Safety Instrumented Systems

Reader Feedback: From the ControlGlobal Community

More Readers Chime in to McMillan's Emergency Shutdown of LPG Tank Farms Article

[Editor's note: The following response is to Greg McMillan's ControlTalk blog post, "How a Young, Small Company Can Maximize Performance," from a reader who signed on as John First.]

Thank you for the the tips you wrote in this article. Having an open, positive and enabling culture fostered by management has recently elevated and accelerated employee knowledge by providing a means to gain key fundamentals and essential concepts, and is really one of the core things that we do at

Also Read "Emergency Shutdown of LPG Tank Farms"

[The following are responses to a question about emergency shutdown in LPG tanks from our Ask the Experts column and posted on LinkedIn (for the original question).]

From Younes Lahliti: When you say level transmitters do you actually mean level switches (high/low)? It's a little bit confusing when I read the article. Those level switches should be used as "endswitches" for safety reasons. An "analog transmitter" should be used, as far as I know. But when you're under the low level switch-> stops the pump/close the outlet valve. When you're above the high level switch-> close the inlet valve.

From our chief ATE expert, Béla Lipták: A transmitter is an analog device generating a 0-100% output signal as the level in the tank rises from 0-100%. When the transmitter signal rises, say to 95%, one can stop the inlet pump, and when it drops to say 5%, one can stop the outlet pump or close the outlet valve. If one already has a transmitter, it's not necessary to install separate high and low level switches on the tank. In fact, it's better to use the transmitter because that way the high and low settings are adjustable, while the nozzle positions of the switches are fixed."