Measuring tank pressure

A solvent storage tank, 15.0 m high contains liquid styrene (sp. gr. 0.909). A pressure gauge is fixed at the base of the tank to be used to determine the level of styrene. 

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Reservoir engineers describe the relationship between the volume of fluids produced, the compressibility of the fluids and the reservoir pressure using material balance techniques. This approach treats the reservoir system like a tank, filled with oil, water, gas, and reservoir rock in the appropriate volumes, but without regard to the distribution of the fluids (i.e. the detailed movement of fluids inside the system). Material balance uses the PVT properties of the fluids described in Section 5.2.6, and accounts for the variations of fluid properties with pressure. The technique is firstly useful in predicting how reservoir pressure will respond to production. Secondly, material balance can be used to reduce uncertainty in volumetries by measuring reservoir pressure and cumulative production during the producing phase of the field life. An example of the simplest material balance equation for an oil reservoir above the bubble point will be shown In the next section. 

Closed Vessels. Liquid level can be measured by the static pressure method also at non atmospheric pressures. However, ia such cases the pressure above the Hquid must be subtracted from the total head measurement. Differential pressure measuriag instmments that measure only the difference ia pressure between the pressure tap at the bottom of the tank and the pressure ia the vapor space are used for this purpose. At each tap, the pressure detected equals the Hquid head pressure plus the vapor pressure above the Hquid. Siace the pressure above the Hquid is identical ia both cases, it cancels out. Therefore, the change ia differential pressure measured by the instmment is due only to the change ia head of Hquid ia the vessel. It is iadependent of the pressure within the tank and is an accurate measure of the level. 

For tank work, inches water column (in. wc) or ounces per square inch (osi) are commonly used to express the value of pressure or vacuum in the vapor space of a tank. These pressures are usually very low relative to atmospheric pressure. The common measures of pressure are compared as follows ... 

Precision mass and volumetric methods use very precise measurements of pressure and/or level in the tank to detect leaks. The tank must be closed so that no Hquid enters or leaves the tank. The threshold of detection and fuimel required to perform a rehable test become greater as tank size increases. 

Gasoline is pumped through a 2 in. sch 40 pipeline upward into an elevated storage tank at 60°F. An orifice meter is mounted in a vertical section of the line, which uses a DP cell with a maximum range of 10in.H2O to measure the pressure drop across the orifice at radius taps. If the maximum flow rate expected in the line is 10 gpm, what size orifice should you use If a water manometer with a maximum reading of 10 in. is used instead of the DP cell, what would the required orifice diameter be ... 

Liquid levels in storage tanks are frequently determined by measuring the pressure at the bottom of the tank. In one such tank the material stored in the tank was changed and an overflow resulted. Why ... 

Bourdon gauges are used on gas cylinders and are also considered a type of aneroid gauge. These devices have a coiled tube (shown in Figure 3.5) and are used to measure the pressure difference between the pressure exerted by the gas in a cylinder and the atmospheric pressure. The coiled tube is mechanically coupled to a pointer (shown in red). As a gas at a pressure above atmospheric pressure enters the coiled tube, it causes it to slightly uncoil, kind of like those New Year s Eve paper noisemakers. This causes the pointer to move over a numerical scale, thereby indicating the gauge pressure in the tank. 

Tank A is connected to tank B through a U - tube and Tank B is connected to the vertical U - tube. The vertical tube can be used to measure the pressure in tank B and the U - tube can be used to relate the pressures of tanks A and B. 

Pressure build-up and boil-off of the main tank will be analyzed on the basis of the measurement of pressure and filling level over time, see Figure 1.9. From the... 

Figure 1.9 (a) Measurement of pressure and filling level in the tank versus time and in more detail ... 

Internal tank pressure is also measured and transmitted to the control panel. If the relief valve is activated, the pressure is released to a line that vents directly to the stack. The normal tank venting system is connected to the process vessel off-gas system in the main plant, which is a filtered system. 

Unfortunately, the barometer can measure only atmospheric pressure. It cannot measure the air pressure inside a bicycle tire or in an oxygen tank. You need a device that can be attached to the tire or tank. This pressure gauge must make some regular, observable response to pressure changes. If you have ever measured the pressure of an inflated bicycle tire, you re already familiar with such a device. 

The steam jacket is supplied with steam at a controlled pressure and the flow of jacket condensate is measured to allow calculation of the heat transferred in the test section. Jacket condensate may also be passed to a measuring tank and a continuous record of level in the tank used to estimate the average heat transfer rates over hourly or longer periods. 

Closure of tank and measurements of pressure increase rates simulating conditions of a maritime transport... 

Example 2.15. A two-fluid manometer is often used to make it unnecessary to read small differences in elevation. The one shown in Fig. 2.15 is measuring the pressure difference between two tanks. What is that pressure difference ... 

The figures are self-explanatory in regard to the test conditions employed, the measured temperatures at each location in the tank, and the saturation temperature corresponding to the tank pressure. The measured temperature profiles and the corresponding profiles predicted by the analytical model are shown for the same time intervals to facilitate a direct comparison. 

The second reason for not making pressure measurements at the standard locations was because the information desired was related to bulk tank pressures and exit pressures. Therefore, even if it were possible to place pressure taps at given locations the overall bulk pressure drop would still be the most important parameter in predicting propellant losses. 

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