310204c Liquid Pumping Flashcards
Do pumps produce flow or pressure?
All pumps produce flow not pressure. Pressure is created by a restriction in the flow path or by the resistance of a load.
What are some types of positive displacement pumps?
Gear pumps, piston pumps, screw love pumps and vane pumps
What are the two categories of positive displacement pumps
- Reciprocating
- Rotary
Reciprocating pumps are classified into 3 types according to the pumping element. What are these 3 types?
- Plunger
- Piston
- Diaphragm
True, or false
Piston pumps are made for lower pressure applications than plunger pumps, but can move more fluid per stroke.
True
Which type of pump relies on check valves?
Reciprocating pumps
What are the 2 classes of rotary positive displacement pumps?
- Single rotor pumps
- Multiple rotor pumps
What are the 5 categories of single rotor pumps?
- Progressive cavity pumps
- External vain pumps
- Peristaltic pumps
- Radial piston pumps
- Sine pumps
Which type of single rotor pump has exceptionally high pressure ratings, but their design makes them sepuhas exceptionally high pressure ratings, but their design makes them susceptible to contaminates?
Radial piston pumps
Which type of single rotor pump can create a significant vacuum and can pump high viscous fluids without causing cavitation?
Sine pumps
What are the 4 types of multiple rotor pumps?
- Gear pumps
- Lobe pumps
- Circumferential piston pumps
- Screw pumps
What is a pulsation dampener?
Reciprocating positive displacement pumps create hydraulic shock and vibrations.
Pulsation dampeners are gas filled chambers or vessels that prevent vibrations from traveling to subsequent stages of the process
They are usually located immediately downstream of a pump outlet.
What are the 3 control options for positive displacement pumps?
- Speed control - varying the pump speed by using a variable frequency drive (VFD) in conjunction with electric motors.
- Bypass - Returns liquid from the pump outlet to the inlet, this recycled liquid reduces the outlet pressure
- Internal or built-in control - uses mechanisms that vary the piston stroke, length or suction cavity volume. The stroke length or suction volume is controlled by a single control signal connected to the pump
A centrifugal pump converts __________ to _________
A centrifugal pump converts input power to kinetic energy
What is the function of the volute on a centrifugal pump?
The volute converts a portion of liquid kinetic energy into pressure energy
What is the formula for calculating centrifugal force.
Under constant RPM, if the density of the liquid going through a pump increases, what effect would it have on the centrifugal force and discharge pressure of the pump?
Under a constant rpm, if the density of the liquid increases, the centrifugal force and subsequent discharge pressure also increase.
What effect does impeller diameter and speed have on flow rate?
They have a linear relationship, if the impeller diameter or speed doubles the flow rate doubles.
What is the relationship between impeller diameter and speed with pump pressure?
Impeller diameter and speed.Have a squared law relationship with pump pressure
For example, if the pump speed or impeller diameter doubles, the resulting pressure is 4 times greater.
What is the relationship between impeller diameter and speed with power consumption?
The impeller diameter and speed have a cubic relationship with power consumption
For example, if the impeller diameter or speed of the impeller doubles, the resulting pump requires 8 times more power.
What is dead head?
The point on the curve wherebthe discharge pressure (pump head) pressure is maximum and the flow rate is 0.
What is pump run out?
When the flow rate of the liquid is too high, the liquid may leave the pump faster than it enters
This creates a very low pressure inside the pump and results in cavitation
Pump run out is the maximum flow rate and corresponding discharge pressure (pump head) to the pump can develop without damage to the pump.
What type of valve is required on the inlet and outlet ports of reciprocating pumps?
A check valve
What is pump head?
Pump head is the height of a vertical column of liquid that the pump holds up
The pump head or column height remains the same for liquids of different densities, because the output pressure of the pump is proportional to the density of the liquid it pumps.
What does NPSH stand for?
Net positive suction head
Is the measurement of liquid pressure at the pump end of the inlet (suction) system?
What does NPSHa stand for?
Net positive suction head available
Is the pressure of the liquid at the suction port of the pump
The piping system design determines the net positive suction pressure available
What does NPSHr stand for?
Net positive suction pressure required
Is the minimum pressure required at the suction port of the pump to keep the pump from cavitation
Pump design determines the net positive suction head required
What determines NPSHr?
The pump design
What determines NPSHa?
The piping system design
Net positive suction head ______ must be greater than the net positive section head _______ to prevent cavitation
Net positive suction head available must be greater than the net positive section head required to prevent cavitation
What pumping element in a reciprocating pump can discharge in both directions?
Double acting piston
If 2 liquids are pumped through the same centrifugal pump, what is the difference in pump head and discharge pressure between them, where liquid A has a relative density of 0.95 liquid B has a relative density of 1.03
They both have the same pump head, but liquid B has a higher discharge pressure
When suction pressure in a centrifugal pump falls below the net positive suction head required (NPSHr) it causes:
Cavitation
The 2 curves used to size a centrifugal pump are:
- System curve
- Pump curve
Explain how net positive suction head required (NPSHr) relates to pump flow
As the flow rate increases, the internal pressure drops within the pump. The lower pressure requires more suction head to prevent cavitation.
What method of control for a positive displacement pump may only require a single control signal?
Internal control
Centrifugal pump affinity laws determine how a change in impala, radius and speed affect:
- Pump flow
- Discharge pressure
- Power consumption
Which positive displacement pump self compensates for wear and is suitable for non lubricating liquids?
External Vane
Which positive displacement pump has superior suction, low shear and maintains a constant volumetric displacement throughout a rotation?
Sine pump
Which pump is used in hygienic applications?
Circumferential piston pumps
Which pump is most suitable for medical applications such as IV fluids and heart-lung machines?
Paristaltic pumps
