Gauges manometers

Gauges. Because there is no way to measure and/or distinguish molecular vacuum environment except in terms of its use, readings related to gas-phase concentration ate provided by diaphragm, McCleod, thermocouple, Pitani gauges, and hot and cold cathode ionization gauges (manometers). 

Specify the geometry of a forming cavity (finished article) and a runner H, B, 8, q0, h0, and point xi of pressure gauges (manometers) along the cavity. 

Save any mercury taken from McLeod gauges, manometers, and diffusion pumps because it can be sold to your mercury supplier for purification and reuse. One company that provides this service is Bethlehem Apparatus Co., Inc., 890 Front St., Hellertown, PA 18055. 

Manometer h. The pressure manometer is connected to the stainless-steel capillary by a capillary T-tube containing a capillary stopcock, X, which can be opened to admit or remove gas from the bulb. During measurements this stopcock is kept closed and the quantity of gas in the bulb and dead space is thereby fixed. The pressure manometer should have a small internal volume and be capable of measuring absolute pressures with a resolution of 1 Torr or better. As discussed in Chapter XVIII, either capacitance or strain-gauge manometers can be used. The latter are generally less expensive, and high-precision versions of these gauges are available. 

The pressure gauge used in this experiment should be a direct-reading gauge with a relatively small and constant internal volume. Reproducibility is more important than absolute accuracy since relative measurements are made on air (the standard gas used for calibration) and the other gases. The critical feature is that the same initial P and final P inlet pressures are used in all runs. Thus, one can use capacitance, reluctance, or strain-gauge manometers (see p. 596-597). The latter manometers are the least expensive and are adequate if models with the best resolution are chosen. 

The common pressure unit of HPLC is bar, but the SI unit is pascal (Pa) 1 Pa = 1 N m. The atmosphere (atm or at, respectively) should no longer be used. The unit psi (pounds per square inch) is American and is still in use. Note the difference between psia = psi absolute and psig = psi gauge (manometer), the latter meaning psi in excess of atmospheric pressure. 

Usually, the force, F, is generated by the dead weight on a piston with well-defined area. A, as illustrated in Fig. 2.2. Accurate determinations of the effective area, and corrections for friction and for the buoyancy of the piston require great care if the best possible (absolute) accuracies are required (that is, accuracies of the order of 10 p.p.m (parts per million) ). For practical applications, other secondary pressure gauges (manometers) are used they are usually commercially calibrated, or they can be recalibrated, if necessary, by comparison with transfer standards. ... 

Measuring and control equipment medical and other thermometers, blood pressure gauges, manometers, pressure valves, gyroscopes... 

There is a difference between psia (= psi absolute) and psig (= psi gauge) (manometer), the latter meaning psi in excess of atmospheric. 

Less/no flow of air to plant units (drying tower)—This can cause loss of production, improper combustion of sulphur in furnace. Hence, it provides an air flowmeter, pressure gauge/manometer in airline. Operate the plant with positive displacement-type air blower. 

Industrial and Control Instruments. Mercury is used in many industrial and medical instmments to measure or control reactions and equipment functions, including thermometers, manometers (flow meters), barometers and other pressure-sensing devices, gauges, valves, seals, and navigational devices (see Pressure measurements Process control Temperature measurement). Whereas mercury fever thermometers are being replaced by... 

Monomer emulsions are prepared in separate stainless steel preemulsification tanks, which are usually equipped with an agitator, manometer level gauge, cooling cods, temperature recorder, mpture disk, flame arrester, and various nozzles for charging the ingredients. Monomer emulsions maybe charged in one shot to the reactor or, more commonly, fed continuously throughout the polymerization. 

Pressure reducing valves should be of steel constmction, designed for minimum and maximum operation conditions. Pressure gauges should be of ak-kon constmction. Pressure rehef valves should be of the spring-loaded type. Rupture disks may be used only as auxkiary equipment. Differential pressure measurements using mercury manometers should be avoided in ammonia service. 

Calibration of Gauges Simple liquid-column manometers... 

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. 

Manometer pressure The pressure recorded on a manometer, measured in Pa or mm water gauge. 

Oil slant gauge An inclined manometer tube using oil as the measuring fluid to record the pressure. 

Slant gauge An inclined calibrated manometer tube. 

Pressure gauges should always be fitted on the discharge side of liquid pumps, to check performance and give warning of a possible drop in flow resulting from dirty strainers. Manometer pressure gauges are required across air filters (see Chapter 2 7). 

The static pressure within a duct is too small to he measured hy a hourdon tuhe pressure gauge, and the vertical or inclined manometer is usually employed (Figure 27.2). Also, there are electromechanical anemometers. The pressure tapping into the duct must he normal to the air flow. 

Although a pressure gauge is more commonly used to measure the pressure inside a laboratory vessel, a manometer is sometimes used (Fig. 4.5). It consists of a U-shaped tube connected to the experimental system. The other end of the tube may be either open to the atmosphere or sealed. For an open-tube manometer (like that shown in Fig. 4.5a), the pressure in the system is equal to that of the atmosphere when the levels of the liquid in each arm of the U-tube are the same. If the level of mercury on the system side of an open manometer is above that of the atmosphere side, the pressure in the system is lower than the atmospheric pressure. In a closed-tube manometer (like that shown in Fig. 4.5b), one side is connected to a closed flask (the system) and the other side is vacuum. The difference in heights of the two columns is proportional to the pressure in the system. 

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