Safety, vacuum

Sizing, 451, 453, 455, 459, 462 Sonic flow, 461 Types, illustrations, 411-421 Rupture disk, liquids, 462, 466 Rupture disk/pressure-relief valves combination, 463 Safely relief valve, 400 See Relief valve Safety valve, 400, 434 Safety, vacuum, 343 Scale-up, mixing, 312, 314—316 Design procedure, 316-318 Schedules/summaries Equipment, 30, 31 Lines, 23, 24 Screen particle size, 225 Scrubber, spray, 269, 270 Impingement, 269, 272 Separator applications, liquid particles, 235 Liquid particles, 235 Separator selection, 224, 225 Comparison chart, 230 Efficiency, 231... 

Figure 1.7 Two safety vacuum systems. The upper arrangement uses parts available in the laboratory. The lower system employs a commercial vacuum overflow trap, in which a float detects the rise of liquid in the trap and activates a solenoid valve, disconnecting the vacuum source.

Safety goggles should always be worn over the eyes when carrying out potentially dangerous operations, e,g. vacuum distillations, distillation of large volumes of inflammable liquids and experiments employing large quantities of metallic sodium. 

Few of the naturally occurring elements have significant amounts of radioactive isotopes, but there are many artificially produced radioactive species. Mass spectrometry can measure both radioactive and nonradioactive isotope ratios, but there are health and safety issues for the radioactive ones. However, modem isotope instmments are becoming so sensitive that only very small amounts of sample are needed. Where radioactive isotopes are a serious issue, the radioactive hazards can be minimized by using special inlet systems and ion pumps in place of rotary pumps for maintaining a vacuum. For example, mass spectrometry is now used in the analysis of Pu/ Pu ratios. 

Another option available with rotary vacuum dmm filters is fiiU enclosure. This enables operation under nitrogen or other atmospheres, for reasons such as safety, prevention of vapor loss, etc. Enclosure may also be used to prevent contamination of the material being filtered or to confine the spray from washing nozzles. The rotary dmm filter also can be enclosed in a pressure vessel and operated under pressure. 

The helium leak detector is a common laboratory device for locating minute leaks in vacuum systems and other gas-tight devices. It is attached to the vacuum system under test a helium stream is played on the suspected leak and any leakage gas is passed into a mass spectrometer focused for the helium-4 peak. The lack of nearby mass peaks simplifies the spectrometer design the low atmospheric background of helium yields high sensitivity helium s inertness ensures safety and its high diffusivity and low adsorption make for fast response. 

Nonmolecular species, including radiant quanta, electrons, holes, and phonons, may interact with the molecular environment. In some cases, the electronic environment (3), in a film for example, may be improved by doping with impurities (4). Contamination by undesirable species must at the same time be limited. In general, depending primarily on temperature, molecular transport occurs in and between phases (5), but it is unlikely that the concentration ratios of molecular species is uniform from one phase to another or that, within one phase, all partial concentrations or their ratios are uniform. Molecular concentrations and species that are anathema in one appHcation may be tolerable or even desirable in another. Toxic and other types of dangerous gases are handled or generated in vacuum systems. Safety procedures have been discussed (6,7). 

Essential Parameters. Traditionally, all vacuum environments are characterized in terms of one parameter, ie, pressure in the gaseous phase. However, when costs, energy, safety, hazardous wastes, and other requirements are taken into account, each system must be characterized by a host of parameters. Their magnitudes must be deterrnined in order to judge system performance. 

NFPA 99C Standard on Gas and Vacuum Systems, 1999 ed. National Fire Protection Association, Quincy, MA.NFPA 101 Code for Safety to Life from Fire in Buildings and Structures. National Fire Protection Association, Quincy, MA. 

Cellulose acetate-propionate (Tenite Propionate-Kodak) is similar to cellulose propionate. With the shorter side chains, cellulose propionate and cellulose acetate propionate tend to be harder, stiffer and of higher tensile strength than CAB. Like CAB they are easy to vacuum form and also tend to be used for similar applications such as steering wheels, tool handles, safety goggles and blister packs. 

Pressure Pressure-Vacuum Relief Valve Pressure Safety Valve ... 

The theoretical maximum suction lift at sea level for water (14.7 psi) (2.31 fi/psi) = 34 ft. However, due to flow resistance, this value is never attainable. For safety, 15 feet is considered the practical limit, although some pumps will lift somewhat higher columns of water. WTen sealing a vacuum condition above a pump, or the pump pumps from a vessel, a seal allowance to atmosphere is almost always taken as 34 feet of water. High suction lift causes a reduction in pump capacity, noisy operation due to release of air and vapor bubbles, vibration and erosion, or pitting (cavitation) of the impeller and some parts of the casing. (The extent of the damage depends on the materials of construction.)... 

Safety around mechanical vacuum pumps is possibly no different than that for other process mechanical rotating machinery. However, there is a decided danger of an... 

Safety valves and vacuum breakers, per inch of nominal size. 1.0... 

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