Pressure, types Gauge

Standard commercial iastmmentation and control devices are used ia fluorine systems. Pressure is measured usiag Bourdon-type gauges or pressure transducers. Stainless steel or Monel constmction is recommended for parts ia contact with fluoriae. Standard thermocouples are used for all fluorine temperature-measuriag equipment, such as the stainless-steel shielded type, iaserted through a threaded compression fitting welded iato the line. For high temperature service, nickel-shielded thermocouples should be used. 

Mechanical Pressure Gauges The Bourdon-tube gauge indicates pressure by the amount of flection under internal pressure of an oval tube bent in an arc of a circle and closed at one end. These gauges are commercially available for all pressures below atmospheric and for pressures up to 700 MPa (about 100,000 Ibfliu") above atmospheric. Details on Bourdon-type gauges are given by Harland [Mach. Des., 40(22), 69-74 (Sept. 19, 1968)]. 

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. 

A pressure instrument has failed on a process line that requires constant monitoring. A bell-type gauge as shown in Fig. PI.87, is available which has oil (density of 0.800 g m ) as a sealant liquid. Construction of the gauge limits the sealant liquid s travel to 12.7 cm before blowout of the oil occurs. What maximum pressures can this gauge measure in kPa ... 

As an UV-light source, a high-pressure mercury lamp supplied with a water filter and quartz light collimator was employed. The catalyst samples were irradiated in the quartz cell at ambient temperature in a circulating flow of NO-CO mixtures of different compositions. The composition of the gas phase above the catalyst was continuously monitored during UV-irradiation with a monopole-type MKh-7304 mass-spectrometer. Pressures of gaseous reactants were measured with a capacity-type gauge VDG-1 with an accuracy of about 3%. 

Pressure Indicating bourdon-type gauge (noneorrosive conditions) ... 

Mixtures of known compositions were prepared by charging pure components into the volume above the mercury in cylinders Ai and A2 (Fig. 2). The temperature, volume, and pressure are then noted for each cylinder with the pressures being measured by reference to cylinder As> By adjusting the height of mercury in As until it is equal to that of Ai or As, the pressure in 3 is equalized with the cylinder in question and the pressure of As is then read on a dead-weight calibrated, Bourdon-type gauge. The amount of each pure gas and... 

Since the cell temperature is measured with a copper-constantan thermocouple, the absolute accuracy is dependent on the accuracy of the thermocouple calibration. This calibration was done in place with reference to the triple point and boiling point of nitrogen and the triple point of argon. The resultant accuracy was estimated to be 0.1°K, while resolution of the potentiometer (L N type K-3) was 0.03 K. In regard to pressure, the accuracy was 0.025 or 0.1 psi, depending on whether a mercury manometer or Bourdon-type gauge was being used. 

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