A sign with the maximum live load capacity in pounds and kilograms shall be attached to the work carrier.

Transcription

1 ASC B77 - Standards for Passenger Aerial Ropeways PROPOSED CHANGE FORM Control Number PC17-21 SUBMITTED BY: NAME: COMPANY: Jeff Peterson Tramway Engineering ADDRESS: PO Box 398 CITY ST ZIP Glenwood Springs, CO PHONE: (970) FAX: (970) jeff@tramway.net RECEIVED: June 13, 2018 ACKNOWLEDGED: June 20, 2018 TO NTSB: July 09, 2018 NTSB ACTION: July 2018 ASSIGNED TO: WC ad-hoc SUBMITTER NOTIFIED: SUBCOMM. ACTION: ASC B77 ACTION SUBMITTER NOTIFIED: PROPOSED CHANGE: (Updated per Snowbird meeting, Jan 22, 2019) SUBCLAUSE: Work carrier design CHANGE: Work carrier design The work carrier, when used, shall be of an approved type for the aerial lift on which it is used. Approval shall be by the ropeway manufacturer or a qualified engineer. Work carriers may be approved to be used on different aerial lifts. If the work carrier is used during public operations and with an interchangeable grip, the work carrier shall be designed by a ropeway manufacturer or qualified engineer, taking into consideration, but not limited to the following: a.) supporting a vertical load equal to the carrier weight plus 5 times the maximum intended load distributed uniformly across the platform area without permanent deformations of the structural members; b.) the grip specified meets through ; c.) work Carrier Line clearance per ; d.) terminal clearances per ; e.) in the event a maintenance person falls from the work carrier while attached to a shock absorbing lanyard, the grip s ultimate vertical capacity must be greater than the summation of the following loads and associated f.) fall protection provisions with the tie off point connection on the carrier hanger; g.) guard rail requirements; h.) kick plate requirements; i.) maintenance personnel work and travel positions and cargo loading (operational procedures); j.) tower line machinery support and hold-down capacities verified by field observations or calculations. If the work carrier usage is limited to maintenance operations with a maximum rope speed of 200 fpm and has a non- interchangeable work carrier grip, the work carrier shall be designed by a ropeway manufacturer or qualified engineer, the following reductions can be applied: a.) the grip slippage factor of safety per may be reduced to 2:1; b.) the grip strength factor of safety per (a) may be reduced to 3:1; c.) the maximum loads per may be shall not exceed 1/10 of the minimum tension. The maximum load must be greater than the summation of the following loads and associated factors of safety: dead loads (1:1), live loads (1:1); d.) line clearances requirements per and terminal clearances per may be reduced to 5 degrees laterally from vertical or 5 degrees longitudinally from vertical or a combination of the two in the carrier s natural empty hanging position. e.) the grip is inspected annually with the approved NDT carrier inspection plan an approved NDT procedure. A sign with the maximum live load capacity in pounds and kilograms shall be attached to the work carrier. Note The live load capacity includes the combined weight of the passenger and materials.

2 Page 2 of 5 For comparison the current 2017 language is below: Work Carrier Design The work carrier, when used, shall be of an approved type for the aerial lift on which it is used. Approval shall be by the ropeway manufacturer or a qualified engineer. Work carriers may be approved to be used on different aerial lifts. The work carrier shall be designed by a ropeway manufacturer or qualified engineer taking into consideration, but not limited to the following: a.) supporting a vertical load 4 times the design dead plus live loads without permanent deformations of the assembly or component parts; b.) the grip specified meets through ; c.) guard rail requirements; d.) kick plate requirements; e.) maintenance personnel work and travel positions; f.) fall protection provisions. A sign with the maximum live load capacity in pounds and kilograms shall be attached to the work carrier Work Carrier Design. Note The live load capacity includes the combined weight of the passenger and materials. ASC B77 Proposed Change Supplement to proposed changes in response to initial comments: The current wording for the proposal is an attempt to reduce confusion over allowing a work carrier to remain on-line when the lift is open to the public. In certain conditions, the area may want to leave a work carrier on-line during public operation. If the work carrier meets all of the requirements of a passenger carrier, the practice may be acceptable. The initial proposal addressed the need for a separate class of work carrier that is only used for maintenance and operated at slow speed. The first part of this revision identifies the requirements for all work carriers. The second part allows the reduction in certain standards if the lift speed is less than 200 fpm when the carrier is on line. SUPPLEMENTAL REASON FOR CHANGE: Requirements for all work carriers: a.) Vertical loads. Currently the work carrier is required to support a vertical load of four times the live load plus the dead load without deforming the supporting members. This amount of load would typically overload a smaller grip with a 6:1 FS. OSHA (e)(4) states that the personnel platform itself must be capable of supporting, without failure, its own weight and at least five times the maximum intended load. The sub-section increases the design load to match the OSHA standard. This design load only affects the structural requirements of the carrier and not the grip.

