Throttling range

Zone temperature control characteristics (set point, type of thermostat, throttling range)... 

Throttling range In a proportional controller, the control point range through which the controlled variable must pass to move the final control element through its full operating range. 

Proportional band, (also called throttling range), is the change in value of the controlled variable that causes full travel of the final control element. Figure 14 shows the relationship between valve position and temperature band for two different proportional bands. 

THROTTLING RANGE - The amount of change in the variable being controlled to make the controlled device more through the full length of its stroke. 

Interestingly enough, valve specifications do not require that a control valve move. A response requirement should be added to the control valve specification that details the stick-slip, dead band, and the response time for a small step in the throttle range [Ref. 6.5]. Ideally, a ramp at the expected rate of change of the loop should be used rather than a step, to reveal the dead time from dead band and the stair case from stick-slip [Ref, 6.6[. 

Bump the set point and increase or decrease the controller gain until there are quarter amplitude oscillations. Note the period of these oscillations. For gain settings larger than 1, the oscillation will be more recognizable in the controller output. Make sure the controller output stays within a good throttle range. 

Permissible operating range without throttling inlet to recovery turbine ... 

Increased - operating range with inlet - throttling -Speed limitation on semilean pump ... 

The fix for the erratic reflux drum pressure problem was to provide for separate pressure control of the fractionator column and the reflux drum. A new pressure control valve was installed upstream of the condenser and the old condenser outlet control valve was removed. A hot gas bypass, designed for 20% vapor flow, was installed around the pressure control valve and condenser. A control valve was installed in the hot gas bypass line. The column pressure was then maintained by throttling the new control valve upstream of the condenser. The reflux drum pressure w as controlled by the hot gas bypass control valve and the psv saver working in split range. The new system is shown in the figure below. 

Probably the most widely used capacity control for the centrifugal compressor is speed control. The capacity curve when used with speed control covers a wide range. While electric variable speed motors offer a continuation to the speed control practice, there are some other alternatives available. Suction throttling has been widely used and offers a r sonable control range for a relatively low cost. 

There is a clear need for other size classifiers which combine a high separation efficiency with flexibility and compactness. Hydrocyclones have a small volume, are simple in operation and are standard size classification equipment, for example in closed circuit grinding applications. The recent development of the flat-bottom hydrocyclone, which permits classification in the coarse size range, creates an additional motive to study the use of hydrocyclones for Crystal Size Distribution (CSD) control. Furthermore, throttling of a flat botom hydrocyclone does not necessarily provoke blockage but allows continuous control of its cut size when a controlled throttling valve is used. There is a clear incentive for its use in this application since it may provide an additional process input. 

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. 

The corresponding pressure drops ranged from 3.54 to 1631 Pa for the largest and smallest throttle sizes [57]. 

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