Hitachi Energy Mechanical Engg. Design Interview Questions and Answers

I have experience working with pumps and vessels in various projects during my diploma in Mechanical Engineering.

• I have hands-on experience in designing, installing, and maintaining pumps and vessels for different industrial applications.

• I am familiar with different types of pumps such as centrifugal pumps, reciprocating pumps, and gear pumps.

• I have worked on sizing and selecting pumps based on the flow rate, head, and...read more

Process gear oil replacement is the procedure of draining out old gear oil from a system and refilling it with fresh gear oil.

• Drain out old gear oil from the system

• Ensure proper disposal of the old gear oil

• Refill the system with fresh gear oil

• Follow manufacturer's guidelines for the type and amount of gear oil to be used

De-ashing process from ESP to silo involves several steps.

• The ash is collected in hoppers located at the bottom of the ESP.

• The ash is then transported to the silo using a pneumatic conveying system.

• The ash is stored in the silo until it can be disposed of properly.

• Regular maintenance of the ESP and pneumatic conveying system is necessary to ensure efficient de-ashing.

• Proper safety measures must be taken during the de-a

The capacity of ESP hoppers varies depending on the size and model of the equipment.

• ESP hoppers can range from a few hundred cubic feet to several thousand cubic feet in capacity.

• The capacity can also depend on the type of material being collected in the hopper.

• It is important to regularly monitor and maintain the hopper to prevent overfilling and potential equipment damage.

To design bearing brackets for a hydro generator, the cross section of arms is determined based on load considerations and materials are selected for their strength and corrosion resistance.

• The design of bearing brackets for a hydro generator involves determining the cross section of arms.

• The cross section of arms is decided based on load considerations such as the weight of the rotor, hydraulic forces, and any additio...read more

The stator core is a crucial component in an electric motor, providing support and magnetic flux. Clamping force, number of bolts, material, and cold rolled sheets are determined based on design requirements.

• The function of the stator core is to support the windings and provide a path for the magnetic flux in an electric motor.

• The clamping force for the stator core is determined based on the mechanical load and the des...read more

The design of a generator shaft involves considering factors such as material selection, stress analysis, and balancing.

• Select appropriate material for the shaft based on factors like strength, corrosion resistance, and cost.

• Perform stress analysis to ensure the shaft can withstand the operating loads and torque.

• Consider factors like shaft diameter, length, and keyway design.

• Balance the shaft to minimize vibrations and...read more

Rotor dynamics is the study of the behavior and performance of rotating machinery.

• Rotor dynamics involves analyzing the vibrations, stability, and performance of rotating components such as rotors, shafts, and bearings.

• Inputs required for rotor dynamics analysis include rotor geometry, material properties, operating conditions, and boundary conditions.

• The output of rotor dynamics analysis includes critical speeds, mode...read more

Types of gearboxes include spur, helical, bevel, worm, planetary, and cycloidal.

• Spur gearbox: simple and efficient, used in low-speed applications

• Helical gearbox: smoother operation, higher load capacity

• Bevel gearbox: used for right angle drives

• Worm gearbox: high reduction ratios, self-locking feature

• Planetary gearbox: compact design, high torque transmission

• Cycloidal gearbox: high shock load capacity, low backlash

Tensioning involves stretching a fastener to a specific load, while torqueing involves tightening a fastener to a specific torque value.

• Tensioning is typically used for critical applications where precise load control is required.

• Torqueing is more commonly used in general applications where a specific torque value is sufficient.

• Tensioning is often used in applications like bolted joints in bridges or aircraft structure...read more

The main reason for gearbox failure is lack of lubrication, leading to increased friction and wear.

• Lack of proper lubrication causing increased friction

• Contamination of lubricant with dirt or debris

• Overloading the gearbox beyond its capacity

• Improper maintenance and servicing

• Manufacturing defects or poor quality materials

• Incorrect alignment of gears

Two stroke engines have power strokes every revolution, while four stroke engines have power strokes every other revolution.

• Two stroke engines have a simpler design with fewer moving parts compared to four stroke engines

• Two stroke engines require a fuel-oil mixture for lubrication, while four stroke engines have a separate oil reservoir

• Two stroke engines produce more pollution due to incomplete combustion, while four s...read more

Wind Turbine Generators (WTG) generate electricity through the conversion of wind energy into mechanical energy and then into electrical energy.

• Wind turns the blades of the turbine

• Blades are connected to a rotor

• Rotor spins a generator to produce electricity

• Electricity is then sent to a transformer for distribution

• Example: Vestas V164-9.5 MW wind turbine

Fluid couplings are used to transmit power from one shaft to another without direct physical contact, allowing for smooth start-ups and overload protection.

• Fluid couplings help in gradual acceleration of heavy machinery, reducing stress on the equipment

• They provide overload protection by slipping when the torque exceeds a certain limit

• Fluid couplings dampen torsional vibrations, reducing wear and tear on the machinery

• T...read more

Gear boxes are used to transmit power from one component to another while changing the speed and torque of the output.

• Gear boxes allow for speed and torque conversion between input and output shafts

• They provide mechanical advantage by increasing or decreasing speed and torque

• Used in various applications such as automobiles, industrial machinery, and power transmission systems

Yes, generator alignment is crucial for efficient operation and preventing damage.

• Generator alignment ensures that the rotating parts are properly positioned to prevent vibration and wear

• Improper alignment can lead to increased maintenance costs and reduced efficiency

• Alignment methods include laser alignment, dial indicators, and alignment jigs

• Regular alignment checks should be performed to ensure optimal performance

• Ex...read more

Various types of gears can be used in a gearbox depending on the application, such as spur gears, helical gears, bevel gears, and worm gears.

• Spur gears are commonly used in applications where simplicity and cost-effectiveness are important.

• Helical gears are used when smooth and quiet operation is required.

• Bevel gears are used to transmit motion between intersecting shafts.

• Worm gears are used for high reduction ratios a...read more

Aviation lamps are used in wind turbine generators (WTG) for aircraft safety and navigation purposes.

• Aviation lamps help to make the wind turbine visible to aircrafts, reducing the risk of collisions.

• They also aid in navigation by marking the location of the wind turbine for pilots.

• The use of aviation lamps is a regulatory requirement to ensure air traffic safety around wind turbines.

• Different colors of aviation lamps ...read more