Pressure casings

Fig. 7. Instmment components of a control loop, where A = process measurement devices, in this case, pressure measurement B = transducer ...

In many cases, pressurized gases in vessels do not behave as ideal gases. At very high pressures, van der Waals forces become important, that is, intermolecular forces and finite molecule size influence the gas behavior. Another nonideal situation is that in which, following the rupture of a vessel containing both gas and liquid, the liquid flashes. 

Example If the shell-side coefficient of a unit is 25 Btu/hr (ft )(°F) and velocity in the shell is doubled, read the new shell-side coefficient, h as 36 (line a). If the tube-side coefficient is 25 and velocity is doubled, read the new tube coefficient, h, as 43.1 (line a). In other cases, pressure drop would increase by a factor of 4. Note This may be used in reverse for reduced flow. 

Frame Nominal Flow Range (cfm) Nominal Max No. of Casing Stages Max Casing Pressure (psig) Nominal Speed (r/min) Nominal Polytropic Efficiency Nominal H/N (per stage) Maximmn Q/N... 

No. stages per case max. 7 Nominal overall eff, % 77 Intake volume range 3,500-12,000 Nominal head per stage, ft 8,500 Nominal speed, rpm 8,100 Max. case pressure 250 psi cast iron... 

Shut in well. Record drill pipe and casing pressure. Circulate out gas or water influx and separate on surface. Calculate mud weight necessary to balance formation pressure. Kill the well. 

Record the pit gain and the shut-in drillpipe and casing pressure. 

Upon shutting in the well, the pressure builds up both on the drillpipe and casing sides. The rate of pressure buildup and time required for stabilization depend upon formation fluid type, formation properties, initial differential pressure and drilling fluid properties. In Ref. [143] technique is provided for determining the shut-in pressures if the drillpipe pressure is recorded as a function of time. Here we assume that after a relatively short time the conditions are stabilized. At this time we record the shut-in drillpipe pressure (SIDPP) and the shut-in casing pressure (SICP). A small difference between their pressures indicates liquid kick (oil, saltwater) while a large difference is evidence of gas influx. This is true for the same kick size (pit gain). 

Step 1. The well is circulated at half the normal pump speed while keeping the drillpipe pressure constant (see Figure 4-352a). This is accomplished by adjusting the choke on the mud line so that the bottomhole pressure is constant and above the formation fluid pressure. To maintain a constant bottomhole pressure the formation fluid is allowed to expand, which usually results in a noticeable increase in casing pressure. This step is completed when the formation fluid is out of the hole. At this time casing pressure should be equal to the initial SIDPP if the well could be shut in. 

Step 2. When the formation fluid is out of the hole, a kill mud is circulated down the drillpipe. To obtain constant bottomhole pressure, the casing pressure is kept constant (see Figure 4-352b) while the drillpipe pressure drops. Once the kill mud reaches the bottom of the hole the control moves back to the drillpipe side. The drillpipe pressure is maintained constant (almost constant) while the new mud fills the annulus. 

Figure 4>352b. Driller s method—Schematic diagram of casing pressure vs. time, t = kick fiuid out the top of the hole t = kick fluid out of the hole t = kill mud at the bottom of the hole t = killing procedure completed.

A qualitative relationship between the drillpipe pressure, casing pressure and circulating time is shown in Figures 4-353a and 4-353b, respectively. 

Note that the term (0.052 7 AV) expresses the expected increase of casing pressure when 1 bbl of pit gain is recorded. 

The magnitude of the casing pressure during kick control is... 

Determination of the maximum expected casing pressure is required for selection of the kick control technique. If the driller s method is used for kick control, the maximum casing pressure (psi) is calculated assuming gas influx into the hole. This is... 

For the engineer s method the maximum expected casing pressure can be calculated from... 

Calculate the maximum expected casing pressure for the driller s and engineer s techniques of kick control for the data as below ... 

Distribution systems can be operated at pressures up to 7 bar but it is practice to operate at as low a pressure as is consistent with supplying users with the agreed supply pressure, which is 21 mbar at the meter inlet in many cases. Pressure reduction takes place at take-offs from the transmission system, at district governor installations serving a large number of users within a geographical area and, for many larger users, at the users premises. 

All compressed air systems that use a positive displacement compressor must be fitted with a pressure relief or safety valve that will limit the discharge or inter-stage pressures to a safe maximum limit. Most dynamic compressors must have similar protection due to restrictions placed on casing pressure, power input and/or keeping out of surge range. 

Variation in the pressure of the reacting gas can affect corrosion processes in two ways. In the cases more usually met with in practice, in which the corrosion rate is controlled by diffusion processes in the surface film of corrosion product, the influence of gas pressure on corrosion rate is slight. If, however, the dissociation pressure of the oxide or of a constituent of the scale lies within the range involved, the stability of the corrosion product will be critically dependent on the pressure. The effect of temperature is, however, far more critical and thus, in practical cases, pressure variations rarely decide the stability of corrosion products. 

The ideal gas law is readily applied to problems of this type. A relationship between the variables involved is derived from this law. In this case, pressure and temperature change, while n and V remain constant. 

It should be emphasized that the enthalpy change includes not only sensible heat effects but also a heat-of-reaction term and in some cases pressure effects. If there are multiple inlet and outlet streams, appropriate averaging techniques must be used to employ this equation. 

The effect of pressure on the ground-state electronic and structural properties of atoms and molecules have been widely studied through quantum confinement models [53,69,70] whereby an atom (molecule) is enclosed within, e.g., a spherical cage of radius R with infinitely hard walls. In this class of models, the ground-state energy evolution as a function of confinement radius renders the pressure exerted by the electronic density on the wall as —dEldV. For atoms confined within hard walls, as in this case, pressure may also be obtained through the Virial theorem [69] ... 

The base case pressure flow calculation and the above viscosity function require that the shear rate be calculated from the screw rotation equations using Eq. 7.41 ... 

OVERHUNG O BETWEEN BEARINGS O BARREL CASE PRESSURE RATING ... 

A196 Case pressure CASE PRESS c 1 1 yes (true) 0 no (teise)... 

Also, in the cold jet case, pressure profiles were measured to assess possible thrust penalty associated with the flow-induced resonance. Near-held pressure prohles, which are plotted in Fig. 29.11 for typical forced and natural cases, again show the faster growth associated with the excitation. In the far held, the static pressure became identical to the ambient pressure. To obtain the thrust force, far-held total pressure prohles were integrated over the jet cross-sectional area. The measurement at 18 exit diameters downstream for the excited case showed that there was a force deheit of about 8% compared to the natural case. This appears to be the maximum amount of thrust penalty caused by periodic impingement of shear how on the cavity trailing edge. 

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