STANDARD HANDBOOK OF PETROLEUM & NATURAL GAS ...

Hoisting System 605
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DT/d RATIOS
D, = tread diameter of sheave, inches (mm) (see Fig. 4-73)
d = nominal rope diameter, inches (mm).
Figure 4-79. Relative service for various Dfd ratios for sheaves [ill.’
See “Diameter of Sheaves,” subparagraph titled ”Variation for Different Service Applications.”
‘Based on laboratory tests involving systems consisting of sheaves only.
For the comparative evaluation of service from rotary drilling lines, the grand
total of ton-miles of work performed will be the sum of the ton-miles for all
round-trip operations (Equation 4-26), the ton-miles for all drilling operations
(Equation 4-27), the ton-miles for all coring operations (Equation 4-29), the tonmiles
for all casing setting operations (Equation 4-30), and the ton-miles for all
short trip operations (Equation 4-33). By dividing the grand total ton-miles for