3 Page 3 of 5 b.) Grip Strength. This sub-section states that a work carrier grip must meet the same requirements as a grip used for passenger carriers. c.) Work carrier line clearance. This sub-section states that a work carrier must comply with the same line clearance requirements used for passenger carriers. d.) Terminal clearance. This sub-section states that a work carrier must comply with the same terminal clearance requirements used for passenger carriers. e.) Fall Protection. By requiring a shock absorbing lanyard, OSHA s required impact loading is reduced to 1,800 lbs (which has a built in FS of 2:1). This condition was added to define the loads a grip must support. The proposed factors of 1.2 for Dead Load and 1.6 for Live Load are recognized as structural design standards under Load and Resistance Factor Design (LRFD). Each of these loadings would be deducted from the grip s ultimate capacity. The posted live load carrier capacity would be reduced by the LRFD standard live load FS of 1.6. The LRFD factors were discussed at the Snowbird meeting. It was pointed out that they are actually higher once you factor in the serviceability requirement F that incorporates a reduction for material irregularities. I believe that the factors without the further increase are appropriate at the level stated in above. Additional reductions can be taken as the work carrier is analyzed by the designer once the materials and modes of failure are defined. f.) Fall protection anchor points. The tie off point for fall protection should be near or above the level of the worker s lanyard attachment point. This proposal requires that the anchor point be attached directly to the hanger assembly to transfer the load directly to the grip. This requirement helps minimize the fall distance, reduce impact to the work carrier and more directly transfer the loading into the grip. j.) Tower machinery loading. There is the potential that a heavily loaded work carrier could overload a support assembly or pull down the rope in a compression assembly. The sub-section recognizes this issue and allows the area to make field observations with a loaded work carrier to confirm proper loadings or determine by calculation. Reductions for work carrier with a dedicated grips & reduced speed: This sub-section allows for several reductions from the standard work carrier language provided the operator dedicates a work carrier specific grip that is not allowed to be used on passenger carriers and limits the speed which the lift can operate to 200 fpm when the work carrier is on the line. The reductions allowed in this subsection were deemed acceptable due to the reduced number of cycles the equipment would experience during maintenance specific operations. a.) Grip slippage. The standard requires the grip not to slip on the haul rope with a force equal to 3 times the force of the maximum carrier loading on the steepest incline of the profile. The grip slip test values will have to be adjusted to reflect the increased weight of the work carrier. This subsection reduces this factor of safety to 2:1 for a work carrier moving at less than 200 fpm. The

4 Page 4 of 5 intent is to allow for increased loads on a work carrier while providing adequate factor of safety from slippage. b.) Grip Strength. The current standard states that no part of the grip can yield when loaded with 6 times the maximum design load. It can be assumed that the manufacturer has designed the grip for this loading. There is little opportunity to increase the loading for a fixed grip double chair because there are always two mechanics in the work carrier that consumes the allowable loading even ignoring the weight of the carrier, tools and materials. The sub-section would reduce the FS to 3:1 for a non-interchangeable grips. This reduction will allow work carriers with non-interchangeable grips to carry twice the current loads. c.) Tension Shear Ratio. B77.1 requires that the tension/shear ratio must be greater than 14:1 to reduce internal damage to the rope. If the allowable work carrier loads are doubled, any ropeway with a tension/shear ratio less than 28:1 would not be in compliance. This proposal allows for a reduction of the tension/shear ratio to 10:1 provided the above conditions are met. The reduction is justified because the work carrier is only temporarily installed on the wire rope and will not experience the same number of fatigue cycles as a continuously circulating carrier. The posted loading has a proposed FS on the live loads of 1:1 to align with the referenced section Maximum loads. If a 1.6:1 factor of safety were to be put on the live load (as originally proposed), it will essentially make the requirement more restrictive than the standard 1/14 tension to shear ratio. d.) Line Clearance. This sub-section addresses line and terminal clearance restrictions that control the size of the work carrier. The angle of swing has been reduced to 5 if the line speed of the lift does not exceed 200 fpm. e.) Work Carrier Grip Inspection. It was recognized that the work carrier grip would be overloaded beyond the current safety factors. This new sub-section requires the work carrier grip be included in the annual NTD testing sample.

