Mahanagar Gas Management, Technical Interview Questions and Answers

A pump is a mechanical device used to move fluids from one place to another. It can be classified based on its principle of operation.

• Pumps are used in various industries such as water supply, oil and gas, chemical processing, and wastewater treatment.

• Classification of pumps can be based on the type of fluid being pumped (e.g., water pump, oil pump), the principle of operation (e.g., centrifugal pump, positive displace...read more

Soap solution can be pumped using various types of pumps depending on the application.

• Diaphragm pumps are commonly used for pumping soap solution.

• Centrifugal pumps can also be used for pumping soap solution.

• Peristaltic pumps are suitable for pumping soap solution with high viscosity.

• Air-operated double diaphragm pumps are often used in industrial settings for pumping soap solution.

• Progressive cavity pumps can handle so

The selection criteria of a pump depend on factors such as flow rate, head, efficiency, power consumption, and cost.

• Flow rate: Determine the required flow rate for the application.

• Head: Consider the total head or pressure required to overcome in the system.

• Efficiency: Look for a pump with high efficiency to minimize energy consumption.

• Power consumption: Evaluate the power requirements and choose a pump accordingly.

• Cost...read more

NPSH stands for Net Positive Suction Head. It is a measure of the pressure available at the suction of a pump.

• NPSH is the difference between the total suction head and the vapor pressure of the pumped liquid.

• It determines the ability of a pump to avoid cavitation, which can damage the pump and reduce its performance.

• Insufficient NPSH can lead to reduced flow rate, decreased efficiency, and increased noise and vibration...read more

There are various types of impellers used in centrifugal pumps, each made of different materials.

• Closed impeller: used for high-pressure applications and made of materials like stainless steel or cast iron.

• Open impeller: used for handling liquids with solids and made of materials like bronze or stainless steel.

• Semi-open impeller: used for applications where solids may be present and made of materials like cast iron or ...read more

Reciprocating pump is called positive displacement pump because it displaces a fixed volume of fluid with each stroke.

• Reciprocating pump uses a piston or plunger to create a reciprocating motion, which displaces a fixed volume of fluid with each stroke.

• The displacement of fluid is achieved by trapping the fluid in a chamber and then forcing it out through a discharge valve.

• Unlike centrifugal pumps, reciprocating pumps ...read more

The stress-strain diagram is a graphical representation of the relationship between stress and strain in a material.

• The stress-strain diagram shows how a material deforms under applied stress.

• It helps in understanding the mechanical properties of a material.

• The diagram consists of various points that represent different stages of deformation.

• The elastic limit point represents the maximum stress a material can withstand...read more

Principal stress refers to the maximum and minimum stresses experienced by a material. They are significant in determining material failure and structural stability.

• Principal stress is the maximum and minimum stress experienced by a material in a given loading condition.

• They are perpendicular to each other and act along the principal planes.

• The principal stress values help in determining the failure criteria of a mater...read more

Different theories of failure and their applicability for ductile and brittle materials.

• Theories of failure include maximum shear stress theory, maximum distortion energy theory, and maximum normal stress theory.

• For ductile materials, the maximum shear stress theory is applicable as it considers the yield strength and shear strength.

• For brittle materials, the maximum normal stress theory is applicable as it considers t...read more

Buckling is the sudden failure of a structural member under compression. Columns and struts are both compression members, but differ in their end conditions.

• Buckling is a failure mode that occurs when a compression member, such as a column or strut, fails due to excessive compressive forces.

• It is characterized by a sudden lateral deflection or bending of the member.

• Columns are vertical compression members that are usua...read more

The slenderness ratio is a measure of the stability of a column. It is defined as the ratio of the effective length to the least radius of gyration.

• Slenderness ratio = Effective length / Least radius of gyration

• It determines the buckling behavior of a column under compressive loads

• Columns can be classified as short, intermediate, or long based on their slenderness ratio

• Short columns have a slenderness ratio less than a...read more

Bending is a process of applying a force to a material, causing it to deform and assume a curved shape.

• Bending is a common phenomenon in engineering and construction.

• It occurs when a material is subjected to an external force, causing it to bend or flex.

• Bending theory is a set of principles and equations used to analyze and predict the behavior of bent materials.

• Assumptions of bending theory include linear elasticity, ...read more

Torsion and bending are two different types of forces that act on structures.

• Torsion is a twisting force that causes an object to rotate around its axis.

• Bending is a force that causes an object to deform by curving or flexing.

• Torsion primarily affects cylindrical objects, while bending affects beams or other elongated structures.

• Torsion can be seen in the twisting of a screwdriver or the rotation of a helicopter rotor.

• ...read more

Enthalpy is the heat content of a system, while entropy is a measure of disorder or randomness.

• Enthalpy is a thermodynamic property that accounts for the heat energy of a system.

• It is represented by the symbol H and is measured in units of energy (e.g., joules).

• Enthalpy change (∆H) is the difference in enthalpy between the products and reactants in a chemical reaction.

