§ 7.428. 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) 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.
Cross References This section cited in 34 Pa. Code § 7.421 (relating to definitions); 34 Pa. Code § 7.422 (relating to applicability); 34 Pa. Code § 7.427 (relating to terminals and stations); 34 Pa. Code § 7.431 (relating to signs); 34 Pa. Code § 7.447 (relating to terminals and stations); 34 Pa. Code § 7.448 (relating to line structures); and 34 Pa. Code § 7.468 (relating to line structures).
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