Coker Drum Switching and De-Heading

Coker drum switching and de-heading poses challenges to safe and reliable operation of the Coker Unit. Safety issues are generally related to release of hydrocarbons to the atmosphere by either opening in an in-service drum and allowing hydrocarbons to enter an open drum. End users have often struggled with identifying the necessary Safety Instrumented Functions (SIF) to prevent these loss of containment events. Preventing these events by implementing the SIF’s in the valve control system PLC means the system is classified as a Safety Instrumented System (SIS) requiring that it be implemented in a safety rated PLC.

The DIAMOND SIS® Coker Drum Switching and De-Heading is a standalone SIS logic solver designed to receive key process variables that are used to determine when the drum is in-service or open. When preset conditions are not met the DIAMOND SIS® outputs prevent the opening of selected valves. Process inputs to the system are overhead pressure, overhead temperature and inlet temperature and outputs from the system are supplied to prevent opening of the vent, drain, top/bottom head, blowdown, overhead to fractionator and inlet feed.

  • This design greatly simplifies the SIS and allows the valve control system to be implemented in a non- safety rated PLC.
  • Each Coker drum is monitored and protected by a stand alone safety system.
  • The failure, maintenance or testing of any one safety system does not affect the operation of the other drums.

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