Dynamic Plantwide Pressure Control
#Pressure is the singular most important parameter for #measurement, #control and most common cause of #shutdown and #trips in all continuous #process #control plants. Being in #Upstream Oil and Gas field also, even though it is discrete system from wells to pipelines to separation and export of Oil and Gas, Pressure is still the most important factor of measurement and control.
Pressure is the fastest varying parameter in a plant and hence timely action after measurement becomes critical in many applications. More safety functions and SIFs are added to Pressure control and shutdown loops in any plant more than any other parameter. Level, flow and temperature are slow varying parameters compared to pressure. Moreover, one pressure is the variable which is the primary energy consumer in a plant i.e. It is pressure, be it of liquid or gas, which is used as a primary motivator to move liquids or gases from end to end in a plant. Variations of pressure in inlet end, pump or compressor suction to the dehydrator or export pumps for example, in an upstream plant application, if studied together with variations in color, as deviations from normal, low or high fluctuations which occur very fast, can help operators take more proactive actions to prevent an escalation in pressure levels in the line or equipment preventing a likely scenario of a trip or a shutdown condition. In other words, process control itself becomes more refined in its approach and operators get a more central role in preventing any trip scenarios, since they understand implications end to end, rather than their own equipment and unit.
End to end dynamic profiling of parameters( see my previous post on profiling), could provide a more sound picture of how the variations of Pressure in plant, the rise and fall of this singular parameter across every node, plant unit, sections within a unit etc vary in relation to one another. Process control or monitoring loops are all the time broken down in equipment or a section loops and captured on operator graphics and this serves very well for plant operations on a day to day basis. Expertise develops in operators to handle all related problems of a particular unit or a set of them, as their own specific area of expertise. However the pressure variation dynamic across every section of the plant, viewed singularly isn't present and how one end of the plant would effect another, with regard to this parameter isn't present in the plant today. Dynamic end to end view of all pressure parameters and how they vary and capturing all of them on a single graphic (large as they maybe, these days very large LCD screens are common in control rooms, and could be easily used to capture end to end plant graphic page). Even the cost of pressure transmitter not being much, additional devices can be also used to enhance the graphical view of pressures across every section and node. Not only that, better control loop tuning can be done to further enhance loop functioning down the line of a given section, based on pressure variations not directly related but which do have an impact on subsequent nodes. Pressure losses or unnecessary gains along the sections of piping can be carefully studied in real time. Pump and compressor efficiencies or lack thereof can be corrected, if possible, due to the variations in suction and discharge pressures due to upstream or downstream pressure variations. Since pressure variations transmit at acoustic speeds through the plant systems, end to end study becomes a very useful tool in overall plant efficiency study in terms of equipment operations, piping design, energy conservation, equipment efficiencies and also maintenance issues that might be observed as a result of such studies.