Pumps Flashcards
What is a dynamic pump?
A pump that uses centrifugal force to spin liquids outwards. Typically used to convey large volumes of fluids
What is pump head?
The pressure the pump has to overcome to move liquid through the system
What is vapour binding?
Formation of vapour in the suction end of the system that prevents liquid flow through the pump (the pump needing to be be primed)
What is cavitation?
When vapour bubbles are transported until they reach an area of high pressure and implode, creating a shockwave which can damage internal pump components
What is slip factor?
The difference in the actual volume of liquid discharged by a pump and it’s theoretical capacity
What is the most common design of pump?
A volute pump
What is the basic operation of a volute pump?
A rotating impeller discharged fluid into a spiral shaped capacity (volute) at high velocity
What is an axial pump?
A pump that moves
Liquid through its casing without changing its direction.
High volume, low pressure pumps
What are two common forms of shaft seals used in pumps?
Compression packing, mechanical seals
What are the 4 basic types of pump casings?
Volute
Double volute
Concentric
Diffuser
What are open and semi open impellers used for?
Severe industrial services
(Slurries, abrasives, chemicals)
What type of impeller is hydraulically balanced?
Double suction impeller. Minimal axial thrust that requires no balancing holes
What is unique about the Francis impeller?
Double curvature veins and heavy construction. Can be up to 10ft diameter
When should wear rings be replaced?
When clearances exceed 3x original clearances
What are common materials of wear rings?
Bronze, chrome steel, cast iron
What do pumps have to reduce axial thrust on impellers?
Wear rings, balancing holes, back pump out vanes, double suction impellers, balancing drums/disks
How do dynamic (non positive displacement pumps) differ from positive displacement pumps?
Dynamic pumps have no seal between suction and discharge sides
What is Specific Gravity?
The ratio of the density of a substance compared to that of water
What is vapour pressure?
Vapour pressure is the pressure a liquid flashes into vapour at a given temperature.
What is the most common centrifugal pump used in industry?
Single stage end suction pump
