Vacuumed pressure atmosphere

Vapor Treatment. The vapors from the tank space can be sent to a treatment system (condenser, absorption, etc.) before venting. The system shown in Fig. 9.1 uses a vacuum-pressure relief valve which allows air in from the atmosphere when the liquid level falls (Fig. 9.1a) but forces the vapor through a treatment system when the tank is filled (Fig. 9.16). If inert gas blanketing is required, because of the flammable nature of the material, then a similar system can be adopted which draws inert gas rather than air when the liquid level falls. 

Vacuum and Atmosphere Melting. A coreless high frequency induction furnace is enclosed in a container or tank which can be either evacuated or filled with a gaseous atmosphere of any desired composition or pressure. Provision is made for additions to the melt, and tilting the furnace to pour its contents into an ingot mold also enclosed in the tank or container without disturbing the vacuum or atmosphere in the tank (Fig. 2). 

For water, SpGr = 1.0 at 62°F, although for general use it can be considered 1.0 over a much wider range. For explanation of vacuum and atmospheric pressure, see Chapter 2. 

Select design pressure drop for operations. Suggested values of below 1.0 in. water/ft. Low-pressure, atmospheric, and pressure columns usually require 0.5 to 0.7 in. water/ft, with absorbers and strippers around 0.2-0.6 in. water/ft. For vacuum distillation low values of 0.05-0.6 in. water/ft are often necessary, usually depending on the required boiling point of the bottoms. 

The process basically forms the sheet after it has been heated to the point at which it is soft and flowable, and then applying differential pressure (atmospheric pressure, air pressure, vacuum, or their combinations) to make the sheet or film conform to the shape of the male or female mold producing many different products (Table 8-23). The more precise and controlled pressure applied, the more efficient in reproducing products at the lowest cost occurs (Fig. 8-50),... 

Vacuum pressure Gauge pressure in psi (gpsi) is the amount by which pressure exceeds the atmospheric pressure of 14 psi (negative in the case of vacuum). The absolute pressure (psia) is measured with respect to zero absolute vacuum [29.92 in. (101 kPa) Hg], In a vacuum system it is equal to the negative gage pressure subtracted from the atmospheric pressure. (Gauge pressure + atmospheric pressure = absolute pressure) (1 in. Hg = 0.4912 psi of atmosphere on a product) (1 psi = 2.036 in. Hg). 

An ultraclean environment is another major reason for generating high vacuum. At atmospheric pressure, every atom on a solid surface is bombarded with gas molecules at a rate of trillions per second. Even under a reasonably high vacuum, 10 atm, a gas molecule strikes every atom on a solid surface about once per second. If the surface is reactive, these collisions result in chemical reactions that contaminate the surface. The study of pure surfaces of metals or semiconductors requires ultrahigh vacuum, with pressures on the order of 10 atm. 

The end of the capillary tube is heated until the glass is soft, then before it has time to cool it is touched on to the surface of a thin bubble of glass and a slight suction applied. This forms the window into a concave shape and draws it slightly down into the capillary, whose ends then protect it from damage. The bubble of thin glass should be thin enough to show interference colours. These windows will stand a vacuum provided atmospheric pressure is on the concave side of the window. If they are subjected to a pressure difference in the other direction, failure occurs due to the reversal of curvature. 

The production of vacuum (sub-atmospheric pressure) is required for many chemical engineering processes for example, vacuum distillation, drying and filtration. The type of vacuum pump needed will depend on the degree of vacuum required, the capacity of the system and the rate of air inleakage. 

Once VOC emissions have been eliminated or reduced at source, then recovery of the VOC for reuse should be considered. Figure 25.6 shows a vapor recovery system associated with an atmospheric storage tank. The storage tank is fitted with a vacuum-pressure relief valve, which... 

Residua are black, viscous materials obtained by distillation of a crude oil under atmospheric pressure (atmospheric residuum) or under reduced pressure (vacuum residuum). They may be liquid at room temperature (generally, atmospheric residua) or almost solid (generally, vacuum residua) depending on the cut point of the distillation or depending on the nature of the crude oil (Speight, 1999 Speight and Ozum, 2002). 

The torr is included in the table only to facilitate the transition from this familiar unit to the statutory units N m, mbar and bar. In future the pressure units tor, mm water column, mm mercury column (mm Hg), % vacuum, technical atmosphere (at), physicalatmosphene (atm), atmosphere absolute (ata), pressure above atmospheric and pressure below atmospheric may no longer be used. Reference is made to DIN 1314 in this context. 2) The unit Newton divided by square meters (N m ) is also designated as Pascal (Pa) 1 N m = 1 Pa. Newton divided by square meters or Pascal is the SI unit for the pressure of fluids. 3) 1 torr = 4/3 mbar fl torr = 1 mbar. ... 

Activation of Silver Powder for Ethylene Epoxidation at Vacuum and Atmospheric Pressures... 

Transient response techniques are used to investigate the activation of silver powder for ethylene epoxidation at vacuum and atmospheric pressures. Results indicate that the activation process is qualitatively the same in both pressure regimes. Numerical simulation of the process indicates that activation involves the concurrent incorporation of oxygen into surface and subsurface sites. The reaction selectivity parallels the incorporation of oxygen into the subsurface. 

Aj) Altitude Test. The purpose of this test is to check the effect of low atmospheric pressure on the fuze, such as leaks. The fuze is placed in the chamber, and the chamber is then evacuated to the desired vacuum pressure (p IIB-31 of Ref 39)... 

One option involves the condensation of (or part of) the permeate under atmospheric instead of vacuum conditions. This requires the use of dry-vacuum pumps , able to compress the permeate vapour from vacuum to atmospheric pressure, after which condensation is performed at a higher temperature [23]. In this case, the operating conditions have to be carefully monitored since these pumps may lead to unsuitable heating of the vapour and eventually aroma deterioration, despite the low residence time. Alternatively, the use of liquid ring vacuum pumps where the service liquid can take some of the aromas from the permeate stream has been proposed [24]. 

Wrong The chief engineer failed to realize that the vacuum pressure indicator was not equipped with a barometric pressure compensator. An ordinary vacuum pressure indicator or pressure gauge reads the pressure difference between the vacuum system and atmospheric pressure. When ambient temperatures drop, the barometer rises or ambient pressure goes up. An ordinary vacuum pressure gauge or indicator would then read an improved vacuum. But in reality, the vacuum has not changed. 

The pressure at P1 is now the 1-psi static head, minus the 5-psi nozzle exit loss, or negative 4 psig (or positive 10.7 psia). That is, the pressure at the drain is a substantial partial vacuum, or a negative pressure, meaning that it is below atmospheric pressure (atmospheric pressure at sea level is 14.7 psia). 

The most satisfactory nonpressure process is known as thermal treatment. The wood to be treated is immersed in a preservative at an elevated temperature. This causes the air in the wood cells to expand so that when the wood is transferred into a preservative bath of lower temperature, the air contracts forming a partial vacuum and atmospheric pressure forces the liquid into the wood. 

As the steam lost energy, it was collected in a separate chamber where it cooled and condensed back into liquid water. In the process of condensing in a sealed chamber, the steam created a vacuum, a space empty of matter. This vacuum allowed atmospheric pressure to drive the piston down again, preparing it for another round of work. 

Nutshe-filter/centrifuge Recovery of solids Liquid-solid Vacuum to atmospheric pressure, -10-100°C... 

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