Pusher

Typical uses. Deliquoring of relatively coarse particulate suspensions where good cake dryness at discharge is required. 

FDS process ratings. 9 C, 7,4,4 (single-stage) 9 C, 8,4,4 (multi-stage). 

Typical particle size and feed concentration range. 40-7000 pm and 10-40% w/w. 

As the open end of a rotating bowl does not have a retaining lip, there is a so-called overflow limit which generally limits solids throughputs to 80 te h  

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The apparatus consists of a tip-position controller, an electrochemical cell with tip, substrate, counter and reference electrodes, a bipotentiostat and a data-acquisition system. The microelectrode tip is held on a piezoelectric pusher, which is mounted on an inchwomi-translator-driven x-y-z tliree-axis stage. This assembly enables the positioning of the tip electrode above the substrate by movement of the inchwomi translator or by application of a high voltage to the pusher via an amplifier. The substrate is attached to the bottom of the electrochemical cell, which is mounted on a vibration-free table [, and ]. A number... 

If, just before the ion beam reaches the ion detector, a pusher electrode is used alongside it to deflect the beam at right angles (orthogonal) to its original direction into the flight tube of a time-of-flight sector (TOP analyzer), the m/z values can be measured by the TOP section. 

The pusher electrode must be operated by placing very short pulses of electric potential on it. The short pulses are required to ensure that all the ions are started at the same time along the TOP analyzer, since the latter must time the flights of the ions very accurately in order to measure m/z values. 

After passing through the hexapoles, the ion beam emerges in front of a pusher electrode built into the end of the TOP analyzer. 

Application of a pulse of high electric potential (about IkV) to the pusher electrode over a period of about 3 psec causes a short section of the ion beam to be detached and accelerated into a TOP analyzer. A positive potential is used to accelerate positively charged ions and vice versa for negative ions. 

The total trajectory of the ions is approximately V-shaped, the top of one leg of the V being the position of the pusher electrode and the top of the other being the position of the ion collector (a microchannel plate detector). 

The TOF analyzer is placed at right angles (orthogonal) to the main ion beam, and therefore the pusher electrode accelerates a short section of this beam at right angles to its original direction. 

The centrifuge is a horizontal basket designed to operate so that the cake formed on the screen is pushed as an increment from the loading end of the basket to the discharge end by a pusher plate operating on a timed cycle. On completion, the nitrocellulose cake is discharged into water in a slurry tub on a lower floor, and purified by conventional procedures. 

Pusher centrifuges require high feed concentrations to enable the formation of a sufficiently rigid cake to transmit the thmst of the piston. The diameters vary from 150 to 1400 mm, the stroke frequency from 20 to 100 strokes per minute, and the soHds handling capacities up to 40 metric tons per hour or more. 

In pusher furnaces, the product (work load) is pushed through the furnace in steps by a hydrauhc or electromechanical mechanism that pushes each load into the furnace, thus pushing all work in the furnace ahead one work space. The walking-beam furnace lifts the work load on a walking beam, advances the load a step, and returns the work to the hearth. The walking beam then returns to its original position (under the hearth) in preparation for the next step. 

At temperatures above 1150°C, alloys used for the hearth or material handling systems in low and medium temperature furnaces lose strength rapidly (2) and temperatures are reached where ceramic refractories are required to support the work. This results in less use of roUer-hearth and belt-type hearths and greater use of pushers or walking-beam designs for continuous furnaces. 

Fig. 4. Drainage of salt crystals in a cylindrical screen pusher-discharge centrifuge (8), where the cake thickness is 3.3 cm, the centrifugal field = 320 U, and the crystals 14 wt % <250 p.m. ( ) Represents moisture in the discharge cake, and (° ) moisture in the cake by material balance with drainage flows line A...

Fig. 17. Multiple-stage pusher centrifuge. Screens 1 and 2 reciprocate with pusher.

Main Seal Body The term seal body makes reference to all rotating pai ts on a pusher seal, excluding shaft packing and seal ring. In many cases it is the chief reason to avoid a particular design for a particular seiwice. 

Shaft-sealing elements can be split up into two groups. The first type may be called pusher-type seals and includes the 0-ring, V-ring, U-cup, and wedge configurations. Figure 10-116 shows some typic pusher-type seals. The second type is the bellow-type seals, which differ from the pusher-type seals in that they form a static seal between themselves and the shaft. 

The pusher-type furnace is relatively free from mechanical problems because all mechanical parts are located outside the hot zone. It employs a roller-conveyor usually and will handle charges weighing considerably more per square meter than a belt-conveyor furnace. Pushers are driven by electric motors, compressed air, or hydraulic systems and can be automatically timed and synchronized with door-... 

In one modification, the pusher plate consists of a conical screen with an angle shghtly greater than the angle of repose of the cake sohds. This accelerates the feed shiny and provides extra area for bulk drainage, permitting operation over a wider range of feed concentrations. 

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