ASME A18.1-2017 pdf download.Safety Standard for Platform Lifts and Stairway Chairlifts.
4.3.1 General Requirements
4.3.1.1 The factor of safety used in the design of the sprockets and sheaves shall be not less than 5 based on the rated load. See section 8 for special requirements for particular drive systems.
4.3.1.2 Driving-machine chains and sprockets shall be of steel and shall conform in design and dimen- sions to the requirements of ASME B29.1.
4.3.1.3 Winding drums, traction sheaves, over- head sheaves, and deflecting sheaves used with suspen- sion and compensating ropes shall be of metal and be provided with finished grooves for ropes or shall be permitted to be lined with nonmetallic groove material, and have a pitch diameter of not less than 30 times the diameter of the suspension ropes. Where 8 ? 19 steel rope or 7 ? 19 steel aircraft cable is used, the pitch diameter of the drums and sheaves shall be permitted to be reduced to 21 times the diameter of the rope or cable. Where the grooves are used to transmit power, suffi- cient traction shall be provided between the rope and groove, and in the event of nonmetallic lining failure, between the rope and the remaining sheave groove, to safely stop and hold the chair with 125% of the rated load.
4.3.2 Hydraulic Driving Machines. Direct-plunger hydraulic driving machines, where used, shall conform to the requirements of para. 8.1 except para. 8.1.2. Roped-hydraulic machines shall also conform to the requirements of para. 8.1 except for paras. 8.1.1, 8.1.3, 8.1.4.3, and 8.1.4.7.
4.3.3 Screw Machines. Screw machines, where used, shall conform to para. 8.2. 4.3.4 Friction Machines. Friction machines, where used, shall conform to para. 8.3.
4.3.6.1 General Requirements. Belt sets shall be selected on the basis of the manufacturer’s rated break- ing strength and a factor of safety of 10. Chain and sprocket sets shall be selected on the basis of recommen- dations set forth in the Supplementary Information sec- tion of ASME B29.1, using a service factor of 2. Offset links in chain are not permitted. Sprockets in a chain drive set and also a driven set shall be assembled onto a common hub, with teeth cut in-line after assembly to assure equal load distribution on all chains. Tooth sheaves for a belt drive shall be constructed in a manner to assure equal load distribu- tion on each belt in the set. Load determination for both the belt and chain sets shall be based on the maximum static loading on the carriage, which is the full load on the chair at rest and at a position in the runway that creates the greatest load, including either the carriage or counterweight resting on its buffer. Chain drives and belt drives shall be guarded to pro- tect against accidental contact and to prevent foreign objects from interfering with drives.ASME A18.1 pdf download.