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1910.66(f) Powered Platform Installations-Equipment
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The following requirements apply to equipment which are part of a powered platform installation, such as platforms, stabilizing components, carriages, outriggers, davits, hoisting machines, wire ropes and electrical components.
Equipment installations shall be designed by or under the direction of a registered professional engineer experienced in such design;
Equipment that is exposed to wind when not in service shall be designed to withstand forces generated by winds of at least 100 miles per hour (44.7 m/s) at 30 feet (9.2 m) above grade; and
Equipment that is exposed to wind when in service shall be designed to withstand forces generated by winds of at least 50 miles per hour (22.4 m/s) for all elevations.
The design shall provide for a minimum live load of 250 pounds (113.6 kg) for each occupant of a suspended or supported platform;
Bolted connections shall be self-locking or shall otherwise be secured to prevent loss of the connections by vibration.
Elevated building maintenance equipment shall be suspended by a carriage, outriggers, davits or an equivalent method.
Carriages used for suspension of elevated building maintenance equipment shall comply with the following:
The horizontal movement of a carriage shall be controlled so as to ensure its safe movement and allow accurate positioning of the platform for vertical travel or storage;
Powered carriages shall not exceed a traversing speed of 50 feet per minute (0.3 m/s);
The initiation of a traversing movement for a manually propelled carriage on a smooth level surface shall not require a person to exert a horizontal force greater than 40 pounds (444.8 n);
Structural stops and curbs shall be provided to prevent the traversing of the carriage beyond its designed limits of travel;
Traversing controls for a powered carriage shall be of a continuous pressure weatherproof type. Multiple controls when provided shall be arranged to permit operation from only one control station at a time. An emergency stop device shall be provided on each end of a powered carriage for interrupting power to the carriage drive motors;
The operating controls(s) shall be so connected that in the case of suspended equipment, traversing of a carriage is not possible until the suspended portion of the equipment is located at its uppermost designed position for traversing; and is free of contact with the face of the building or building guides. In addition, all protective devices and interlocks are to be in the proper position to allow traversing of the carriage;
Stability for underfoot supported carriages shall be obtained by gravity, by an attachment to a structural support, or by a combination of gravity and a structural support. The use of flowing counterweights to achieve stability is prohibited.
The stability factor against overturning shall not be less than two for horizontal traversing of the carriage, including the effects of impact and wind.
The carriages and their anchorages shall be capable of resisting accidental over-tensioning of the wire ropes suspending the working platform, and this calculated value shall include the effect of one and one-half times the stall capacity of the hoist motor. All parts of the installation shall be capable of withstanding without damage to any part of the installation the forces resulting from the stall load of the hoist and one half the wind load.
Roof carriages which rely on having tie-down devices secured to the building to develop the required stability against overturning shall be provided with an interlock which will prevent vertical platform movement unless the tie-down is engaged;
An automatically applied braking or locking system, or equivalent, shall be provided that will prevent unintentional traversing of power traversed or power assisted carriages;
A manual or automatic braking or locking system or equivalent, shall be provided that will prevent unintentional traversing of manually propelled carriages;
A means to lock out the power supply for the carriage shall be provided;
Safe access to and egress from the carriage shall be provided from a safe surface. If the carriage traverses an elevated area, any operating area on the carriage shall be protected by a guardrail system in compliance with the provisions of paragraph (f)(5)(i)(F) of this section. Any access gate shall be self-closing and self-latching, or provided with an interlock;
Each carriage work station position shall be identified by location markings and/or position indicators; and
The motors shall stall if the load on the hoist motors is at any time in excess of three times that necessary for lifting the working platform with its rated load.
Every davit installation, fixed or transportable, rotatable or non-rotatable shall be designed and installed to insure that it has a stability factor against overturning of not less than four.
The following requirements apply to roof rigged davit systems:
Access to and egress from the working platform shall be from a safe surface. Access or egress shall not require persons to climb over a building's parapet or guard railing; and
The working platform shall be provided with wheels, casters or a carriage for traversing horizontally.
The following requirements apply to ground rigged davit systems:
The point of suspension shall not exceed 300 feet (91.5 m) above a safe surface. Guide system(s) shall be provided which meet the requirements of paragraph (e)(2) of this section;
Access and egress to and from the working platform shall only be from a safe surface below the point of suspension.
A rotating davit shall not require a horizontal force in excess of 40 pounds (177.9 n) per person to initiate a rotating movement.
The following requirements shall apply to transportable davits:
A davit or part of a davit weighing more than 80 pounds (36 kg) shall be provided with a means for its transport, which shall keep the center of gravity of the davit at or below 36 inches (914 mm) above the safe surface during transport;
A davit shall be provided with a pivoting socket or with a base that will allow the insertion or removal of a davit at a position of not more than 35 degrees above the horizontal, with the complete davit inboard of the building face being serviced; and
Means shall be provided to lock the davit to its socket or base before it is used to suspend the platform.
Transportable outriggers may be used as a method of suspension for ground rigged working platforms where the point of suspension does not exceed 300 feet (91.5 m) above a safe surface. Tie-in guide system(s) shall be provided which meet the requirements of paragraph (e)(2) of this section.
