bicable tramways, when there is no conductor in a cabin, the maximum speeds specified in paragraphs (1) and (2) shall be reduced by 25%, and speeds when passing over tower saddles shall be reduced to 2/3 of the speeds permitted elsewhere. It is also assumed that track cable saddles are so designed that the carriage wheels ride directly on the track cables over the saddles as well as in the spans and do not come in contact with or ride on any part of the saddles, or retaining clips if used. Where such a condition does not exist, speed over the saddles shall be reduced to a maximum of 800 feet per minute.

 (a)  Power source. Electrical and internal combustion energy may be utilized as a power source, as follows:

   (1)  Electrical. Exposed electrical transmission wiring shall be so located that in case of collapse or breakage of the power line it will not come in contact with cars, cables or passengers. All electrical work shall comply with the American Standard National Electrical Code, C1-1959 and the American Standard National Electrical Safety Code, C2 (R 1947). Transformer stations and other electrical equipment shall be so protected as to prevent unauthorized persons from entering the area or coming in contact with any portion of the equipment or wiring. Power equipment shall be protected against overloads by proper circuit breakers or fuses.

   (2)  Internal combustion. Fuel tanks shall be of adequate capacity to permit uninterrupted operation during normal operating hours. In any event, the tank shall be refilled while there is still enough fuel in such tank to bring the fuel to the stations. Fuel tanks shall be buried or so located as to be free of fire hazard. The engine shall always be shut down during refueling. The fuel entry opening shall be capped and located to avoid toxic fumes and fire hazard during refueling. Liquid fuels shall be stored and handled in accordance with the standards of the National Board of Fire Underwriters as outlined in Pamphlet No. 30, Flammable Liquids, June 1959. Also, liquefied petroleum gas installations shall be made in accordance with the standards of the National Board of Fire Underwriters, as outlined in Pamphlet No. 58, Liquefied Petroleum Gases, as amended through 1959.

 (b)  Prime movers. Prime movers shall have the capacity to handle the most unfavorable design loading conditions. An auxiliary power unit with an independent power source shall be provided which may readily be used to move the cabins to the terminals in the event of power failure, unless other means are provided to return the cabin to the terminal. Internal combustion engine exhaust shall be discharged into the atmosphere.

 (c)  Speed reducers and gears. Speed reducers and gears shall comply with accepted standard practices, and have the capacity for starting the tramway under the most unfavorable design load conditions.

 (d)  Bearings, couplings and shafting. Shafting shall be designed in accordance with accepted standard practices. Provision shall be made for the adjustment and lubrication of all bearings and couplings when required. Bearings and couplings shall be selected on the basis of the published recommendations of the manufacturer for the particular use in question. If published data are not available to cover the use, the approval of the manufacturer shall be obtained for the intended use. Bearings and couplings of special design, when used, shall have the approval of a competent mechanical engineer.

 (e)  Clutches. Any clutch device used between the prime mover and the drive sheave shall meet the requirements for bearings and couplings specified in subsection (d).

 (f)  Acceleration and speed control. Acceleration and speed controls are required to avoid discomfort to passengers caused by undue longitudinal swinging of the cabin or by excessive acceleration or deceleration and in order to start and stop the cabins smoothly and safely. The following points shall be considered in the design:

   (1)  Provision shall be made for smooth deceleration of the tramway prior to the actuation of one of the automatic motor brakes specified in subsection (g).

   (2)  Cabins shall be brought to a stop for loading and unloading, and provision made to make the tramway immobile during loading and unloading periods. The control room shall contain, in full view of the operator, indicators which show the location of the cars at all times.

   (3)  Provision shall be made for an overhauling load so that the system always operates at a controlled speed not exceeding the rated speed by more than 10%. The power developed by the overhauling load shall be automatically dissipated electrically, hydraulically or pneumatically.

 (g)  Brakes and stops. Each tramway system shall have brakes and manual stops as follows:

   (1)  Brakes. Each tramway system shall include the following brakes:

     (i)   An automatic brake to stop and hold the tramway system under maximum load when power is shut off or the tramway is stopped for any reason. Such brake shall be applied to a drive shaft such that there is no clutch, V-belt, chain drive or similar device between the brake and the drive wheel. The brake shall be electrically released and applied by springs or gravity, except in cases where another type of brake is specifically approved by the authority having jurisdiction. In all cases the brake shall normally be in the applied position. It shall be held open for operation of the tramway by a device which is automatically cut out if power is shut off or the tramway stopped. Such device shall, without exception, be placed in operation before the tramway is started.

     (ii)   An automatic overspeed device which actuates the brake specified in subparagraph (i) or a similar independent brake when the speed of the prime mover exceeds its rated value by more than 10%.

     (iii)   A manually-operated brake on the main drive sheave with controls located near the operator.

     (iv)   On bicable tramways, an automatic track cable brake. Reference should be made to §  7.429(b)(3)(ii) (relating to line equipment).

   (2)  Stops. Electric switches to stop tramways shall be installed on both terminal platforms. One shall also be installed on the control board of the conductor in each cabin, unless no conductor is required. The stopping system shall be so arranged that the tramway cannot be started until the device that stopped the tramway is reset and the operator obtains clearance from the point at which the device is actuated. It is desirable that a wind gage be installed on the most exposed point along the tramway line. In such case, a conspicuous warning device shall function to alert the operator when wind velocity reaches the established maximum. When wind conditions make operations dangerous, as determined by such a device or by observation of an attendant or the operator, the tramway shall be unloaded and stopped. The tramway shall never be started except by the operator. Reference should also be made to subsections (f) and (t) and §  7.428(d) (relating to line structures).

 (h)  Machine rooms. Motive power shall be housed in a well-ventilated machine room in a manner which permits proper maintenance and keeps the public away from the machinery. Adequate lighting and protection against lightning and static electricity shall be provided. A minimum of 18 inches clearance shall be provided between machinery and machine room enclosures, and passageways between units of machinery shall have the same minimum width. A fireproof room is preferable, but in any event, fire prevention measures and fire fighting devices shall be installed. A door with a suitable lock shall be installed on all machine rooms.

 (i)  Protection against moving parts. Moving machine parts which may normally be within reach of personnel shall be fitted with safety guards conforming to American Standard B15.1-1953.

 (j)  Bull wheels. Bull wheel frames shall be so designed that they will retain the wheel in the event of shaft breakage. The minimum diameter for bull wheels shall be 72 times the diameter of the rope, provided that no gripping device passes around the bull wheel. The minimum diameter for bull wheels shall be 96 times the diameter of the rope if gripping devices travel around the bull wheel. In the latter instance, the angle formed by the cable as it enters and leaves the grip body when passing around the bull wheel shall not exceed seven degrees. The mounting that travels under the action of the counterweight shall be supported on rigid straight rails by means of wheels. The available travel shall be such that the frame does not reach either limit of motion during normal operation and until the hauling rope needs to be resocketed or respliced for other reasons, or replaced.

 (k)  Sheaves and bearings in terminals. Sheaves and bearings in terminals shall conform to the following:

   (1)  All drive sheaves. All drive sheaves shall meet the requirements of this subsection.

   (2)  Hauling rope deflecting sheaves. Hauling rope deflecting sheaves in terminals shall be designed to withstand static and dynamic loads. The tread diameter shall be not less than that recommended by the manufacturer of the hauling rope for the intended use. Standard recommendations are as follows:

     (i)   For the purposes of this section, the following words and terms shall have the following meanings:

       Condition A—Where bending over sheaves is of major importance.

       Condition B—Where bending over sheaves is important but some sacrifice in rope life is acceptable to achieve reduction in weight, economy of design, and the like.

       d—Nominal diameter of rope.

     (ii)   When unlined grooves are used they shall be V-shaped with rounded bottoms having a radius equal to 55% of the rope diameter. Sheave mountings and bearings shall satisfy the recommendations of the manufacturers of the bearings.

     (iii)   Provision shall be made for grounding the wire rope. When such rope is used as a conductor in the communication system, lightning protection shall be provided and the rope grounded when the tramway is not in operation.

   (3)  Counterweight rope sheaves. Counterweight rope sheaves are subject to the requirements set forth in paragraph (1), except that antifriction bearings shall be selected to avoid a tendency for flat spots to develop on the rollers or balls.

