ASME HST-1-2017 pdf – Performance Standard for Electric Chain Hoists.
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., of rated load. Operation with random loads is considered on an equal-time basis for the operating time remaining after accounting for the time the hoist is operating at no load and with rated load. Randomly distributed loads will result in a mean effective load factor of 0.65.
1-1.4.1 GeneraL
(a) If the operation consists of lowering loads over long distances of more 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 of starts is not appreciably affected by the load on the hook and therefore the limits imposed by Columns 3 through 6 of Table 1- 1.3-1 are applicable for the motor regardless of the load being handled.
1-1.4.2 FundamentaL AppLication AnaLysis
It is not necessary to perform a detailed application analysis or calculate mean effective load factor if all of the conditions listed below are met.
(a) The hoist is operating at no load during one-half of its operating time (load probability equals 0.5).
(b) The hoist is operating with rated load for a period of time not exceeding 20% of its operating time (load probability equal to or less than 0.2).
(c) Other loads applied to the hoist during the remainder of its operating time are randomly distributed.
Conditions wherein the above operating criteria are met will result in a mean effective load factor of 0.65 or less. If any one of these conditions cannot be met, or if a below- the-hook lifting device is attached to the load hook, a detailed application analysis using a calculated mean effective load factor should be conducted.
1-1.4.3 DetaiLed AppLication AnaLysis
The following general method may be used to make a detailed application analysis. Several examples of this detailed analysis method are given in Nonmandatory Appendix B.
(a) Select a hoist class from Table 1-1.3-1 based on the general descriptions given in Column 2.
(b) Select a hoist with a rated load equal to or greater than maximum load to be lifted.
(c) Using the information in Columns 3 through 6, select the hoist speed that will meet the operational time ratings for hoist duty class.
(d) Determine value of K. IfKis greater than 0.65, select a hoist with a higher rated load rating and recalculate K to make sure it is equal to or less than 0.65.
(e) If the requirements of the operational time values in Table 1-1.3-1 and K equal to or less than 0.65 cannot be met, contact the manufacturer.
1-1.5.1 Lift
Most electric chain hoists are manufactured with standard lifts of 10 ft (3.1 m), 15 ft (4.6 m), and 20 ft (6.1 m). One of these standard lifts will normally be adequate for the particular requirement. It is recommended that the purchaser specify the required lift on his/her inquiry or bid request.
1-1.5.2 Headroom
Headroom should be specified if it is important to the application.
1-1.5.3 Reach
Reach should be specified if important to the application.
Hoisting equipment is available over a wide range of hoist and trolley speeds. Listed in Table 1-1.6-1 are typical speed ranges commonly available. Hoist and trolley speeds may vary ±10% from the specified speed.
NOTE: Table 1-1.6-1 is to be used as a guide only and is not intended to restrict either the manufacturer or buyer from offering or specifying speeds outside the ranges shown, nor should it be inferred that speeds above or below the range shown are not compatible with the required class of hoist.
Hoist trolleys are available in plain, hand-chain-operated, and motor-driven types. Selection of each type depends upon the application.