Emergency shut down

• PGC


  Chemical Process Technology
• Emergency Shut-down of a PGC

  1. When further operation will post a danger to the plant

  2. When there is a total loss of power supply to the PGC

  3. When there is loss of air supply to the PGC
• Lost Power


  1. Electronic controller stop

  2. Solenoid valves go to fail-safe positions

  3. Switching valves hold last positions

  4. Sample and carrier gas trapped in columns and tubing

  5. Isothermal oven and electronic box still purged by air

  6. Positive pressure environment maintained
• Lost Air Supply


  1. Solenoid valves go fail-safe positions

  2. Switching valves hold last positions

  3. Sample and carrier gas trapped in the columns and tubing

  4. Fans in isothermal and programmable oven stop

  5. The oven and electronic box no longer purged

  6. Positive pressure environment not maintained

  7. Power to electronic box and oven cut-off
• Likely Impact


  • PGC will be out of service following recovery from emergency situation
  • PGC need to be purged, cleaned and calibrated
  • Out of service at least for a few days, if no other damage occurs
  • Gasket and switching valves components may fail
  • If parts damaged, extensive period of out of service, as many of the parts in a PGC are customized to the particular PGC only
• Remedial Actions


  1. Extensive displacement runs can sometimes remove any sample and contaminants that be left in the systems and restore to operational level

  2. Salvage from old units or spare units, or obtained from vendors for more common parts
• Adapted from the following Yokogawa instruction manuals
• 09 IM11B03A03-01E_050 Overview
• 10 IM11B03A03-02E_041 Basic Operation
• Emergency Shut Down (ESD) is the process to stop production, prevent damage or injury, and protect people.
• The ESD system consists of an initiating device that detects abnormal conditions, such as high temperature, low pressure, or loss of power supply, and sends a signal to activate the emergency shutdown valve(s).
• There are two types of ESD systems: local and centralized.
• The ESD procedure must be followed when there is an unplanned event such as equipment failure, loss of utility supply, etc.