Modular skid systems are increasing in popularity in the process industry as a way for owner/operators, OEMs, and plant engineers to fabricate their unit operations. This post discusses level and flow instrumentation for gas compression skid systems and is part of a Magnetrol® occasional blog series on solutions for modular skid system applications.
Gas compressors are used wherever higher pressures or lower volumes of a gas are required, including: natural gas pipeline transport, refrigeration, combustion air, gaseous fuels, and process gas compression. Gas compression systems are typically used in petroleum refineries, natural gas plants, petrochemical plants, and chemical facilities.
Gas Compression Skid
Commonly found in power generating, steel making, and boiler plants, this compression system increases the pressure of the fuel gas to a level suitable for optimum combustion in a gas turbine, furnace, or boiler. Natural gas and biogas are frequently compressed.
Supported by a lubrication and cooling system, an electric motor drives the fuel gas compressor. After the gas is compressed, it is scrubbed in a separator and routed to the application.
Level and Flow Applications
1. Lube Oil System
The skid’s integral lubricating system prevents damage to the skid motor and compressor caused by excessive friction. Lubricating oil stored in larger integral stainless steel or carbon steel tanks is monitored for level.
Continuous Level: Eclipse® Model 706 Guided Wave Radar Transmitter or E3 Modulevel® Displacer Transmitter
Point Level: Tuffy® II Float Switch; Model B35 External Cage Float Switch; or Echotel® Model 961/962 Ultrasonic Switch
Flow Alarm: Thermatel® Model TD1/TD2 Thermal Dispersion Switch
2. Inlet Separator
The gas inlet separator vessel provides liquid/condensate removal prior to gas compression. A level switch actuates a high level alarm, shutdown protection, or opens a dump valve for disposal of accumulated liquid.
Point Level: TUFFY II Float Switch; or ECHOTEL Model 961/962 Ultrasonic Switch
3. Discharge Separator
A dual-chamber discharge separator for oil/condensate removal features high-efficiency coalescing filter elements to limit oil carry-over. Level switches in the separator’s lower and upper chambers provide high level alarm and shutdown capabilities.
Point Level: TUFFY II Float Switch; Model B35 External Cage Float Switch; or ECHOTEL Model 961/962 Ultrasonic Switch
4. Gas Flow To Turbine
Movement of skid gas destined for the turbine—be it natural gas, methane, syngas, or biogas—is frequently monitored for mass flow. A flow switch offers alarm or shutdown protection in the event of gas flow interruption.
Continuous Gas Flow: THERMATEL Model TA2 Thermal Dispersion Mass Flow Meter
Flow Alarm: THERMATEL Model TD1/TD2 Thermal Dispersion Switch