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Since then, Zenith has provided pumps for virtually every polymer utilized in the plastics extrusion industry. Over the years, Zenith has continually developed and improved its pump designs to meet the stringent demands made by new polymers and new processes. Zenith Pumps' line of PEP-II polymer extrusion pumps has a unique positive displacement design, which provides consistent, accurate polymer delivery under varying extruder output conditions of pressure, temperature and viscosity. These virtually pulseless gear pumps are the ideal interface between the extruder and the die of extrusion systems, and provide a homogeneous melt at increased throughputs and tighter gauge tolerances. Benefits For years, polymer processors have utilized gear-pump-assisted extrusion to solve critical issues in the diverse plastics industry. The Zenith gear pump optimizes the extrusion process by allowing the screw to melt and homogenize the polymer. As the pump generates the needed pressure, it relieves the extruder of work; therefore, reducing heat from the shear, lowering the torque required, and eliminating surging. All this optimizes the performance of the extruder and offers the following benefits: • Improved Dimensional Stability— Effectively isolates the die from upstream fluctuations. • Controlled Melt Quality—Regulates the extruder back pressure while it reduces residence time, stabilizes the plasticating action, and lowers melt temperature. • Increased Production—Provides very high efficiency regardless of its pressure building requirement. • Reduced Raw Material Usage— Provides a narrower finished product gauge variation. • Eliminates Surging and Screw Beat— Effectively handles problems caused by melt density or extruder parameters. • Increased Extruder Flexibility— Allows varying process conditions such as higher regrind levels, temperatures, pressures, etc. • Crowned Root Gear Design— Reduces shear internal to the pump, lowering the temperature and increasing the production rate per power required. • Streamlined Operation and Start-up— Closed-loop controls provide easy operator interface. • Extended Extruder Life—Reduces work required by the extruder such as pressure and torque. • Lower Operational Costs—Provides a more efficient method of conveying, eliminating material giveaway, and increasing production per pound of extrudate, etc. Specifications Capacities: 0.16 to 750 cc/rev. Operating Speed: 10 - 90 rpm on most extrusion processes depending upon process parameters Differential Pressure: Up to 5,000 psi (345 bar) Body Pressure: 10,000 psi (690 bar). Temperature: To 645° F (340° C), (950° F maximum with special fasteners and seals). Zenith® Pumps and The Extrusion Process ZENITH ELECTRIC PEP-II ZENITH HEAT PLATE ADDITIVE PUMP INJECTION SYSTEM EXTRUDER CHANGER PTP INLET PUMP DISCHARGE PRESSURE TEMPERATURE PRESSURE Zenith Pumps can handle all your extrusion pumping applications including additive injection for on-line compounding of tackifiers, colorants, stabilizers, etc. Design The PEP-II pump is constructed of two gears rotating in mesh within a closely fitted housing that is comprised of three plates. The center, or gear plate, fits closely around the outside diameter of the metering gears and bearings. The front and rear, or cover plates, sandwich the center plate and restrict axial movement of the gears and bearings. In capacities of 5 cc/rev and larger, the driving gear is manufactured integral with the drive shaft, and the driven gear is machined integral with its shaft. In capacities of 3.0 cc/rev and below, the gears are keyed to their respective shafts. In all capacities the shafts are supported by “D” shaped bearings which fit into the center plate. In capacities of 40 cc/rev and above, these bearings are located by two screws which pass through the cover plates. In capacities of 20 cc/rev and below, the bearings are keyed to each other for accurate location. Each cover plate is secured to the center plate by 10 screws (6 screws for below 5 cc/rev). Each side of the center plate has a circular port in the center of a bolt circle for the mounting of adapter flanges that fit the pump to your equiment. Threaded holes are provided on the top and bottom of the center plate for the mounting of heat plates and for the mounting of the pump to its stand. Thermocouple wells (1/8-27 NPT) are located on the body of the pump. A Zenith Rheoseal assembly secured to each cover plate (front cover plate only on 3.0 cc/rev and below) prevents leakage around the shaft, using both dynamic and static types of sealing mechanisms. A Rheoseal consists of a helical groove on the inner diameter, a cooling jacket and a static, backup seal counter bore and gland. These spiral grooves allow the Rheoseal to act as a screw-type pump. As the fluid attempts to leave the gear pump, the shaft's rotary motion forces the fluid into the grooves. This creates a pressure greater than the pressure forcing polymer out of the pump, thus return...