   (4)  Track cable deflecting sheaves. Track cable deflecting sheaves in terminals shall be designed to withstand static and dynamic loads. Their tread diameter shall be not less than that recommended by the manufacturer of the track cable for the particular installation and shall also satisfy the allowable bearing load limits of the material with which their grooves are lined. When unlined grooves are used they should be V-shaped with rounded bottoms having a radius equal to 55% of the cable diameter. Sheave mountings and bearings shall satisfy the recommendations of the manufacturers of the bearings. Provision shall be made for grounding the cable. When the cable is used as a conductor in the communication system, lightning protection shall be provided, and the cable shall be grounded when the tramway is not in operation.

 (l)  Track cable saddles. The requirements for track cable saddles are the same as those set forth in §  7.428(e), except that if saddles in the terminals are located so that the carriage wheels do not pass over them, §  7.428(e)(1)(ii) and (iv) need not apply.

 (m)  Anchor connections for hauling ropes, track cables, counterweight ropes, tower or station anchor cables or guys, and the like. Rope and cable sockets shall be designed so that they will not be stressed beyond the yield point of the material used when the ropes or cables which they anchor are under tensions equal to their catalog breaking strength. Anchor connections shall be above ground. Any part of the anchorage below ground shall be protected against loss of strength due to corrosion.

 (n)  Counterweight ropes. Counterweight ropes shall have a minimum factor of safety of six, when new, based on their catalog strength. A copy of the specifications of the wire rope manufacture shall be available to the authority having jurisdiction. Such specifications shall include size, grade rope, construction, type of core, and breaking strength, based on values as published in United States Department of Commerce, National Bureau of Standards Simplified Practice Recommendations 198-50. Before installation the manufacturer shall test to destruction a sample of the rope furnished, and submit a certified report of the results. In the case of ropes of foreign origin, a test shall be made by a reputable testing agency approved by the authority having jurisdiction in order to obtain adequate proof. No splices are permitted in counterweight ropes. Counterweight ropes should be lubricated regularly with a lubricant specifically recommended for this type of service to avoid corrosion. They shall be adjusted so that the counterweight will reach the end of its travel when the corresponding bull wheel carriage comes within not less than 6 inches of the end of its travel.

 (o)  Counterweights. Counterweights shall be provided for all hauling ropes and be so arranged as to move freely up and down. Enclosures for counterweights shall be provided when necessary to prevent snow or ice from accumulating under and around such counterweights and interfering with their free movement. When snow enclosures are not required, guard rails or enclosures shall be provided to prevent unauthorized persons from coming in contact with or passing under the counterweights. Counterweights shall have sufficient travel to take care of all normal operating changes in loading and temperature. Furthermore, it should preferably have a travel equal to that of the bull wheel carriage, as described in subsection (j), which moves in response to it. If this amount of travel is not available, means shall be provided to shorten the counterweight ropes so that the counterweight will be in full suspension at all times. When counterweights are used for track cables, the same provisions shall apply.

 (p)  Structures. With respect to static loads, terminal structures shall be designed on the basis of the following:

   (1)  Steel. American Standard A57.1-1952; American Welding Society Standard Code for Arc and Gas Welding for Building Construction; American Standard for Testing and Materials (ASTM) A6-57T; American Standard for Testing and Materials (ASTM) A7-58T.

   (2)  Timber. National Lumber Manufacturers Association Wood Structural Design Data.

   (3)  Concrete. American Standard A89.1-1957 (ACI 318-56).

   (4)  All structures. The following apply to all terminal structures subject to this subsection:

     (i)   Applied design loads include dead, live, snow and wind loads, plus impact, and earthquake loadings. They shall satisfy the requirements of American Standard A58.1-1955.

     (ii)   Attention shall be paid to those portions of the structure which are subject to vibration from moving parts. In such cases, the governing criterion may be deflection or natural period of vibration. The design shall be made or reviewed by an engineer competent to handle such problems.

     (iii)   Terminals located in snow creep areas shall be designed for such loads or be protected by snow breakers or shears.

     (iv)   Pressure due to snow creep may be approximated by use of the following:

       (A)   Formula.

       (B)   For the purposes of this section, the following symbols shall have the following meanings:

       P_s—Total pressure on the object in pounds.

       W—Width of snow in pounds per cubic foot.

       B—Width of object in feet.

       D—Vertical depth of snow in feet.

       —Angle between horizontal and slope of ground surface.

     (v)   All terminals should be grounded so as to satisfy all national and local codes. The local electric power company is normally a good source of information regarding such code requirements.

 (q)  Foundations. Foundations for vertical loads shall satisfy the design requirements of subsection (p). For foundations for inclined or horizontal loads the structure of the anchorage shall satisfy the design requirements of subsection (p). In determining the resistance of the earth to motion of the anchorage, the subsoil conditions at the site shall be considered, including any buoyancy due to ground water which may be present. If the resistance of the soil is not practically determinable, the anchorage should be designed as a gravity anchor, using a coefficient of friction appropriate to the general character of the soil. Reference should also be made to §  7.428(b).

 (r)  Loading and unloading platforms. Steps should be avoided in all loading and unloading areas if possible. Platforms should be as level as practical and there shall be sufficient space for passengers waiting to ascend and descend. Railings shall be provided to guide passengers safely to and from cabins. Deadman controls shall be provided to stop the tramway in case the operator suddenly becomes incapacitated. Guide rails with curved ends shall be provided so that entrance and exit of cabins to and from platforms may be accomplished smoothly and without impact when the cabins are deflected from the vertical by ten degrees.

 (s)  Attendants. At least one trained platform attendant shall be present each time a cabin enters or leaves a terminal. The car conductor may serve as such an attendant if no loading passengers are permitted on the platform until it is cleared of all unloading passengers. There shall be a conductor who has knowledge of normal and emergency duties in each car having a capacity of more than six passengers during each trip. Reference should be made to §  7.429(b)(4) (relating to line equipment). The tramway operator shall be located where he has the best possible view of the tramway. His controls and communicating devices shall be within his reach without leaving his position.

 (t)  Safety stops. Limit switches or equivalent devices shall be installed to take over the operation of the drive automatically if the operator fails to decelerate the tramway when the cabin enters the terminal area. A further limiting device shall be installed to cut power and stop the tramway before the cabin reaches its limit of travel. An adequate bumper system shall also be installed. Limit switches may be installed to stop the tramway before any counterweight or bull wheel carriage reaches either end of its travel. Electrical stop circuits shall be closed circuits so that, in the event of power failure or of malfunction of a stop switch, the system will fail safe. Circuits shall be all metallic and ungrounded, unless otherwise approved by the authority having jurisdiction. After any actuation of a safety stop, the cause shall be determined and removed. The safety stop shall be reset. Safety stop circuits shall not be bypassed during passenger operation. The tramway shall never be started except by an experienced operator. Reference should be made to subsections (f) and (g) of this section and §  7.428(d).

 (a)  Towers. The design of towers shall satisfy the requirements of §  7.427(p) (relating to terminals and stations) and all of the following:

   (1)  If clearance is not adequate, towers shall be equipped with guards designed to prevent the cabins from swinging into the towers. Reference should also be made to subsection (c).

   (2)  If guyed towers are used and guys intersect the ground within or near ski runs, the guys shall be marked for visibility, preferably with boards painted with black and yellow stripes.

   (3)  All towers shall be equipped with access ladders located in such a manner as to prevent any moving parts from becoming engaged in the rungs.

   (4)  All towers should be grounded by individual grounds, by buried ground wires connecting all towers, or by tying all towers into a suspended ground wire, which may also be used as a ground for the signal system, and is itself grounded. The ground shall satisfy all national and local codes. The local electric power company is a good source of information regarding such requirements.

   (5)  Towers shall be clearly identified with successive numbers.

 (b)  Foundations. The structure of foundations shall be designed to satisfy the requirements of §  7.427(p) and (q). Foundations shall be designed to resist overturning or sliding with a factor of safety of two with respect to dead load and live load, and 1 1/2 with respect to such loadings and wind acting simultaneously. Under the action of all loads, pressure on the underlying earth shall not exceed allowable values for the subsurface material encountered. Bottoms of foundations shall be below the normal frost line unless they rest on solid rock, and tops shall be a minimum of 6 inches above finish grade. Foundations on rock shall be firmly anchored to the rock.

 (c)  Guards. The clearance between fixed objects, such as intermediate towers, rocks, and the like, and the cabin shall be sufficient to allow the latter to swing ten degrees laterally from the vertical. If this cannot be done without reducing the clearance to less than 18 inches, suitable guards shall be provided.

