ASC B77 - Standards for Passenger Aerial Ropeways. PROPOSED CHANGE FORM Control Number PC17-05

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1 ASC B77 - Standards for Passenger Aerial Ropeways SUBMITTED BY: Name Paul Ehlert Title Design Engineer Company Doppelmayr USA Address 3160 W 500 S City, St Zip Salt Lake City, UT Phone (801) paul.ehlert@doppelmayrusa.com PROPOSED CHANGE FORM Control Number PC17-05 RECEIVED: 1/22/2018 ACKNOWLEDGED: 1/26/2018 TO NTSB: 1/26/2018 NTSB ACTION: 2/5/2018 Approved ASSIGNED TO: Sec-4 SUBMITTER NOTIFIED: 2/5/2018 SUBCOMM. ACTION: ASC B77 ACTION SUBMITTER NOTIFIED: PROPOSED CHANGE: SUBCLAUSE: Rollback device and Rollback detection CHANGE: Change the requirement for the device to bring the lift to a stop before the rope travels 36 inches to actuating the device before the rope travels 36 inches when the device is a brake. Harmonize the wording with the detachable section Rollback device The rollback device shall act directly on the drive bullwheel assembly or on the haul rope. When it has been determined that under the most unfavorable design loading condition, haul rope slippage will not occur, the rollback device may be located at the return bullwheel assembly. However, the rollback device shall not be located at other than the drive station, unless its location will not decrease the factor of safety of the haul rope below the minimum permissible value whenever the rollback device is statically engaged. Under the most unfavorable design loading condition, the rollback device shall automatically stop reverse rotation of the aerial lift before the haul rope travels in excess of 36 inches (915 mm) in the reverse direction control reverse rotation of the lift, as defined herein (see for electrical requirements). a) If actuation of the rollback device applies impact loads on the bullwheel or the haul rope, the rollback device shall stop reverse rotation of the aerial lift before the haul rope travels in excess of 36 inches (915 mm) in the reverse direction; or b) If the rollback device is a brake, the rollback device shall bring the tramway to a stop if unintentional reverse rotation occurs. The rollback device shall be activated before the haul rope travels in excess of 36 inches (915 mm) in the reverse direction Rollback detection reverse rotation occurs. The rollback device shall automatically stop reverse rotation of the aerial lift before the haul rope travels in excess of 36 inches (915 mm) in the reverse direction (see be activated in order to meet the requirements of ).

2 REASON FOR CHANGE: History: This requirement has evolved over the years with various editions of the standard. The first edition of the B77.1 standard, approved in 1960 gave this requirement for a rollback device: Brake (3) A backstop to prevent reverse rotation of the tramway, unless the gearing will prevent gravity reversal. This changed for aerial lifts in the 1970 edition to state: Backstop Brake. A backstop brake to prevent reverse rotation of the tramway. The backstop brake shall act directly on a bull wheel, ring gear attached to a bull wheel, or the haul rope. The backstop brake shall not be located on other than the drive sheave unless its location on other bull wheels will not decrease the factor of safety of the haul rope below the minimum permissible value when the backstop brake operates. (Refer to 1.2.4) In the 1976 Edition this paragraph was added: The bull wheel backstop brake and any other low- or high-speed backstop installed in addition to the bullwheel backstop brake shall have the capability of being inactivated during testing periods. In the 1982 edition, the fixed and detachable requirements were separated, the clause numbering and requirements changed and the requirement for stopping the lift within 3 feet, was added. In this edition, the requirements were identical in the detachable and fixed grip sections. [3] Bull Wheel or Cable Backstop. The backstop shall act directly on the drive sheave assembly or on the haul rope. When it has been determined that, under the most adverse design loading condition, haul rope slippage will not occur, the backstop may be located at the return sheave assembly. However, the backstop shall not be located at other than the drive station unless its location will not decrease the factor of safety of the haul rope below the minimum permissible value whenever the backstop is statically engaged. Under the most unfavorable design loading conditions, the backstop shall automatically prevent reverse rotation of the lift for more than 3 feet (0.9 meter). A qualified engineer shall furnish a written procedure for testing. Performance of the backstop device shall be demonstrated during the load test. (See ). In the 1990 edition, the wording changed to refer to the backstop as a rollback device and the paragraph below was deleted from the fixed grip section. Under the most unfavorable design loading conditions, the backstop shall automatically prevent reverse rotation of the lift for more than 3 feet (0.9 meter). In the same edition, the detachable requirement was changed to: The rollback device shall act directly on the drive sheave assembly or the haul rope. Under the most unfavorable design loading condition, the rollback device shall automatically control reverse rotation of the lift, as defined herein. The rollback device shall bring the tramway to a stop if unintentional reverse rotation occurs. The rollback device shall be activated if the tramway travels in excess of 3 feet in the reverse direction. In the 1992 edition, the detachable section remained the same except for changing 3 feet to 36 inches (91 cm) and the fixed grip section removed the paragraph about the qualified engineer s written procedure and added this paragraph: Under the most unfavorable design loading condition, the rollback device shall automatically prevent reverse rotation of the aerial lift before the haul rope travels in excess of 36 inches (91 cm) in the reverse direction. The 1999 edition changed 91 cm to 915 mm. Otherwise the clauses remained the same. In the 2006 edition, both clauses were renumbered to [3] and (See [3] for electrical requirements), which references the rollback detection device, was added to each one. The electrical requirements were: Rollback detection device reverse rotation occurs. The rollback device shall be activated if the haul rope travels in excess of 36 inches (915 mm) in the reverse direction.

