Geared pumps

Dry Spinning. On a worldwide basis, about 90% of all spandex fibers are produced by various adaptations of dry spinning (15,16). The solution dry spinning process is illustrated in Figure 5. The polymer spinning solution is metered at a constant temperature by a precision gear pump... 

Rota.ry Lobe Pumps. Rotary lobe pumps are similar to gear pumps in principle. These pumps have an added advantage of noncontacting metal parts by use of external gears, which reduces the wear, but adds complexity. Low wear and improved shear characteristics make these pumps apphcable to the food industry, where cleanliness and absence of contamination are required. These pumps produce a strong pulsing flow that must be addressed. 

There are many suppHers of urethane systems in the United States. The TSE Company suppHes the mbber form many companies supply the prepolymer forms. It is estimated that close to 68,000 t of these mbbers are used in the United States if aU forms are included. Uses include sport wheels (roUer blades, ski wheels) printing, paper, and steel processing roUs gears pump liners appHance components and soHd industrial tires. 

After the SO converter has stabilized, the 6—7% SO gas stream can be further diluted with dry air, I, to provide the SO reaction gas at a prescribed concentration, ca 4 vol % for LAB sulfonation and ca 2.5% for alcohol ethoxylate sulfation. The molten sulfur is accurately measured and controlled by mass flow meters. The organic feedstock is also accurately controlled by mass flow meters and a variable speed-driven gear pump. The high velocity SO reaction gas and organic feedstock are introduced into the top of the sulfonation reactor,, in cocurrent downward flow where the reaction product and gas are separated in a cyclone separator, K, then pumped to a cooler, L, and circulated back into a quench cooling reservoir at the base of the reactor, unique to Chemithon concentric reactor systems. The gas stream from the cyclone separator, M, is sent to an electrostatic precipitator (ESP), N, which removes entrained acidic organics, and then sent to the packed tower, H, where SO2 and any SO traces are adsorbed in a dilute NaOH solution and finally vented, O. Even a 99% conversion of SO2 to SO contributes ca 500 ppm SO2 to the effluent gas. 

Screw Pumps A modification of the helical gear pump is the screw pump. Both gear and screw pumps are positive displacement... 

Collection and analysis of vibration signatures is a complex procedure. By looking at a vibration spectrum, one can identify which components of the pump system are responsible for a particular frequency component. Comparison of vibration signatures at periodic intervals reveals if a particular component is deteriorating. The following example illustrates evaluation of the frequency composition of an electric motor gear pump system. 

An ideal vibration spectra for this motor-gear pump assembly would appear as shown in Fig. 10-62. 

F-G F Thermoforming, injection, blow, rotational and extrusion molds Business machine and camera housings, blowers, bearings, gears, pump impellers... 

Mnciple materials and the same between material and screw case of single screw extruder on gear pump principle... 

Exiernal Gear Pump Internal Gear Pump Three-Lobe Pump Discharge... 

Figure 3-65B. Typical rotary gear pump. (By permission. Viking Pump, Inc., Unit of Idex Corporation.)...

Trent, A. W., Metering tvith Gear Pumps, Chem. Engineering, Jan. 20, 1975, p. 107. 

McKelvey, J. M., U. Naire, and F. Haupt, Flow Gear Pumps and Screw Pumps Perform in Polymer-Processing Applications, Chem. Eng., V. 83, No. 20, 1976. 

Figure 3-58. Gear pump (double rotor type) [17],...

Since discrete quantities are trapped and transferred, the delivery pressure and flow varies, as shown in Figure 32.21, which also illustrates how increasing the number of cylinders in a reciprocating pump reduces fluctuations. In the case of lobe and gear pumps the fluctuations are minimized by speed of rotation and increasing tooth number, but where, for control or process reasons, the ripple in pressure is still excessive, means of damping pulsations has to be fitted. Often a damper to cope with this and pressure pulses due to valve closure is fitted, and two types are shown in Figure 32.22. 

The screw compressor can be visualized as a development of the gear pump. For gas pumping, the rotor shapes are modified to give maximum swept volume and no clearance volume where the rotors mesh together, and the pitch of the helix is such that the inlet and outlet ports can be arranged at the ends instead of at the side. The solid portions of the screws slide over the gas ports to separate one stroke from the next, so that no extra inlet or outlet valves are needed. 

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