ASME HST-1 pdf free download

ASME HST-1 pdf free download Performance Standard for Electric Chain Hoists
SECTION 1-1.1:GENERAL
All equipmentselected in accordance with this Standardis designed to perform satisfactorily when used in accor-dance with Chapters 16-2 through 16-4 of ASME B30.16and used within the rated load and hoist duty service clas-sification.All equipment shall provide speeds, lifts, andheadroom in accordance with the manufacturer’s speci-fications or to specifications agreed upon by the manufac-turer and the user.
SECTION 1-1.2: HOIST DUTY SERVICE
CLASSIFICATION
Service conditions have an important influence on theperformance of the wearing parts of a 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 user to eval-uate the application, and to obtain a hoist designed foroptimum performance and minimum maintenance.Ifdoubt exists regarding hoist selection, the hoist suppliershould be consulted. Many factors enter into the selectionof the proper hoist to perform a given function.Hoistingequipment consists of both mechanical and electricalcomponents and both must be considered when analyzingthe service the hoist must perform.
The factors that influence the mechanical and electricalperformance of any hoist include the following:
(a) Load Distribution. The actual distribution orproportion of full and partial loads to be handled bythe equipment, including lifting devices, has an importanteffect on the life of power transmission components.Forexample, ball-bearing life varies according to the cube ofthe load.A 2-ton (1 814.4-kg) hoist operated at a meaneffective load of 1 ton (907.2 kg) will have a ball-bearinglife eight times that of the same hoist used steadily at itsrated load.
(b) Operational Time. Operational time is the totalrunning time of the hoist per hour or per work period.(c] Work Distribution. This is determined by whetherthe operational time is uniformly distributed over thework period or concentrated in a short time span.Work distribution generally does not appreciably affectmechanical wear, but does materially affect the electricalcomponents such as motors,brakes, and controls.For example, a hoist motor designed to operate 15 min outof each hour of an 8-hr shift cannot handle 2 hr ofsteady run and 6 hr of idle time even though either condi-tion only requires 2 hr of operational time per 8-hr shift.(d) Number of Starts and Stops. This directly affects allelectromechanical devices, such as motors, contactors,brakes, and solenoids.
(e) Repetitive Long Lowering Operations. Such opera-tions generate heat in control braking means.
fEnvironmental Conditions. Hoist equipment isdesigned to operate in ambient temperatures between0°F (-18C) and 104°F (40°C) and in atmospheres reason-ably free from dust, moisture, and corrosive fumes unlessotherwise specified.
lg) Hazardous Locations. If hoists are used in hazardouslocations as defined by NFPA 70 or other special codes,modifications or additional precautions not covered bythis Standard may be required. In these locations, onlyhoists designed in a manner suitable for the conditionsencountered shall be used.
SECTION 1-1.3: DUTY CLASSIFICATION
While all the factors listed in Section 1-1.2 must beconsidered in selecting the proper class of hoist, mostindustrial applications, having randomly distributedloads or uniform loads up to 65% of rated loadhandled periodically throughout the work period,canbe generalized according to the type of work shop orarea of application. Listed in Column 1 of Table 1-1.3-1are the three duty classes that have been establishedfor electric chain hoists. In Column 2 are listed typicalareas of application where each class can normally beapplied. The majority of hoist applications will fall intoone of the two categories, H2 or H3, and the use of thegeneralized description in Column 2 of Table 1-1.3-1for selection of the hoist will be adequate.
1-1.3.1 Operational Time Ratings
lf in doubt as to the required duty classification for anapplication, refer to the data in Columns 3 through 6 ofTable 1-1.3-1, which show the operational time ratings foreach class.
(a) Uniformly Distributed Work Periods (1) Maximum On Time in Minutes per Hour (Column 3). The maximum running time in minutes per hour permitted for duty class when hoist utilization is uniformly distributed over a given work period. (2) Maximum Number ofStarts perHour (Column 4). The maximum numberofmotorstarts perhourpermitted for the duty class when hoist utilization is uniformly distributed over a given work period.