Control valve station single

Whenever it is necessary to control the process level, pressure, temperature, etc., a control station is installed. A control station may be as simple as a single control valve or it may contain several control vahes, block valves, bypass valves, check valves, and drain or vent valves. 

An industry-standard programmable logic control has been added to a RTM valve, which allows a single pump to feed ten stations and can give remote flushing without removing the gun from the mold. The control works in concert with the computer-controlled process monitor, operated by remote keypad and, in combination, greatly improves and facilitates the RTM process. 

There is a traditional pattern of what is called instrumentation in the chemical and petroleum industries based on single-loop control (sometimes called SISO—single input, single output). Each process operation has a number of independent or single loops for feedback control of temperatures, pressures, flows, liquid levels, and sometimes compositions. The term single loop means there is one measurement, one controller, and one final control element, usually a valve. Many, but not all, of these loops are represented in the central control room (CCR) by control stations. 

If cascade control is involved, as, for example, liquid level control cascaded to flow control, the secondarv station not only has manual-automatic switching, but also another function— remote-local. In the remote position, the secondary controller set point comes from the output of the primary controller. In the local position, valve position may be set manually or the controller set point may be set by the operator ( local-auto ). Although cascade functions are sometimes combined into one station (or CRT faceplate ) for space and money-saving reasons, we recommend dual stations. Most single-station designs with which we are familiar are ver inflexible and complicated they do not permit ready implementation of feedforward, overrides, and so forth. 

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