Aux-machinery marine engineering (1).pptx

Marine machinery

1. AUXILIARY MACHINERY 1

2. TYPE OF PUMPS

3. 10. Explains the purpose of an air vessel fitted to the discharge
11. Describe the characteristics of a reciprocating pump referring to:
- Suction Lift
- Priming
- discharge pressure
- vapour , or gas, in the fluid being pumped
12. Explains the principle of rotary displacement pumps.
13. Sketch a single line diagram to show the principle parts of:
- a gear pump
- a rotary vane pump
- a screw displacement pump 14. Questions related to the topic Learning Objectives

4. Explains the purpose of an air vessel fitted to the discharge AIR VESSELS
An air vessel is a closed chamber containing compressed air in the top portion and liquid at the bottom of the chamber.

At the base of the chamber there is an opening through which the liquid may flow into the vessel or out of the vessel.

5. When the liquid enters the air vessel, the air gets compressed further and when the liquid flows out the vessel, the air will expand in the chamber.

6. So overall, the purpose of an air vessel in a pump is to maintain steady pressure and flow of water by providing a cushion of air that helps reduce water hammer effects, controls pressure variations, and increases the overall efficiency of the pump system.

7. -Suction Lift
-Priming
-discharge pressure
- vapour , or gas, in the fluid being pumped Describe the characteristics of a reciprocating pump referring to:

8. Suction Lift:

The suction lift refers to the vertical distance between the liquid source and the pump’s inlet. Reciprocating pumps can achieve a higher suction lift compared to other types of pumps due to their ability to create a strong vacuum in the suction line. However, the actual achievable suction lift is limited by the atmospheric pressure and the vapor pressure of the fluid.

9. Priming:

Reciprocating pumps typically require priming, which means the pump and the suction line must be filled with the fluid before starting. Priming is necessary because the pump needs to displace air or any gas present in the suction line to create the vacuum needed for lifting the fluid. Without proper priming, the pump may fail to operate effectively, leading to issues like cavitation.

10. Discharge Pressure:

Reciprocating pumps are capable of delivering high discharge pressures, making them suitable for applications that require pumping fluids at high pressures. This is because they can generate pressure by trapping a fixed amount of fluid and forcing it through the discharge line. The discharge pressure is generally independent of the flow rate, allowing these pumps to handle a wide range of pressures without significant changes in performance.

11. Vapor or Gas in the Fluid Being Pumped:

The presence of vapor or gas in the fluid can negatively impact the performance of a reciprocating pump. Vapor or gas can cause cavitation, where vapor bubbles collapse violently as they move from the low-pressure side to the high-pressure side, potentially damaging the pump components. Additionally, gas entrainment can reduce the pump’s efficiency since the pump is designed to move liquids, not compressible gases.

12. Sketch a single line diagram to show the principle parts of:
- a gear pump
- a rotary vane pump
- a screw displacement pump

13. Gear Pump Diagram: [Inlet Port]  |Casing|  [Drive Gear]  [Driven Gear]  |Casing|  [Outlet Port] A gear pump is a type of positive displacement pump, where the fluid is moved by the mechanical action of rotating gears.

14. Principal Parts Motor – Power source that drives the pump.
Shaft – Connects the motor to the gears.
Driving Gear – The gear attached to the shaft, driven by the motor.
Driven Gear – The gear meshing with the driving gear; rotates due to the interaction with the driving gear.
Pump Casing – Encloses the gears; where fluid enters and exits.
Inlet Port – Where fluid enters the pump.
Outlet Port – Where fluid exits the pump.

15. Rotary Vane Pump Diagram: [Inlet Port]  |Casing|  [Rotor]  [Vanes]  |Casing|  [Outlet Port] A rotary vane pump is another type of positive displacement pump, which uses vanes mounted on a rotor to move fluid through the pump chamber.

16. Principal Parts of a Rotary Vane Pump: Rotor: Rotates inside the casing, offset from the center.
Vanes: Slide in and out of the rotor, trapping and moving fluid.
Casing: Encloses the rotor and vanes.
Inlet Port: Where fluid enters.
Outlet Port: Where pressurized fluid exits.
Shaft: Connects the rotor to the motor.

17. Screw Displacement Pump (Screw Pump): Diagram: [Inlet Port]  |Casing|  [Drive Screw]  [Driven Screw(s)]  |Casing|  [Outlet Port] A screw displacement pump, or screw pump, is a type of positive displacement pump that uses one or multiple intermeshing screws to move fluid along the axis of the screw.

18. Principal Parts of a Screw Displacement Pump:
Drive Screw (Rotor): This is the main screw that is powered by a motor. It rotates to create fluid movement.

Driven Screw(s): These screws mesh with the drive screw. They rotate in synchronization to move the fluid forward.

Pump Housing (Casing): The outer casing that encloses the screws and forms the chamber through which the fluid flows.

Inlet Port: The opening where the fluid enters the pump. The fluid is drawn into the spaces between the screw threads.

19. Outlet Port: The opening where the fluid exits after being moved along by the rotating screws.

Bearing: Supports the screw shafts and reduces friction, allowing the screws to rotate smoothly.

Shaft Seal: Prevents leakage of the fluid around the rotating shafts.

20. THANK YOU!