Setback load, rated

Rated setback load The maximum weight of tubular goods that the substructure can withstand in the setback area. 

Mast setup distance The distance from the centerline of the well to a designated point on the mast structure defined by a manufacturer to assist in the setup of the rig. Maximum rated static hook load The sum of the weight applied at the hook and the traveling equipment for the designated location of the dead line anchor and the specified number of drilling lines without any pipe setback, sucker rod, or wind loadings. 

API Standard 4A (superseded by Standard 4F) provides rating of derrick capacities in terms of maximum safe load.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 ... 

Under the rigging conditions given on the nameplate, and in the absence of setback or wind loads, the static hook load under which failure may occur in masts conforming to this specification can be given as only approximately twice the maximum rated static hook load capacity. 

The manufacturer shall establish the reduced rated static hook loads for the same conditions under which the maximum rated static hook loads apply, but with the addition of the pipe-setback and sucker-rod loadings. The reduced rated static hook loads shall be expressed as percentages of the maximum rated static hook loads. Thus, the portable mast ratings in Standard 4D include a safety factor of 2 to allow for wind and impact loads, and require the manufacturer to specify further capacity reductions due to setback. 

Each structure shall be rated for the following applicable loading conditions. The structures shall be designed to meet or exceed these conditions in accordance with the applicable specifications set forth herein. The following ratings do not include any allowance for impact. Acceleration, impact, setback, and wind loads will reduce the rated static hook load capacity. 

Rated static hook load for wind velocities varying from zero to maximum rated wind velocity with full rated setback and with maximum number of lines to the traveling block. 

Maximum rated combined load of setback and rotary table beams. 

Wind load with rated pipe setback composed of the following loads in combination ... 

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