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.
