Vacuum pumps operating ranges

The pumping speed S of a vacuum pump operating in the rough and medium vacuum range is commonly stated in m h . ... 

The vacuum plate drwer is provided as pari of a closed system. The vacuum dryer has a cylindrical housing and is rated for fiill-vacuum operation (typical pressure range 3-27 kPa absolute). The exhaust vapor is evacuated try a vacuum pump and is passed through a condenser for solvent recovery. There is no purge-gas system required for operation under vacuum. Of special note in the vacuum-drying system... 

If the pump is a filter pump off a high-pressure water supply, its performance will be limited by the temperature of the water because the vapour pressure of water at 10°, 15°, 20° and 25° is 9.2, 12.8, 17.5 and 23.8 mm Hg respectively. The pressure can be measured with an ordinary manometer. For vacuums in the range lO" mm Hg to 10 mm Hg, rotary mechanical pumps (oil pumps) are used and the pressure can be measured with a Vacustat McLeod type gauge. If still higher vacuums are required, for example for high vacuum sublimations, a mercury diffusion pump is suitable. Such a pump can provide a vacuum up to 10" mm Hg. For better efficiencies, the pump can be backed up by a mechanical pump. In all cases, the mercury pump is connected to the distillation apparatus through several traps to remove mercury vapours. These traps may operate by chemical action, for example the use of sodium hydroxide pellets to react with acids, or by condensation, in which case empty tubes cooled in solid carbon dioxide-ethanol or liquid nitrogen (contained in wide-mouthed Dewar flasks) are used. 

Mechanical separations, 224 Mechanical vacuum systems, 342 Applications, 352, 353 Barometric iniercondenser, 349 Evacuation times, 387 Operating range, 355 Performance curves, 386 Pump down, 380... 

Vacuum capacities and operating ranges, table, 344, 355 Ejectors, 344, 357 Integrated systems, 344 Liquid ring pumps, 344 Rotary lobe blowers, 344 Rotary piston pumps, 344 Rotary vane pumps, 344 Vacuum equipment, 343 Applications diagram, 352 ASME Code, 344 Pumps, 382 Steam jets, 357 Vacuum flow,... 

In the case of operations ranging between 760 and 10 3 torr, the two-stage rotary pump is adequate. Ultimate vacuum, using the diffusion pump installation, is better than 10-6 torr. 

The chemical Industry requires vacuum pumps which are highly reliable and which do not produce waste materials such as contaminated waste oil or waste water. If this can be done, the operating costs of such a vacuum pump are low in view of the measures otherwise required for protecting the environment (disposal of waste oil and water, for example). For operation of the simple and rugged ALL-ex pump from LEYBOLD there are no restrictions as to the vapor flow or the pressure range during continuous operation. The ALL-ex may be operated within the entire pressure range from 5 to 1000 mbar without restrictions. 

A vacuum up to 10 mmHg can be produced by a rotary (or mechanical) pump. Steam-jet pumps operate within the range from 10- ... 

Vacuum pumps produce subatmospheric pressures in process equipment. Often they are compressors operating in reverse but other devices also are employed. Operating ranges of some commercial equipment are stated in Table 7.3. 

There are numerous designs for vacuum electrochemical cells, ranging from very simple to extremely complex. In operation, the vacuum electrochemical cell parts are first cleaned, washed with solvent, and dried in an oven at 200°C. The hot cell parts should then be quickly assembled and evacuated on the vacuum line for several hours or overnight. Once the electrochemical cell has been pumped down, it should be closed off and transferred to a dry box, where the air-sensitive sample and the electrolyte can be added to it. Alternatively, the solid electrolyte could be added into the electrochemical cell before assembly. 

Since APCI and ESI interfaces operate at atmospheric pressure and do not depend upon vacuum pumps to remove solvent vapor, they are compatible with a wide range of HPLC flow rates. HPLC methods that have been developed using conventional detectors such as UV/VIS, IR, or fluorescence are usually transferable to LC/MS systems without adjustment. However, the solvent system should contain only volatile solvents, buffers, or ion-pair agents to reduce fouling of the mass spectrometer ion source. In the case of chlorophyll solvent systems, isocratic and gradient combinations of methanol, acetonitrile, water, acetone, and/or ethyl acetate have been used for APCI or ESI LC/MS. Unlike continuous-flow FAB/LSIMS, no sample matrix is necessary. 

Then such a system can be operated at one base pressure, which due to the small volume of the device can be generated by a small vacuum pump. Since a wide range... 

In this chapter, those pumps that are frequently encountered throughout the range of vacuum pressures are dealt with (see Table 3.1). Where necessary, to support the calculations, the operating principles and pump characteristics are reviewed. With gas-transfer pumps operating in the HV/UHV range (typically diffusion or turbomolecular pumps), continuous operation of backing (forevacuum) pumps is required for efficient performance. In such cases, the combination is considered. 

Chapter 3 summarised initially the various types of vacuum pump available and the pressure ranges in which they normally operate. Subsequent sections dealt specifically with types of pump and, in some cases, to support calculations, reviewed the operating principles and characteristics. For example, aspects of oil-sealed rotary pump operation were discussed (Examples 3.1-3.5) and Roots pumps, widely used in applications where large gas loads at pressures in the rough-medium range have to be handled, were examined (Examples 3.7-3.9). 

The pump set on a vacuum system has to evacuate the system, starting from atmospheric pressure down to the required pressure, often in a given time. It must be able to maintain this pressure during operation of the vacuum process. Chapter 3 reviews the range of vacuum pumps available and the combinations that are used over the range from atmospheric pressure down to our current limits of measurement in the EHV range. 

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