ASME HST-5:1999 pdf download

ASME HST-5:1999 pdf download PERFORMANCE STANDARD FOR AIR CHAIN HOISTS
trolley-suspended:suspension of hoist from a trolley;the hoist can be connected to trolley by hook,clevis,or lug suspension,or the hoist can be integral withtrolley.
valve:a device for starting, stopping,or changing theflow in a pneumatic circuit.
welded link chain:a chain consisting of a series ofinterwoven links formed and welded.
NOTE: Hand chain and load chain properties do not conform tothose shown in ASME B30.9.
PERFORMANCE
2.1 General
All equipment selected in accordance with this Stan-dard is designed to perform satisfactorily when installedin accordance with para.4.4，used in accordance withpara.4.5, and used within the rated load and hoistduty service classification. All equipment shall providespeeds,lifts,and headroom in accordance with themanufacturer’s specifications, or to specifications agreedupon 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 performanceof wearing parts of a hoist such as gears，bearings,load chain，sprockets，brake linings,load and lift limitdevices，wheels, and pneumatic components. Carefulconsideration of the hoist duty service classificationsdescribed in this Section will enable the user to evaluatethe 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 selec-tion of the proper hoist to perform a given function.Hoisting equipment consists of both mechanical andpneumatic components and both must be consideredwhen analyzing the service the hoist must perform.The factors that influence the performance of any hoistinclude:
(a) Load Distribution.The actual distribution or pro-portion of full and partial loads to be handled by theequipment，including lifting devices;
(b) Operational Time. The total running time of thehoist per hour or per work period;
(c) Repetitive Long Lowering Operations. Such oper-ations generate heat in mechanical load brake;
(d) Ervironmerntal Conditions. Examples are high orlow ambient temperatures，dust，moisture,corrosivefumes，etc.
2.2.2 Hazardous Locations. When hoists are usedin hazardous locations as defined by ANSI/NFPA 70or other special codes，modifications or additional pre-cautions not covered by this Standard may be required.In these locations，only hoists designed in a mannersuitable for the conditions encountered shall be used.
2.2.3 Duty Classification. While all the factorslisted in para. 2.2.1 must be considered in selectingthe proper class of hoist，most industrial applicationscan be generalized according to the percentage of ratedload normally handled and the running time.Listed inTable l are the two duty classes that have beenestablished for air powered chain hoists.The majorityof 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 manufacturedwith standard lifts of 10 ft,15 fit,and 20 ft (3.3 m,4.9 m, and 6.6 m). One of these standard lifts willnormally be adequate for the particular requirement.’ It’is AsaEommerded that the purchaser specify the reqired 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.
3 MECHANICAL REQUIREMENTS3.1 Design Stresses
(a) The hoist and the means of suspension suppliedwith the hoist shall be designed to withstand all stressesimposed under normal operating conditions while han-dling loads within the rated load.
(b) Load suspension parts shall be designed so that