What are the two classifications of pumps?
kinetic (dynamic) and positive displacement
Define pump capacity.
The rated volumetric flow rate for a specific set of system parameters.
Define pump head terms.
Head refers to fluid levels above the eye of a pump.
Define pump lift terms.
Lift refers to fluid levels below the eye of a pump
Define pump Net positive suction head (NPSH).
The difference between the pump inlet, or suction, pressure and the saturation pressure of the fluid being pumped is called available net positive suction head.
Define Pump efficiency.
The ratio of work required by an ideal pump to the work required by a real pump. The difference between the input pump power and the useful pump power actually converted to head is the power lost to friction in the pump. This energy is converted to heat and is carriedaway by the fluid.
What is suction lift?
The suction lift of a pump is the work performed when a pump “lifts” a fluid the maximum distance possible. As pump suction lift increases (becomes more negative), the suction pressure approaches the vaporization point of the water. Water vaporizes when pump suction pressure reaches saturation pressure.
What is velocity head?
A pump moves a fluid; therefore, this fluid obtains a certain velocity. Velocity head is the work required to maintain this velocity. This head is equal to the height the fluid would reach due to its kinetic energy.
What is static suction head?
The energy available due to the actual vertical distancebetween the fluid level and the eye of the pump, as well as pressure exerted on the fluid surface.
What is the relationship between psi and feet of head for pure water at room temperature?
1 psi = 2.3 feet of pure water at room temperature.
What is total static head?
The vertical distance, normally in feet, between the free level of the liquid on the pump suction side and the free level of the liquid on the pump discharge side.
What is the relationship between inches of Mercury vacuum and head?
For every inch of mercury (Hg) vacuum, approximately one additional foot of suction lift on the pump is required.
Describe cavitation, including symptoms, effects on centrifugal pump operation and methods of prevention.
Formation and collapse of vapor in a pump due to suction pressure approaching saturation pressure. Can cause reduced capacity, noise, vibration, and pump damage. Decrease fluid temperature, increase static suction head, decrease fluid flow, decrease pump speed to correct.
State the purpose of the pump casing.
It houses the majority of the major pump components. The inlet (suction) and outlet (discharge) connections are integral to the pump casing.
State the purpose of the pump gaskets.
Semi-soft flexible materials used to seal mating surfaces or flanges
State the purpose of the pump Impeller.
The rotating component of the pump that converts the mechanical energy of the prime mover (the pump motor) into kinetic energy (speed) in the fluid.
State the purpose of the pump volute.
A gradually expanding spiral that is integral to the casing. It reduces fluid velocity and increases fluid pressure.
State the purpose of the pump shaft.
The shaft connects the prime mover to the impeller
State the purpose of the pump bearings.
Bearings provide two types of support, radial support forside to side motion and axial support for movement along the axis. The radial support is provided by anti-friction journal bearings. The bearings that provide the axial support are called thrust bearings.
State the purpose of the pump seal rings.
They provide the seal needed between the impeller and the casing. This seal prevents high-pressure discharge water from leaking back to the low-pressure suctionside of the impeller. The wearing rings also prevent excessive wearing of the pump casing. The casing ring fits into the casing and the wearing ring fits onto the impeller and rotates with it. There is a very close clearance between the rings. The wearing ring is replaceable, as it is softer than the casing ring and is designed to wear.
State the purpose of the pump shaft seals.
Seals where the shaft penetrates the casing to prevent the pumped fluid from leaking out around the rotating shaft
Describe the operation of Volute and diffuser centrifugal pumps.
As fluid fills the volute, it slows down, and its energy of motion (kinetic energy) is converted into pressure (flowenergy). Diffuser pumps have a volute enhanced with stationary vanes. The diffuser vane helps balance the radial thrust loads on the impeller, shaft, and journal bearings for varying flow conditions.
Describe the operation of Radial-flow, axial-flow and mixed-flow centrifugal pumps.
By radically changing the direction of flow and directing the fluid through a volute, radial-flow pumps are able to create a high discharge pressure. In contrast, axial-flow pumps can move tremendous volumes of fluid but at relatively low discharge pressures. Axial flow impellers provide flow where the main flow through the pump is along the axis of the shaft. Mixed-flow pumps combine the functions of radial-flow pumps and axial-flow pumps. Mixed-flow impellers are designed to discharge fluid at an angle greater than 0° and less than 90°.
What are the three centrifugal pump affinity laws?
These laws apply only to centrifugal pumps in closed systems
Change in RPM directly proportional to Volumetric Flow. Change in RPM results in a Square of the pressure. Change in RPM results in a Cube of the Power
