|
| |
TM 10-4320-307-10
1-13 PUMP ASSEMBLY.
a.
Operation. The pump is of the centerline supported design having an axially split casing with suction
and discharge manifolds cast into the lower casing. This design allows ready access to rotating assemblies
without removal of suction and discharge piping or disconnecting the pump shaft from the speed increasing
gear. The pump has a double suction first stage impeller and opposed second and third stage impellers that
provide the pump with balanced thrust. This arrangement of three stages minimizes hydraulic pressure against
the mechanical seals while also providing axial hydraulic balance. The double volute design of the pump
maintains radial hydraulic balance. After the pump is primed and pumping begins, fluid flow is as follows:
(1)
Fluid in the supply piping enters the suction manifold.
(2)
The fluid enters the pump casing and the double suction first stage impeller.
(3)
The impeller rotating at high speed throws the fluid outward from the center of the impeller. This
creates a partial vacuum at the center of the impeller, drawing additional fluid from the suction
manifold.
(4)
The fluid forced out by the first stage impeller passes through a crossover to the second stage
impeller.
(5)
As fluid passes to the second stage impeller, two cyclone separators divert pumped fluid to the
pump seals. The cyclone separators supply the mechanical seals with clean fluid and at the same
time return contaminated fluid to the pump suction manifold.
(6)
The fluid passes to the second stage impeller and is forced outward from the center of the impeller
into a cross-over to the third stage impeller.
(7)
From the third stage (center) impeller, the fluid is forced through the discharge manifold into the
discharge piping.
(8)
As the sequence continues, pump speed may be adjusted between 1270 and 3459 rpm by varying
engine speed from 770 to 2100 rpm.
(9)
With a fixed piping system, increasing pump speed will increase pump capacity and head. At a
fixed pump/engine speed, partially closing the discharge valve will reduce capacity and increase
head.
1-10
|