5 Work Carrier Calculation Example Bashor Christie III Lift type Fixed Double Lift Type Fixed Triple Passenger Carrier Weight 139 lb. Passenger Carrier Weight 176 lb. 2 Passenger Weight 340 lb. 3 Passenger Weight 510 lb. Total 479 lb. 686 lb. *Per B77 Grip Loading has a Dead Load + 6:1 FS on Live Load Theoretical Work Carrier Wt. 278 lb. Theoretical Work Carrier Wt. 352 lb. * Work Carrier is assumed to weight 2X the weight of a passenger carrier in these example calcs. Ultimate Grip Rating 1:1 2,179 lb. Ultimate Grip Rating 1:1 3,236 lb. Design Grip Rated 3:1 726 lb. Design Grip Rated 3:1 1,079 lb. Grip Strength Verification All loads have a 3:1 FS based on design grip strength Two Mechanics (1:1) 340 lb. Two Mechanics (1:1) 340 lb. Work Carrier Weight (1:1) 278 lb. Work Carrier Weight (1:1) 352 lb. Cargo Load (1:1) 108 lb. Cargo Load (1:1) 387 lb. Design Grip Total 726 lb. Design Grip Total 1,079 lb. Posted Live Load (1:1) 448 lb. Posted Live Load (1:1) 727 lb. Assumed Mechanic Load 340 lb. Assumed Mechanic Load 340 lb. Remaining Cargo Load 108 lb. Remaining Cargo Load 387 lb. Tension/ Shear Verification Final live loads have a 1:1 FS to align with the current requirements of Btm. Tensioning 27,500 lb. Btm Tensioning 24,000 lb. Min. Cable Tension 13,750 lb. Min. Cable Tension 12,000 lb. Max. Load (10:1) 1,375 lb. Max. Load (10:1) 1,200 lb. Two Mechanics (1:1) 340 lb. Two Mechanics (1:1) 340 lb. Work Carrier Weight (1:1) 278 lb. Work Carrier Weight (1:1) 352 lb. Cargo Load (1:1) 757 lb. Cargo Load (1:1) 508 lb. 1,375 lb. 1,200 lb. Posted Live Load (1:1) 1,097 lb. Posted Live Load (1:1) 848 lb. Assumed Mechanic Load 340 lb. Assumed Mechanic Load 340 lb. Remaining Cargo Load 757 lb. Remaining Cargo Load 508 lb. Fall Protection Verification Final live loads have a 1.6:1 FS to ensure the ultimate grip loading is maintained One Remaining Mech. (1.6:1) 272 lb. One Remaining Mech. (1.6:1) 272 lb. Work Carrier Weight (1.2:1) 334 lb. Work Carrier Weight (1.2:1) 422 lb. Cargo Load (1.6:1) -227 lb. Cargo Load (1.6:1) 742 lb. Impact Loading (Per OSHA) 1,800 lb. Impact Loading (Per OSHA) 1,800 lb. Ultimate Grip Total 2,179 lb. Ultimate Grip Total 3,236 lb. Posted Live Load (1:1) 28 lb. Posted Live Load (1:1) 634 lb. Remaining Mechanic Load 170 lb. Remaining Mechanic Load 170 lb. Remaining Cargo Load -142 lb. Remaining Cargo Load 464 lb.