Pressure required to break circulation - Drill string

Input(s)

y: Gel Strength of drilling fluid $\left(\mathrm{lb} / 100 \mathrm{ft}^{2}\right)$

L: Length of Drill String (ft)

$\mathrm{d}$: Inside diameter of drill pipe (in.)

Output(s)

$P_{g s}$: Pressure to overcome mud's gel strength inside drill string (psi)

Formula(s)

$$ P_{g s}=\left(y * \frac{L}{300 * d}\right) $$

Reference(s)

Formulas and Calculations for Drilling, Production and Workover, Second Edition, Lapeyrouse, Page: 79.