Instruction and Operation Manual
17
3. Open the discharge valve on the second unit
so that the design flow of both units is
maintained.
Note: Do not operate the pumps at their peak
head capability.
Sundyne recommends that separate flow
controls be used on each pump to provide a
lower minimum flow range than is achieved by
pressure control.
Operation of Sundyne Pumps
Under normal operation, several factors must be
taken into consideration to ensure successful
pump operation. Experienced pump operators
will be aware of jeopardizing factors and their
effects.
Suction Conditions
Improper flow of liquid into the impeller is the
most common operational abuse of centrifugal
pumps. Two conditions must exist to prevent
turbulence at the eye of the impeller.
•
Proper suction piping, see suction piping
section.
•
Liquid reaching the impeller eye must
have enough vapor pressure to prevent
the fluid from flashing to a gas in the
impeller. If this condition occurs, it will
cause cavitation, which can damage the
impeller and inducer. When centrifugal
pumps cavitate the noise sounds like the
pump is “pumping gravel”. In high speed,
single stage pumps, this sound may not
be discernable. Cavitation can be
prevented by maintaining suction pressure
at a high enough level and suction
temperatures low enough to maintain Net
Positive Suction Head (NPSH) available
greater than Net Positive Suction Head
(NPSH
r
) required by the pumps.
Minimum Flow Conditions
Vibration and noise will occur during operation of
centrifugal pumps if either of two conditions
exist:
•
Internal
flow
separations
•
Recirculation at low flow conditions
If the operator is noticing excessive noise or
vibration, operation must be suspended until the
cause is determined and corrected. Continued
use may cause damage to the pump.
Resonance in the discharge line can accentuate
noise, vibration, and damage to the pump,
primarily when a control valve is located an
excessive distance downstream from the pump.
Entrained Gases
The head and capacity of centrifugal pumps will
be reduced by gas that is drawn in with the
liquid. Under normal operating conditions,
centrifugal pumps can tolerate up to 2% of gas
(by volume). Entrained gases can cause
damage to mechanical seals with the exception
of double seals. If you have entrained gas,
contact Sundyne for further instruction.
System Head Curve
The point of intersection between the system
curve and the pump characteristic curve
determines the flow or operation for the
centrifugal pump. For steady flow to occur, the
system curve must intersect the pump
characteristic curve at a significant angle. The
following diagram gives examples of satisfactory
and unsatisfactory angles of intersection.
Figure 8. Typical Operation
FLOW
HE
AD
System (Head) Curves
Good
Angle of
Intersection
Valve Partially Closed
Valve
Wide
Open
2
1
E
D
B
A
Note: The curve for pump A has a significant
angle of intersection with system curves
D and E. The system curve D could
represent a system with the control
valve wide open while curve E could
represent the same system but with the
throttle valve closed to reduce flow from
flow 1 to flow 2. Pump curve B, on the
other hand, will provide only flow 2,
even with the control valve wide open
Summary of Contents for LMV-313
Page 1: ...SUNDYNE LMV 313 PUMPS Instruction and Operation Manual August 2007 ...
Page 36: ...Instruction and Operation Manual 32 Figure 15 Inducer Housing Shim Adjustment ...
Page 40: ...Instruction and Operation Manual 36 Figure 17 Service Check Points ...
Page 69: ...Instruction and Operation Manual 65 Figure 22 Gearbox Components ...
Page 70: ...Instruction and Operation Manual 66 Figure 23 Pump Nomenclature ...
Page 71: ...Instruction and Operation Manual 67 Figure 24 Exploded View ...
Page 72: ...Instruction and Operation Manual 68 Shaft Assemblies Figure 25 Shaft Assemblies ...