 (d)  Hauling rope sheaves (or rollers) and mounts. Hauling rope sheaves (or rollers) and mounts shall conform to §  7.427(k)(1), except that this application is that of a tower roller, not a large-angle deflection sheave. The following shall also apply:

   (1)  The recommended diameter should not be less than 10 times the diameter of the rope. Grounding of the hauling rope is not necessary at each tower. The allowable load on each sheave should be determined after consultation with the manufacturers of the material, if any, with which the sheave groove is lined.

   (2)  Sheave grooves shall be designed with deep flanges to discourage the rope from leaving the sheaves. In addition, suitable guards shall be installed to prevent the rope from falling into dangerous positions either within or outside of the tower structure in case it does leave the sheaves, and suitable devices should be installed to stop the tramway in such event.

   (3)  Rope grips should be designed in relation to the sheave groove so as not to contact sheave flanges during normal operations, taking into consideration the anticipated amount of wear on the grooves. Furthermore, rope grips, sheave flanges, and hanger guides shall be designed so that hangers may not be caught behind guides, and ropes and grips may not be derailed from sheaves, if the carrier is swinging as it approaches or passes the tower.

   (4)  If the gage of the tramway is varied at any point along the line, the horizontal departure at any one tower shall be kept to a minimum so that the rope cannot become derailed from the sheaves due to such departure.

   (5)  Sheave mounts or mounting frames should be designed to be adjustable laterally and rotationally, so that sheave units may be lined up and held in the plane of the rope.

   (6)  On monocable tramways, single sheave units shall not be used except for bull wheel guide sheaves. Sheave units shall be completely articulated to provide uniform distribution of pressure.

   (7)  The effect of tower height and location on sheave units shall be governed by §  7.425 (relating to towers).

 (e)  Track cable saddles and mounts. Track cable saddles and mounts shall comply with the following:

   (1)  The radius of a track cable saddle shall be determined by whichever one of the following criteria requires the largest radius:

     (i)   That it be large enough to minimize bending stresses in the cable and thus prolong cable life. Wire rope manufacturers are a good source of recommendations on this point.

     (ii)   That it be large enough to provide smooth transition of the carriage from span to span.

     (iii)   That it be large enough to reduce the bearing pressure to a value that permits the cable to slide in the saddle groove.

     (iv)   That it be large enough so that if the carriage were to travel over the saddle at three times normal speed the centrifugal force would not produce enough uplift to make the carriage wheels lose contact.

   (2)  The saddle shall be long enough to ensure that under maximum loading conditions the cable will not come into contact with the end of the saddle groove.

   (3)  Saddles shall be so designed so that the track cable brake, if any, may function at the time the cabin is passing the saddle without derailment of the tracks.

   (4)  Saddles shall permit free passage of the carriage even when the cabin is swinging laterally as it approaches or passes the tower.

   (5)  If the gage of the tramway is varied at any point along the line, horizontal departure at any one tower shall be kept to a minimum to avoid derailment of the carriage as it passes over the saddle.

   (6)  The effect of tower height and location on saddles shall be governed by §  7.425.

 (a)  Hauling ropes. Hauling ropes shall conform to the following:

   (1)  Specifications and tests. A copy of the wire rope specifications of the manufacturer shall be available to the authority having jurisdiction. Such specifications shall include size, grade of rope, construction, type of core, and breaking strength based on values as published in United States Department of Commerce, National Bureau of Standards Simplified Practice Recommendations 198-50. Before installation, the manufacturer shall test to destruction a sample of the rope furnished and submit a certified report of the results. In the case of ropes of foreign origin, a test shall be made by a reputable testing agency approved by the authority having jurisdiction in order to obtain adequate proof.

   (2)  Tension limitation. Hauling ropes shall have a minimum static factor of safety of five when new, in that section in which the highest tension is encountered. Operating tension shall be controlled by the use of a freely moving counterweight.

   (3)  End fittings or splices. Splicing of hauling ropes on bicable tramways is not permitted, unless this rule would result in a shipping package that is too large to handle by existing means of transportation. In such a case, attention should be paid to the selection and splicing of the rope, based on the recommendations of the wire rope manufacturer. When splices are required on monocable tramways, they shall satisfy the requirements of §  7.446(3) (relating to capacity, speed and loading interval).

   (4)  Sockets. Sockets shall be so designed that no part is stressed in excess of the yield point of the materials used when the ropes are stressed to their catalog strength.

   (5)  End attachments other than current standard types. If types of end attachments are proposed which are other than the current standard types used in this country, their suitability shall be established by tests. The authority having jurisdiction may approve or disapprove the use of such proposed connection even though such tests are made.

 (b)  Cars. All parts of cars, including cabins, frames, and carriage trucks, shall be designed in accordance with accepted practices of design. The adequacy of designs is considered primarily on the basis of prior successful use, if any, and the competency of the designing engineers. The following specifics shall also apply:

   (1)  Cabin body. Passenger cabins shall be enclosed and ventilated and be equipped with doors that fill the entire entrance opening. Each door shall be locked during every trip in such a manner that it cannot be unlocked except by the conductor or other authorized personnel. The key shall be kept where it is not accessible to the public or passengers. A key shall also be placed under glass and posted to prohibit use except under specified emergency conditions. The capacity of each cabin shall be posted in a conspicuous place in the cabin. Means of emergency evacuation of passengers, acceptable to the authority having jurisdiction, shall be provided. All windows shall be of shatterproof material.

   (2)  Frame. The frame shall be securely fastened to the carriage trucks and the cabin in such a manner that it cannot work loose. The frame hanger shall be of sufficient length vertically so that under the worst condition of longitudinal sway the top of the cabin will not strike the hauling rope or the bottom of a tower saddle and thus expose the trucks to danger of derailment. The hanger may be shorter in length if effective sway dampers are used. See also paragraph (3)(iii).

   (3)  Trucks. Trucks shall comply with the following:

     (i)   Wheels. On bicable tramways, the weight of the cabin, frame and carriage shall be so distributed over all wheels that the load per wheel does not exceed that recommended by the track cable manufacturer. Wheels shall be designed to prevent them from leaving the track cable under all operating conditions. The diameter of wheels should be selected on the basis of whichever of the following criteria requires the greatest diameter:

       (A)   The recommendation of the track cable manufacturer.

       (B)   The allowable bearing pressure on the material, if any, with which the wheels are lined.

     (ii)   Track cable brakes. Each carriage on a bicable tramway shall be equipped with a brake that will grip the track cable. Such brake shall be capable of holding a fully loaded car at the point of maximum slope, and shall function automatically in case of a hauling rope failure and be capable of being manually applied by the cabin conductor. The authority having jurisdiction may permit the brake to be omitted if two or more hauling ropes are used, or if the profile of the tramway will not permit an uncontrolled cabin to gain abnormal speed or crash into a terminal.

     (iii)   Sway dampers. Sway dampers to reduce the longitudinal sway of cars shall be used if recommended by the tramway designer or the authority having jurisdiction. When used, they shall be designed to operate smoothly and without danger of derailment of the carriage trucks.

   (4)  Attendants. Each tramcar having a capacity of more than six passengers shall be served by a conductor trained in tramcar operation, emergency control and evacuation.

 (c)  Track cables. Track cables shall conform to the following:

   (1)  Specifications and tests. A copy of the specifications of the track cable manufacturer shall be available to the authority having jurisdiction. Such specifications shall include size, grade of track cable, construction and breaking strength. Before installation, the manufacturer shall test to destruction a sample of the cable furnished and submit a certified report of the results. In the case of cables of foreign origin, a test shall be made by a reputable testing agency approved by the authority having jurisdiction in order to obtain adequate proof.

   (2)  Tension limitations. Track cables shall be designed to have a minimum static factor of safety of three when new. Provisions shall be made to properly maintain track cable tension. Under the dynamic load applied by the track cable brake, this factor shall not be reduced below 2-1/2.

   (3)  Sockets. Sockets shall be so designed that no part is stressed in excess of the yield strength of the materials used when the cables are stressed to their catalog strength. Rules applying to unusual or special types of fittings are provided in subsection (a).

   (4)  Couplings. Track cable couplings shall not be used without the consent of the authority having jurisdiction. In the case of long track cables, couplings may be necessary, but such a situation should not preclude the use of a carriage brake designed accordingly. Track cable couplings shall not be reused.

