High process temperatures. Variable ambient temperatures. It’s a combination that has caused a lot of companies with a lot of challenges. One such company is a large Texas refinery with a strong commitment to the environment and safety. Back in 2005, the company had a serious overfill incident, which spurred a major initiative to fill any safety gaps. It also resulted in the creation of a new crude unit on which overfill protection was required because crude levels in the tower can rise rapidly with catastrophic results, requiring a fast level measurement to the SIS system. The crude tower overfill protection requires three independent level measurements to achieve 2-out-of-3 voting for SIS logic. The big challenge arose because process temperature runs around 665oF and traditional high temperature fill fluids in remote seals are simply too slow in relatively low ambient temperatures. Time response could be too slow for process control or the unit could stop responding altogether.
Traditionally, this mismatch between process temperature and ambient has been solved by heat tracing, which is complicated and expensive. New technology from Emerson – the Rosemount 3051S Thermal Range Expander – eliminates the need for heat tracing at a fraction of the cost. This unique system utilizes two fill fluids in a single system allowing each to operate in their optimal temperature ranges and minimizing the impact of low ambient temperatures. (Learn more about this unique technology in this interesting video.)
Since the Rosemount Thermal Range Expander is SIL 2/3 certified, the refinery was able to apply it along with Rosemount ERS Systems to measure the 80-foot span on the crude tower in a 2-out-of-3 voting scheme, providing fast DP level measurements where no other technology would fit.
The business results achieved included higher reliability in both critical measurements, reduced downtime, improved safety, reduced environmental impact, ease of troubleshooting, preservation of crude product and expensive chemically-treated water, and lower maintenance costs. In addition, six costly heat trace circuits on the crude unit and one on the steam drum were eliminated. Above all, the primary objective of the refinery was achieved – safety. Check out this video for more on the unique thermal range expander technology.
Do you have a mismatch between your high heat process and relatively low ambient temperatures? How do you solve it?