WNS Interview Questions and Answers

The line size of pump suction is bigger than pump discharge to reduce friction losses and increase efficiency.

• Bigger suction line reduces friction losses and allows for easier flow of fluid into the pump

• Smaller discharge line increases pressure and helps in maintaining flow rate

• This design helps in optimizing pump performance and efficiency

Suction pressure in a pump can be calculated by adding the atmospheric pressure to the gauge pressure.

• Calculate gauge pressure by subtracting the pressure at the pump outlet from the pressure at the pump inlet.

• Add the atmospheric pressure to the gauge pressure to get the suction pressure.

• Suction Pressure = Atmospheric Pressure + Gauge Pressure

• Example: Atmospheric pressure = 14.7 psi, Gauge pressure = 5 psi, Suction pressure = 14.7 + 5 = 19.7 psi

Line sizing criteria is based on factors like flow rate, pressure drop, fluid properties, and velocity.

• Consider the maximum flow rate the line needs to handle

• Calculate the pressure drop allowed for the system

• Take into account the properties of the fluid being transported

• Ensure the velocity of the fluid is within acceptable limits

• Use industry standards and guidelines for sizing criteria

• Example: For a water distribution system, line sizing would depend on the expected flow rate...read more

NPSH stands for Net Positive Suction Head and is a critical parameter in pump calculations.

• NPSH is the measurement of the amount of suction head required by a pump to prevent cavitation.

• It is calculated by subtracting the vapor pressure of the liquid from the total suction head of the pump.

• NPSH is important to ensure the pump operates efficiently and does not experience cavitation which can damage the pump.

• Low NPSH values can lead to cavitation, while high NPSH values indicat...read more

If NPSH is negative, increase the suction pressure or decrease the fluid temperature to prevent cavitation.

• Increase the suction pressure by using a booster pump or increasing the tank level

• Decrease the fluid temperature to increase the vapor pressure margin

• Check for any restrictions or blockages in the suction line

• Ensure the pump is properly sized for the application

Line sizing involves determining the appropriate diameter of pipes for a given flow rate, while pump hydraulic calculation involves calculating the pump head and power requirements.

• Determine the required flow rate for the process

• Calculate the pressure drop along the pipeline

• Select the appropriate pipe material and schedule based on process conditions

• Use hydraulic calculation formulas to determine pump head and power requirements

• Consider factors such as friction losses, elevat...read more