Existing installations requirements

Appendix D applies to electric powered platform installations for exterior building maintenance completed after August 27, 1971 and no later than July 23, 1990 that are exempt from the revised paragraphs of 1910.66. Appendix D sets mandatory building and equipment requirements for those existing installations and requires that all such installations also comply with 1910.66(g)-(j) and Appendix C. See 1910.66 App D for the full scope and the cross-reference to the rest of the standard.

A powered platform is defined as the equipment that provides access to the exterior of a building for maintenance and includes the suspended, power-operated working platform, a roof car, or other suspension means and the required operating and control devices. A roof car is defined as a structure for the suspension of a working platform that provides for horizontal movement to working or storage positions. A working platform is the suspended structure arranged for vertical travel which provides access to the exterior of the building or structure. These definitions are in 1910.66 App D (a) and are used throughout the appendix to determine applicable equipment and installation rules.

Yes — Appendix D requires that powered platform installations completed as of August 27, 1971 (and no later than the date specified in the appendix) meet the design, construction, and installation requirements of parts II and III of [ANSI A120.1-1970]. In practice this means existing electric powered platforms must follow the detailed safety and equipment specifications in ANSI A120.1-1970 (as referenced in 1910.66 App D), including structural, rope, braking, and control specifications called out by the appendix.

Yes — Appendix D permits powered platforms using non-electric power so long as they provide adequate protective devices for the type of power used and otherwise provide reasonable safety of life and limb to users and others who may be exposed. Appendix D states this limitation explicitly and allows non-electric installations provided equivalent protective measures are in place (1910.66 App D (b)(2)).

Type F platforms must be suspended by at least four wire ropes and be designed so that the failure of any one wire rope will not substantially alter the platform's normal position; only one layer of hoisting rope is permitted on winding drums. Type T platforms must be suspended by at least two wire ropes; failure of one rope would not permit the platform to fall to the ground but could upset its normal position. Both Type F and Type T must comply with Appendix C of the standard (1910.66 App D (b)(3)).

The maximum rated horizontal traversing speed for a power-traversed roof car is 50 feet per minute. This speed limit is specified in 1910.66 App D (c)(1)(ii) to limit hazards during horizontal movement of the roof car.

Roof cars must be protected from leaving the roof or entering roof areas not designed for travel, have positive control of horizontal motion to ensure correct movement and positioning, and include positioning devices to place and retain the working platform in the correct position for vertical travel and storage. Those protective measures, including mechanical stops to prevent travel beyond limits, are required by 1910.66 App D (c)(2).

Operating devices for traversing the roof car must be continuous-pressure, weatherproof electric type and may be located on the roof car, the working platform, or both; if more than one is provided, traversing must be possible from only one operating device at a time. The operating device must not be operable until the working platform is at its uppermost position and not in contact with the building face or fixed vertical guides and until all protective devices and interlocks are in position for traversing. These requirements are in 1910.66 App D (c)(3)(v)(a)–(b).

Roof car stability must be shown using whichever method results in the greater required strength: (i) continuous stability checked by overturning moment using 125 percent of rated load plus maximum dead load and prescribed wind loading, or (ii) capability of the roof car and its anchorages to resist accidental over-tensioning of suspension wire ropes, including the effect of one-and-one-half times the calculated value. These stability calculations and the inclusion of wind effects are required by 1910.66 App D (c)(3)(iii).

When calculating stability, the simultaneous effect of one-half the wind load must be included, and the resulting design stresses must not exceed the allowable stresses referenced in the appendix. Appendix D specifically requires inclusion of one-half wind load in those calculations (1910.66 App D (c)(3)(iv)).

Anchorages and the roof car must be capable of resisting accidental over‑tensioning of the suspension wire ropes, and that calculated resisting value must include the effect of one-and-one-half times the over-tensioning value. Appendix D explicitly notes this one-and-one-half multiplier when addressing roof car anchorages (1910.66 App D (c)(3)(iii)(ii)).

If the load on the motors ever exceeds three times the load required for lifting the working platform with its rated load, the motor must stall. Appendix D requires this motor-stall condition to limit overspeed or runaway conditions (1910.66 App D (c)(3)(iii)(iii)).

