AOpen DE7200 Series Betriebsanleitung PDF herunterladen (Seite 14)

INTRODUCTION

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DE-7200VFDCentrifuge

The case is bolted onto the welded steel base assembly, which contains mounting provisions for

the bearing pillow blocks. The base assembly supports the centrifuge components and contains

hollow rubber vibration isolators that engage with centering pins attached to the mounting

platform.

MECHANICAL OPERATION

The centrifuge receives slurry at the liquid discharge end of the machine. For best performance,

the slurry should be screened to 74 microns in vibrating screening machines before being fed to

the centrifuge. The slurry flows through a feed tube into the rotating bowl, where centrifugal force

separates liquid from the solids. Liquid flows out the liquid discharge connection, while solids are

conveyed to the solid discharge where a chute should be installed to receive the material.

G forces produced by the high-speed rotation of the cylindrical bowl separate solids from the feed

slurry. Centrifuge performance is based on three variable factors:

• G force exerted on the fluid - Gravitational force pulling fluid against the outside wall of the

centrifuge

• Retention time in the centrifuge - The longer the slurry remains in the centrifuge the smaller

the particle that can be separated

• Differential speed of conveyor - The faster the conveyor rotates, the wetter the solids and the

more solids that can be discharged

All three factors may be manipulated to alter the liquid and solids discharge. The G force is

adjusted by varying the bowl RPM. Retention time is controlled by adjusting the weir plates on the

liquid bowl head to change the pond depth (liquid level), and the conveyor differential speed

(difference between the bowl and conveyor speeds) may be adjusted on the operator control

panel. Bowl speed and differential speed are adjusted on the operator control panel, which

continuously displays current operating conditions.

All parameters other than pond depth may be changed quickly and easily while the centrifuge is

operating. These adjustments permit the operator to optimize efficiency in response to varying

feed conditions. Another method of altering the discharge results is to change the feed rate. For

best performance, the slurry should be screened to 74 microns in vibrating screen machines

before passing it to the centrifuge for processing.

During centrifuge operation, slurry is pumped through the feed tube into the center of the rotating

conveyor (Figure 1-4), where it splashes against the feed accelerator. The slurry is accelerated to

the bowl speed and then dispersed out six feed nozzles on the periphery of the conveyor cylinder

into the bowl, which rotates at a slower speed than the conveyor.

As the slurry flows in the channels between the conveyor flights, the heavy particles settle at an

accelerated rate due to the G force imposed by the rotating bowl. Sand particles settle almost

instantly; then the finer, lighter particles settle. Particles that cannot be settled under the present

settings will be discharged with the liquid through the adjustable weirs on the liquid bowl head.

Liquid exiting the liquid bowl head is directed through the liquid discharge outlet.

The settled solids form a cake inside the bowl and are transported by the conveyor toward the

narrow end of the bowl (beach). As the solids travel across the beach, their free liquid film is lost

due to centrifugal squeezing and drainage, and they are discharged at high velocity through the

solid discharge ports on the bowl.

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