Section 2 - Centrifugal Pumps Flashcards
What are the 7 key components of a basic centrifugal pump?
The Casing The Shaft The Suction Flange The Discharge Flange The Shaft Seal The Bearing Housing The impeller.
What is the purpose of a pump casing?
The pump casing supports, and contains the rest of the pump components.
Access to the pump is via a vertical split at the back of the casing.
What is the purpose of the suction flange of a pump?
The suction flange directs liquid entering the pump casing into the impeller.
What is a pump impeller?
A pump impeller imparts the kinetic energy into the liquid.
What is the pump Shaft?
The shaft connects the impeller to the primary driver, or motor, through a coupling.
What is the purpose of the bearing housing?
The bearing housing serves to support the shaft.
What is the purpose of the shaft seal?
The shaft seal prevents liquid escaping from the casing along the shaft.
What are three additionally important, internal components of a basic impeller centrifugal pump?
Wear Rings
The Balance Holes
The Packing
What is the purpose of Impeller Wear rings?
These act as the seal between the high pressure discharge, and low pressure suction of the impeller. These wear in preference to the impeller, acting as protection, and can be replaced when worn.
What is the purpose of balance holes?
The balance holes allow the packing to operate at suction pressure rather than discharge pressure - reducing he DP across the packer and impeller, reducing thrust forces.
What is the purpose of the packing?
The packing prevents liquid from escaping the casing.
What are the three main impeller types?
Open
Semi Open
Closed
Which is the most expensive impeller design and why?
Closed impellers are the most expensive - due to special techniques which are needed to weld the vanes inside the shroud.
What would you expect as impeller design considerations in low pressure, high capacity systems?
Large Diameter Impeller
Low Impeller Speed
What design characteristics would you consider with impellers requiring high pressure, high capacity throughout?
Small diameter impeller, with high rotating speed.
What shape is a single volume centrifugal pump?
This pump takes the shape of an upside down comma, or at operator.
How does a single volute pump impart pressure energy?
Liquid is thrown into a channel where it is slowed down. The channel has an increasing area of cross section. This is designed to capture maximum energy transfer, and forces the fluid toward the discharge flange.
How does a diffuser casing generate pressure?
The liquid leaves the tips of the impeller and moves through a set of Angled vanes - diffusers - these guide the fluid into the outer casing, decreasing velocity and increasing pressure energy.
What is the purpose of the discharge flange?
The discharge flange directs the liquid away from the pump as it exits the casing.
What is thrust force?
Thrust force is force directed along the axis of the pump shaft - arising because of the differences in pressure between the discharge and suction side of the impeller.
How does the thrust bearing operate?
It’s mounted between two vertical plates, allowing the shaft to turn with a minimum of friction as it takes up this thrust force.
What are slinger rings?
The slinger rings are two slender rings, often of brass, which slide up and down the shaft as it rotates. The slinger rings dip into the lubricating oil and centrifugal forces through the lube oil outward and cool the bearing faces and lubricate them.
In a packed seal, what are the main components?
Packing
Packing follower
Lantern Ring
What is the purpose of a lantern ring?
A lantern ring is fitted between sections of packing, so that any liquid which has been leaked along the shaft, can be removed.
