How accurate is your SIL Loop flow meter?

 When designing a SIL loop, engineers usually will rely on a FMEDA tool by renowned companies like TüV or Exida. These tools include the safety relevant factors of a broad range of sensors, logic solvers and actuators provided by Endress+Hauser and alternative suppliers. When designing our new generation flowmeters, we designed these according to IEC 61508, striving to reach the best safety factors on the market. Our Prowirl 200, as an example, has a lambda(du) of only 70 FIT, resulting in a PFD_avg (1 year) of 0.00031. This allows the meter to be used in SIL 2 loops or the Dualsens version (1 meter body with 2 independent sensors and electronics) even in SIL3 loops (1oo2 architecture).  When we launched our new product line in 2013, these values were un-matched on the market.

Just recently, however, I found another vortex manufacturer publishing similar safety values. I soon found out, how they were able to reach these values: In their SIL handbook, they published an uncertainty that is much worse than for the standard device: Instead of the standard uncertainty of 0.75% for liquids and 1% for gas and steam, they claimed an uncertainty of 4%! An increased uncertainty allows to cover more drift of the electronic components resulting in better safety values. Our Prowirl 200, however, specifies its values at the standard uncertainty of 0.75%/1%! The additional uncertainty of alternative suppliers, however, is not reflected in the FMEDA tools mentioned above. We recommend to always read the SIL handbook carefully. In summary, Prowirl 200 is still the best vortex solution available for SIL loops today helping to increase safety and comply with safety relevant standards. In addition to reducing random failures, it also reduces systematic faults through its robust design.

Do you want to learn more about SIL and the safety relevant parameters of SIL capable certified measurement family? Please follow this link:

https://www.endress.com/SIL