ASME HST5 pdf free download

ASME HST5 pdf free download PERFORMANCE STANDARD FOR AIR CHAIN HOISTS
2 PERFORMANCE
2.1 General All equipment selected in accordance with this Stan- dard is designed to perform satisfactorily when installed in accordance with para. 4.4, used in accordance with para. 4.5, and used within the rated load and hoist duty service classification. All equipment shall provide speeds, lifts, and headroom in accordance with the manufacturer’s specifications, or to specifications agreed upon by the manufacturer and user.
2.2 Hoist Duty Service Classification
2.2.1 General Considerations. Service condi- tions have an important influence on the performance of wearing parts of a hoist such as gears, bearings, load chain, sprockets, brake linings, load and lift limit devices, wheels, and pneumatic components. Careful consideration of the hoist duty service classifications described in this Section will enable the user to evaluate 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 selec- tion of the proper hoist to perform a given function. Hoisting equipment consists of both mechanical and pneumatic components and both must be considered when analyzing the service the hoist must perform.
The factors that influence the performance of any hoist include:
(a) Load Distribution. The actual distribution or pro- portion of full and partial loads to be handled by the equipment, including lifting devices;
(b) Operational Time. The total running time of the hoist per hour or per work period;
(c) Repetitive Long Lowering Operations. Such oper- ations generate heat in mechanical load brake;
(d) Environmental Conditions. Examples are high or low ambient temperatures, dust, moisture, corrosive fumes, etc.
2.2.2 Hazardous Locations. When hoists are used in hazardous locations as defined by ANSI/NFPA 70 or other special codes, modifications or additional pre- cautions not covered by this Standard may be required. In these locations, only hoists designed in a manner suitable for the conditions encountered shall be used.
2.2.3 Duty Classification. While all the factors listed in para. 2.2.1 must be considered in selecting the proper class of hoist, most industrial applications can be generalized according to the percentage of rated load normally handled and the running time. Listed in Table 1 are the two duty classes that have been established for air powered chain hoists. The majority of hoist applications will fall into the A4 category.
2.3 Specifications of Lift, Headroom, and Reach
2.3.1 Lift. Most air chain hoists are manufactured with standard lifts of 10 ft, 15 ft, and 20 ft (3.3 m, 4.9 m, and 6.6 m). One of these standard lifts will normally be adequate for the particular requirement. It is recommended that the purchaser specify the required
2.3.2 Headroom. Headroom should be specified ifimportant to the application.
2.3.3 Reach. Reach should be specified if importantto the application.
2.4 Hoist and Trolley Speeds
Hoisting equipment is available over a wide rangeof hoist and trolley speeds.Listed in Table 2 are typicalspeed ranges commonly available.
2.5 Types of Trolleys
Hoist trolleys are available in plain,hand chainoperated,and motor driven types. Selection of eachtype depends upon the application.
2.5.1 Plain Type. This type is recommended wheretrolley motion is infrequent or relatively short. Due tothe required force to manually operate this type oftrolley,it is also recommended that the use of plaintrolleys be limited to a maximum load of 3 tons or3,000 kg with the elevation of the beam not more than20 ft (6 m) above the operator’s floor level.
2.5.2 Hand Chain Operated. This type is recom-mended where trolley motion is relatively infrequentor short and for those loads and beam heights wherea plain-type trolley would be impractical. The handchain operated trolley provides good load spottingability obtained by pulling on the hand chain,which isconnected to trolley wheels through gears or sprockets.2.5.3 Motor Operated. This type is recommendedwhere the operating frequency , distance of travel, or thetype of load being handled would cause unsatisfactoryoperation if the trolley were the plain or hand chainoperated type. Design of motor operated trolleys shallbe based on operation on a straight beam,unlessotherwise specified. Where trolley travel involves acurved beam, beam switches,or execptionally longruns, special design may be required, and full particularsshould be provided with the inquiry.