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Pump questions and answers
Q: What is a pump?
A: A device used to move fluids from one location to another.
Q: What is the purpose of a pump?
A: To transfer fluids.
Q: What are the different types of pumps?
A: Centrifugal pumps, positive displacement pumps, axial flow pumps, and mixed flow pumps.
Q: What is the difference between a centrifugal pump and a positive displacement pump?
A: A centrifugal pump uses an impeller to move fluid through a piping system, while a positive displacement pump moves fluid by trapping a fixed amount of fluid and then forcing it into the discharge pipe.
Q: What is a multistage pump?
A: A pump with two or more impellers, used to achieve higher pressures.
Pump Head
Q: What is pump head? A: The pressure that a pump produces.
Q: How is pump head measured?
A: In units of length, such as feet or meters.
Q: What is the difference between total head and dynamic head? (Types of pumps)
A: Total head is the sum of static head and dynamic head, while dynamic head is the head required to overcome friction in the piping system.
Q: How does pump head affect the flow rate of a pump?
A: The higher the pump head, the lower the flow rate.
Q: What is NPSH and how does it relate to pump head?
A: NPSH (Net Positive Suction Head) is a measure of the pressure required to prevent cavitation in a pump. It relates to pump head because the higher the NPSH required, the higher the pump head must be to prevent cavitation.
Pump Design
Q: What factors are considered when designing a pump?
A: Flow rate, pressure, temperature, viscosity, and the characteristics of the fluid being pumped.
Q: What is the difference between a single-stage and a multistage pump?(pump questions and answers)
A: A single-stage pump has one impeller, while a multistage pump has two or more impellers.
Q: What is the purpose of a volute in a centrifugal pump?
A: To convert the kinetic energy of the fluid into pressure.
Q: What is the purpose of a diffuser in a centrifugal pump?
A: To convert the high velocity, low pressure fluid leaving the impeller into high pressure, low velocity fluid.
Q: What is the purpose of a mechanical seal in a pump?
A: To prevent leakage of the pumped fluid.
Pump Calculation
Q: How is pump power calculated?
A: Power (in watts) = flow rate (in m3/s) x head (in meters) x density (in kg/m3) x gravity (9.81 m/s2)
Q: What is the affinity laws?
A: The affinity laws are a set of mathematical formulas that describe the relationship between flow rate, head, and power in a pump.
Q: What is specific speed and how is it calculated?
A: Specific speed is a dimensionless number that describes the pump’s geometry. It is calculated as N x Q1/2 / H3/4, where N is the pump speed in rpm, Q is the flow rate in m3/s, and H is the head in meters.
Q: What is the purpose of pump curves?
A: To provide information on a pump’s performance, including flow rate, head, and power consumption.
Q: How is pump efficiency calculated?
A: Pump efficiency = (output power / input power) x 100%
Q: What is the purpose of pump testing?
A: To verify a pump’s performance and ensure it meets specifications.
Q: What is pump cavitation and how can it be prevented?
A: Pump cavitation is the formation of vapor bubbles in the pump due to low pressure. It can be prevented by maintaining proper suction pressure, avoiding excessive flow rates, and selecting a pump with the appropriate NPSH requirements.
Q: What is the difference between pump efficiency and motor efficiency?
A: Pump efficiency is a measure of the pump’s ability to convert input power into output power, while motor efficiency is a measure of the motor’s ability to convert electrical power into mechanical power.
Q: What is pump suction lift?
A: The vertical distance between the pump centerline and the liquid surface in the suction vessel.
Q: What factors affect pump suction lift?
A: Atmospheric pressure, fluid density, and friction losses in the suction piping.
Q: How can pump cavitation be detected?
A: By the sound of the pump, vibrations, and changes in flow rate or pressure.
Q: What is the purpose of pump selection criteria?
To ensure that the selected pump is appropriate for the application, including flow rate, pressure, temperature, and the characteristics of the fluid being pumped.
Q: What is pump priming?
A: The process of removing air or gas from the pump and suction piping prior to startup.
Q: What are the different methods of pump priming?
A: Manual priming, automatic priming, and self-priming.
Q: What is the difference between a pump curve and a system curve?
A: A pump curve shows the pump’s performance characteristics, while a system curve shows the relationship between flow rate and head for the entire piping system.
Q: What is the purpose of pump impeller trimming?
A: To adjust the pump’s flow rate and head by trimming the impeller diameter.
Q: What is the purpose of pump vibration analysis?
A: To detect and diagnose the cause of abnormal pump vibrations.
Q: What is pump shut-off head?
A: The maximum head that a pump can produce when the flow rate is zero.
Q: What is the difference between a constant speed pump and a variable speed pump?
A: A constant speed pump operates at a fixed speed, while a variable speed pump can adjust its speed to maintain a constant flow rate or pressure.
Q: What is pump flow rate?
A: The volume of fluid that a pump can move per unit time.
Q: What is the purpose of a pump seal flush? A: To cool and lubricate the pump seal, and to prevent the buildup of solids or gases that can damage the seal.
Q: What is the difference between a gland packing and a mechanical seal?
A: A gland packing is a rope-like material that is wrapped around the shaft to prevent fluid leakage, while a mechanical seal uses two flat faces to create a seal.
Q: What is pump affinity?
A: The relationship between a pump’s geometry and its performance characteristics.
Q: What is the difference between pump head and system head?
A: Pump head is the pressure that a pump produces, while system head is the total head required by the piping system to transport the fluid from the pump to the destination.
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