**** Don't Alarm your Operators! ****
Short Article by Karthikeyan (Karthik) Balan.
Its true, why continuously add more and more Alarms/Shutdowns which are not truly needed. They confuse personnel especially with an ongoing incident. They also add greatly to central control room daily Alarms to be deactivated, and the huge amount of field instruments involved require an army of instrument technicians to perform P.M.s.
We performed an Alarm/Shutdown reduction exercise at the commisioning stage of a Refinery Clean Fuels Project for the major rotating equipment trains and auxiliaries. We reduced them by about 30% across the board. These eleven trains have not had any DCS shutdowns so far in 2.5 yrs due to this trip reduction exercise. I can also advise:
1- Removing excess instruments-controls when possible during detail design stage of process plants,
2- Adding control logic to process shutdown loops so that an instrument shutdown will require an AND command to justify a unit shutdown, in collaboration with another instrument. [When A AND [ B OR C ] have reached trip= Shutdown Unit]. This reduces the need for the many, expensive 2oo3 voting installations. Notice that we must use at least one of two other instruments to justify a shutdown. This is in case of B malfunctioing, at least C will work with A to shutdown. But operators must be taught that DCS is using AND commands.
3- Trip reduction survey for all major rotating equipmnet trains should be mandatory evaluation at Detail design or commisioning stage.
4- Combined Process Trip reduction surveys & Hazop analysis should be applied to complete existing process plant, with following options:
A-Eliminating some trips entirely, and relying on Alarm only.
B- Maintaining a Trip point but extending its process parameter limit to higher range above original design, limit to reduce possibility of shutdowns when a process variation upset occurs.
See this excellent presentaion to Help your Reduction Study:
https://lnkd.in/dMtTaz8K
#processengineer #processcontrol #DCS