Abstract

This chapter discusses man-machine interface. PLC has to “connect” to human operators, accepting commands from them and displaying the status of the plant in a form that can readily and easily be understood. A digital display driven in BCD normally uses one of the unused binary codes, 1010 to 1111, to generate a blank display. Simple digital inputs (pushbuttons, joysticks, switches) are normally allocated one input per motion and do not require anything particularly special. Concerning PLC with analog signals, flows, temperatures, pressures, etc., these will usually be displayed to the operator. A graphics terminal has just two connections to the outside world, a serial link connection and a power supply. The Allen Bradley Panelview family was designed to replace switches, pushbuttons, numeric displays, and similar devices. The Panelview built up a graphics screen with semigraphic characters placed on a screen with a “pick and place” menu approach. Siemens provides a vast range of operator terminals from simple text-only message displays to complete computer-based Scada systems. One major advantage of graphical displays is that mistakes can be rectified without leaving scars, albeit at some cost. The operator will need to input data and initiate actions. Where a simple text message is to be displayed, possibly with embedded data, message displays driven by a simple serial link carrying ASCII coded characters can be used. PCs have much better graphics capability than the average PLC, so it is not surprising that PCs are increasingly being used as the link between humans and PLC systems. Document type: Part of book or chapter of book

Abstract

This report covers the design and fabrication of a conformable eddy current array useful for the mapping and measurement of external corrosion on a transmission pipeline. The feasibility of the basic measuring approach was demonstrated and the general guidelines for sensor design were disclosed in a previous project. This project was concerned with design of a practical array, development of interface electronics, and design of the operation and analysis software. A prototype system was constructed, checked out, and demonstrated on natural corrosion in a field environment. Document type: Report

Abstract

The extensive network of high-pressure natural gas transmission pipelines covering the United States provides an important infrastructure for our energy independence. Early detection of pipeline leaks and infringements by construction equipment, resulting in corrosion fractures, presents an important aspect of our national security policy. The National Energy Technology Laboratory Strategic Center for Natural Gas (SCVG) is and has been funding research on various applicable techniques. The WVU research team has focused on monitoring pipeline background acoustic signals generated and transmitted by gas flowing through the gas inside the pipeline. In case of a pipeline infringement, any mechanical impact on the pipe wall, or escape of high-pressure gas, generates acoustic signals traveling both up and down stream through the gas. Sudden changes in flow noise are detectable with a Portable Acoustic Monitoring Package (PAMP), developed under this contract. It incorporates a pressure compensating microphone and a signal- recording device. Direct access to the gas inside the line is obtained by mounting such a PAMP, with a 1/2 inch NPT connection, to a pipeline pressure port found near most shut-off valves. An FFT of the recorded signal subtracted by that of the background noise recorded one-second earlier appears to sufficiently isolate the infringement signal to allow source interpretation. Using cell phones for data downloading might allow a network of such 1000-psi rated PAMP's to acoustically monitor a pipeline system and be trained by neural network software to positively identify and locate any pipeline infringement. Document type: Report