Valves throttling

The proportional controller is reverse-acting so that the control valve throttles down to reduce steam flow as the hot water outlet temperature increases the control valve will open further to increase steam flow as the water temperature decreases. 

If the measured variable drops below the setpoint, a positive error is developed, and the control valve opens further. If the measured variable goes above the setpoint, a negative error is developed, and the control valve throttles down (opening is reduced). The 50% proportional band causes full stroke of the valve between a +50°F error and a -50°F error. 

The vacuum chambers were pumped down by means of an oil diffusion pump backed by a rotary vane vacuum pump. The base pressure achieved was 1 x 10 5 Torr (1.33 x 10 Pa). High-purity argon gas was bled into the chamber, the high-vacuum valve throttled, and the chamber pressure maintained as close as possible to 2 x 10 2 Torr (2.66Pa). For some of the experiments, the dc self-bias on the magnetron electrode was also measured. 

C. PRESSURE LOOPS. Pressure loops vary from very tight, fast loops (almost like flow control) to slow averaging loops (almost like level control). An example of a fast pressure loop is the case of a valve throttling the flow of vapor from a vessel, as shown in Fig. 7.15o. The valve has a direct handle on pressure, and... 

We have to make a distinction here between electric controllers (e.g. PID controllers) with a proportional valve as actuator and mechanical diaphragm controllers. In a regulation system w/ith electric controllers the coordination between controller and actuator (piezoelectric gas inlet valve, inlet valve A/ith motor drive, butterfly control valve, throttle valve) is difficult because of the very different boundary conditions (volume of the vessel, effective pumping speed at the vessel, pressure control range). Such control circuits tend to vibrate easily when process malfunctions occur. It is virtually impossible to specify generally valid standard values. 

Example 7.2 is of cases with control valve throttling and pump speed control. In large systems, the value of power saved can easily overbalance the extra cost of variable speed drives, either motor or steam turbine. 

Example 7.2 is of cases with control valve throttling and pump... 

X Straig ht-way valve Throttling valve CS Back-pressure valve S Redueingvalve... 

The letdown flow outside containment isolation valve is a normally closed, fail closed, air-operated globe valve that isolates letdown to the liquid radwaste system. This valve automatically opens and closes on a plant control system signal from the pressuriser level control system or a containment isolation signal from the protection and safety monitoring system. Ibis valve operates in the same fashion as the letdown flow inside containment isolation valve. The letdown flow outside containment isolation valve eloses more quickly than inside containment letdown flow isolation valve to limit seat wear of inside containment isolation valve. This valve operator has a flow restricting orifice in the air line, so it opens more slowly than inside containment letdown flow isolation valve. In addition, during brief periods of shutdown, when the reactor coolant system is water solid, this valve throttles to maintain the reactor coolant system pressure. Manual control is also provided in the main control room and at the remote shutdown workstation. 

All solution check valves, throttling valves, and control valves... 

Valve designs used in HRE-2. The valve designs used on the EIRE-2 are all quite similar. E4gure 8-17(a) illustrates the "letdown valve, which is typical. This valve throttles a mixture of cooled gas and liquid from the 2000-psi high-pressure system to the low-pre.ssure storage tanks. The flow is introduced under the seat to keep the bellow s on the low-pressure... 

Valve, throttling (vacuum technology) A valve used to control the pumping speed. It may... 

The main heat exchangers of an absorption chiller are condenser, boiling pot (desorber), evaporator and absorber. These elements can be installed inside a single or double jacket, depending on the type and size of device (see Fig. 5.90). Large plants incorporate the double jacket solution, which enables easier transportation and installation. Additional elements of a chiller are a counter-current heat exchanger (for heat recovery), solution circulation pump, refrigerant circulation pump and valves, and a control expansion valve (throttle). 

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