• Entropy is a measure of the degree of randomness or...read more

A Moliere diagram is a graphical representation of the relationships between different elements in a system or process.

• Moliere diagrams are often used in project management to visualize the flow of tasks and dependencies.

• They can also be used in software development to illustrate the relationships between different modules or components.

• Moliere diagrams can help identify bottlenecks, optimize processes, and improve ove...read more

Nozzle and diffuser are both fluid flow devices, but they have opposite functions.

• Nozzle is a device that increases the velocity of a fluid by decreasing its cross-sectional area.

• Diffuser is a device that decreases the velocity of a fluid by increasing its cross-sectional area.

• Nozzle is used to accelerate the flow of fluid, while a diffuser is used to decelerate the flow.

• Nozzle is commonly used in applications like roc...read more

When water is filled in a compressor and air is filled in a pump, it can lead to damage and malfunction of both the compressor and the pump.

• Water in a compressor can cause corrosion and damage to the internal components, reducing its efficiency and lifespan.

• Air in a pump can cause cavitation, which is the formation and collapse of air bubbles in the pump, leading to damage and reduced performance.

• Both the compressor an...read more

The iron-carbon equilibrium diagram illustrates the phases and transformations of iron-carbon alloys at different temperatures.

• The diagram shows the relationship between carbon content, temperature, and the phases of iron-carbon alloys.

• It helps in understanding the behavior of steel and cast iron.

• Different temperature zones on the diagram correspond to different invariant reactions.

• In the ferrite-pearlite zone, the rea...read more

Curie temperature is the temperature at which a material loses its ferromagnetic properties. Iron-carbon alloy exhibits different magnetic behaviors in different temperature zones.

• Curie temperature is the temperature at which a material transitions from being ferromagnetic to paramagnetic.

• For iron-carbon alloy, the Curie temperature is around 770°C.

• Below the Curie temperature, iron-carbon alloy behaves as ferromagnetic...read more

Welding is a process of joining two or more metal pieces together using heat and pressure.

• Welding is commonly used in industries like construction, automotive, aerospace, and manufacturing.

• Some popular welding processes include arc welding, MIG welding, TIG welding, and spot welding.

• Arc welding uses an electric arc to create heat and melt the metal pieces together.

• MIG welding uses a wire electrode to create an electric...read more

The machining process used for surface finishing operations is called grinding.

• Grinding is a process that uses an abrasive wheel to remove material from a workpiece's surface.

• It is commonly used to achieve a smooth and flat surface finish.

• The average height of roughness, also known as Ra value, depends on various factors such as the grinding wheel grit size, feed rate, and material being ground.

• For example, in precisio...read more

A turbine is a device that converts the energy from a fluid into mechanical energy. Impulse and reaction turbines differ in how they convert this energy.

• A turbine is a machine that extracts energy from a fluid, such as steam, gas, or water, and converts it into rotational motion.

• Impulse turbines work by directing a high-velocity jet of fluid onto the blades of the turbine, causing it to rotate.

• Examples of impulse turbi...read more

Compounding is the process of earning interest on both the initial principal and the accumulated interest.

• Compounding refers to the concept of reinvesting the interest earned on an investment to generate additional earnings.

• It involves the exponential growth of an investment over time.

• The more frequently compounding occurs, the faster the investment grows.

• Compound interest can be calculated using the formula A = P(1 + ...read more

The Rankine cycle is a thermodynamic cycle used in power plants to generate electricity.

• The Rankine cycle consists of four main components: a pump, a boiler, a turbine, and a condenser.

• On a P-V diagram, the cycle starts at point 1 with the pump, where the working fluid is compressed to a high pressure.

• From point 1 to point 2, the fluid is heated in the boiler, resulting in a phase change from liquid to vapor.

• The vapor ...read more

The inlet valve is larger in size compared to the exhaust valve to optimize the flow of air/fuel mixture into the combustion chamber.

• The larger size of the inlet valve allows for a greater volume of air/fuel mixture to enter the combustion chamber during the intake stroke.

• This helps in achieving better combustion efficiency and power output.

• The exhaust valve, on the other hand, is smaller in size as it only needs to al...read more

Rockwell hardness is more preferred over Brinell hardness due to its higher accuracy, versatility, and ease of use.

• Rockwell hardness provides a more accurate measurement of hardness compared to Brinell hardness.

• Rockwell hardness is more versatile as it can be used for a wide range of materials, including both hard and soft metals.

• The Rockwell test is easier to perform and requires less time compared to the Brinell test...read more

Pelton wheel, Francis turbine, and Kaplan turbine are types of hydraulic turbines used for generating electricity.

• Pelton wheel is an impulse turbine used for high head applications.

• Francis turbine is a reaction turbine used for medium head applications.

• Kaplan turbine is a propeller-type reaction turbine used for low head applications.

• Pelton wheel has a capacity range of 1 MW to 200 MW.

• Francis turbine has a capacity ran...read more