Pressure capacity

Pilot-operated valves may be satisfactorily used in vapor or liquid services up to a maximum back pressure (superimposed plus built-up) of 50% of set pressure, provided that the back pressure is incorporated into the sizing calculation. At higher back pressures, capacity becomes increasingly sensitive to small changes in back pressure. As an exception, back pressure up to 7% of set pressure may be used, provided that this disadvantage is recognized. 

Typically, in specifying a unit, the suction and discharge pressures, capacity (MMsefd), inlet temperature, and gas properties are given. The actual sizing of the cylinders is left to the manufacturer from his specific combinations of standard cylinders, pistons, and liners. However, once a proposal is received from a manufacturer, sometimes it is beneficial to check the cylinder sizing and make sure that indeed the compressor will perform. Sometimes it is necessary to size a new cylinder for an existing compressor or to verify that an existing compressor will perform in a different service. 

Type Lowest recommended suction pressure Capacity range, ft /min... 

Figure 12-100. Pressure-capacity characteristic comparison of an axial compressor with adjustable stator blades with a centrifugal compressor. (Reprinted with permission Lowell, W. O. Petroleum Refiner, V. 34, No. 1, 1955. Gulf Publishing Company. All rights reserved.)...

Frame Loads. The window frame must develop the static design strength of the glass pane, r, given in Table II. Otherwise, the design is inconsistent with f rame assumptions, and the peak blast pressure capacity of the window assemblies will produce a failure rate in excess of the prescribed failure rate. This results... 

Figure 1. Peak blast pressure capacity for tempered glass panes a/b = 1.00, t = 1/4 and 5/16 in.

Figure 3. Peak blast pressure capacity for polycarbonate a/b =1.0 t = 1/2 and 1 in.

Figure 7.20. Applications ranges of compressors and fans (Worthington) (a) Pressure-capacity ranges for air at 1 atm, 60°F, 0.075 Lb/cuft. (b) Head-capacity ranges for all gases. Similar charts are given by Ludwig (1983, Vol. 1, p. 251) and Chemical Engineers Handbook (1984, p. 6.21).

Compatible with fouling and dirty service Limitation in pressure/sizes Highly affected by backpressure (set pressure, capacity, stability) Not easily testable in the field... 

Feed material Compacting pressure Capacity Press drive power Ring speed... 

Choose the fan size from the capacity table. Check the capacity table to be sure that it lists fans suitable for induced-draft (elevated temperature) service. Turn to the 11-in static-pressure-capacity table and find a capacity equal to 110,355 ft3/min. In the engineering data used for this fan, the nearest capacity at 11-in static pressure is 110,467 ft3/min, with an outlet velocity of 4400 ft3/min, an outlet velocity pressure of 1.210 U1H2O, a speed of 1222 r/min, and an input horsepower of 255.5 bhp. The tabulation of these quantities is of the same form as that given for the forced-draft fan (step 2). The selected capacity of 110,467 ft3/min is entirely satisfactory because it is only (110,467 — 110,355)/110,355 = 0.00101, or 0.1 percent, higher than the desired capacity. 

According to Cool and Vansant (1996), pores between 0.7 and 1.1 nm are probably present in all pillared clays, whereas the narrow and wider pores are particular features of the Zr-laponite and Zr-hectorite. A relatively high adsorption affinity (i.e. the low pressure capacity) of Zr-laponite for cyclohexane was attributed to the presence of a large number of narrow pores, giving rise to enhanced adsorbate-adsorbent interactions. 

Heat transfer constraints Heat must be transferred into the liquid in the reboiler to boil off the vapor needed to provide the vapor-liquid contacting in the column. If the base temperature becomes too high and approaches the temperature of the heating source, the heat transfer rate will decrease and vapor boilup will drop. The same result occurs if the reboiler fouls and the heat transfer coefficient drops. In the condenser, heat must be transferred from the hot vapor into the coolant stream to remove the heat of condensation. If the column is operating at its maximum pressure, capacity maybe limited by condenser heat removal. 

All pyrolysis experiments were carried out in the thermo-gravimetric apparatus (TGA) having a pressure capacity of up to 1000 psi. A schematic of the experimental unit is shown in Figure 1. It consists of the DuPont 1090 Thermal Analyzer and the microbalance reactor. The latter was enclosed inside a pressure vessel with a controlled temperature programmer and a computer data storage system. The pressure vessel was custom manufactured by Autoclave Engineers. A similar set-up was used previously by others.( )... 

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