Transportable outriggers shall be used only with self-powered, ground rigged working platforms.
Each transportable outrigger shall be secured with a tie-down to a verified anchorage on the building during the entire period of its use. The anchorage shall be designed to have a stability factor of not less than four against overturning or upsetting of the outrigger.
Access to and egress from the working platform shall be from and to a safe surface below the point of suspension.
Each transportable outrigger shall be designed for lateral stability to prevent roll-over in the event an accidental lateral load is applied to the outrigger. The accidental lateral load to be considered in this design shall be not less than 70 percent of the rated load of the hoist.
Each transportable outrigger shall be designed to support an ultimate load of not less than four times the rated load of the hoist.
Each transportable outrigger shall be so located that the suspension wire ropes for two point suspended working platforms are hung parallel.
A transportable outrigger shall be tied-back to a verified anchorage on the building with a rope equivalent in strength to the suspension rope.
The tie-back rope shall be installed parallel to the centerline of the outrigger.
Raising and lowering of suspended or supported equipment shall be performed only by a hoisting machine.
Each hoisting machine shall be powered only by air, electric or hydraulic sources.
Flammable liquids shall not be carried on the working platform.
Each hoisting machine shall be provided with a primary brake and at least one independent secondary brake, each capable of stopping and holding not less than 125 percent of the lifting capacity of the hoist.
The primary brake shall be directly connected to the drive train of the hoisting machine, and shall not be connected through belts, chains, clutches, or set screw type devices. The brake shall automatically set when power to the prime mover is interrupted.
The secondary brake shall be an automatic emergency type of brake that, if actuated during each stopping cycle, shall not engage before the hoist is stopped by the primary brake.
When a secondary brake is actuated, it shall stop and hold the platform within a vertical distance of 24 inches (609.6 mm).
Each hoisting machine shall be capable of raising or lowering 125 percent of the rated load of the hoist.
Moving parts of a hoisting machine shall be enclosed or guarded in compliance with paragraphs (a)(1) and (2) of ยง1910.212 of this part.
Winding drums, traction drums and sheaves and directional sheaves used in conjunction with hoisting machines shall be compatible with, and sized for, the wire rope used.
Each winding drum shall be provided with a positive means of attaching the wire rope to the drum. The attachment shall be capable of developing at least four times the rated load of the hoist.
Any component of a hoisting machine which requires lubrication for its protection and proper functioning shall be provided with a means for that lubrication to be applied.
Each hoisting machine shall be capable of arresting any overspeed descent of the load.
Each suspended unit component, except suspension ropes and guardrail systems, shall be capable of supporting, without failure, at least four times the maximum intended live load applied or transmitted to that component.
Each suspended unit component shall be constructed of materials that will withstand anticipated weather conditions.
Each suspended unit shall be provided with a load rating plate, conspicuously located, stating the unit weight and rated load of the suspended unit.
When the suspension points on a suspended unit are not at the unit ends, the unit shall be capable of remaining continuously stable under all conditions of use and position of the live load, and shall maintain at least a 1.5 to 1 stability factor against unit upset.
Guide rollers, guide shoes or building face rollers shall be provided, and shall compensate for variations in building dimensions and for minor horizontal out-of-level variations of each suspended unit.
Each working platform of a suspended unit shall be secured to the building facade by one or more of the following methods, or by an equivalent method:
Continuous engagement to building anchors as provided in paragraph (e)(2)(i) of this section;
Intermittent engagement to building anchors as provided in paragraph (e)(2)(iii)(A) of this section;
Button guide engagement as provided in paragraph (e)(2)(iii)(B) of this section; or
Angulated roping and building face rollers as provided in paragraph (e)(2)(iii)(C) of this section.
Each working platform of a suspended unit shall be provided with a guardrail system on all sides which shall meet the following requirements:
The system shall consist of a top guardrail, midrail, and a toeboard;
The top guardrail shall not be less than 36 inches (914 mm) high and shall be able to withstand at least a 100-pound (444 n) force in any downward or outward direction;
The midrail shall be able to withstand at least a 75-pound (333 n) force in any downward or outward direction; and
The areas between the guardrail and toeboard on the ends and outboard side, and the area between the midrail and toeboard on the inboard side, shall be closed with a material that is capable of withstanding a load of 100 pounds (45.4 KG.) applied horizontally over any area of one square foot (.09 m2). The material shall have all openings small enough to reject passage of life lines and potential falling objects which may be hazardous to persons below.
Toeboards shall be capable of withstanding, without failure, a force of at least 50 pounds (222 n) applied in any downward or horizontal direction at any point along the toeboard.
Toeboards shall be three and one-half inches (9 cm) minimum in length from their top edge to the level of the platform floor.
Toeboards shall be securely fastened in place at the outermost edge of the platform and have no more than one-half inch (1.3 cm) clearance above the platform floor.
Toeboards shall be solid or with an opening not over one inch (2.5 cm) in the greatest dimension.
The requirements of paragraphs (f)(5)(ii) (A) through (K) of this section shall also apply to a single point working platform.
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