ASME HST-1–2017 pdf download.Performance Standard for Electric Chain Hoists.
SECTION 1-1.2: HOIST DUTY SERVICE CLASSIFICATION Service conditions have an important influence on the performance ofthe wearingparts ofa hoist, such as gears, bearings, load chain, sprockets, electrical equipment, brake linings, load and lift limiting devices, and wheels. Careful consideration of the hoist duty service classifica- tions described in this Section will enable the userto eval- uate the application, and to obtain a hoist designed for optimum performance and minimum maintenance. If doubt exists regarding hoist selection, the hoist supplier should be consulted. Many factors enter into the selection of the proper hoist to perform a given function. Hoisting equipment consists of both mechanical and electrical components andboth mustbe considered whenanalyzing the service the hoist must perform. The factors thatinfluence the mechanical and electrical performance of any hoist include the following: (a) Load Distribution. The actual distribution or proportion of full and partial loads to be handled by the equipment, including lifting devices, has an important effect on the life of power transmission components. For example, ball-bearing life varies according to the cube of the load. A 2-ton (1 814.4-kg) hoist operated at a mean effective load of1 ton (907.2 kg) will have a ball-bearing life eight times that of the same hoist used steadily at its rated load. (b) Operational Time. Operational time is the total running time of the hoist per hour or per work period. (c) Work Distribution. This is determined by whether the operational time is uniformly distributed over the work period or concentrated in a short time span. Work distribution generally does not appreciably affect mechanical wear, but does materially affect the electrical components such as motors, brakes, and controls.
1-1.3.3 Randomly Distributed Loads Randomly distributed implies that loads applied to the hoist are assumed to be evenly distributed within the rated load of the hoist in decreasing steps of 20% of the previous load value. Random loads are, therefore, considered as 100%, 80%, 64%, 51%, 41%, 33%, 26%, etc., ofrated load. Operation with random loads is consid- ered on an equal-time basis for the operating time remaining after accounting for the time the hoist is oper- atingatno loadandwith ratedload. Randomlydistributed loads will result in a mean effective load factor of 0.65.
SECTION 1-1.4: APPLICATION ANALYSIS 1-1.4.1 General (a) Iftheoperationconsists ofloweringloads overlong distances ofmore than 50 ft (15 m), the mechanical load brake heat dissipation capability (overheating) may become a factor. Consult manufacturer for particulars. (b) Motor heating generated by the number ofstarts is notappreciablyaffectedbytheloadonthehookandthere- forethelimits imposedbyColumns 3 through6 ofTable1- 1.3-1 are applicable for the motor regardless of the load being handled.ASME HST-1 pdf download.