STANDARD HANDBOOK OF PETROLEUM & NATURAL GAS ...

Mud Pumps 627
MUD PUMPS
Mud pumps consume more than 60% of all the horsepower used in rotary
drilling. Mud pumps are used to circulate drilling fluid through the mud circulation
system while drilling. A pump with two fluid cylinders, as shown in Figure 4-99, is
called a duplex pump. A three-fluid-cylinder pump, as shown in Figure 4-100,
is called a triplex pump. Duplex pumps are usually double action, and triplex
pumps are usually single action.
Mud pumps consist of a power input end and a fluid output end. The power
input end, shown in Figure 4-101, transfers power from the driving engine
(usually diesel or electric) to the pump crankshaft. The fluid end does the actual
work of pumping the fluid. A cross-section of the fluid end is shown in
Figure 4-102.
Suction Manifold
Pump Installation
The hydraulic horsepower produced by mud pumps depends mainly on the
geometric and mechanical arrangement of the suction piping. If suction-charging
centrifugal pumps (e.g., auxiliary pumps that help move the mud to the mud
pump) are not used, the pump cylinders have to be filled by the hydrostatic head.
Incomplete filling of the cylinders can result in hammering, which produces
destructive pressure peaks and shortens the pump life. Filling problems become
more important with higher piston velocities. The suction pressure loss through
the suction valve and seat is from 5 to 10 psi. Approximately 1.5 psi of pressure
is required for each foot of suction lift. Since the maximum available atmospheric
pressure is 14.7 psi (sea level), suction pits placed below the pump should be
Figure 4-99. Duplex slush (mud) pump. (Courtesy National Oilwell.)