Static pressure connection

FIG. M-10 (a) Static-pressure connection, (b) Static tube, Impact tubei (<9 Combination pitot-static tube, (e) Cross connection, (f) Typical pressure-gauge piping arrangements. (Source Demag Delaval.)... 

Local Static Pressure In a moving fluid, the local static pressure is equal to the pressure on a surface which moves with the fluid or to the normal pressure (for newtonian fluids) on a stationary surface which parallels the flow. The pressure on such a surface is measured by maldng a small hole perpendicular to the surface and connecting the opening to a pressure-sensing element (Fig. The hole is... 

After catalyst charging and the flow vs. RPM measurement is done, the reactor should be closed and flushed out with nitrogen while the impeller runs, until O2 drops below a few tenths of a percent. Then a static pressure and leak test should be made by turning off the forward pressure controller and the flow controller. If an observable drop of pressure occurs within 15 minutes, all joints and connections should be checked for leaks and fixed before progressing any fijither. 

Static pressure recovery method. The diameters are selected in such a way that the same static pressure is available before every connection. The duct reduction is selected in such a way that the gain of static pressure is in balance with the friction losses up to the next connection point. This method may result in fewer control devices at connection points or outlets. Low velocities and large diameters at the end of the system may be the result of this design approach. 

For some hood types, measurements usually seen as indirect method, are used to measure the hood s performance to determine regulatory compliance. For example, regulations specify minimum and maximum face velocities for laboratory fume hoods and static pressure (negative) inside enclosed hoods. Continuously monitoring instruments can be connected to alarms that sound when the measurement is outside the specified limits. 

Figure 12-143 shows the curves for identical fans. When unlike fens are placed in series, the individual static and total pressure curves are placed on the graph. The individual curves for assumed fans No. 1 and No. 2 and the system resistance curve define the system. The combined total pressure curve is the sum of the individual values at the same capacity. Then total combined pressure curve = Pft (No. 1) + Pft (No. 2). The new combined operating static pressure curve is the sum of the individual static pressure valves at the same capacity and exists only at the oudet of the second fan then, the total combined static pressure = Pfti + Pftg — Ps. Any losses in connections between the fans will reduce the values of the total static and system total pressures. 

Review the system illustrated in Figure 40.8. Chamber A is under pressure and is connected by a tube to chamber B, which is also under pressure. The pressure in chamber A is static pressure of lOOpsi. The pressure at some point (X) along the connecting tube consists of a velocity pressure of lOpsi exerted in a direction parallel to the line of flow, plus the unused static pressure of 90psi. The static pressure (90psi) follows Pascal s law and exerts equal pressure in all directions. As the fluid enters chamber B, it slows down and its velocity is reduced. As a volume of liquid moves from a small, confined space into a larger area, the fluid will expand to fill the greater volume. The result of this expansion is a reduction of velocity and a momentary reduction in pressure. 

When the static pressure in a moving fluid is to be determined, the measuring surface must be parallel to the direction of flow so that no kinetic energy is converted into pressure energy at the surface. If the fluid is flowing in a circular pipe the measuring surface must be perpendicular to the radial direction at any point. The pressure connection, which is known as a piezometer tube, should terminate flush with the wall of the pipe so that the flow is not disturbed the pressure is then measured near the walls where the velocity is a minimum and the reading would be subject only to a small error if the surface were not quite parallel to the direction of flow. A piezometer tube of narrow diameter is used for accurate measurements. 

Air at 323 K and 152 kN/m2 pressure flows through a duct of circular cross-section, diameter 0.5 m. In order to measure the flow rate of air, the velocity profile across a diameter of the duct is measured using a Pitot-static tube connected to a water manometer inclined at an angle of cos-1 0.1 to the vertical. The following... 

The measured pressure difference AP is the difference between the stagnation pressure in the velocity probe at the point where it connects to the DP cell and the static pressure at the corresponding point in the tube connected to the wall. Since there is no flow in the vertical direction, the difference in pressure between any two vertical elevations is strictly... 

Constant superimposed backpressure Usually backpressures that occur when a safety valve outlet is connected to a static pressure source and doesn t change appreciably under any conditions of operation. In this case, conventional valves may be used if the valve spring setting is reduced by the amount of the constant backpressure (Figure 3.8). 

When the gas-inducing impeller rotates in a fluid, the sudden acceleration of the fluid elements causes reduction in the static pressure. In all the designs, the reduced pressure area is connected to the gas space, and the gas is induced if the reduction in pressure is sufficient to overcome all the resistance in the path of the gas. 

Description The unique reactor design uses a simple vertical U-shaped leg connected to a horizontal gas-liquid separation vessel. Reactant gases are fed to the bottom of the U where they dissolve and combine under sufficient static pressure to prevent boiling in the reaction zone. Above this zone, the heat of reaction produces vapor bubbles that flow upwards into the horizontal vessel. A natural circulation of EDC is induced by the density difference in the two legs of the U. ... 

Valve to provide a static pressure standard for the pressure transducer Valve connecting the operating side of the pressure transducer to the system System manifold... 

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