Drilling fluid - Surface Pressure losses

Surface Pressure Losses

System pressure loss calculations begin with the determination of the type/ class of surface circulating equipment. These include the standpipe, rotary hose, swivel, and kelly (if present). Though hardly ever consistent, four  types/classes have been recognized by the IADC as the most common.

They are:

When calculating surface pressure losses, choose the class which is closest to the present rig equipment; if necessary, extrapolate. Most modern rigs will have a surface pressure coefficient between 2 and 10. The coefficient is then used in the following formula:

Pls = 10^-5 x ks x MD x Q^1.86

where: Pls = Surface Pressure Loss (psi)

ks = Surface Pressure Coefficient

MD = Mud Density (lb/gal)

Q = Flow Rate (gal/min)

When extrapolating, bear in mind that increased lengths will increase the coefficient, while increased I.D.'s will decrease the coefficient.