Pumps pumping speed

Fig. 2.11 Motor power of a rotary piunger pump (pumping speed 60 mVh) as a function of...

The ratio S( Sy (theoretical pumping speed of the Roots pump / pumping speed of the backing pump) is termed the gradation kj. From (2.15) one obtains... 

The maximum permissible backing pressure (the critical backing pressure, pcrit) for a diffusion pump (pumping speed = Seff Dp) is 2 x 10 l mbar. If the pump is used only at inlet pressures (/ in) of 10 3mbar or below, calculate the speed of the backing pump (Sback) in terms of Seff DP. 

The insulation space was evacuated with a 4-in. oil diffusion pump model NRC-0121 and reinforced with an NRC-6S rotary pump. Pumping speed was sufficient to permit full evacuation to less than 10 Hg within an 8-hr period with the assumption of a vacuum-tight system. 

The theoretical Roots pump pumping speed is taken to be 1000 m h . ... 

Pumi cites B. pumilis Pummel test Pummerer reactions Pumpingnumber Pumpingnumbers Pumping speed Pumpkin... 

A small (25-kg), portable apheresis system, available in 1993, is designed to meet a wide variety of blood cell separation needs. The role of the apheresis system is to control the behavior, separation, and collection of blood components from the bowl while maintaining maximum donor safety. The system controls the flow rates of blood and components through variable pump speeds. It directs the flow of components out of the bowl, by fully automatic opening and closing of valves based on the output of the system sensors. The system monitors the separation of blood components in the bowl by an optics system that aims at the shoulder of the bowl. A sensor on the effluent line monitors the flow of components out of the bowl. 

DP Speed Factor. Pumping-speed efficiency depends on trap, valve, and system design. For gases having velocities close to the molecular velocity of the DP top jet, system-area utilization factors of 0.24 are the maximum that can be anticipated eg, less than one quarter of the molecules entering the system can be pumped away where the entrance area is the same as the cross-sectional area above the top jet (see Fig. 4). The system speed factor can be quoted together with the rate of contamination from the pump set. Utilization factors of <0.1 for N2 are common. 

Vacuum flow is usually described with flow variables different from those used for normal pressures, which often leads to confusion. Pumping speed S is the actual volumetric flow rate of gas through a flow cross section. Throughput Q is the product of pumping speed and absolute pressure. In the SI system, Q has units of Pa m vs. 

For a vacuum pump of speed withdrawing from a vacuum vessel through a connecting line of conductance C, the pumping speed at the vessel is... 

Practically, the NPSH required for operation without cavitation and vibration in the pump is somewhat greater than the theoretical. The actual (NPSH)r depends on the characteristics of the liquid, the total head, the pump speed, the capacity, and impeller design. Any suction condition which reduces (NPSH ) below that required to prevent cavitation at the desired capacity will produce an unsatisfactoiy installation and can lead to mechanical dimculty. 

As the mechanical integrity of the pump system changes, the amplitude of vibration levels change. In some cases, in order to identify the source of vibration, pump speed may have to be varied, as these problems are frequency- or resonance-dependent. Pump impeller imbalance and cavitation are related to this category. Table 10-11 classifies different types of pump-related problems, their possible causes and corrective actions. 

Equation (18-36) is the general expression for impeller-induced nucleation. In a fixed-geometry system in which only the speed of the circulating pump is changed and in which the flow is roughly proportional to the pump speed, Eq. (18-36) may be satisfactorily replaced with... 

The pump operates until the system temperature is normal and then the pump speeds up and cavitates. 

Erratic pump speed. Pump changes speed every few minutes. 

Agitator or pump speed and power, whieh are determined by partiele size and suspension density. 

Buffer citric acid (40g/L) 80mL 2L Buffer Pump Speed 400 Vditage 200V stepped Average Current 150.5mA Sample piperoxan (0.125 mgth) Sample Pump Speed 100... 

Buffer 1.5g SCO citric acid 40g/L) SOmL 2L Buffer Pump Speed 400 Voltage 200V stepped Average Current 186mA Sample piperoxan (0.25 mgml )... 

Normal electric motor speeds run from the standard induction speeds for direct connection of 3600, 1800 and 1200 rpm to the lower speed standards of the synchronous motors, and then to the somewhat arbitrary speeds established by V-belt or gear drives. For some cases, the pump speed is set by the type of drivers available, such as a gasoline engine. 

When the Imer is rotated past the no flow" point, the volume above the rotor exceeds that below, and net flow reverses direction even though pump speed and rotation have not changed (Limited to approx 30 cof lull forward How on all models)... 

Discharge pressure of pump, psia = Intake pressure of pump Mth closed intake, psia = Final pressure in system, in. Hg abs Gas constant, = 1544/mol weight Pump speed, revolutions (or strokes) per second Pump speed, liters/sec Pump speed at P ", liters/sec Pump speed at P/, liters/sec Temperature, °R = 460 + °F Evacuation pump dowmtime, min Evacuation pump downtime, sec Ambient air temperature, °F Temperature of mixture at ejector suction, °F Temperature of steam on downstream side of nozzle, °F... 

Step 1. The well is circulated at half the normal pump speed while keeping the drillpipe pressure constant (see Figure 4-352a). This is accomplished by adjusting the choke on the mud line so that the bottomhole pressure is constant and above the formation fluid pressure. To maintain a constant bottomhole pressure the formation fluid is allowed to expand, which usually results in a noticeable increase in casing pressure. This step is completed when the formation fluid is out of the hole. At this time casing pressure should be equal to the initial SIDPP if the well could be shut in. 

Phase 3. The formation fluid is circulated out of the hole while heavier mud fills the annulus. Again the choke operator maintains the drillpipe pressure constant and constant pumping speed. 

If the constant speed characteristic of a pump is superimposed on a system curve, there is usually one intersection point, shown in Figure 32.39. If a flat system curve is being matched with a mixed or axial flow machine there can be flow instability, as illustrated in Figure 32.40, which is only corrected by changing pump speed or the static lift, or selecting a different pump. 

Since changes in pump speed affect volumetric output, some pumps are rated by their displacement. Pump displacement is the amount of fluid the pump can deliver per cycle or complete rotation. Since most pumps use a rotary drive, displacement is usually expressed in terms of cubic inches per revolution. 

The reason for speed variations in constant-speed machinery is variation of process load. For example, a centrifugal pump s load will vary due to the viscosity of the fluid being pumped or changes in suction or discharge pressure. The pump speed will change because of these load changes. 

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