3 Rollback detection device reverse rotation occurs. The rollback device shall automatically stop reverse rotation of the aerial lift before the haul rope travels in excess of 36 inches (915 mm) in the reverse direction (see ). There were no changes to the fixed grip section in the 2011 edition, leaving the clauses as shown below: Rollback device The rollback device shall act directly on the drive bullwheel assembly or on the haul rope. When it has been determined that under the most unfavorable design loading condition, haul rope slippage will not occur, the rollback device may be located at the return bullwheel assembly. However, the rollback device shall not be located at other than the drive station, unless its location will not decrease the factor of safety of the haul rope below the minimum permissible value whenever the rollback device is statically engaged. Under the most unfavorable design loading condition, the rollback device shall automatically stop reverse rotation of the aerial lift before the haul rope travels in excess of 36 inches (915 mm) in the reverse direction (see for electrical requirements) Rollback detection device reverse rotation occurs. The rollback device shall automatically stop reverse rotation of the aerial lift before the haul rope travels in excess of 36 inches (915 mm) in the reverse direction (see ). The detachable section changed to the following: Rollback device The rollback device shall act directly on any drive terminal bullwheel assembly that meets the requirements of or on the haul rope. Under the most unfavorable design loading condition, the rollback device shall automatically control reverse rotation of the aerial lift, as defined herein. The rollback device shall bring the aerial lift to a stop if unintentional reverse rotation occurs. The rollback device shall be activated if the haul rope travels in excess of 36 inches (915 mm) in the reverse direction. Electrical detection systems shall comply with Rollback detection device The rollback device shall act directly on the drive sheave assembly or the haul rope. Under the most unfavorable design loading condition, the rollback device shall automatically control reverse rotation of the lift, as defined herein. The rollback device shall bring the tramway to a stop if unintentional reverse rotation occurs. The rollback detection device shall activate the rollback device and bring the aerial lift to a stop if unintentional reverse rotation occurs. The rollback device shall be activated if the haul rope travels in excess of 36 inches (915 mm) in the reverse direction. Other Standards: The Canadian standard CSA Z98-14 has the following requirements for anti-rollback devices which apply to fixed grip and detachable aerial ropeways: 4.23 Brakes and antirollback device Each brake and antirollback device (when a brake) shall meet the following requirements: a) it shall be capable of stopping the ropeway or conveyor under all applicable design load conditions; b) it shall be capable of holding the maximum design load; c) it shall facilitate periodic testing; d) the braking force shall be adjustable; e) application of any brake shall disconnect the driving power; f) it shall be capable of stopping the ropeway or conveyor if unintended reverse rotation occurs; g) it shall be capable of decelerating the ropeway or conveyor in a smooth and controlled manner without any jerk or excessive rope or belt bounce; and h) it shall be applied by stored energy Antirollback device Each antirollback device shall be capable of a) holding the maximum design load; and b) stopping the ropeway if unintended reverse motion occurs The antirollback device shall act on the drive sheave or haul rope.

