Control valves valve application technology

Valve Application Technology Functional requirements and the properties of the controlled fluid determine which valve and actuator types are best for a specific apphcation. If demands are modest and no unique valve features are required, the valve-design style selection may be determined solely by cost. If so, general-purpose globe or angle valves provide exceptional value, especially in sizes less than 3-inch NFS and hence are very popular. Beyond type selection, there are many other valve specifications that must be determined properly in order to ultimately yield-improved process control. 

The Cv Concept. From a quantitative standpoint, steam loss can be estimated through the application of the C, concept. A familiar term in control valve technology, C, expresses the flow capability of a fluid-controlling device—in this case, a steam trap. A large C,. means a high flow rate a low C, means a low flow rate. 

From a dynamic response standpoint, the electronic adjustable-speed pump has a dynamic characteristic that is more suitable in process control applications than those characteristics of control valves. The small amplitude response of an adjustable-speed pump does not contain the dead band or the dead time commonly found in the small amplitude response of the control valve. Nonlinearities associated with friction in the valve and discontinuities in the pneumatic portion of the control valve instrumentation are not present with electronic variable-speed drive technology. As a result, process control with the adjustable-speed pump does not exhibit limit cycles, problems related to low controller gain, and generally degraded process loop performance caused by control valve nonlinearities. 

Distributive controi systems combine some of the most innovative technologies into an interactive network of intelligent microprocessors, application software, and communication networks. The hardware for a DCS includes a host CPU or programmable logic controller (PLC), intelligent field devices (transmitters, controllers, and control valves), remote CPU, and keyboard. This type of system offers the highest level of operator interaction. 

A design consideration for an environmental application of TSS technology is location. In a PRT unit, the TSS is always located in a hot flue gas position. However, a cold flue gas position could be used for environmental applications. Depending upon the pressure control scheme, the TSS can also be located at high pressure before the flue gas slide valve and orifice chamber. This offers significant cost savings, lower material cost, and requires less plot space. On two ERA consent decree applications, this benefit was 40% lower capital cost. 

Limitations of the platform are related to the material properties of PDMS for example, chemicals which the elastomer is not inert to cannot be processed, and elevated temperatures such as in micro-reaction technology are not feasible. Also for the implementation of applications in the field of point-of-care diagnostics, where a handheld device is often required, the LSI platform seems not to be beneficial at the moment. Thereto external pressure sources and valves would have to be downsized to a smaller footprint, which is of course technically feasible, but the costs would be higher in comparison to other platform concepts. However, as a first step towards downsizing the liquid control equipment, the use of a Braille system was successfully demonstrated [143]. 

Oil applications are based on pressure atomization technology even if small power application solutions are available based on oil evaporation by heat. Electronic control of the fuel/air ratio previews an actuator to move a butterfly for controlling the air flow and an actuator to move the oil pressure regulator. For gas, two actuators control two butterflies, one for gas and one for air, even if fhe gas pneumatic valves (whose working principle is based on a pneumatic feedback) are widely used. More advanced burners control air flow changing the fan speed, reducing the pressure drop in the hydraulic pipes and valves. Despite this, a butterfly valve is often necessary to control startup operation, especially for high power applications. 

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