Pumps Page 69 Flashcards
- List EIGHT reasons why a bilge pump may not be able to remove water from an engine-room bilge (8)
• Pipe line is damaged, holed, inducting air
• Suction or discharge valve of pump not opened, or damaged
• Pump damage, seals worn or driving spindle snapped
• Motor not operating, electrical failure, fuses, circuit-breaker or control circuit
• Pump strainer blockage
• Very Viscous medium being pumped
• Insufficient quantity of fluid in bilge well to be pumped
• Another bilge well valve not properly closed
- List EIGHT reasons why a bilge pump may not be able to remove water from an engine-room bilge (8)
• Pipe line is damaged, holed, inducting air
• Suction or discharge valve of pump not opened, or damaged
• Pump damage, seals worn or driving spindle snapped
• Motor not operating, electrical failure, fuses, circuit-breaker or control circuit
• Pump strainer blockage
• Very Viscous medium being pumped
• Insufficient quantity of fluid in bilge well to be pumped
• Another bilge well valve not properly closed
- a) With reference to a gear pump suitable for use with fuel or lubricating oil;
Sketch a cross-section indicating flow of fluid (8)
Pumps are used to increase pressure in system
F.O & L.0 = Gear Pumps
Bilge Water = Screw Pump
Water = Centrifugal Pump
- a) With reference to a gear pump suitable for use with fuel or lubricating oil;
Sketch a cross-section indicating flow of fluid (8)
b) 3. a. Explain the operating principle (8)
• The two toothed wheels shown mesh together and are a close fit in casing. Initially the air or gas is trapped
between each pair of consecutive teeth and the same is dragged along the casing from suction to discharge
side till no more air is left on the suction side. Liquid from the tank will then rise up into the suction line
under atmospheric pressure, subsequently this liquid will now be trapped between each pair of two
consecutive teeth and dragged along the casing into the discharge side and pumping of liquid will commence.
• The two toothed wheels shown mesh together and are a close fit in casing. Initially the air or gas is trapped
between each pair of consecutive teeth and the same is dragged along the casing from suction to discharge
side till no more air is left on the suction side. Liquid from the tank will then rise up into the suction line
under atmospheric pressure, subsequently this liquid will now be trapped between each pair of two
consecutive teeth and dragged along the casing into the discharge side and pumping of liquid will commence.
- With reference to centrifugal pumps
State why the pump can be started with the discharge valve closed (8)
- With reference to centrifugal pumps
State why the pump can be started with the discharge valve closed (8)
• It is not positive displacement
• If it’s a centrifugal pump which would cause no movement of liquid and not over pressurise
• The pump is self-priming
• The starting current is greatly reduced, increasing motor life
• Less stressed is placed upon electrical system due to maximum loading of the pump
State four possible reasons for the pump failing to achieve suction from a double bottom tank (8)
• Strainer or filter blocked
• Insufficient level within tank
• Pump wear-rings and seals damaged
• Pipe-work damaged inducting air
