Case study

Question 1

3-Phase Motor

Answer 1

An electric motor that operates on three alternating currents, each out of phase by 120 degrees, providing a rotating magnetic field.
Generally more efficient than single-phase motors, with a smoother power delivery and higher torque.
Used in industrial applications - requires 3-Phase power supply

Question 2

Single-Phase Motor

Answer 2

An electric motor that operates on a single alternating current, creating an oscillating magnetic field rather than a rotating one.
Less efficient than 3-phase motors, with a pulsating torque that can lead to vibrations and less smooth operation.

Question 3

Open Electric Motor

Answer 3

An electric motor with openings in its housing, allowing air to freely flow through and cool the motor.
Vulnerable to dust, moisture, and other contaminants

Question 4

Closed Electric Motor

Answer 4

An electric motor with a sealed or enclosed housing that prevents external elements from entering. Protected against contaminants, moisture, and harsh environments.
Less effective cooling

Question 5

Packed Gland Seal

Answer 5

Commonly used in low to moderate-pressure pumps, mixers, and valves, especially in older or simpler systems.
Advantages: Simple design, easy to install, cost-effective, and relatively easy to maintain.
Limitations: Requires frequent maintenance and adjustment to prevent leakage (LEAKS TO LUBRICATE FIBRES); friction between packing and shaft can lead to wear and energy loss.

Question 6

Mechanical Seal

Answer 6

A sealing system consisting of two flat, smooth seal faces (typically one rotating and one stationary), which are pressed together to prevent leakage between a rotating shaft and the housing.
Advantages: Low leakage, less friction and wear on the shaft, longer service life, and less frequent maintenance.
Limitations: More complex and costly than packed gland seals; installation and repair require specialized knowledge.

Question 7

Rigid Coupling

Answer 7

A type of coupling that connects two shafts with no allowance for misalignment.
Advantages: Strong and straightforward design, suitable for applications where alignment is perfect.
Limitations: Cannot accommodate misalignment or absorb vibrations, which can lead to excessive wear on components.

Question 8

Flexible Coupling

Answer 8

A coupling that allows for slight misalignment and can absorb vibrations between two shafts.
Applications: Ideal for applications where slight misalignment or shock absorption is required, such as in pumps and compressors.
Advantages: Reduces wear on components by accommodating misalignment and absorbing shocks.
Limitations: May be more complex and costly than rigid couplings, with lower torque capacity in some designs.

Question 9

Centrifugal Pump

Answer 9

Uses rotating impeller to move fluid - converting rotational kinetic energy to hydrodynamic energy
Advantages: Simple design, high flow rate, low maintenance, and cost-effective.
Limitations: Not suitable for high-viscosity fluids or applications requiring very high pressures.

Question 10

Positive Displacement Pump

Answer 10

Moves fluid by trapping fixed amount and forcing it through discharge.
Advantages: Can handle high-viscosity fluids, precise flow control, and self-priming.
Limitations: Typically produces a lower flow rate than centrifugal pumps and can be more complex and costly.