Safe access to the roof car and from the roof car to the working platform must be provided; when access at any point of travel is not over the roof area (or when otherwise necessary for safety), self-closing, self-locking gates are required. Appendix D further requires that access comply with the requirements of Subpart D of part 1910 (1910.66 App D (c)(4)). See OSHA guidance on fall protection for roof work for related employer duties when employees access roofs or roof equipment (Fall protection on low slope roofs interpretation).

Appendix D requires means to run the roof car away from the roof perimeter when necessary and to provide a safe area for maintenance, repairs, and storage, and it requires provisions to secure the machine in the stored position; for machines subject to wind, special design and anchorage requirements in ANSI A120.1-1970 apply. These requirements are in 1910.66 App D (c)(5).

Mechanical stops installed to prevent the roof car from traversing beyond its normal limits must be capable of withstanding a force equal to 100 percent of the inertial effect of the roof car in motion with traversing power applied. This mechanical-stop strength requirement is specified in 1910.66 App D (c)(3)(iv).

Appendix D defines "continuous pressure" as operation by buttons or switches that control movement of the working platform or roof car only while the button or switch is manually held in the actuating position. Controls must be arranged accordingly so that motion continues only while the operator maintains pressure on the control (1910.66 App D (a)(8)).

Yes — Appendix D requires all existing installations subject to the appendix to also comply with paragraphs [1910.66(g), (h), (i), (j)] and [Appendix C] of the standard. Appendix D is explicitly written as a limited-exemption approach but mandates compliance with those specified remaining parts of the standard (1910.66 App D; see also 1910.66AppC).

Yes — Appendix D says it is not the intent to prohibit powered platforms using other types of hoisting machines (for example, traction drum, air‑powered, hydraulic, or internal-combustion machines) provided adequate protective devices are used and reasonable safety to users and others is assured. However, the requirements in the appendix were written with winding‑drum hoisting machines in mind, so alternative hoisting types must provide equivalent protection (1910.66 App D (b)(3)(iv)).

A traveling cable is an assembly of electrical or communication conductors that provides electrical connection between the working platform and the roof car or other fixed point. Appendix D requires equipment be weatherproof or protected so exposure to weather will not interfere with proper operation, so traveling cables and other exposed components must be constructed or protected to maintain safe operation in weather conditions (1910.66 App D (a)(23),(24)).

Appendix D directs employers to consult parts II and III of [ANSI A120.1-1970] for detailed specifications and special installation rules, because Appendix D sets out mandatory requirements but references ANSI A120.1-1970 for the technical details. See 1910.66 App D (b)(1) for the requirement to use ANSI A120.1-1970 as the detailed design source.

The working platform must have a front guardrail between 36 inches and 42 inches high and side/rear guardrails at least 42 inches high. This is required by the existing installations provisions for powered platforms in 1910.66AppD.

• An intermediate guardrail must be provided around the entire platform between the top guardrail and the toeboard.

(See 1910.66AppD for the full guardrail specifications.)

The working platform must have a minimum net width of 24 inches. Appendix D explicitly sets this minimum size requirement for working platforms in powered platform installations (1910.66AppD).

• "Net width" means unobstructed usable width of the platform; guardrails, controls, or equipment that reduce usable width should be considered when confirming the 24-inch minimum.

A four-inch toeboard is required along all sides of the working platform. Appendix D states this explicit toeboard requirement for powered-platform working platforms (1910.66AppD).

• Toeboards must be continuous at exposed edges and installed so they will block small tools and debris from falling off the platform.

Spaces between the intermediate guardrail and platform toeboard on the building side, and between the top guardrail and toeboard on other sides, must be filled with metallic mesh or similar material that will reject a 1-inch-diameter ball and withstand a 100-pound horizontal load over any 144 square inches. Appendix D prescribes these mesh performance and size criteria (1910.66AppD).

• Exception: If the gap between platform and building face does not exceed 8 inches and the platform is restrained by guides, the mesh may be omitted on the front side.

(See 1910.66AppD for full detail.)

Platform flooring must be nonskid and, if open construction, must reject a 9/16-inch-diameter ball or have a screen beneath the floor that rejects a 9/16-inch ball. Appendix D sets these flooring performance requirements for powered platforms (1910.66AppD).

• Use nonskid finishes or properly rated grating/screens to meet the ball-rejection requirement and prevent foot or small-tool drop-through.

