Phosphorus trichloride storage tank interlock
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There are existing phosphorus trichloride storage tanks, and a high liquid level SIS interlock is required; what is suitable for this purpose? An opening has been made on the side. Level gauge? Level switch? Which one is recommended for each case?
SIS interlocks recommend level switches, and the specifications also suggest the use of switch-type signals
If the tank itself already has a level transmitter and interlock is required, it is recommended to install another level transmitter for two-out-of-two redundant measurement. Another level switch can also be installed to provide redundant measurement along with the transmitter for use in interlocks. Level transmitters allow for an intuitive observation of the liquid level, as well as the detection of trends in that level, which facilitates troubleshooting during subsequent maintenance.
What level switch should be used? Float ball? Capacitor? A tuning fork? There’s mainly also the price issue
Many specifications require switches, but for stability, it is recommended to use level gauges
For level gauges, level switches are fine for use in alarm systems, but they’re a disaster when used in SIS systems. Moreover, many technical specifications now specify that switches must not be used for safety-related applications