Manometers readings

Distance from duct Manometer Reading centre line (m) (mm)... 

A manometer containing an oil with a specific gravity (SG) of 0.92 is connected across an orifice plate in a horizontal pipeline carrying seawater (SG= 1.1). If the manometer reading is 16.8 cm, what is the pressure drop across the orifice in psi What is it in inches of water ... 

A mercury manometer is used to measure the pressure drop across an orifice that is mounted in a vertical pipe. A liquid with a density of 0.87 g/cm3 is flowing upward through the pipe and the orifice. The distance between the manometer taps is 1 ft. If the pressure in the pipe at the upper tap is 30 psig, and the manometer reading is 15 cm, what is the pressure in the pipe at the lower manometer tap in psig ... 

A mercury manometer is connected between two points in a piping system that contains water. The downstream tap is 6 ft higher than the upstream tap, and the manometer reading is 16 in. If a pressure gage in the pipe at the upstream tap reads 40 psia, what would a pressure gage at the downstream tap read in (a) psia, (b) dyn/cm2 (c) Pa (d) kgf/m2 ... 

The three-fluid manometer illustrated in Fig. 4-P11 is used to measure a very small pressure difference (P1 — P2). The cross-sectional area of each of the reservoirs is A, and that of the manometer legs is a. The three fluids have densities pa, ph, and pc, and the difference in elevation of the interfaces in the reservoir is x. Derive the equation that relates the manometer reading h to the pressure difference P1 — P2. How would the relation be simplified if A al... 

A tank that is vented to the atmosphere contains a liquid with a density of 0.9 g/cm3. A dip tube inserted into the top of the tank extends to a point 1 ft from the bottom of the tank. Air is bubbled slowly through the dip tube, and the air pressure in the tube is measured with a mercury (SG =13.6) manometer. One leg of the manometer is connected to the air line feeding the dip tube, and the other leg is open to the atmosphere. If the manometer reading is 5 in., what is the depth of the liquid in the tank ... 

An inclined manometer is used to measure the pressure drop between two taps on a pipe carrying water, as shown in Fig. 4-P13. The manometer fluid is an oil with SG = 0.92, and the manometer reading (L) is 8 in. The manometer reservoir is 4 in. in diameter, the tubing is 4 in. in diameter, and the manometer tube is inclined at an angle of 30° to the horizontal. The pipe is inclined at 20° to the horizontal, and the pressure taps are 40 in. apart. 

Water is flowing in a horizontal pipe bend at a velocity of 10 ft/s. The radius of curvature of the inside of the bend is 4 in., and the pipe ID is 2 in. A mercury manometer is connected to taps located radically opposite each other on the inside and outside of the bend. Assuming that the water velocity is uniform over the pipe cross section, what would be the manometer reading in centimeters What would it be if the water velocity were 5 ft/s Convert the manometer reading to equivalent pressure difference in psi and Pa. 

A tank contains a liquid of unknown density (see the Fig. 4-P25). Two dip tubes are inserted into the tank, each to a different level in the tank, through which air is bubbled very slowly through the liquid. A manometer is used to measure the difference in pressure between the two dip tubes. If the difference in level of the ends of the dip tubes (H) is 1 ft, and the manometer reads 1.5 ft (h) with water as the manometer fluid, what is the density of the liquid in the tank ... 

A Newtonian fluid with SG = 0.8 is forced through a capillary tube at a rate of 5 cm3/min. The tube has a downward slope of 30° to the horizontal, and the pressure drop is measured between two taps located 40 cm apart on the tube using a mercury manometer, which reads 3 cm. When water is forced through the tube at a rate of 10 cm3/min, the manometer reading is 2 cm. 

SAE 10 lube oil (SG = 0.93) is being pumped upward through a straight 1/4 in. sch 80 pipe that is oriented at a 45° angle to the horizontal. The two legs of a manometer using water as the manometer fluid are attached to taps in the pipe wall that are 2 ft apart. If the manometer reads 15 in., what is the oil flow rate, in gal/hr ... 

An orifice with a 1 in. diameter hole is installed in a 2 in. sch 40 pipeline carrying SAE 10 lube oil at 100°F. The pipe section where the orifice is installed is vertical, with the flow being upward. Pipe taps are used, which are connected to a manometer containing mercury to measure the pressure drop. If the manometer reading is 3 in., what is the flow rate of the oil, in gpm ... 

The water activity of food samples can be estimated by direct measurement of the partial vapor pressure of water using a manometer. A simple schematic diagram is shown in Figure A2.4.1. A sample of unknown water activity is placed in the sample flask and sealed onto the apparatus. The air space in the apparatus is evacuated with the sample flask excluded from the system. The sample flask is connected with the evacuated air space and the space in the sample flask is evacuated. The stopcock across the manometer is closed and temperatures are read. The equilibrium manometer reading is recorded (/, ). The stopcock over the sample is closed and the air space is connected with the desiccant flask. The manometer reading in the legs is read to give h2. The water activity of the sample is then calculated (Labuza et al., 1976) as ... 

As mentioned in Section 5.1.B, the transmission of vibration from the mechanical pump to a vacuum rack decreases the accuracy of manometer readings. To minimize this problem, it is generally best to mount the pump on the floor below a vacuum rack and to connect the pump to the system with a short length of heavy-walled rubber tubing, Tygon tubing, or flexible metal tubing. 

The gas pressure in the bulb equals the difference between the outside pressure and the manometer reading. The manometer reading indicates that the pressure of the gas in the bulb is less than atmospheric because the liquid level is higher on the side connected to the sample. Because mercury is more dense than mineral oil by a factor of 13.6/0.822, or 16.5, a given pressure will hold a column of mercury only 1/16.5 times the height of a column of mineral oil. 

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