BASIC APPLICATION OF FLOW COMPUTERS AND TELEMETRY SYSTEMS Class #3050

摘要

Prior to the evolution of flow computers being commonly used in the measurement of hydrocarbons,most telemetry systems were used to collect control information and real time data and provide control commands to a Remote Terminal Unit at major pump and compressor stations.Most of the local metering was being handled by chart recorders and local data collection by operations.These charts and reports were sent to a central facility where the information was used to provide custody transfer reports and or operations reports.Most of the commonly used chart recorders used the standard circular chart format and were mostly pneumatic devices.The collection of the circular charts and the processing of the information to provide billing information was a cumbersome and costly task.The measurement departments often had to deal with discrepancies in data and information that was often months old.There was a strong need for collecting real time information for metering and custody transfer.Although there were telemetry systems in place,collecting real time information and getting this information to a central office was not easily accomplished with the types of SCADA systems in place.Most of the early RTU/SCADA systems were used for control purposes,such as start/stop,open/close and alarm reporting.Some units did have analog signal capabilities,and could be used to download remote set points and collect valve positions etc.This was all about to change with the advent of the microprocessor.In the early seventies,the advent of microprocessor systems allowed for the development of intelligent controls such as the PLC,DCS and also EFM devices to name a few.By the mid-seventies,microprocessor systems were being implemented in RTU designs as well,thus allowing remote controls utilizing advanced communication protocols,such as HDLC,Modbus,TiWay,etc.