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Controls for Dehy Skids

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At the new unmanned gathering stations, gas flow and pressure are monitored. The flow rate signal is routed to the Dehydration Skid's Control Panel, which then regulates the glycol level in the contactor, the burner temperature, and the glycol recirculation rate. If the flame goes out, the panel triggers a re-ignition sequence and annunciates an alarm if the burner fails to start after a number of tries.

To increase efficiency and lower costs, this gas company wanted their gathering stations to operate unmanned under standardized automation systems. They called on SKW to specify the instrumentation required and to develop an electronic control system to optimize operations.

Maintaining safety while replacing pneumatic with more capable electronic controls was of the highest importance. In addition, operations group wanted to be immediately notified of outages and emergencies. Previously, a skid could be down for 24 to 48 hours without notification.

The new skid control system can be "mass produced" at the factory and more easily maintained, while fewer electrical connections have to be made in the field for continuous operation – or in rare cases, warning of a failure – prevents the formation of ice or hydrates that can harm instruments and block the line.

The new skid control system is comprised of three components: a Control Panel houses the PLC skid controller and HMI. A VFD Panel holds the variable frequency drive for the glycol recirculation pump, better regulating its operation while saving energy. The Battery Panel contains back-up power in the event of a power interruption.

Optimal placement of the Control Panel necessitated an analysis of hazardous area requirements to ensure compliance with NFPA rules for Hazardous Classification. The panel was mounted safely at an appropriate classification level. SKW provided a drawing set specifying P&ID, panel layout, electrical interconnections, and terminal block layout and assignments. The scope of work includes development of a Operating Procedures Manual and services for panel installation on multiple skids.