Rear hub

To the rearmost end of the beach is fitted the bowl s rear hub. There are a number of possible configurations involving these two components, to... 

The cake discharges at the rear of the beach, between the beach proper and the rear hub. In its simplest form, the cake discharge will he a series of radial holes around the beach end. These holes will usually be lined with some form of erosion protection, quite often in the form of a sintered tungsten carbide... 

In some old designs a beach is not used at all. A simple flat rear hub is used with cake discharge holes. The conveyor is tapered as if there were a beach, and the cake then forms its own beach. This design can work reasonably well with stiff cohesive cakes, but very high conveyor torques can result. 

The precise design of the rear hub will vary from decanter to decanter and from manufacturer to manufacturer. There will be variations according to the method of lubrication of the rear conveyor bearing. The bowl design speed and the type of bearings used will affect the detailed design. These details will not affect process performance. 

In some applications it is found necessary to surround the cake discharge area with a stationary collector, fixed to the casing, to prevent cake sticking to the main casing. The function of the collector is assisted by impellers, which are bolted to the outer surface of the beach and/or the rear hub. The impellers sweep clean the inside of the collector, although they also add to the noise level of the decanter. 

The conveying action can induce a large axial thrust towards the end of the bowl opposite to the beach. On the larger horizontal decanters. Alfa Laval employs a tension bar on the conveyor to counterbalance this thrust and take off the load that could be placed on the front bowl hub. The tension bar consists of a substantial hollow bar bolted to the rear face of the conveyor. It projects through the spindle of the rear hub and is locked in position with a large nut outboard of the spindle. The hollow centre affords access for the feed tube. 

At the rear hub there is a finite clearance between the hub and the end of the conveyor. Depending upon the precise design, this clearance can be quite large. The reaction of the conveyor can shift the conveyor forward a further... 

In this dead area, between the end of the conveyor and the inside face of the rear hub, cake can build up and become very compacted and eventually cause considerable wear. To combat this problem a small flight with negative pitch is often welded 180° from the main flight end. This not only scrolls cake back into the path of the main flight, but also serves to counterbalance the non-symmetry of a single lead helical flight. 

A more elaborate form of pigeon (b) is made by procuring a frame as shown. This consists of a vertical wheel frame with a heavy slotted hub. A row of 4 wheel cas are faSiened to the rim and four I lb. rockets sre secured to the long slots in hub, two pointing each wsy. The pigeon Starts with one of the wheel cases, the rear end of which is conne fted to one of the rockets. This in turn is matched to the second wheel case and that to the next rocket, poinbng in the opposite direction. 

In reverse-Gear position, the drive of transmission is sent to the clutch hub through the input shaft and rear clutch piston. In this condition, the description of each function unit of transmission is shown as follows ... 

Take out the retainer which fix the clutch C3 hub on the rear end of clutch cylinder, then take out the hub. 

Hub It is the portion immediately behind the flight that prevents the escape of the plastic. A sealing device is used to prevent leakage of plastic back around the screw hub, usually attached to the rear of the feed section. 

The co-current flow conveyor will have its feed zone at the front (large diameter) end and some return channels will be built into the conveyor hub to lead the clarified centrate from the foot of the beach back to the front hub. between the exit ports of the feed zone. The countercurrent conveyor has its feed zone in the conveyor but abreast of the foot of the beach. Clarified liquor is free to flow around or through the conveyor flights to the front hub while the cake is scrolled to the rear, and up the beach. 

STEP 18 Inspect Left Rear Tractor Area Wheels, Rims, Hubs and Tires... 

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