4. When operator response can be effective, provide an independent high level alarm at a setpoint that gives the operator sufficient time to top accumulation of level before the trip setpoint is reached.
5. When an overfill leads to release of highly hazardous chemicals or to significant equipment damage, design and implement an automated overfill-protection system.
6. Determine the technology most appropriate for detecting level during abnormal operation. This technology may differ from the one applied for level control or custody transfer.
7. Finally, provide means to fully proof test any manual or automated overfill-protection system to demonstrate its ability to detect level at the specified setpoint and take action in a timely manner.
Angela E. Summers, Ph.D., is president of SIS-TECH Solutions, LP, Houston. E-mail her at email@example.com.
1. "1998 Esso Longford Gas Explosion," Wikipedia, http://en.wikipedia.org/wiki/1998_Esso_Longford_gas_explosion.
2. "Texas City Refinery (BP)," Wikipedia, http://en.wikipedia.org/wiki/Texas_City_Refinery_(BP).
3. "The Buncefield Incident 11 December 2005: The Final Report of the Major Incident Investigation Board," Buncefield Major Incident Investigation Board, London (2008). Available online at www.buncefieldinvestigation.gov.uk/reports/index.htm#final
4. "Buncefield blast could cost ₤1 billion," British Broadcasting Corp., London (December 11, 2008). Available online at http://news.bbc.co.uk/2/hi/uk_news/england/7777539.stm.
5. Boyes, W., "First the Application, Then the Product," p. 45, Control (Feb. 2007). Available online at http://www.controlglobal.com/articles/2007/022.html.