casting of the centrifugal pump
casting of the centrifugal pump
The pump casing creates the first resistance. The liquid decelerates still more in the discharge nozzle, where its velocity is converted to pressure
Casings are generally either volute or circular.
A volute is a curved
funnel that increases in size to the discharge port. As its size increases, the
volute reduces the speed of the liquid and increases the output
pressure.
This helps to balance hydraulic pressure on the shaft; however,
running volute-style pumps at slow speeds puts undue stress on the shaft, which
in turn increases wear-and-tear on the seals and bearings, as well as on the
shaft itself.
Volute casings build a higher head, but circular casings
are generally used on higher capacity pumps. Circular casings have stationary
diffusion vanes around the impeller that convert velocity energy to pressure
energy. Diffusers are typically used in multi-stage pumps.
Casings are
either solid or split.
In a solid casings design the entire casing is in
one piece. Split casings are made of two or more parts fastened together, split
either horizontally (axially split), or vertically (radially split). Wear rings
seal the casing from the impeller.
Suction and discharge nozzles are
built into the casings. They are typically made in one of the following
ways:
-
End suction/Top discharge. The discharge nozzle is perpendicular to the shaft.
-
Side suction / Side discharge. Both nozzles are perpendicular to the shaft. This pump can have either an axially or radially split case type.
The space between the shaft and casing is called the chamber.
If a
mechanical seal is used in the pump, the chamber is commonly referred to as a
Seal Chamber.
If packing is used to form the seal, the chamber is
referred to as a Stuffing Box.
Both the seal chamber and the stuffing box
protect the pump against leakage where the shaft passes through the casing. They
also maintain proper temperature control.
An adjustable gland helps the
packing or the seal fit properly on the shaft sleeve. The throat or throttle
bushing forms a close clearance around the sleeve. An internal circulating
device (pumping ring) circulates fluid through a cooler or reservoir.
More products of pumps
2012-06-05
