Back pressure control valve

A fixed-bed reactor system was employed (Figure 32.2). Each of the two reactors was charged with 38 cc of Amberlyst BD20 catalyst. Sample ports located at the exit of each reactor enabled increased acquisition of residence time data. Pressure was maintained by a back pressure control valve to maintain methanol in the liquid phase. After charging, the 1st and then 2nd reactors were connected to the pumps and filled with the reaction mixture while vapor was released from each through the top vent valve. Once each reactor was filled with liquid and emptied of vapor, the pressure regulator was connected to the output and both reactors were immersed into the water bath. 

The cooling section, Fig. 6, is of double pipe construction. Cooling water and sterile media pass countercurrently. The back pressure control valve (for sterilization) is located at the low point of the piping. A Masoneilon Camflex valve is a suitable design for this service. A steam bleed should be located on each side of this valve in order to sterilize the sterilizer forward from the steam injector and backward from the fermenter. 

The equilibrium in Reaction 1 was determined as follows. A C02—N2 mixture of known composition and pressure was used to fluidize the acceptor bed. The fluidizing gas entered the reactor axially down through a diptube, reversed direction, and fluidized the acceptor. The effluent gas was throttled to atmospheric pressure through the back pressure control valve B. The effluent gas and feed gas were passed through the thermal conductivity cell where the feed gas served as reference gas. The electrical output of the cell, which was connected in a wheatstone bridge circuit, was recorded by a strip chart potentiometer. 

The rig consists of four 600-ml high-pressure sample cylinders. Usually, two are filled with water (brine), and two are filled with oil. With the aid of four motor-driven high-capacity piston pumps, water and oil are pumped through the choke valves. The four pumps are independent of each other, but in most of the experimental series the total flow has been kept constant. The pressure drops through the choke valves are back-pressure controlled. The pressure in the separation cell is regulated by a back-pressure controlled valve. The maximum pressure in the cell is 200 bar. The cell is filled with gas, inert or natural gas, to the desired pressure before the filling of water and oil into the separation cell starts. The separation cell (450 ml) is... 

Suppose the refrigeration system does not have an accumulator drum. Figure 10-2 shows such a system. Note that the throttle valve is now called a back-pressure control valve. Although this represents an inferior design, many refrigeration systems don t have an accumulator drum. 

The trick is to set the back-pressure control valve properly. Too high a back pressure wastes compressor horsepower. Too low a back pressure allows uncondensed refrigerant to blow through the throttle valve (see Fig. 10-2). As indicated in the figure, 10% of the compressor capacity is wasted. 

TO EXISTING AIR EJECTORS DRUCK AND BY-PASS LINE GHC/GCH4 AND GN2 PRESSURANT LINE MAIN VENT line - BACK PRESSURE CONTROL VALVE... 

Answer—suddenly increase the pressure in the drum by partly closing the back-pressure control valve shown in Fig. 36.4. This will instantly increase the pressure at the suction of the pump. It is true, as we said before, that raising the pressure in a drum does not increase the available NPSH, assuming that the vapor and liquid are at equilibrium. The idea of equilibrium assumes that the vapor is at its dew point and the liquid is at its bubble point. 

A back-pressure control valve on a wet gas absorber should fail in an open position on loss of instrument air pressure. 

Let us refer again to Fig. 41.1. Suddenly, there is an increase in the molecular weight of the wet gas. This causes the density of the gas to increase. This results in an increase of the compressor AP. As the compressor AP increases, the compressor s suction pressure decreases. Why If the discharge pressure is kept constant by the absorber back-pressure control valve, then a bigger AP must drag down the suction pressure. The reduced suction pressure increases the suction volume (ACFM) of gas... 

Hot, rich glycol at reduced pressure generates flash gas that can be used as a fuel gas to the regenerator reboiler or as a stripping gas or for both. Excess flash gas is normally vented to the flare system. The flash separator pressure is maintained through a back-pressure control valve on the gas outlet line from the separator. The liquid flow is maintained through a level-control valve. 

In most units, the flue gas pressure is reduced to atmospheric pressure across an orifice chamber. The orifice chamber is a vessel containing a series of perforated plates designed to maintain a given back-pressure upstream of the regenerator pressure control valve. 

Back pressure regulation valves (Figure 9.5) can be used in the suction line, and their function is to prevent the evaporator pressure falling below a predetermined or controlled value, although the compressor suction pressure may be lower. 

Facility is provided to bring the equipment up to the desired absolute pressure without subjecting the test unit to excessive pressure difference between its interior and exterior. This is accomplished by first filling the test cell with water by means of a hand operated hydraulic pump(17 in Figure 1) to a suitable value as indicated on the Bourdon dial gauges(P in Figure 1). The pressure thus developed is used also to control the appropriate back-pressure relief valve... 

Each of the eight reaction product streams leaving the reactor module are fed into a Valeo stream selection valve where one of the eight effluents is selected and sent to a GC for on-line analysis. The remaining channels, combined, are sent through a back pressure controller to a waste. The selected channel from each... 

The P7T ratio is a process variable or parameter to be affixed by the operator. Furthermore, it can be assumed that Pl and Py are set by back-pressure controllers on gas streams L and V. The feed rate Emay be increased or reduced by a valve in the line (e.g., by a flow controller), where the upstream feed pressure is sufficiently high. Ordinarily, it would be set at a constant rate, at a fixed reject pressure Pj. ... 

Figure 4 shows schematically the STS Multiplex ICP etching system. The source plasma is generated by an inductively coupled coil supplied by a 1-3 kW 13.56 MHz RF generator. Another 13.56 MHz generator is used to power the platen electrode which allows independent control of the bias potential of the wafer relative to the source plasma. The wafer temperature is maintained at typically less than 80 C through temperature-controlled, pressurized helium supplied to the back of the wafer. Wafers may be either mechanically or electrostatically clamped to the platen electrode. Typical base pressures are in the 10 torr range. The system is equipped with an automatic pressure control valve which can operate in one of two modes. In fixed automatic pressure control (APC) mode, the APC position remains constant, and the chamber pressure is a function of gas flows and RF powers. In automatic APC mode, the APC valve adjusts to maintain the chamber pressure at a constant value. The tool has been developed... 

If the reflux drum pressure started to rise, the pressure control valve would start to close. The compressor would then move up (i.e., to the left) on its operating curve. This would automatically pull the reflux drum pressure back down to 20 psig. In this way the pressure of the riser also... 

In our extraction facility, regenerated caustic was supplied to us by another unit. During one period when the mercaptan level of treated butylenes was excessive, the mercaptan content of our regenerated caustic was discovered to be higher than our spent caustic. Insufficient addition of 10% caustic was the major problem. The pressure control valve on the effluent butylene had to be pinched back on hot days to keep butylene from vaporizing in the settler. The higher pressure backed regenerated 10%... 

For a period of one week, unknown to the FCCU operating crew, the molecular weight of the gas from the reflux drum had dropped from 34 to 29. The compressor was slowly pushed back on its curve by the automatic closing of the pressure control valve, which was trying to maintain the 180 psig differential pressure between the reflux drum and the gas plant absorber. When this pressure control valve was shut, the flow of gas to the suction of the compressor was only 10,000 ACFM. This was also the absolute minimum flow that the compressor needed to prevent surge. 

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