644
Drilling and Well Completions
(text
continued
from
page
631)
The required pump working pressure PWP (psi) can be calculated as
PWP
=
APs
+
APd
+
APa
+
AP,,
(4-35)
where
APs
=
pressure loss through surface equipment in psi
APd
=
pressure
loss
through the inside of the drill string in psi