 (d)  Grounding. Hauling ropes and track cables shall be connected metallically to one or both terminal structures so as to be grounded through such structures. When hauling ropes are used as conductors in the communication system, lightning protection should be provided while the tramway is in operation. At all other times, the ropes should be grounded.

 (a)  A communication system shall be provided. The following types of communication are recommended for major installations:

   (1)  Terminal-to-terminal two-way telephone or radiophone communication independent of all other forms of communication.

   (2)  Two-way telephone communication or radiophone communication from operating room to all attended tramcars and to the opposite terminal platform.

   (3)  Two-way pushbutton signal (buzzer system) communication from the operating room to all attended tramcars and to the opposite terminal.

 (b)  A reduction of the system of communication for less important installations may be approved by the authority having jurisdiction.

 No signs are required other than those specified elsewhere in § §  7.421—7.432 if attendants and conductors are placed as specified. Signs, if used, should be short, simple, bold in design, and to the point.

 Tram cabins shall be equipped with a trap door and either a rope ladder or boatswain’s chair capable of reaching the ground from the highest point. Consideration should be given to the provision of auxiliary emergency cars for the evacuation of unusually timid or invalid or physically handicapped passengers, or in cases of extreme heights. An auxiliary hauling rope or emergency car system shall be provided in cases of extreme height or hazardous terrain.

   This section cited in 34 Pa. Code §  7.421 (relating to definitions); 34 Pa. Code §  7.422 (relating to applicability); and 34 Pa. Code §  7.431 (relating to signs).

CHAIR LIFTS, GONDOLA LIFTS AND SKIMOBILES

§ 7.441. Definitions.

 (a)  The following words and terms, when used in this section and § §  7.442—7.453, have the following meanings, unless the context clearly indicates otherwise:

   Carriers—Open chairs, cars, or gondolas, which may be permanently attached to the hauling rope, or detached at the terminals.

   Monorail life—A tramway in which the carriers are supported on a rigid overhead rail of I-beam or similar construction.

   Tramways—Those of the bicable, monocable, or monorail type.

 (b)  The definitions specified in §  7.421 (relating to definitions) shall also apply.

 The provisions of § §  7.441—7.453 apply to that class of aerial tramways in which the carriers circulate around the system, traveling from one terminal to the other along one path of travel and returning along another path of travel, making U-turns in both terminals. Such provisions do not apply to tramways in which passengers are in contact with the ground or snow during the trip. Skimobiles and similar devices, though they might not be denoted as aerial tramways, are subject to such provisions.

 The location of chair lifts, gondola lifts, and skimobiles is subject to the requirements specified for single and double reversible aerial tramways in §  7.423 (relating to location).

 Clearings for chair lifts, gondola lifts, and skimobiles are subject to the requirements specified for single and double reversible aerial tramways in §  7.424 (relating to width of clearing).

 (a)  Towers shall be located to conform to the profile of the terrain and to provide for the proper deflection of the hauling rope so that passengers will not be higher above the ground than necessary, nor so close as to encourage them to disembark at locations other than established stations.

 (b)  The adjustment of tower sheave heights, if made, shall be done in a manner to avoid overloading or underloading tower sheave units. In the furthering of this purpose, there shall be made available to the designer not only the profile of the natural terrain along the line but also profiles, approved by the owner, of the various anticipated snow depths for which the tramway is to be designed. The designer shall select one set of tower locations which will be suitable for all of such profiles. For each profile he shall determine the proper number and height of sheaves for each tower. The sheave units furnished for each tower shall be suitable for all of the profiles. Each tower shall be marked with the location of the assigned height for the sheave units for each profile, giving each profile a serial number or letter, such as A,B,C,D or the like. The operating instructions shall clearly state that when the sheaves on one tower are at location A, for example, then the sheaves on all towers shall also be at location A, and similarly for all other serial letters. The instructions shall also include a standard procedure for determining which serial designation to use to suit the snow conditions existing at any time. The owner shall make sure that these instructions are followed. After any such change the lift shall not be started until the horizontal alignment of the sheave units is checked.

 (c)  The interrelation between the location and height of towers, and design of sheave units and track cable saddles, shall be subject to the provisions of §  7.448 (d) and (e) (relating to line structures).

 (d)  Towers and ropes shall be so arranged as to prevent the collision of passing carriers in the event of lateral swinging due to wind.

 (e)  The distance between two carriers, if swung ten degrees inward from the vertical, shall be at least two feet six inches. The distance between cables, for purposes of this check shall be considered as equal to the gage of the line.

 (f)  Since the skimobile line is supported by a trestle closely following the profile of the ground, most of the provisions of this section are irrelevant, except that the trestle shall be bridged over ski trails with an opening wide enough and high enough to permit the passage of skiers. The same is true of the monorail type, except that subsections dealing with wind action and lateral swing are relevant.

 (g)  When ski runs cross under the line, the tower shall be high enough to assure clearance for the skiers under the chairs or cars.

 (h)  Local wind conditions shall be taken into consideration in every instance.

 No chair lift, gondola lift or skimobile shall be operated beyond their design capacity and speed. The following specifics shall also apply:

   (1)  Single chair lifts. Lifts shall never be operated beyond their design capacity and speed. Single chair lifts shall not operate for the use of skiers at speeds in excess of 600 feet per minute, nor with chair spacings less than would produce a loading interval of 6 seconds. Outside of the skiing season, or if there is no skiing, such lifts shall operate at lower speed, preferably 350 feet per minute. Such speeds may be increased if a lift is slowed or stopped for loading and unloading. Variations in speed and loading intervals may be approved by the authority having jurisdiction.

   (2)  Double chair lifts (including monorail lifts). Double chairs lifts should not generally be operated for the use of skiers at speeds in excess of 550 feet per minute, nor with chair spacing less than would produce a loading interval of eight seconds. Outside of the skiing season, or if there is no skiing, such lifts shall be operated at a lower speed, preferably 350 feet per minute. These speeds may be increased if a lift is slowed or stopped for loading and unloading. Variations in speed and loading intervals may be approved by the authority having jurisdiction.

   (3)  Detachable chair lifts and gondola lifts. The design capacity of each carrier shall be posted in a conspicuous place on the carrier. Permissible speed of travel is dependent on the facilities provided at the terminals for detaching, attaching, decelerating, and accelerating carriers. The hauling rope is to be continuously moving at a constant speed. Smooth and relatively slow acceleration of the carrier shall be accomplished at full rope speed. Rope speed shall not exceed 600 feet per minute, unless approved by the authority having jurisdiction. Means shall be provided to space the carriers at prescribed intervals, never less than those contemplated in the design.

   (4)  Skimobiles. Skimobiles shall not generally be operated at speeds in excess of 550 feet per minute. Loading intervals for single passenger cars shall not be less than four seconds. The speed may be increased if a lift is stopped and started for loading and unloading. Higher speeds and shorter intervals may be approved by the authority having jurisdiction if a proposed scheme is satisfactorily shown to represent a safe operation.

 (a)  Power source. Electrical and internal combustion energy may be utilized as a power source, under the requirements set forth in §  7.427(a) (relating to terminals and stations).

 (b)  Prime movers. Prime movers shall have the capacity to handle the most unfavorable design loading conditions. An auxiliary power unit with an independent power source shall be provided which may readily be used to unload the line in the event of power failure unless an exception is granted by the authority having jurisdiction. Internal combustion engine exhaust shall be discharged in the atmosphere.

 (c)  Speed reducers and gears. Speed reducers and gears shall comply with accepted standard practices, and have the capacity for starting the tramway under the most unfavorable design load conditions.

 (d)  Bearings, couplings, and shafting. All bearings, couplings, and shafting shall conform to the provisions of §  7.427(d).

 (e)  Clutches. Any clutch device used between the prime mover and the drive sheave shall meet the requirements for bearings and couplings specified in subsection (d).

