Vacuum pumps sizing

Adjustment may also be required for differences in altitude between the test site and the commercial installation. In general terms, if the plant elevation is higher, the vacuum pump size must be increased, and conversely. 

Dry vacuum pump size for usual discharge pressure 20-35 kPa gauge to allow for downstream discharge. Vacuum pumps run hot 50-70 °C. Allow 30 min warmup period before putting on-line. Allow 60 min purge before shutdown. Try not to have the pump discharge into a common header. Multistage pumps... 

Hafnium hydride is brittle and easily cmshed to very fine particle sizes. It is usually produced as an intermediate in the process of making hafnium powder from massive hafnium metal. The hydrogen can be removed by high vacuum pumping above 600°C. 

Capillary Suction Processes. The force needed to remove water from capillaries increases proportionately with a decrease in capillary radius, exceeding 1400 kPa (200 psi) in a 1-p.m-diameter capillary. Some attempts have been made to use this force as a way to dewater sludges and cakes by providing smaller dry capillaries to suck up the water (27). Sectors of a vacuum filter have been made of microporous ceramic, which conducts the moisture from the cake into the sector and removes the water on the inside by vacuum. Pore size is sufficiently small that the difference in pressure during vacuum is insufficient to displace water from the sector material, thus allowing a smaller vacuum pump to be effective (126). 

The te.st is carried out by using an apparatus shown in Figure 11.8, consisting of a closed test chamber in which talcum powder can pass through a sieve having square openings of 75 fim, and is held in suspension by an air current. The amount of talcum powder is supplied at 2 kg per cubic metre size of the test chamber. The enclosure under lest is placed inside the chamber and is connected to a vacuum pump which maintains, inside the enclosure, a differential pressure equivalent to not more than a 200 mm eolumn of water. 

In order to estimate an acceptable air inleakage rate for sizing a vacuum pump for use in the medium to high vacuum system, consider ... 

Capacity of the vacuum pump at the working vacuum Example Vessel size = 200 ft ... 

Although the thermal efficiencies of various mechanical vacuum pumps and even steam jet ejectors vary with each manufacturer s design and even size, the curves of Figure 6-34 present a reasonable relative relationship between the types of equipment. Steam jets shown are used for surf ace intercondensers with 70°F cooling water. For non-condensing ejectors, the efficiency would be lower. 

Incoming water is sprayed through a packed column, which provides for an enlarged surface area, and aids the release of gases from the thin film of water produced in the packing. Depending on the DA size and design, the applied vacuum is maintained either by vacuum pumps or by stream-jet eductors. 

Into a size 6A porcelain boat (88 X 13 X 10 mm.) is placed 10.0 g. (0.0113 mol) of Ag2ReBr6 (as much as 15 g. may be processed readily), and the boat is positioned near the sealed end of a 25 X 300 mm. Pyrex tube fitted with an inner 29/44 S.T. sleeve joint. The tube is connected to a mechanical vacuum pump (capable of reducing the pressure to ca. 50 p) via either a trap cooled by liquid nitrogen or a trap cooled by a Dry Ice-isopropyl alcohol slush, which is in turn connected to an 11-mm. Vycor combustion tube packed with copper gauze and maintained at 600° by means of a furnace. (Either protective system between the tube and the pump will serve to remove bromine, one of the reaction products.)... 

The number of wells manifolded to an individual pump primarily reflects the depth to groundwater, but is also in part dependent on the pump size. In low-permeability formations, wells are typically pumped dry. As long as the pumps sustain sufficient vacuum to all wells at the intake depth, LNAPL eventually enters the well and is evacuated. In higher-permeability formations, fluid is pumped consistently from each well at a maximum rate. In both low- and high-permeability formations, individual pumps work harder to pump from greater depths. Decreasing... 

The throughput value is important in determining the size of the backing pump in relationship to the size of a high vacuum pump with which it is connected in series in order to ensure that the backing pump will be able to take off the gas moved by the high vacuum pump (see Section 2.32). 

Liquid-Piston Type This type is illustrated in Fig. 10-97. These compressors are offered as single-stage units for pressure differentials up to about 0.52 MPa (75 Ibf/in ) in the smaller sizes and capacities up to 6.8 X 10 mVh (4000 fF/min) when used with a lower pressure differential. Staging is employed for higher pressure differentials. These units have found wide application as vacuum pumps on wet-vacuum service. Inlet and discharge ports are located in the impeller hub. As the vaned impeller rotates, centrifugal force drives the sealing liquid... 

The choice of vacuum pumps for the sample preparation line will depend on the size of its volume and the budget. In general it is advantageous to have somewhat higher pumping speeds available for the vacuum line, but this can well be provided by a conventional oil diffusion pump, which is less expensive than a turbomolecular device, backed again by a rotary pump. 

Approximate particle size Feed solids cone, wt % Filtration rate (9) kg/(m )(hr) Vacuum Pump (9) ... 

Gas flow through the sampling orifice is of interest since its volume rate of flow determines the size of vacuum pumps necessary for the mass spectrometer. In addition, orifice flow behaves as a first-order removal process that can lead to erroneous kinetics if it is too large. The perturbation of flow in the reactor has been discussed in Section IV.B. 

---