Each working platform must bear a manufacturer's load rating plate, conspicuously posted, stating the maximum permissible rated load; the plate must be noncorrosive and have letters/numbers at least one-quarter inch high. Appendix D specifies these load-rating plate requirements (1910.66AppD).

• The plate must be stamped, etched, or cast with the information and be readily visible to platform users.

Yes. Where access gates are provided on powered-platform working platforms, they must be self-closing and self-locking. Appendix D contains this access gate requirement (1910.66AppD).

• Ensure gates are maintained so they continue to self-close and self-lock during normal operations.

The normal operating device must be located on the working platform and be a continuous-pressure weatherproof electric type; it must only be operable when electrical protective devices and interlocks are in position for normal service and any roof car is at its established operating point. Appendix D requires the location and type of the platform operating device (1910.66AppD).

• "Continuous pressure" means the device operates only while the control is continuously actuated; it is a safety measure to prevent unattended motion.

Roof-powered platforms must have an emergency electric operating device near the hoisting machine mounted in a locked compartment with the legend "For Emergency Operation Only. Establish Communication With Personnel on Working Platform Before Use," and a key must be mounted in a break-glass receptacle near the emergency device. Appendix D sets these emergency device and key-storage requirements (1910.66AppD).

• Employers must ensure personnel establish two-way communication with occupants on the stalled platform before using the emergency device (see emergency communications requirements in 1910.66AppD).

Manual emergency operation must be designed so that not more than two persons are required to perform it, must automatically make the machine electrically inoperative while under manual operation, and the emergency brake must be operative at or below governor tripping speed. Appendix D prescribes these design and safety features for manual cranking provisions (1910.66AppD).

• The design must prevent accidental re-energization and ensure the emergency brake functions during manual operation.

Hoisting machines must have two independent braking means, each capable of stopping and holding the working platform with 125 percent of the rated load. Appendix D sets this braking redundancy and capacity requirement (1910.66AppD).

• Both primary and secondary brakes must be maintained and tested so that either can hold the platform safely under rated-overload conditions.

Working platforms must be suspended by wire ropes of 6×19 or 6×37 construction (preformed or nonpreformed) and must meet a minimum factor of safety of 10 as calculated by F = S × N / W. Appendix D specifies rope construction and the safety-factor formula (1910.66AppD).

• S = manufacturer's rated breaking strength of one rope; N = number of ropes under load; W = maximum static load on all ropes with platform and rated load at any point of travel.
• Ropes must be no less than 5/16 inch in diameter and must have at least three turns of rope remaining on the drum at the lowest landing.

No. The lengthening or repairing of wire rope by joining two or more lengths (splicing to lengthen) is prohibited for hoisting ropes. Appendix D expressly prohibits joining rope lengths (1910.66AppD).

• If a rope is damaged or too short, replace it with a single new rope of the correct length and specification rather than splicing.

A metal data tag must be securely attached to one wire rope fastening and must show the rope diameter, construction classification, whether preformed or nonpreformed, grade of material, manufacturer's rated breaking strength, rope manufacturer's name, and the month and year the ropes were installed. Appendix D lists these required rope-tag data elements (1910.66AppD).

• Keep this tag legible and securely fastened; it is essential for inspections and verifying rope service life.

Powered platforms must have electrical grounding, an independent circuit supplied through a fused disconnect switch, protection of conductor parts against accidental contact, and grounding of controller cabinets, motor frames, hoisting machines, the working platform, roof car and related noncurrent-carrying parts. Appendix D describes grounding and power-supply protections for powered platforms (1910.66AppD).

• The controller must be designed so a single ground or short won't prevent both the normal and final stopping devices from stopping the platform, and means must be provided for grounding portable tools on the roof car and platform.

Electrical receptacles on roofs or other exterior locations must be weatherproof, located to avoid contact with water or accumulated snow, grounded, and have a cable that includes a grounding conductor; the plug and receptacle must be designed to avoid hazards during insertion/removal and must prevent cable strain on the plug. Appendix D sets these weatherproofing and receptacle requirements (1910.66AppD).

• Use weatherproof covers and properly strain-relieved cord connections to reduce electrocution and shock risks.

