Paddles, hopper

The negative system usually sucks on a cyclone and/or filter/receiver mounted above the receiving storage hopper or bin. Solids are usually sent down to the hopper with a rotary air lock feeder. Air is sucked into the transfer pipe or duct at the pickup end of the sy.stem. A variety of feeders can be used to introduce solids into the flowing air stream such as rotary air lock feeders, pan-type manifolds under rail car hoppers, paddle-type rail car unloaders, screw conveyors, etc. 

Figure 5.7. A screw conveyor assembly and some of the many kinds of screws in use. (a) Screw conveyor assembly with feed hopper and discharge chute, (b) Standard shape with pitch equal to the diameter, the paddles retard the forward movement and promote mixing, (c) Short pitch suited to transfer of material up inclines of as much as 20°. (d) Cut flight screws combine a moderate mixing action with forward movement, used for light, fine, granular or flaky materials, (e) Ribbon flights are suited to sticky, gummy or viscous substances.

The hopper is usually made of stainless steel and has the shape of a funnel to contain and deliver the product to be compressed. It may be provided with a window for the observation of the product level and may also be provided with low-level sensors that signal an alarm, shut off the engine, or activate the feeding mechanism to deliver the product when it falls below this level. The feeder system usually consists of three sections (in the case of force feeders) and is ideal for press performance at high speed. The first section of a force feeder system is where the hopper is connected and is responsible for the flow of the product from the hopper to the next sections. The second section is where the die cavities are filled to their maximum capacities, and the third section is where the weight control adjustment takes place. These sections contain paddle systems which prevent packing of the product. The... 

Hopper (paddle) oscillates and powder falls into two collectors placed under the hopper (paddle). 

FIGURE 7 Subsampling (a) coning and quartering (b) table sampler [6] (c) oscillating hopper (paddle) sample divider [6] (d) spinning riffler (BSI) (e) riffle/chute splitter (BSI) if) revolving sample splitter [14]. 

In the oscillating hopper sample divider [23] ](Figure 1.29), the feed hopper is pivoted about a horizontal axis so that it can oscillate while emptying. Two collectors are placed under the hopper outlet so that the powder falls into them alternately so that at each step the sample is halved. The contents of one box are retained so that at each step the weight of the sample is halved. The oscillating paddle sample divider (Figure 1.30) works in a similar way. 

It is important to maintain correct levels in the hoppers into which the elevators discharge. Too high a level causes spillage of catalyst, and too low a level results in insufficient pressure in the reactor seal leg. Hoppers in some units are equipped with a continuously rotating vertical shaft with paddles which ride on the surface of the catalyst the position of the upper end of the shaft is communicated to the control room by means of a pneumatic transmitter (185,191). 

In a plant with more than one satarator, individual flow meters should be installed in each feed line to permit manual balancing of the flows. Inserted paddle-type flow meters with local indicators would be suitable for this application. Some saturator designs (Section 1.2.2.2) allow salt to fall into the vessel by gravity from an attached hopper and therefore require no instrumentation. Other systems rely on periodic additions of salt to... 

Star feeders may provide highly uniform withdrawal along a slot hopper opening. They normally comprise six paddles whose ends converse in a common point forming a radial arrangement, or a six-point star when... 

Low shear mixing can be accomplished with anything from a drum tumbler to a variety of planetary mixers. Planetary mixers have low speed screws or paddles that mix the ingredients in the bin or hopper. A charge of no more than 80% of the mixer s capacity is good practice. 

Alternatively, paddle shafts can be installed at the head end of a discharge conveyor for sticky materials such as loam or chalk. With this arrangement the material is, as it were, chopped or sliced off as it emerges from the hopper outlet and is then fed in a uniform layer to the conveyor (Fig. 39). 

Hopper function and operating mechanism. The hopper is main part/ components of the pasting machine. The paste is dropped into the hopper s form cone feeder and by the combined action of rotating paddles and roller. 

Fig. 12.3. Operation principle of (a) a horizontal des-temmer and (b) a vertical centrifugal destemmer. Key (1) hopper (2) shaft with arm and paddles (3) perforated cylinder (4) stem outlet (5) destemmed grape outlet...

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