Pumps rotary

These pumps are low in cost, require small space, and are self priming. 

Some can be rotated in either direction, have close clearances, require over-pressure relief protection on discharge due to positive displacement action, and have low volumetric efficiency [8], 

Flow proportional to speed and almost independent of pressure differential. 

Four-Lobe Pump Sliding Vane Pump 

External Gear Purnp Internal Gear Pump Three-Lobe Pump 

As the rotor turns, the vanes remain in contact with the pump housing forming a moving seal. Pockets of gas, captured at the pump inlet, are swept through the chamber and is compressed as it nears the exhaust outlet thus creating a positive preasure that ejects the gas through the outlet, past a check valve. 

Another problem is that back streaming of the lighter components of the pump oil can contaminate both the ion source and analyzer e.g., contamination in El sources results in the appearance of characteristic hydrocarbon fragments, while contamination of analyzers leads to loss of resolution and sensitivity. 

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The flow of droplets is directed through a small orifice (Skimmer 1 Figure 12.1) and across a small region that is kept under vacuum by rotary pumps. In this region, approximately 90% of solvent and injected helium is removed from the incipient particle beam. Because the rate of diffusion of a substance is inversely proportional to its molecular mass, the lighter helium and solvent molecules diffuse away from the beam and are pumped away. The heavier solute molecules diffuse more slowly and pass through the first skimmer before they have time to leave the beam the solute is accompanied by residual solvent and helium. 

Few of the naturally occurring elements have significant amounts of radioactive isotopes, but there are many artificially produced radioactive species. Mass spectrometry can measure both radioactive and nonradioactive isotope ratios, but there are health and safety issues for the radioactive ones. However, modem isotope instmments are becoming so sensitive that only very small amounts of sample are needed. Where radioactive isotopes are a serious issue, the radioactive hazards can be minimized by using special inlet systems and ion pumps in place of rotary pumps for maintaining a vacuum. For example, mass spectrometry is now used in the analysis of Pu/ Pu ratios. 

In 1840 a hydrauHc power network, which involved large reciprocating pumps that were driven by steam engines, suppHed fluid power to London. However, concurrent technology in steam (qv) turbines and the electric generators outmoded such networks until hydrauHc systems were improved with the use of rotary pumps and oil. The rotary piston pump marked the transition from use of water to oil as the hydrauHc fluid (4). The use of vacuum-distilled, refined mineral oils were instmmental in the success of rotary axial piston pumps and motors such as the Waterbury variable speed gear... 

From the definition of specific speed (eqs. 9 and 10), it follows that reciprocating pumps operate at high pressures and low flow rates. Conversely, centrifugal pumps are appHed at lower pressures and higher flow rates. Many rotary pumps are selected for viscous Hquids having pressures equal to or less than, and capacities lower than, centrifugal pumps. However, these limits are relative and a gray area exists as some pump types cross boundaries into the domain of other types. 

Rotary Pumps In rotary pumps the liquid is displaced by rotation of one or more members within a stationary housing. Because internal clearances, although minute, are a necessity in all but a few special types, capacity decreases somewhat with increasing pump differentia pressure. Therefore, these pumps are not truly positive-displacement pumps. However, for many other reasons they are considered as such. 

FIG. 10-54 Positive-displacement gear-type rotary pump. 

Two vacuum systems are used to provide both the high vacuum needed for the mass spectrometer and the differential pumping required for the interface region. Rotary pumps are used for the interface region. The high vacuum is obtained using diffusion pumps, cryogenic pumps, or turbo pumps. 

Kreisel-pumpe, /. centrifugal pump rotary pump, -rad, n. turbine turbine rotor, turbine impeller, -verdichter, m. turbocompres-sor. 

Wurgelpumpe, /. rotary pump, wurgen, v.t. choke strangle destroy gulp. — v.t. choke retch. 

There are many different types of positive displaee-ment rotary pumps [29] as illustrated in Figure 3-64 and Figures 3-65A, B, C. 

Figure 3-64. Rotary pumps. (By permission, Dolman, R. E., Chemical Engineering, Mar. 1952, p. 159.)...

Suction and discharge heads are determined the same as for centrifugal pumps. Total head and capacity are used in selecting the proper rotary pump from a manufacturer s data or curves. Since viscosity is quite important in the... 

Figure 3-65C. Sliding vane rotary pump. (By permission, Blackmer Pump, Dover Resources Co.)...

S" = Slip, quantity of fluid that leaks through internal clearances of rotary pump per unit time, GPM SpGr = Specific graHty of liquid at pumping temperature referred to water =1.0 s = Stroke, in. 

Classifications 458. General Calculations 461. Reciprocating Pumps 463. Rotary Pumps 468. 

Rotary pumps are classified in two basic groups and several subgroups. These are ... 

In general, rotary pumps with discharge pressure of up to 100 psi are considered low-pressure pumps. Rotary pumps with pressure between 100 and 500 psi are considered moderate-pressure pumps. Pumps with pressure beyond 500 psi are considered to be high-pressure pumps. 

Rotary pumps with volume capacities up to 50 gal/min are considered to be small-volume capacity pumps. Pumps with volume capacities from 50 to 500 gal/min are moderate-volume capacity pumps. And pumps with volume capacities beyond 500 gal/min are large-volume capacity pumps. 

There are several important calculations which are needed to properly evaluate and select the appropriate rotary pump [17]. These calculations are used in conjunction with Equations 3-32-3-37. 

The capacity of a rotary pump operating with zero slip is called displacement capacity, q (gpm). Thus, the actual capacity of a rotary pump q (gpm) is... 

Pump horsepower P is the power actually imparted to the fluid by the rotary pump in Equation 3-32. 

The definitions for the various power terms and efficiencies for the rotary pumps are the same as those discussed above for the reciprocating pump namely. Equations 3-33-3-37. 

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