Drill pipe load capacity

To evaluate the load capacity of drill pipe (e.g., allowable tensile load while simultaneously a torque is applied), the maximum distortion energy theory is... 

Determine the tensile load capacity of a 4 4in., 16.6-lb/ft, steel grade X-95 new drill pipe subjected to a rotary torque of 12,000 ft-lb if the required safety factor is 2.0. 

Substituting Equations 4-59, 4-60, 4-56, and 4-55 into Equation 4-54 and solving for the tensile load capacity of drill pipe yields... 

Find the tensile load capacity of 5-in., nominal weight 19.5-lb/ft, steel grade E, premium class drill pipe exposed to internal drill pipe pressure = 3,000 psi and rotary torque T = 15,000 ft-lb. 

The reduction in the tensile load capacity of the drill pipe is 311,400 -260,500 = 50,900 lb. That is about 17% of the tensile drill pipe resistance calculated at the minimum yield strength in uniaxial state of stress. For practical purposes, depending upon drilling conditions, a reasonable value of safety factor should be applied. 

Tool Joint dimensions for drill pipe grades E, X, G and S (recommended by API) are given in Table 4-84. Selection of tool Joints should be discussed with the manufacturer. This is due to the fact that, up to the present time, there are no fully reliable formulas for calculating load capacity of tool Joints. It is recommended that a tool Joint be selected in such a manner that the torsional load capacity of the tool Joint and the drill pipe would be comparable. The decision can be based on data specified in Tables 4-85 through 4-88. 

Normally, not more than two sections are designed but, if absolutely necessary, even three sections can be used. To calculate the tensile load capacity of drill pipe, it is suggested to apply Equation 4-58 and use the recommended makeup torque of the weakest tool joint for the rotary torque. 

Pj = load capacity of drill pipe based on minimum yield strength in lb Dj = outside diameter of drill pipe in in = length of slips (L = 12-16 in.)... 

From Table 4-80, the minimum tensile load capacity of selected drill pipe P, = 501,090 lb. 

The tensile load capacity of drill pipe corrected for the effect of the maximum allowable torque, according to Equation 4-58 is... 

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