 (f)  Acceleration and speed control. The primary requirement is to have means of preventing runaway speeds particularly when overhauling loads are being carried. Specific provision other than brakes shall be made for maintaining normal speed under overhauling loads. The power developed by such overhauling load may be dissipated electrically, hydraulically, or pneumatically. Provision shall also be made for slowing and stopping the tramway drive automatically if the line velocity exceeds design values by more than 15%. Drive equipment shall be designed to accelerate the line smoothly and to avoid discomfort to passengers under any loading condition. When carriers are detachable, they shall be accelerated and decelerated to and from the rope speed at such rates as not to cause discomfort to passengers. When carriers are fixed to the rope, there shall be an attendant to assist the passengers mounting and dismounting. The drive shall be capable of rotating the unloaded system at reduced speed for rope inspection. In the case of systems involving detachable carriers, unbalanced loading shall be controlled by automatic car counters or other suitable devices.

 (g)  Brakes and stops. Every chair lift, gondola lift and skimobile shall be provided with at least the following:

   (1)  Brakes. Every such lift shall include the following brakes:

     (i)   An automatic brake to stop and hold the system under maximum load when power is shut off or the lift is stopped for any reason. Such brake shall be electrically released and applied by springs of gravity, except in cases where another type of brake is specifically approved by the authority having jurisdiction. In all cases the brake shall normally be in the applied position. It shall be held open for operation of the tramway by a device which is automatically cut out if power is shut off or the tramway stopped. Such device shall, without exception, be placed in operation before the tramway is started. The brake shall be applied to a drive shaft so that there is no clutch, V-belt or chain drive, or similar device between the brake and the drive wheel. This restriction on the location of the brake is not required in cases where the gear pitch or gear reduction is such that the lift cannot overhaul with a capacity load plus 10% after the interruption of power.

     (ii)   A manually-operated brake on the main drive sheave with controls located near the operator.

     (iii)   A backstop to prevent reverse rotation of the tramway, unless the gearing will prevent gravity reversal.

   (2)  Stops. Electric switches affecting all power shall be installed at all loading and unloading points and be so located as to be immediately available to the attendants. The stop system shall be so arranged that the lift cannot be started until the device that stopped the lift is reset and the operator obtains clearance from the point at which the device is actuated. It is desirable that a wind gage be installed on the most exposed point along the tramway line. In such case, a conspicuous warning device shall function to alert the operator when the wind velocity reaches the established maximum. When wind conditions, as determined by such a device or by observation of an attendant or the operator, make operations dangerous, the tramway shall be unloaded and stopped. The tramway shall be started only by the operator or with his approval, unless the plan of operations set by the management of the tramway permits other attendants to start the lift under certain specified conditions. Reference should be made to subsections (f) and (t) of this section and §  7.448(d) (relating to line structures).

 (h)  Machine rooms. Machine rooms shall conform to the requirements specified in §  7.427(h), except that a door with a suitable lock is not required for a cabinet type unit. In all cases, all safety devices, such as backstops, brakes, relays, and the like, shall be protected from the weather.

 (i)  Protection against moving parts. Moving machine parts which may normally be within reach of personnel shall be fitted with safety guards conforming to American Standard B15.1-1953.

 (j)  Bull wheel. Bull wheel frames shall be so designed that they will retain the wheel in the event of shaft breakage. If this is not feasible, shaft design working stresses shall be not more than 60% of those otherwise allowable. The minimum diameter for bull wheels shall be 72 times the diameter of the rope, if no gripping device passes around the bull wheel. The minimum diameter for bull wheels shall be 96 times the diameter of the rope in cases where the gripping devices travel around the bull wheel. In such instances, the angle formed by the cable as it enters and leaves the grip body when passing around the bull wheel shall not exceed seven degrees. The bull wheel mounting at all terminals shall be supported from the ground by rigid structures. The mounting that travels under the action of the counterweight shall be supported on rigid straight rails by means of wheels. The available travel should be such that the frame does reach either limit of motion during normal operation and until the hauling rope needs to be resocketed or respliced for other reasons, or replaced. On fixed-grip lifts, guides shall be provided to prevent the carriers from excessive swinging while passing around the bull wheel. On skimobiles, provision shall be made in the design of the turntable to prevent the car from leaving the track.

 (k)  Sheaves and bearings in terminals. All sheaves and bearings in terminals shall conform to the following:

   (1)  Drive sheaves. Drive sheaves shall be designed to withstand static and dynamic loads. Sheave mountings and bearings shall satisfy the recommendations of the manufacturers of the bearings. When sheaves are mounted on vertical shafts, such shafts shall be equipped with bearings which adequately resist the vertical thrust. Drive sheaves shall be so designed that the hauling rope will not slip in the sheave groove which involves the friction between the bull wheel or its groove liner and the rope, as well as the relative levels of tensions of the rope entering and leaving the bull wheel.

   (2)  Hauling rope sheaves. Guide sheaves shall be placed to prevent misalignment of the rope entering and leaving the bull wheels. Sheaves shall meet the specifications of §  7.448(d), and carry no figured load from the rope. When necessary to prevent the rope from leaving the sheaves, counter sheaves shall be installed adjacent to them. Provision shall be made for grounding the wire rope to offset the effects of static electricity and electrical storms. When deflecting sheaves are required they shall also satisfy the requirements of §  7.427(k)(2).

   (3)  Counterweight rope sheaves. Counterweight rope sheaves are subject to the specifications prescribed in paragraph (2) of this subsection, except that if antifriction bearings are considered, they shall be selected to avoid a tendency for flat spots to develop on the rollers or balls since counterweight sheaves are subject to very little motion and often stand without moving for long periods of time.

   (4)  Track cable deflecting sheaves (bicable lifts only). Track cable deflecting sheaves in the terminals shall be designed to withstand static and dynamic loads. Their tread diameter shall be not less than that recommended by the manufacturer of the track cable for the particular installation and shall also satisfy the allowable bearing load limits of the material with which their grooves are lined. When unlined grooves are used they should be V-shaped with rounded bottoms having a radius equal to 55% of the cable diameter. Sheave mountings and bearings shall satisfy the recommendations of the manufacturers of the bearings. Provision shall be made for grounding the cable. If the cable is used as a conductor in the communication system, lightning protection shall be provided, and the cable shall be grounded when the tramway is not in operation.

 (l)  Track cable saddles. The requirements for track cable saddles are the same as those set forth in §  7.428(e)(1)—(5) of this Title (relating to line structures), except that if saddles in the terminals are so located that the carrier wheels do not pass over them, subparagraphs (ii) and (iv) of paragraph (1) of that subsection need not apply.

 (m)  Anchor connections for track cables, counterweight ropes, tower or station anchor cables or guys, and the like. Rope and cable sockets shall be designed so that they will not be stressed beyond the yield point of the material used when the ropes or cables which they anchor are under tensions equal to their catalog breaking strength. Anchor connections shall be above ground. Any part of the anchorage below ground shall be protected against loss of strength due to corrosion.

 (n)  Counterweight ropes. Counterweight ropes shall conform to the specifications prescribed in §  7.427(n).

 (o)  Counterweights. Counterweights shall conform to the specifications prescribed in §  7.427(o), except that reference shall be made to subsection (j) in regard to bull wheels.

 (p)  Structures. The structures of chair lifts, gondola lifts, and skimobiles shall conform to the specifications prescribed in §  7.427(p).

 (q)  Foundations. The foundations of chair lifts, gondola lifts, and skimobiles shall conform to the specifications prescribed in §  7.427(q).

 (r)  Loading and unloading areas. All loading and unloading areas shall conform to the following:

   (1)  Chair and monorail lifts. Loading and unloading areas shall have sufficient level length to load and unload passengers safely and, in the case of unloading, to clear them from the platform. The minimum length shall be 16 feet, which shall be level except for unloading areas for skiers, which may be inclined so that passengers may ski away from the lift. Handrails, safety nets, or ramps shall be provided on all sides of each platform for the protection of passengers. Attention should be given to intermediate and upper unloading areas for double chair lifts. Since there may be a hazard involved in attempting to disembark both passengers from a carrier to the same side of the lift, this should be overcome either in the design or operation of the lift. Towers adjacent to loading points shall be covered with guards to prevent ski tips of starting passengers from becoming entangled in the towers. The outer ends of unloading platforms shall be fitted with inclined guards to prevent the ski tips of unwary passengers from being caught under the edges of such platforms. The distance between hauling rope supports on either side of each loading area shall be such that the distance between chair and ground does not diminish excessively under the impact of loading passengers. The same distance shall be used between hauling rope supports at unloading areas.