4 The antirollback device shall be actuated by unintended reversal of the drive sheave by not more than 500 mm, measured at the circumference. Clause above, was changed in the 2014 edition to allow 500 mm (19.7 inches) for actuation of the antirollback device. The previous versions of the standard allowed 200 mm (7.9 inches). This recent change was to align more closely with the ANSI standard and to eliminate nuisance trips on lifts that have slight rollbacks at the bullwheel when the service brake is holding the lift. Rollback brakes are not required by European standards. Conclusions: The requirements for stopping reverse rotation of an aerial lift have evolved over the many years of the ANSI B77.1 standard. Most lifts built under the early standards had anti rollback devices that dropped a pawl into teeth or spokes of the drive bullwheel to immediately stop reverse rotation. When these devices are used, the 36 inch requirement makes sense to minimize the impact loads. More recently, caliper brakes have been used to reduce impact loads. For more reliable activation, improved rollback detection devices have been implemented that do not rely on friction of a wheel or block on the bullwheel flange. These brakes typically have similar braking capacity as the drive sheave (emergency) brake except that they are not required to decelerate a lift moving forward at full speed in a specified distance. They typically apply at near zero speed due to quick detection of a rollback. In practice, these brakes apply well within 36 inches of reverse rope travel, but due to the time of detection, the slight delay between detection and actual application of the brake on the bullwheel, the stopping distance may be somewhat longer than 36 inches. If the braking force is adjusted to stop the lift in just a few inches once it applies, the brake is much stronger than needed and could potentially contribute to a violent stop if applied with other brakes in the forward direction. In the past, brakes would typically have flow control valves to control the rate of the application of the brakes. Adjustability of the rate of application of the brake was required until the 2006 edition of the standard. More recent installations typically do not control the rate of application of the brakes, but have adjustable torque capacity to provide the necessary braking while reducing the possibility of excessive braking should all the brakes apply together. The B77.1 standard requires reliable means of detecting unintentional reverse rotation and automatically sets both the bullwheel brake and the rollback brake. As of the 2017 standard, lifts are required to have either torque proving or a high speed rollback in the drive train to prohibit rollback. The probability of the lift rolling back and only the rollback brake applying to stop it is very small. The standard also requires the automatic setting of an additional brake if one system fails to decelerate the lift. The standard has been changed for detachable lifts to require detection and actuation of the brake without specifying a stopping distance. This is also the case for the Canadian standard for both fixed grip and detachable lifts. Harmonizing with the detachable section to state unintentional reverse rotation allows for a lift to be operated in reverse to unload a rider who has passed the stop gate or one who is hanging from a chair out of reach of the operator. This has been a function and possibility for fixed grip lifts in Canada and can now be a possibility in the US for lifts without a high speed backstop. The detachable section requires activation of the device if the rope travels in excess of 36 inches. This proposal would require the device to be activated before the haul rope travels in excess of 36 inches to provide direction to actuate the device as quickly as possible. The rollback brake force may be adjusted to provide adequate deceleration of the ropeway in the case of a rollback to assure the lift will come to a stop. This will minimize the possibility of excessive braking if all brakes apply in the forward direction. The redundancy of the brake systems will provide adequate protection against a significant rollback. The change to the electrical clause no longer repeats the design clause stopping requirement. It only addresses the actuation of the rollback device and refers back to the design clause for the stopping requirements. This also harmonizes with the detachable section.

5 COMMENTS AND SUBCOMMITTEE ACTION: January 16, 2018 The concepts of this proposal were discussed at the Section 4 Fixed Grip Subcommittee meeting. The submitted proposal is based on the discussions.