Vacuum system, operation

Lower pressure drop for vacuum systems Allows for better low pressure and vacuum system operation and lower bottoms temperature, with less degradation of bottoms product. 

Starting a vacuum system should include the following trap use procedures for safe and efficient vacuum system operation ... 

Zone 2A hydraulic elevator operation fire detection system operation fire suppression system operability process vacuum system operation standby electrical power system operation ... 

It was detemtined that a 97 percent reduction in emissions would result from switching from an existing solvent cleaning machine to a vacuum-to-vacuum cleaning machine. This determination came from data taken from Vacuum to Vacuum systems operating in the field for over 10 years. Units have now been in the field for over 15 years..."... 

The design of these distillation systems and the operating conditions used depend on the physical properties of the alkylphenols involved and on the product requirements. Essentially all alkylphenol distillation systems operate under vacuum, but the actual pressures maintained vary considerably. Vacuum operation allows reasonable reboder temperatures (200—350°C) so that thermal dealkylation reactions of the alkylphenols are slow. 

A vacuum system can be constmcted that includes a solar panel, ie, a leak-tight, instmmented vessel having a hole through which a gas vacuum pump operates. An approximate steady-state base pressure is estabUshed without test parts. It is assumed that the vessel with the test parts can be pumped down to the base pressure. The chamber is said to have an altitude potential corresponding to the height from the surface of the earth where the gas concentration is estimated to have the same approximate value as the base pressure of the clean, dry, and empty vacuum vessel. 

J. L. Ryans and D. L. Roper, Process Vacuum System Design and Operation, McGraw-HiU, Inc., New York, 1986. 

Uses of Ejectors For the operating range of steam-jet ejectors in vacuum applications, see the subsection Vacuum Systems. ... 

For materials of moderate to low porosity, a good starting vacuum level is 0.6 to 0.7 bar (18 to 21 in Hg), as the capacity of most vacuum pumps starts to fall off rapidly at vacuum levels higher than 0.67 bar (20 in Hg). Unless there is a critical moisture content which requires the use of higher vacuums, or unless the deposited cake is so impervious that the air rate is extremely low, process economics will favor operation at vacuums below this level. When test work is carried out at an elevation above sea level different than that of the plant, the elevation at the plant should be taken into account when determining the vacuum system capacity for high vacuum levels (>0.5 bar). 

The cost of the filter station includes not only the installed cost of the filter itself but also that of all the accessories dedicated to the filtration operation. Examples are feed pumps and storage facihties, precoat tanks, vacuum systems (often a major cost factor for a vacuum filter station), and compressed-air systems. The dehvered cost of the accessories plus the cost of installation of filter and accessories generally is of the same order of magnitude as the dehvered filter cost and commonly is several times as large. Installation costs, of course, must be estimated with reference to local labor costs and site-specific considerations. 

Vacuum systems are typically used when flows do not exceed 6800 kg/h (15,000 Ib/h), the equivalent conveyor length is less than 305 m (1000 ft), and several points are to be supplied from one source. They are widely used for finely divided materi s. Of special interest are vacuum systems designed for flows under 7.6 kg/min (1000 Ib/h), used to transfer materials short distances from storage bins or bulk containers to process units. This type of conveyor is widely used in plastics and other processing operations where the variety of conditions requires flexibility in choosing pickup devices, power sources, and receivers. Capital investment can be kept low, often in the range of 2000 to 7000. 

Lubricating and seal oil systems cleaned Instrumentation and controls checked Preliminary operation of lubricating and seal oil systems Operation with air Vacuum Equipment Alignment run-in testing Pumps... 

A vacuum system capable of operating at pressures ranging from 10 to 10" Pa... 

Electron spectroscopic techniques require vacuums of the order of 10 Pa for their operation. This requirement arises from the extreme surface-specificity of these techniques, mentioned above. With sampling depths of only a few atomic layers, and elemental sensitivities down to 10 atom layers (i. e., one atom of a particular element in 10 other atoms in an atomic layer), the techniques are clearly very sensitive to surface contamination, most of which comes from the residual gases in the vacuum system. According to gas kinetic theory, to have enough time to make a surface-analytical measurement on a surface that has just been prepared or exposed, before contamination from the gas phase interferes, the base pressure should be 10 Pa or lower, that is, in the region of ultrahigh vacuum (UHV). 

A vacuum system typically consists of one or more pumps which are connected to a chamber. The former produces the vacuum, the latter contains whatever apparatus requires the use of the vacuum. In between the two may be various combinations of tubing, fittings and valves. These are required for the system to operate but each introduces other complications such as leaks, additional surface area for outgassing and added resistance to the flow of gas from the chamber to the pumps. Additionally, one or more vacuum gauges are usually connected to the system to monitor pressure. 

Figure 2-46. Typical flow velocities for vacuum lines. Note 1 torr = 1.33 mb = 133.3 Pa. 1.0 ft/sec = 0.3048 m/seo. By permission, Ryans, J. L. and Roper, D. L., Process Vacuum System Design Operation, McGraw-Hill Book Co., Inc., 1986 [18].

It is necessary to consult manufacturers for final and specific selecdons. However, the followang guide data is reliable and should serve to check recommendations or to specify a system. It is advisable to try to accomplish the specific operation wth as few ejectors as possible, because this leads to the most economical operation and lowest first cost in the majority of cases. Figures 6-9A, B, and C are a basic comparison guide for vacuum systems. 

For systems operating under vacuum, the maximum initial pressure shall be taken as no less than atmospheric pressure (0.0 psig or 0.0 kPa gage). 

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