   (2)  Detachable chair and gondola lifts. Sufficient terminal floor space shall be provided so that passengers may board and leave the carriers without being crowded. Carriers shall be secured or controlled to prevent excessive swinging during loading and unloading. Provision shall be made at all stations for the separation of incoming and outgoing passengers. Stations shall be so arranged that the carriers can enter and leave safely even when swinging laterally. Beyond the points of attachment and detachment of the grips, devices shall be installed to avoid damage to equipment or injury to persons in the event of faulty detachment or attachment. Such devices shall support the grip and carrier safely as it travels the distance necessary to stop the lift after the operation of a safety stop, to which 50% should be added as a safety margin. The devices shall include bumpers wherever the carriage or carrier could become freewheeling on an openend or deadend track. Switches in the track system shall be provided with safety devices to prevent malfunction. Reference shall also be made to §  7.449(b)(2)(i) (relating to line equipment).

   (3)  Skimobiles. Loading and unloading terminal platforms shall have a minimum level length of 30 feet and the surface shall be maintained in a nonslippery condition. There shall be a guardrail between incoming and outgoing tracks. At intermediate stations used for unloading only, the slope of the platform shall be the same grade as the track.

 (s)  Attendants. Attendants shall be provided as follows:

   (1)  Chair lifts and skimobiles. There shall be a minimum of one attendant at each station when it is being used for loading and unloading. One attendant shall also be placed in charge of the operating crew. Primary tramway controls and communication systems shall be immediately available to him. He shall have enough time from other duties to discharge this responsibility and keep the operation under observation at all times. At least one attendant shall be available to service each carrier to be loaded or unloaded. At times of peak load on double chair lifts with minimum interval between chairs, it may be necessary for safe operation to have two attendants available for each chair.

   (2)  Detachable chair and gondola lifts. The requirements for detachable chair and gondola lifts are the same as those prescribed in paragraph (1), except that additional attendants may be required to handle the carriers in the stations. When carriers are not mechanically controlled in the stations, one or more additional attendants may be required, one to handle incoming cars and the other to handle outgoing cars during peak periods of operation.

   (3)  All installations. All personnel subject to the provisions of this subsection shall be carefully instructed in tramway operation, including the acquisition of a knowledge of possible emergency situations and methods of handling them.

 (t)  Safety stops. Safety stops shall be provided as follows:

   (1)  Chair lifts and monorail lifts. When danger to passengers or equipment may result if a passenger remains on the carrier while it travels around a bull wheel, a safety stop shall be provided at each such terminal to stop the lift before exposure to such danger. The distance from such stop to the first obstruction shall not be less than the distance travelled by the unloaded lift operating at maximum speed after application of such a stop, to which should be added a safety margin of 50%.

   (2)  Detachable chair and gondola lifts. Automatic safety stops shall be provided in each terminal to stop the lift in the event a carrier does not properly disengage from, or reattach to, the hauling rope. The provisions of subsection (r)(2) shall also be complied with.

   (3)  All installations. Limit switches shall be installed to stop the tramway before any counterweight or bull wheel carriage reaches either end of its travel. Electrical stop circuits shall be closed circuits so that, in case of power failure or of malfunction of the stop switch, the system will fail safe. The circuit shall be all metallic and ungrounded, unless otherwise approved by the authority having jurisdiction. After any actuation of a safety stop, the cause shall be determined and removed, and the safety stop reset. Safety stop circuits shall not be bypassed during passenger operation. In the case of such stops, the tramway shall never be started except by the operator. Reference should also be made to subsections (f) and (g) and §  7.448(d).

 (a)  Towers, trestles, and monorails. Towers, trestles and monorails shall conform to the following:

   (1)  Towers. The design of towers shall satisfy the requirements of §  7.427(p) (relating to terminals and stations) and all of the following:

     (i)   When clearance is not adequate, towers shall be equipped with guards designed to prevent the carriers from swinging into the towers. The provisions of subsection (c) shall also apply.

     (ii)   When guyed towers are used and guys intersect the ground within or near ski runs, the guys shall be marked for visibility, preferably with boards painted with black and yellow stripes.

     (iii)   Means shall be provided for ready access from the ground to all tower tops. This requirement is fulfilled if the tower structure is such that it is safe to climb. Otherwise, means such as permanent or light portable ladders shall be provided. The latter shall be in at least sufficient quanity to be available at each point where attendants are stationed.

     (iv)   Towers shall be grounded by individual grounds, by buried ground wires connecting all towers, or by tying all towers into a suspended ground wire, which may also be used as a ground for the signal system, and is itself grounded. The ground shall satisfy all National and local codes. The local electric power company is a good source of information regarding such requirements.

     (v)   Towers shall be clearly identified with successive numbers.

     (vi)   When towers are designed to permit variations in rope height, sheave unit supports shall be guided and attached so as to prevent misalignment by rotation during raising or lowering, as well as during normal operation.

   (2)  Trestles and monorails. The design of trestles and monorails shall satisfy the requirements of §  7.427(p) (relating to terminals and stations) and any further portions of paragraph (1) relevant to the particular design. Provision shall be made for the expansion and contraction of the actual track or rail. Facilities shall be provided for maintenance and emergency access to the trestle track deck from the ground at intervals not exceeding 800 feet, and to the monorail at any point. Bents shall be clearly identified with successive numbers.

 (b)  Foundations. Foundations shall comply with the provisions of §  7.428(b) (relating to line structures).

 (c)  Guards. Towers shall be equipped with devices to prevent the carriages from swinging into the towers. The clearance shall be sufficient to allow the car to swing 10° laterally from the vertical. When this cannot be done without reducing the clearance to less than 18 inches, suitable guards shall be provided. When, on chair lifts, clearance between the chair in normal position and the tower is less than 30 inches, guards shall be provided to keep skis from being caught in the tower structure. Such guards should be at least 48 inches in height, extending 24 inches above and 24 inches below foot level. Clearance shall not be less than 24 inches.

 (d)  Hauling rope sheaves (or rollers) and mounts. Hauling rope sheaves (or rollers) and mounts shall conform to §  7.428(d)(1)(6). If, under the most adverse loading conditions, the load on a group of support sheaves at a tower may become less than 1/2 the permissible load on one sheave, depression sheaves shall be installed to ascertain that the rope will not lift out of the support sheaves. The reverse requirement shall be applied to depress towers.

 (e)  Track cable saddles and mounts. Track cable saddles and mounts shall conform to the requirements of §  7.428(e)(1)—(5), except that the rules there relating to cabins shall here apply to carriages. In addition, tower heights and locations shall be so arranged that the track cables will never lift out of their saddles under any operating conditions, including surge.

 (a)  Hauling ropes. Hauling ropes shall conform to the following:

   (1)  Specifications and tests. Specifications and tests shall comply with the provisions of §  7.429(a)(1) (relating to line equipment).

   (2)  Tension limitation. The tension of ropes shall comply with the provisions of §  7.429(a)(2).

   (3)  Splices and other connections. Splicing of the main hauling rope shall be done only by an experienced splicer acceptable to the authority having jurisdiction. If a breakdown occurs during operations and it is impossible to obtain an acceptable splicer without delaying the resumption of operation, the splice shall be made by an experienced splicer following the standard printed instructions of the wire rope manufacturer for the splice. Such splice shall be inspected by an acceptable splicer at the first opportunity. When cable links with swaged end fittings are used, as in monorail lifts, the end fittings shall be so designed and applied that, in a test of a complete link, the rope will break without slippage of the fitting. When good performance has been shown by previous experience, or when permitted by the authority having jurisdiction, if cable links with swaged end fittings are used, as in the case of monorail lifts, the rope shall be all metallic, with an independent wire rope cord or a strand core rather than a fiber core. An adequate safety wire rope shall also be installed to safeguard the carriers, to the satisfication of the authority having jurisdiction, in the event of failure or disengagement of cable links, the parts which connect them, or other parts of the hauling system. When the above requirements are met, in a test of a complete link, there shall be no slippage of the fittings at a tension equal to five times the working tension in the link when that tension is held for 15 minutes, and the rope shall not break at any tension below five times the same working tension.

 (b)  Carriers. All carriers shall be clearly identified with numbers and also conform to the following:

   (1)  Safety and seating requirements. Carriers shall comply with the following:

     (i)   Chairs and hangars. Chairs and hangers shall be designed with a minimum factor of safety of six based on the ultimate load. For this purpose, ultimate load is defined as that load at which the whole assembly, supported at the location of the rope and loaded in the normal manner will be distorted beyond a usable condition, regardless of whether any component parts actually rupture. Each chair may be equipped with an approved safety bar and foot rest, or safety belt if deemed desirable.