Appendix D requires multiple automatic electrical protective devices, including a device to cut power in the up direction if load exceeds 125% of normal tension, a device to cut power and apply brakes if any hoisting rope becomes slack (down direction), upper and lower directional limit devices, and final terminal stopping devices that disconnect power and apply both primary and secondary brakes. See 1910.66AppD for the full list and functions.

• Tests and maintenance procedures should verify these automatic devices function reliably to prevent over-travel, overloads, and rope slack conditions.

Each powered platform must be provided with emergency communication equipment that establishes two-way voice communication between the working platform and designated personnel continuously available while the platform is in use, and, for roof-powered platforms, with personnel operating the emergency device near the hoist. Appendix D prescribes these emergency communications requirements (1910.66AppD).

• Approved types include telephone connected to the central exchange or a limited telephone system or an approved two-way radio system provided designated personnel are available to receive messages while the platform is in use.

Type T powered platforms must be suspended by at least two wire ropes, and self-powered Type T platforms must not move vertically faster than 35 feet per minute. Appendix D states these Type T suspension and speed limits (1910.66AppD).

• In addition, other hoisting, braking, rope, and electrical requirements in Appendix D apply to Type T platforms as indicated in the Type T subsection.

Final terminal stopping devices must be provided as a secondary means to prevent over-travel at terminals, set to function as close to each terminal landing as practical without operating during normal terminal stops, and must open the potential relay for vertical travel to disconnect power and apply both primary and secondary brakes. Appendix D details the final terminal stopping device performance and mounting requirements (1910.66AppD).

• The upper final terminal device must be mounted so it is operated directly by the platform motion itself.

The circuit protection limitation requires that the powered-platform electrical service system and all operating and control equipment meet the specifications in part 2, section 26 of ANSI A120.1-1970. In other words, existing Type T powered platforms must be equipped and protected in accordance with the ANSI specifications referenced by the rule.

• See the rule text in 1910.66AppD which directs compliance with part 2, section 26 of ANSI A120.1-1970.

Cited authority: 1910.66AppD.

Yes. The appendix explicitly states that the requirements for electrical protective devices found in paragraphs (c)(22)(i) through (viii) apply to Type T powered platforms, so employers must meet those listed device requirements for existing installations.

• Refer to 1910.66AppD for the statement that the requirements of paragraph (c)(22) apply.
• For the specific device requirements, consult 1910.66(c)(22) and each subparagraph 1910.66(c)(22)(i) through 1910.66(c)(22)(viii).

Cited authority: 1910.66AppD and 1910.66(c)(22).

It means the allowable voltages and related electrical potential limits for the powered platform must be set and controlled according to the same ANSI specification referenced for circuit protection: part 2, section 26 of ANSI A120.1-1970. Employers must ensure the platform electrical system meets those circuit-potential specifications.

• The appendix language is explicit: the "circuit potential limitation" shall follow the specifications in part 2, section 26 of ANSI A120.1-1970; see 1910.66AppD.

Cited authority: 1910.66AppD.

Yes. Emergency communications requirements for Type T powered platforms are required because the appendix says that "all the requirements of paragraph (c)(23) of this appendix shall apply to Type T powered platforms."

• The directive appears in 1910.66AppD. For the detailed content of those emergency-communications requirements, consult 1910.66(c)(23).

Cited authority: 1910.66AppD and 1910.66(c)(23).

The appendix references the ANSI A120.1-1970 specifications as the standard that the powered-platform electrical service systems, operating services, and control equipment must meet; it does not provide a separate compliance schedule in the excerpt. Employers must therefore ensure existing Type T installations comply with the referenced ANSI requirements as required by the appendix.

• See the requirement language in 1910.66AppD which directs compliance with part 2, section 26 of ANSI A120.1-1970 for both circuit protection and circuit potential limitations.

Cited authority: 1910.66AppD.

You should consult the appendix itself and the specific cross-referenced paragraphs: the appendix text directs you to the detailed electrical-device requirements in 1910.66(c)(22) (and its subparagraphs 1910.66(c)(22)(i) through 1910.66(c)(22)(viii)) for electrical protective-device requirements, and to 1910.66(c)(23) for emergency communications requirements.

• Start with 1910.66AppD which identifies those cross-references.

Cited authority: 1910.66AppD, 1910.66(c)(22), and 1910.66(c)(23).