Fluid Mechanics Laboratory Centrifugal Pump Investigation(6)

March 24, 2009 – 12:23 am

V. Centrifugal Pump Report Treatment.
A formal written report is not required for this experiment. You are responsible for the plots, table,
and the discussion questions listed below. Your responses to the discussion questions are to be typed
with 1-1/2 to double spacing, using a character font no smaller than 12 point on 8

CGA CENTRIFUGAL PUMP(WITH OPEN IMPELLERS)

(2900r.p.m.)
-Insulation Class B/F
-IP44 Protection

Centrifugal Pumps Material:
-Pump body: Cast Iron
-Impeller: Brass
-Motor Shaft: Hi-Cr 45 plated # Steel/2Cr13 # Stainless Steel/SS # 304 Welding shaft
-Mechanical seal: Ceramic/Graphite

Centrifugal Pumps Application:

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CHF CENTRIFUGAL PUMP(MEDIUM FLOW)

(2900r.p.m.)
-Centrifugal Pumps Insulation Class B/F
-IP44 Protection

Material:
-Centrifugal Pumps body: Cast Iron
-Impeller: Brass
-Motor Shaft: Hi-Cr 45 plated # Steel/2Cr13 # Stainless Steel/SS # 304 Welding shaft
-Mechanical seal: Ceramic/Graphite

Application:

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Adjustable Speed Drives As Applied To Centrifugal Pumps

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Adjustable Speed Drives As Applied To Centrifugal Pumps -1

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Adjustable Speed Drives As Applied To Centrifugal Pumps -2

May 6, 2009 – 6:11 pm

Figure 6. Combined Curves

Figure 7 shows a typical Centrifugal Pump and efficiency curve for operation
at a fixed speed. It can be seen that for fixed speed operation,
the efficiency varies as flow is adjusted. For adjustable speed
operation however, the affinity laws predict that the Centrifugal Pump  curve
will shift downwards for reduced speed and the efficiency curve
will shift to the left in such a way that efficiency will remain constant
relative to points on the Centrifugal Pump  curve for reduced flows.

Figure 7. Fixed Speed Pump Efficiency

FLOW CONTROL TECHNIQUES
Historically, fixed speed AC motors have driven centrifugal pumps
and reduced flow has been achieved by using control valves as
shown in figure 8. Closing the valve reduces the flow by increasing
the friction in the system. The modified system curve and the
new operating point can be represented as shown in figure 9.
Note that the desired reduction in flow has been achieved, but at
the expense of increased system pressure relative to 100% flow.

An alternative approach to valve control is shown in figure 10.
Reducing the Centrifugal Pump  speed causes the Centrifugal Pump  curve to shift downwards
as shown in figure 11. Since the operating point is still
determined by the intersection of the reduced speed Centrifugal Pump  curve
and the system curve, it is possible to achieve the same reduced
flow as achieved with a valve, but at significantly less pressure.

Figure 9. Throttle System

In addition to energy savings, which are discussed in detail later,
operation at reduced pressures can result in longer Centrifugal Pump  seal
life, reduced impeller wear, and less system vibration and noise.
These benefits could provide additional savings over potential
energy savings.

Figure 10. Adjustable Speed Control
ENERGY SAVINGS
The Centrifugal Pump  output power, or hydraulic power, can be expressed as:
Horsepower
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Centrifugal Pumps modes of Operation

March 29, 2009 – 11:11 pm

Centrifugal Pumps ,The SMC Flex controller provides the following modes of operation as Standard:

Soft Start
This method covers the most general applications. The motor is
given an initial torque setting, which is user adjustable. From the
initial torque level, the output voltage to the motor is steplessly
increased during the acceleration ramp time, which is user
adjustable.
Centrifugal Pumps Selectable Kickstart
The kickstart feature provides a boost at startup to break away
loads that may require a pulse of high torque to get started. It is
intended to provide a current pulse, for a selected period of time.
Current Limit Start
Centrifugal Pumps ,This method provides current limit start and is used when it is
necessary to limit the maximum starting current. The starting current
is user adjustable. The current limit stating time is user adjustable.
Dual Ramp Start
This starting method is useful on applications with varying loads,
starting torque, and start time requirements.Centrifugal Pumps , Dual Ramp Start offers
the user the ability to select between two separate start profiles with
separately adjustable ramp times and initial torque settings.

Centrifugal Pumps Full Voltage Start
This method is used in applications requiring across-the-line
starting. The SMC controller performs like a solid-state contactor.
Full inrush current and locked-rotor torque are realized. The SMC
may be programmed to provide full voltage start in which the output
voltage to the motor reaches full voltage in 1/4 second.
Linear Speed Acceleration
With this type of acceleration mode, a closed-loop feedback system
maintains the motor acceleration at a constant rate. The required
feedback signal is provided by a DC tachometer coupled to the
motor (tachometer supplied by user 0
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