Pumps generally

Fortified rosin can also be converted to high free-rosin emulsions by using various stabilizers. Typically, these are 35% soHds emulsions, which exhibit exceUent stabiHty in relation to storage and mechanical action, such as is found in transfer pumps. Generally, fortified rosin emulsions are more efficient sizes than their soap-based Hquid or paste counterparts. 

Tests conducted to operate centrifugal pumps as hydrauhc turbines throughout the head-capacity-speed range show that a good centrifugal pump generally makes an efficient hydraulic turbine. From theoretical considerations it is possible to state that at the same speed... 

Surface finish of internal surfaces - Kffieicney inerea,ses from better surface finishes are mostly attributable to the specific speed Ns (discussed in Chapter 6) of the pump. Generally, the improvements in surface finishes are economically justifiable in pumps with low specific speeds. 

Assume a velocity, v, ft/sec consistent with Figure 2-46. Use Table 2-21 for short, direct connected connections to the vacuum pump. Base the final specifications for the line on pump specifications. Also the diameter of the line should match the inlet connection for the pump. General good practice indicates that velocities of 100 to 200 ft/sec are used, w ith 300 to 400 ft/sec being the upper limit for the rough vacuum classification. 

Condensate pumps generally deliver CR either to a deaerator or to a FW tank (ideally in an uncontaminated condition). The condensate pumps are controlled by a regulator similar to a FW regulator and may be adjusted by reference to the condensate level as seen through a condensate tank sight glass. 

At the beginning of a pump down process, the gas ballast pump should always be operated with the gas ballast valve open. In almost all cases a thin layer of water will be present on the wall of a vessel, which only evaporates gradually. In order to attain low ultimate pressures the gas ballast valve should only be closed after the vapor has been pumped out. LEYBOLD pumps generally offer a water vapor tolerance of between 33 and 66 mbar. Two-stage pumps may offer other levels of water vapor tolerance corresponding to the compression ratio between their stages -provided they have pumping chamber of different sizes. 

Vane pumps generally have good efficiency and durability. They are effective within a wide pressure range, displacement volume, and speed. A typical vane pump is shown in FIGURE 9-4. 

The mechanical fore pump is a heavy item which sets up considerable vibration. This vibration disrupts the menisci of mercury manometers and is otherwise undesirable. To minimize the transfer of vibrations to the vacuum line, the fore pump generally is mounted on the floor (rather than on the bench of the vacuum rack) and the connection between the fore pump and the vacuum system is made with heavy-walled vacuum tubing or flexible corrugated metal tubing. 

C. Diffusion Pump Design and Operation. The pumping speed of a two-stage mechanical pump generally drops very rapidly below 10 J torr. By contrast, Fig. 6.3 shows that a typical diffusion pump has good pumping speed below this pressure. Therefore, a tandem arrangement of a diffusion pump with a... 

Efficiency of heat pumping—generally decreases with... 

For gas-transfer pumps generally, the compression ratio (k) can be defined as ... 

Stommel and Farmer (1952) showed that the partitioning of flow at the mouths of estuaries results in higher salinities during flood than ebb flow this will produce a net salt flux in the landward direction. Tidal pumping generally results from a correlation between... 

Liquids are usually moved by pumps, generally rotating equipment The same equations apply to adiabatic pumps as to adiabatic compressors. Thus, Eqs. (7.25) through (7.27) and (7.29) are valid. However, application of Eq. (7.26) for the calculation of = —Aff requires values of the enthalpy of compressed liquids, and these are seldom available. The fundamental property relation, Eq. (6.8), provides an alternative. For an isentropic process,... 

Pumps general purpose centrifugal (single and two stage, single suction). Price includes pump, steel base, and coupling, but no motor. Small numbers... 

In this situation, if the pressure filtration stays unchanged, the filtrate rate will decrease with time. When unacceptable values of the filtrate rate are reached, the process must be stopped and the membrane cleaned or replaced. This mode of operation is uneconomical. One solution to this problem is to increase the transmembrane pressure in order to maintain the flow rate but, in this case, the pumping flow rate has to be reduced because pumps generally present a pre-established and characteristic flow rate-pressure relation which is, a priori, unchangeable. Consequently, when the pressure is continuously increased, the clogging rate will increase faster than when a high tangential velocity is used in the unit. 

For instance, when the plasma polymerization of a hydrocarbon is carried out in a flow system that has a liquid N2 trap, an increase in system pressure due to plasma polymerization is observed because the liquid N2 trap cannot trap the H2 produced and the pumping-out rate of the system drastically decreases for the product gas. However, when the same plasma polymerization is carried out without a liquid N2 trap (in this case the initial pressure of the system is much higher than in the previous case), a decrease in system pressure due to plasma polymerization is observed because a mechanical pump generally pumps H2 faster than a larger organic molecule. 

Efficient high-vacuum pumps generally do not operate well near atmospheric pressure. Thus the vacuum system must have a mechanical vacuum pump to evacuate the system to a pressure where the high-vacuum pumps are effective. Mechanical pumps require routine maintenance, such as ballasting and replacing the pump oil. The diffusion pump is the least expensive and most reliable high-vacuum pump. Turbomolecular pumps and cryopumps are also used on mass analyzers. The high-vacuum pumps also require... 

The structures of F class and V class ion pumps are sIm liar to one another but unrelated to and more complicated than P-class pumps. F- and V-class pumps contain several different transmembrane and cytosolic subunits. All known V and F pumps transport only protons. In a process that does not Involve a phosphoprotein Intermediate. V-class pumps generally function to maintain the low pH of plant vacuoles and of lysosomes and other acidic vesicles In animal cells by pumping protons from the cytosolic to the exoplasmic face of the membrane against a proton electrochemical gradient. F-class pumps are found In bacterial plasma membranes and In mitochondria and chloroplasts. In contrast to V pumps, they generally function to power the synthesis of ATP from ADP and Pj by movement of protons from the exoplasmic to the cytosolic face of the membrane down the proton electrochemical gradient. Because of their Importance In ATP synthesis in chloroplasts and mitochondria, F-class proton pumps, commonly called ATP synthases, are treated separately In Chapter 8. 

The pumps generally have a capacity of 100 ml for a full pump stroke. The sample volume taken can be controlled by the number of pump strokes taken for each tube. Pumps must be properly maintained and procedures for leak testing and for measuring the volume and flow rate can be obtained from the manufacturers. The volume of the pump should be accurate to 5 % of the value stated. Detector tubes made by one manufacturer should not be used with a pump made by a different manufacturer since the pumps have different flow characteristics and could cause different lengths of stain. Each lot of detector tubes is calibrated by the manufacturer using his specific pump design. 

Pump mix- Special concrete that will be used in a concrete pump. Generally, the mix has smaller rock aggregate than regular mix. 

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