Improved controls

Clean Air Act and its amendments ia 1970, 1977, and 1990 1967 Air Quahty Standards and National Air Pollution Acts and 1970 National Environmental PoHcy Act) (2) better waste disposal practices (1965 SoHd Waste Disposal Act 1976 Resource Conservation and Recovery Act) (see Wastes, industrial Waste treatment, hazardous wastes) (i) reduced noise levels (1972 Noise Control Act) (4) improved control of the manufacture and use of toxic materials (1976 Toxic Substances Control Act) and (5) assignment of responsibiUty to manufacturers for product safety (1972 Consumer Product Safety Act) (15,16). 

The western WetheriU. furnace is like the eastern furnace except that a block of 12 or more furnaces has a common combustion chamber. This results in improved control and uniformity of product. Clinker usually contains 8—15 wt % zinc, which is often recovered in a Waelz kiln (24). 

Control. Energy savings for improved control are surprisingly high. A 2 to 20% savings from a series of control projects has been reported (17). 

A reflux reduction of 15% is typical. Improved control achieves this by permitting a reduction in the margin of safety that the operators use to handle changes in feed conditions. The key element is the addition of feed-forward capabiUty, which automatically handles changes in feed flow and composition. One of the reasons for increased use of features such as feed-forward control is the reduced cost of computers and online analy2ers. 

Positioner Application Positioners are widelv used on pneumatic valve actuators, VIore often than not, thev provide improved process-loop control because thev reduce valve-related nonlinearitv, Dvnarnicallv, positioners maintain their abilitv to improve control-valve performance for sinusoidal input frequencies up to about one half of the positioner bandwidth. At input frequencies greater than this, the attenuation in the positioner amplifier netvv ork gets large, and valve nonlinearitv begins to affect final control-element performance more significantlv. Because of this, the most successful use of the positioner occurs when the positioner-response bandwidth is greater than twice that of the most dominant time lag in the process loop. 

Digital Field Communications An increasing number of valve-mounted devices are available that support digital communications in addition to, or in place of, the traditional 4—20 mA current signal. These control-valve devices have increased functionality, resulting in reduced setup time, improved control, combined functionality of traditionally separate devices, and control-valve diagnostic capabihty. Digital communications also allow the control system to become completely distributed where, for example, the process PID controller could reside in the valve positioner or in the process transmitter. 

A change in approach is clearly necessary in order that the full benefit of integrated plant condition management and control can be recognized and exploited. Improved control and enhanced performance monitoring will enable shutdown intervals to be extended without increasing the risk of premature or unexpected failure. In turn, this will increase the confidence of operations, inspection and management personnel in the effectiveness of unified plant administration. 

Add insulation to walls Raise compressor efficiency Add insulation to ceiling Switch to demand defrost Improve controls Improve heat exchanger Improve door seals... 

Improved control of liquid to evaporators, less flashing at evaporators. 

SG Service typical of petrol engines in present cars, vans and light trucks. Oils developed for this service provide improved control of engine deposits, oil oxidation and engine wear relative to oils developed for previous categories. Oils meeting SG may be used wherever SF, SE, SF/CC or SE/CC are recommended. 

Percec and coworkers327 331 reported in situ fonnation of active CuCl/CuCL catalyst from the initiator, CinO, Cu(0) and combinations of these in conjunction with ligand (bpy) and various polyethers or ethylene glycol and suggested that improved control was obtained under these conditions. 

In practice, the addition of a small amount of phosphate to a chelant program is recommended as an aid in improving control and reducing the potential impact of chelant corrosion. 

Any item of equipment fitted to a boiler to improve control or a major component within one of the many boiler plant systems and sub systems. 

Some of the most significant developments in the CVD of Si02 include experiments in plasma CVD at 350°C via electron cyclotron resonance (ECR) to gain improved control of the deposition rate and obtain a quality equivalent to that of the thermally grown oxide (see Ch. 5). Deposition from diacetoxyditertiarybutoxy silane at 450°C has also been shown to significantly improve the Si02 film properties. " ]... 

Better modeling will allow the design of processes that are easier and safer to operate. Improved control methodology and sensors will overcome the current inability to model certain processes accurately. 

For optical fibers, improved control over the stracture of the thin films in the preform will lead to fibers with improved radial gradients of refractive index. A particnlar challenge is to achieve this sort of control in preforms created by sol-gel or related processes. 

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