Mercury inches

Inch, mercury Inches of mercury Inch-pound Inch-pound Inch, water, 4°C Inch, water, 4°C Inch, water, 4°C Inch, water, 4°C Inch, water, 4°C Inch, water, 4°C... 

There are a number of units that can be used to measure barometric pressure. For example, millimeters can be converted into inches thus, a standard pressure of 760 mm Hg can also be recorded as 30.0 inches of mercury. Inches of mercury are the units used for weather reports in the United States. Three other very common units that correspond to 760 mm Hg are ... 

Pressure difference may be in pounds per square inch, atmospheres, bars, pascals, centimeters of mercury, inches of water, or whatever chosen. (It may be noted that pressure is ordinarily expressed in mass-distance units, as mass per unit area, rather than as stress in force-distance units, as force per unit area, with the pascal being an example of the latter.) For convenience, a few conversion factors are supplied in Table 19.8. 

CAN YOU ANSWER THIS Atmospheric pressure at elevations of 8000 ft average about 0.72 atm. Convert this pressure to millimeters of mercury, inches of mercury, and pounds per square inch. Would a cabin pressurized at 500 mm Hg meet federal standards ... 

Given a gas pressure in atmospheres, torr, millimeters (or centimeters) of mercury, inches of mercury, pascals, kilopascals, bars, or pounds per square inch, express that pressure in each of the other units. 

We have discussed the American system inches of mercury (inches Hg) in Chap. 10, "How Instruments Work." Of more immediate interest is Table 23.1. To do any sort of vacuum calculation, we need to convert to the absolute system, in millimeters of mercury (mm Hg). Unfortunately, we also need to correct measurements made with an American-type (inches Hg) vacuum gauge for atmospheric pressure. You can interpolate between the two sets of data in Table 23.1, to correct for almost the entire range of typical atmospheric pressures. 

Atmospheres Inches of mercury at 32 F 29.921 Centigrade heat units B.t.u. 1.8... 

Bars Atmospheres 0.9869 Centimeters of mercury at 0 C. Pounds per square inch 0.19.3.37... 

To convert milhmeters of mercury to pounds-force per square inch, multiply by 0.01934. 

The term vacuum is used to e.xpress pressures less than atmospheric pressure (sometimes represented as a negative psi on pressure gauges). Another scale frec]uently used is inches of mercury . The conversion is 14.7 psia = 29.92" Hg. Another scale gaining in popularity is the kilopascal (Kp) scale. 14.7 psia = 100 Kp... 

Note that there are many ways to express vacuum. Simple gauges record vacuum negative psig. Compound gauges record vacuum as a positive psia. The v-t h.-uses inches of mercury in the daily forecast, and millibars ("GOO i ... 

It is the energy in the liquid rec]uired to overcome the friction los.ses from the suction nozzle to the eye of the impeller without causing vaporization. It is a characteristic of the pump and is indicated on the pump s curve. It varies by design, size, and the operating conditions. It is determined by a lift test, producing a negative pressure in inches of mercury and converted into feet of required NPSH. 

Station pressure, inches of mercury, four digits Dry bulb temperature, °F, three digits"... 

Where e, is in units of inches of water per day. Up is the wind speed 2 feet above the ground expressed in miles per day, and e and e, are the saturation vapor pressures at mean air and mean dew-point temperatures, respectively (expressed in inches of mercury). For development of the wind function, an adjustment in the psychrometric constant is generally made to account for the sensible heat conducted... 

A number of units are used to express a pressure measurement. Some are based on a force per unit area for e.xample, pound (force) per square inch (psi) or dyne per square centimeter (dyne/enr). Otliers are based on a fluid height, such as inches of water (in H O) or millimeters of mercury (iimiHg) units such as these are convenient when tlie pressure is indicated by a difference between two levels of a liquid, as in a imuiometer or barometer. Barometric pressure is a measure of the ambient air pressure. Standard barometric pressure is 1 atm and is equivalent to 14.696 psi and 29.921 in Hg. 

Absolute zero pressure is absolute vacuum. This is 0 psia, also known as 29.92 inches of mercury below atmospheric pressure, or 33.931 feet of water below atmospheric, all referenced at sea level,... 

If pressure is expressed as inches of mercury vacuum, the reading of the local barometer (or a reference barometer) is necessary to establish the absolute sucdon pressure, or pressure in the vacuum system. 

A distillation column is operating at 27.5 inches mercury vacuum, referenced to a 30-inch barometer. This is the pressure at the inlet to the ejector. Due to pressure drop through a vapor condenser and trays of a distillation column, the column bottoms pressure is 23 inches vacu-... 

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