Derrick load capacity

Standard Derricks 501. Load Capacities 506. Design Loadings 508. Design Specifications 511. Maintenance and Use of Drilling and Well Servicing Structures 515. Derrick Efficiency Factor 521. 

API Standard 4A (superseded by Standard 4F) provides rating of derrick capacities in terms of maximum safe load. This is simply the load capacity of a single leg multiplied by four. It does not account for pipe setback, wind loads, the number of lines between the crown block and the traveling block, the location of the dead line, or vibratory and impact loads. Thus, it is recommended that the maximum safe static load of derricks designed under Standard 4A exceed the derrick load as follows ... 

This is an API Standard 4A rating capacity and should not be confused with the actual derrick load that will be discussed in the section titled Derricks and Portable Masts."... 

All conditions listed in the section titled Load Capacities, subsection titled Mast and Derricks under Dynamic Conditions," are to be specified by the user. Forces resulting from wind and vessel motion are to be calculated in accordance with the formulas presented in the section titled Design Specifications, paragraphs titled Wind, Dynamic Loading (Induced by Floating Hull Motion). ... 

In addition to withstanding some minimum load or loads (sections titled Load Capacities and Design Specifications ), derricks and masts that satisfy API standards must also satisfy certain requirements regarding materials, allowable stresses, wind, dynamic loading, earthquakes and extremes of temperature. 

Subpart N provides provisions for cranes, derricks, hoists, helicopters, conveyors, and aerial lifts. This subpart delimits many common safety requirements for material-handling equipment and reinforces the need to follow the manufacturer s requirements regarding load capacities, speed limits, special hazards, and unique equipment characteristics. A competent person must inspect all cranes and derricks before daily use and a thorough inspection must be accomplished annually by an OSHA-recognized qualified person. A record must be maintained of that inspection for each piece of hoisting eqnipment. 

Derrick efficiency factor (DEF) is often used to rate or classify derrick or mast structural capacity [1,7,8]. The derrick efficiency factor is defined as a ratio of actual load to an equivalent load that is four times the force in the derrick leg carrying the greatest load. Thus the ratio is... 

A qualified person has determined that the set-up and rated capacity of the crane/derrick (including the hook, load line and rigging) meets or exceeds the requirements in 1926.502(d)(15). 

E) The total weight of the loaded personnel platform and related rigging shall not exceed 50 percent of the rated capacity for the radius and configuration of the crane or derrick. 

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