     (ii)   Gondolas. Gondolas are subject to the provisions of §  7.429(b)(1), except that equipment for emergency evacuation is not required for each gondola. The number of passengers in a gondola is limited to a maximum of six persons unless a conductor rides in each gondola.

     (iii)   Skimobile cars. Skimobile cars shall comply with relevant requirements of subparagraph (i), except that in determining the ultimate load the car shall be considered as being supported at the maximum grade existing on the line, and as being supported by its wheels on the tracks as well as by the hauling rope. There shall be a shield or dashboard on the front of the car, an adequate step, and a handrail to facilitate embarking and disembarking. If operated for skiers, ski racks shall also be provided.

   (2)  Rope grips. A rope grip, whether detachable or fixed, shall be of a type which has proved to give satisfactory service or has been specifically approved by the authority having jurisdiction. Unless so exempted, a rope grip shall be designed so as to resist a force tending to slide it along the cable, which is at least three times as great as the force required to drag the loaded carrier along the steepest incline of the lift under such unfavorable conditions as ice or excessive lubrication on the cable. A factor of safety of at least six shall exist in the component parts of all grips. By inspection, using methods approved by the authority having jurisdiction, confirmation shall be obtained that the grip and its parts meet these requirements. The following shall also apply:

     (i)   Detachable rope grips. Detachable grips shall be designed to pass smoothly over and under line sheaves which have flanges of adequate depth to discourage the rope from leaving the sheave, and grip the rope positively without damaging the rope and so that it cannot become accidentally uncoupled, even by rope vibrations. Each terminal shall be equipped with devices designed to prevent the start of grips that are incorrectly coupled to the rope. Reference should also be made to §  7.447(r) and (t) (relating to terminals and stations). The maximum total vertical load on a single detachable grip shall not exceed 1/14 of the least tension in the rope. A single spring arrangement for holding grip jaws closed about the rope is not permissible. If two springs are used, each spring shall be sufficiently strong to hold the grip safely closed against the design loads.

     (ii)   Fixed rope grips. Fixed grips shall be designed to pass smoothly over and under line sheaves and bull wheels which have flanges of adequate depth to discourage the rope from leaving the sheave. Grips shall be moved at least once in every 24-calendar months. They shall be moved a uniform distance each time, in the same direction. The instructions of the designer or of the authority having jurisdiction shall be followed if they are more restrictive than the provisions of this subparagraph. Reference shall also be made to § §  7.413 and 7.414 (relating to inspections and tests; and maintenance). As each grip is moved, the rope shall be examined for deterioration at or near the grip location, and the rope shall be thoroughly inspected at least once each year.

   (3)  Carriage wheels. The provisions of §  7.429(b)(3)(i) shall apply to carriage wheels, which ride on trestles or monorails with appropriate modifications where necessary.

   (4)  Track brakes. Track brakes shall conform to the provisions specified in §  7.447(g).

 (c)  Track cables. Track cables (bicable lifts only) shall conform to the following:

   (1)  Specifications and tests. Specifications and tests shall be in compliance with §  7.429(c)(1).

   (2)  Tension limitations. Tension limitations shall be in compliance with §  7.429(c)(2).

   (3)  Sockets. Sockets shall be so designed that no part is stressed in excess of the yield strength of the materials used when the cables are stressed to their catalog strength. If types of end attachments are proposed that are other than the current standard types used in this country, their suitability shall be established by tests. The authority having jurisdiction reserves the right to approve or disapprove the use of the proposed connection even when such tests have been made.

   (4)  Couplings. Track cable couplings shall not be used without the consent of the authority having jurisdiction, nor where track cable brakes are used. Track cable couplings shall not be reused.

 A two-way voice communication system shall be provided between the motor control point and all loading and unloading stations. A public address system reaching all points along the line is recommended.

 (a)  The following signs, if relevant to the type of lift, shall be posted where they may be read by all persons using the tramway:

   (1)  If not familiar with use of lift, ask attendant for instructions.

   (2)  Prepare to unload (at a distance of not less than 50 feet ahead of unloading area).

   (3)  Keep ski tips up.

 (b)  Additional signs may be advisable at some installations.

 (c)  Signs should be bold in design and easily readable.

 A system of planned evacuation of passengers from the lift, in the event of power failure or breakdown, shall be established to the satisfaction of the authority having jurisdiction. Adequate equipment for such evacuation shall be available at all times for immediate use.

 In addition to the requirements provided in §  7.415 (relating to operation), reference shall be made to §  7.427(g) (relating to terminals and stations) or §  7.447(g) (relating to terminals and stations).

   This section cited in 34 Pa. Code §  7.441 (relating to definitions); 34 Pa. Code §  7.442 (relating to applicability); 34 Pa. Code §  7.462 (relating to applicability); and 34 Pa. Code §  7.472 (relating to operation).

T-BAR LIFTS, J-BAR LIFTS, PLATTER LIFTS AND
SIMILAR DEVICES

§ 7.461. Definitions.

 The definitions specified in §  7.421 (relating to definitions) shall apply to this section and § §  7.462—7.472.

 The provisions of § §  7.461—7.472 apply to that class of aerial tramways subject to the provisions of § §  7.441—7.453, but is limited to those devices in which the passengers are in contact with the ground or snow during the trip. Such devices are normally of the monocable type.

 The location of T-bar lifts, J-bar lifts, platter lifts, and similar devices is subject to the requirements specified for single and double reversible aerial tramways in §  7.423 (relating to location). In addition, the location shall be selected so that the ski track will always have, or may be made to have, a level or an upward slope. No reverse slopes are permitted except for very mild inclines at loading and unloading points. Selection of the site shall also involve consideration of the maximum permissible slope of the ski track. In no case shall it be steeper than a grade of 100% for single towing outfits, or 80% for double towing outfits. Surface water which might make icy tracks shall be avoided. The site selected shall avoid the intersection of the lift line with possible ski trails.

 Clearings for T-bar lifts, J-bar lifts, platter lifts, and similar devices are subject to the requirements specified for single and double reversible aerial tramways in §  7.424 (relating to width of clearing).

 (a)  Towers shall be located to conform to the profile of the terrain and be so located that, under the most adverse loading conditions, the towing device is unable to lift any passenger off the snow. Also, under the most adverse conditions, the hauling rope shall be high enough to clear the passenger’s head by at least 2 feet. Towers shall also be so arranged that descending empty towing outfits are clear of the snow.

 (b)  Towers shall be of a height and so located that, if the rope comes off the supporting sheaves of a tower, the towers on either side will support the rope clear of grade by at least 2 feet.

 (c)  In areas of deep snow, it may be imperative to use variable tower heights. In such cases, changes in tower height shall be made in a manner to avoid overloading or underloading of tower sheave units. This control, when necessary, shall be provided in the manner prescribed in §  7.445(b) (relating to towers).

 The combination of rope speed and action of the towing outfit shall be such that the skiers are accelerated at a safe rate as they are mounting the lift. When the average level of ability of the skiers to mount the lift is relatively low, acceleration shall be reduced by changing the traveling speed of the rope. The minimum loading interval for T-bars shall be 5 seconds plus the time required to extend the towing outfit to such a point that the skiers begin to move. The minimum loading interval for single passenger outfits shall be three seconds plus the time required to extend the towing outfit to such a point that the skier begins to move. These figures represent capacities of something less than 1,400 and 1,200 passengers per hour, respectively.

 (a)  Power source. Electrical and internal combustion energy may be utilized as a power source, as follows:

   (1)  Electrical. The utilization of electrical energy shall conform to the provisions of §  7.427(a)(1) (relating to terminals and stations).

   (2)  Internal combustion. Fuel tanks shall be buried or so located as to be free of fire hazard. The engine shall always be shut down during refueling. The fuel entry opening shall be capped and located to avoid toxic fumes and fire hazard during refueling. Liquid fuels shall be stored and handled in accordance with the standards of the National Board of Fire Underwriters as outlined in Pamphlet No. 30, Flammable Liquids, June 1959. Also liquefied petroleum gas installations shall be made in accordance with the standards of the National Board of Fire Underwriters, as outlined in Pamphlet No. 58, Liquefied Petroleum Gases, as amended through 1959.

