Manometer Bourdon

Gages which depend on mechanical force for response, such as liquid manometers, Bourdon tubes, and aneroid bellows, are very useful in... 

Pressure Manometers Bourdon-tube elements With floats or displacers... 

There are numerous types of primary element used for measuring pressure that could be studied however, this discussion will be limited to some of the most common types encountered. These include manometers. Bourdon tubes, and differential pressure (DP)... 

The most frequently applied mechanical manometers in ventilation applications are fluid manometers, bur the following types are also used. The Bourdon tube is a small-voiume tube with an elliptic cross-section bent to the shape of a circular arc, the C-type. One end is open to the applied pressure while the other end is closed. The pressure inside the tube causes an elastic defonnation ot the tube and displaces the closed end, which is then converted, by means of a linkage mechanism, into the movement of a pointer. The Bourdon tube may be of a spiral or helical design as well. 

The solubility experiments were carried out in a stainless steel system. It had a manifold with ports for adding hydrogen, for evacuating, and for attaching metal chambers of a known volume (a few hundred cubic centimeters). Also connected to the ports were Ashcroft bourdon gages for measuring pressures of 1-100 atm and a mercury manometer for measuring pressures below 1 atm. The ports were equipped with valves, and the volumes of all spaces accessible to the manifold were known accurately. 

Pressure is measured extensively in the chemical processing industries and a wide variety of pressure measuring methods has been developed. Some of these have already been discussed in Volume 1, Section 6.2.2, viz. the manometer (which is an example of a gravity-balance type of meter), the Bourdon gauge (an example of an elastic transducer) and mention is made of the common first element in most pressure signal transmission systems—the differential pressure (DP) cell (Volume 1, Section 6.2.3). The latter also frequently forms part of a pneumatic transmission system and further discussion of this can be found in Section 6.3.4. 

G. Bourdon Gauges. As an alternative to mercury manometers there is a variety of gauges based on mechanical or electrical pressure transducers. This section presents a description of purely mechanical gauges which still find use in this electronic age.4 The metal Bourdon gauge (Fig. 7.5) is fashioned around a semicircular thin-walled metal tube with mechanical linkage to a pointer. Fused-quartz spiral gauges are also available. In this case, a thin spiral is sensitive to a pressure differential, and the deflection is balanced with air pressure in the surrounding envelope. The air pressure is then measured with a manometer. 

Pressure Composition Studies. Pressure composition studies were performed in small, calibrated U-traps fitted with a manometer or Bourdon gage. A measured sample of the less volatile component was condensed in the trap, and successive small amounts of the more volatile component added. The trap was then brought to the appropriate temperature and allowed to equilibrate until the pressure became constant (usually 15-30 minutes were required). The aata were plotted vs. the composition of the liquid phase. The results are summarized in Table I. 

We limit our discussion here to Bourdon gauges and manometers but recognize the importance of other methods in modem process sensors. 

Bourdon gauges are used to measure fluid pressures from nearly perfect vacuums to about 7000 atm. More accurate measurements of pressures below about 3 atm are provided by manometers. 

What is the pressure drop (mm Hg) from point (a) to point (b)7 3.44. An open-end mercury manometer is connected to a low-pressure pipeline that supplies a gas to a laboratory. Because paint was spilled on the arm connected to the line during a laboratory renovation, it is impossible to see the level of the manometer fluid in this arm. During a period when the gas supply is connected to the line but there is no gas flow, a Bourdon gauge connected to the line downstream from the manometer gives a reading of 7.5 psig. The level of mercury in the open arm is 900 mm above the lowest part of the manometer. 

The pressure was measured using a borosilicate glass Bourdon gage which was sensitive to 0.1 mm. of mercury as a null instrument to a mercury manometer. The final pressure was measured after the reaction vessel had been heated above 200° C. for 8 hours or longer. The maximum dead space of 14 cc. was efficiently flushed with oxygen at the start of each experiment and was duly corrected for in the calculation (2) of the ozone concentrations. The hollow-bore vacuum stopcocks used in the system were lubricated with Halocarbon (high temperature grade) stopcock lubricant. The usual precautions were taken to minimize the amount of mercury vapor in the system. 

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