Safety Systems for Tank Overfill Protection, Part 4

This is the last of 4 parts of a white paper by Tom Jeansonne who is technical product manager at Emerson Process Management Valve Automation, Waller, TX.  He has more than 30 years of experience in the valve and valve automation industry with both distributors and manufacturers.  He can be reached at tom.jeansonne@emersonprocess.com

Why Use an Integrated System?

The oil and gas industry, with its storage and handling of hazardous liquids, recognizes the need for a formal SIS and a FCE comprised of components applied to specific SIL levels.  It is prudent and advantageous for the entire FCE to be provided in a fully integrated, factory-tested and certified package that can be installed easily at the terminal. 

This integrated systems approach allows the end user to specify functionality, rather than attempting to select individual components to be merged together in a SIS system. This integrated control solution system should contain the actuator, valve, DVC, relief valves, regulators, air relays, solenoids and all tubing and hardware needed.  The simplest FCE might consist of as little as a solenoid, actuator and valve. The systems should be comprised of all new components. No remanufactured, rebuilt or existing equipment shall be used. All components shall be of new and latest construction, assembled and tested as a integrated package.

The SIL data utilized, and the resulting report and certification for these integrated solutions shall have been verified through a third party independent entity.  The certification process provides functional safety assessments of the components intended for SIS.  A certification shall be issued describing the product analysis, components and the application criteria needed to continually meet the SIL level requirement and certification. 

Impact of FCE in Overfill

In addition to reducing risk and exposure to the facility personnel, civilians and assets, the following FCE overfill implications should be considered

  • Preserving and protecting the environment,
  • Mitigation of the affects of any overfill,
  • Legal actions and resultant regulations
  • Lower operating costs, reduction of downtime
  • Clean up cost savings
  • Fines, penalties and property damage claims
  • Lost revenue, goods and production
  • Human “alarm overload”, inexperience and reaction time
  • Transportation, outside business disruption and emergency support dilution
  • Damaged reputation, corporate citizenship, socio-economic issues
  • A deterrent to product theft and better inventory control.
  • Effect on future expansion, permits, locations or scope plans 
  • Your very own disaster marker on an internet map
  • PFD values can be increased by partial stroke testing (PST)
  • Partial Stoke Testing (PST) can safely extend time between plant shutdowns
  • PST Allows SIL Rating To Be Maintained for Longer Continuous Operating Periods

Conclusion

The application of a qualitative, risk assessment and/or hazard operability (HAZOP) study followed by the institution of a proactive SIS provided by a true solution integrator and well considered emergency management plan will benefit all.  Periodic testing using a partial stroke technique and diagnostic DVC allows a quantifiably higher level of operating confidence with very minimal disruption to the facilities operation or investment. 

The best SIS in the world is not effective if the SIF cannot be carried out because of a inoperable or deficient FCE. How do you know yours will function when required?