 (b)  Prime movers. Prime movers shall have the capacity to handle the most unfavorable design loading conditions. Internal combustion engine exhausts shall be discharged into the atmosphere.

 (c)  Speed reducers and gears. Speed reducers and gears shall comply with accepted standard practices, and have the capacity for starting the tramway under the most unfavorable design load conditions.

 (d)  Bearings, couplings, and shafting. Bearings, couplings, and shafting shall conform to the provisions of §  7.427(d).

 (e)  Clutches. Any clutch device used between the prime mover and the drive sheave shall meet the requirements for bearings and couplings specified in subsection (d) of this section.

 (f)  Acceleration and speed control. When necessary to satisfy the requirements of §  7.466 (relating to capacity, speed and loading interval), a variable speed drive shall be used, so that the speed of the rope may be changed to suit variations in snow conditions and the ability of skiers to mount the lift. The drive equipment shall be able to accelerate the line safely under all conditions of loading.

 (g)  Brakes and stops. Every system shall be provided with the following:

   (1)  Brakes. The lift shall have a backstop to prevent reverse rotation of the lift under full load.

   (2)  Stops. Electric switches affecting all power shall be installed at all loading and unloading points, and be so located as to be immediately available to the attendants. The tramway shall be started only by the operator or other designated attendant. Reference should also be made to subsection (s) and §  7.468(d) (relating to line structures).

 (h)  Machine rooms. Motive power shall be housed in a well-ventilated machine room in a manner which permits proper maintenance. Adequate lighting and protection against lighting and static electricity shall be provided. A minimum of 18 inches clearance shall be provided between machinery and machine room enclosures, and passageways between units of machinery should have the same minimum width. A fireproof room is preferable but in any event, adequate fire-prevention measures and fire fighting devices shall be installed, except for a cabinet type unit. In all cases, all safety devices, such as backstops, brakes, relays, and the like, shall be protected from the weather.

 (i)  Protection against moving parts. Moving machine parts which may normally be within reach of personnel shall be fitted with safety guards conforming to American Standard B15.1-1953.

 (j)  Bull wheels. Bull wheel frames should be so designed that they will retain the wheel in the event of shaft breakage. Where this is not feasible, the shaft design working stresses shall be not more than 60% of those otherwise allowable. The minimum diameter for bull wheels shall be 72 times the diameter of the rope, if no gripping device passes around the bull wheel. The minimum diameter for bull wheels shall be 80 times the diameter of the rope in cases where the gripping devices travel around the bull wheel. In such instances, the angle formed by the cable as it enters and leaves the grip body when passing around the bull wheel shall not exceed seven degrees. The bull wheel mounting at all terminals shall be supported from the ground by rigid structures. The mounting that travels under the action of the counterweight shall be supported on rigid straight rails by means of wheels. The available travel should be such that the frame does not reach either limit of motion during normal operation and until the hauling rope needs to be resocketed or respliced for other reasons, or replaced. Guides shall be installed to lead the towing outfits in and out of terminals and around the bull wheel without danger to themselves, terminal structures or equipment, or personnel.

 (k)  Sheaves and bearings in terminals. Sheaves and bearings in terminals shall conform to the following:

   (1)  Drive sheaves. Drive sheaves shall meet the requirements of §  7.427(k)(1).

   (2)  Hauling rope sheaves. Guide sheaves shall be placed to prevent misalignment of the rope entering and leaving the bull wheels. Sheaves shall meet the specifications of §  7.468(d). When necessary to prevent the rope from leaving the sheaves, counter sheaves shall be installed adjacent to them. Provision shall be made for grounding the wire rope to offset the effects of static electricity and electrical storms. When deflecting sheaves are required, they shall satisfy the requirements of §  7.427(k)(2).

   (3)  Counterweight rope sheaves. Counterweight rope sheaves shall conform to the provisions of §  7.427(k)(3).

 (l)  Anchor connections for counterweight ropes, tower or station anchor cables or guys, and the like. Rope and cable sockets shall be so designed that they will not be stressed beyond the yield point of the material used when the ropes or cables which they anchor are under tensions equal to their catalog breaking strength. Anchor connections should be above ground. Any part of the anchorage below ground shall be protected against loss of strength due to corrosion.

 (m)  Counterweight ropes. Counterweight ropes shall conform to the specifications prescribed in §  7.427(n).

 (n)  Counterweights. Counterweights shall conform to the specifications prescribed in §  7.427(o), except that reference shall be made to subsection (j) in regard to bull wheels.

 (o)  Structures. The structures of chair lifts, gondola lifts and skimobiles shall conform to the specifications prescribed in §  7.427(p).

 (p)  Foundations. The foundations of chair lifts, gondola lifts, and skimobiles shall conform to the sepcifications prescribed in §  7.427(q).

 (q)  Loading and unloading areas. All loading areas shall be of sufficient length and grade to permit starting of skiers with maximum ease and comfort and to permit them to become adjusted to the towing outfit before they start uphill. All unloading areas shall be at least 16 feet long and approximately level, but may be inclined slightly to aid the passengers to ski away from the towing device. The distance between the unloading area and upper terminals guides shall be sufficient to allow the towing outfits to become retracted and to permit their oscillation to diminish adequately before they enter the terminal. This requirement will result in a different distance for each type of towing outfit and each line velocity.

 (r)  Attendants. There shall be at least one attendant at each station, one of whom shall be in charge of all operations.

 (s)  Safety stops. A safety stop actuated by contact with a passenger or towing device shall be provided at the unloading terminal to stop the lift before a passenger or unretracted towing device comes in contact with any mechanism or obstruction. The distance from such stop to the first obstruction shall be not less than the distance traveled by the unloaded lift operating at maximum speed after application of the stop, to which shall be added a safety margin of 50%. The safety stop shall be marked by a red flag or other attention-arresting device. Limit switches shall be installed to stop the tramway before any counterweight or bull wheel carriage reaches either end of its travel. All electrical stop circuits shall be closed circuits so that, in case of power failure or malfunction of the stop switch, the system will fail safe; it shall also be all metallic and ungrounded, unless otherwise approved by the authority having jurisdiction. After any actuation of a safety stop, the cause shall be determined and removed, and the safety stop reset. Safety stop circuits shall not be bypassed during passenger operation. In the case of such stops, the lift shall never be started except by the operator. Reference should also be made to subsection (g) and §  7.468(d) (relating to line structures).

 (a)  Towers. The design of towers shall satisfy the requirements of §  7.427(p) (relating to terminals and stations) and all of the following:

   (1)  A minimum clearance of 36 inches shall be maintained between the base of a tower and the vertical plane of the upward traveling cable. With respect to the downward traveling cable a minimum clearance of 24 inches shall be provided between the towing outfit in its normal position and the tower.

   (2)  If guyed towers are used and the guys intersect the ground within or near ski runs, the guys shall be marked for visibility, preferably with boards painted with black and yellow strips.

   (3)  Means shall be provided for ready access from the ground to all tower tops. This requirement is fulfilled if the tower structure is such that it is safe to climb. Otherwise, means such as permanent or light, portable ladders shall be provided. The latter, if used shall be in at least sufficient quantity to be available at each point where attendants are stationed.

   (4)  All towers should be grounded by individual grounds, by buried ground wires connecting all towers, or by tying all towers into a suspended ground wire, which may also be used as a ground for the signal system, and is itself grounded. The ground shall satisfy all national and local codes. The local electric power company is a good source of information regarding such code requirements.

   (5)  Towers shall be clearly identified with successive numbers.

   (6)  When towers are designed to permit variations in rope height, sheave unit supports shall be attached so as to prevent misalignment by rotation during normal operation.

 (b)  Foundations. Foundations shall comply with the provisions of §  7.428(b) (relating to line structures).

 (c)  Guards. Guards shall comply with the provisions of §  7.428(c).

 (d)  Sheaves and mounts. Sheaves and mounts shall conform to §  7.427(k)(1), except that this application is that of a tower roller, not a large-angle deflection sheave. The following shall also apply:

   (1)  The provisions of §  7.428(d)(1),(3)—(6).

   (2)  Sheave grooves shall be designed with deep flanges to discourage the rope from leaving the sheaves. In addition, suitable guards shall be installed to prevent the rope from falling into dangerous positions within the tower structure in case it does leave the sheaves, and suitable devices shall be installed to stop the tramway in the event the cable leaves the sheave on either side.

   (3)  When, under the most adver