Engineered Automation & Power Solutions

Vapor Recovery Application Note

Application Overview

The Environmental Protection Agency mandated that all oil refinery marine holding terminals eliminate the release of hydrocarbon vapor into the environment during shiploading operations.

The vapors are produced as gasoline or other petrochemical substances displace the atmosphere in the ship or barge holding container. As a result of the mandate the industry incorporated Marine Vapor Recovery Units (MVRU) in many of their facilities.

IT McGill, an International Technology Corporation (IT) subsidiary, subcontracted Engineered Software Products to implement the control system for the MVRU’s. The installations were carried out at multiple sites throughout the United States. There are two types of MVRU systems used in the industry. The Thermal Oxidizer Unit draws the vapors from the container and burns them in either a flare or thermal oxidizer. The Recovery Unit recycles the exhaust through carbon filters to reclaim the vapors for subsequent reprocessing and resale.

IT McGill

Application Highlights

  • The MVRU control system used a GE Fanuc PLC with distributed I/O and a Cimplicity Operator Interface Terminal (OIT). Each dock, where the vessels are loaded, has a hardwired control panel, which the dock operator uses to control and monitor the system.
  • ESP also provides support service with a direct connection to the system via a modem. This service allows ESP to quickly respond to support issues without spending time traveling to the site.
  • The Cimplicity OIT is utilized for central monitoring and control. The OIT displays the system status, allows the operator to tune the PID loop parameters, change alarm limits and manually step the Thermal Oxidizer through its start-up sequence.
  • The OIT also displays any I/O or PLC fault detected within the system. The tri-state inputs, used with the distributed I/O, provide feedback data on open or faulty wiring circuits to the field devices.
  • The fault detection system is a very useful tool for the maintenance electrician troubleshooting the system. Since downtime during a load is very costly, this feature enables plant personnel to efficiently evaluate and resolve problems quickly.

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