Startup overide list

My best guess is that the process conditions are not 'normal' during startup of a plant, process or unit.

So, some of the interlocks, alarms or permissives that are built into the PLC, DCS or hardwire control logic will need to be bypassed or overridden during startup, and then placed back into service once the unit is up and running.

Your company/plant should have a process for such things. Operations needs to be aware of what is overridden before they start and while they are running. The engineer or technician should be very explicit in what work is being performed (or that the process is in startup), and Operations needs to sign each item on the override list and it should be posted. Each item should also have a maximum time that it can be overridden. It can be on a simple excel spreadsheet.

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This is normally the space where people post something insightful.

In complex processes there can be many out-of-bounds control regions all present at the same time causing alarms and logical blocks preventing other systems from operating. This is all well and good during production when you don't want bad/out-of-spec product running thru the system but can be a circular problem preventing a cold start up from ever succeeding.

Hence a startup list that allows certain alarms and blocks to be bypassed and quenched to get things up and running. They are listed as they usually come from a well thought-out start-up plan that can include many potential problems and disasters if not handled correctly. All overrides would normally be expected to be removed sequentially as the system reaches nominal conditions.

It's usually part of the operations manual. A chapter on start-up.

Keith Cress
kcress -

Startup overrides are identified in the plant shutdown matrix or cause and effects diagram. The description for the SOS should be in the process control narratives or the process safeguarding memorandum (PSFM) / narratives. Startup overrides should be manually armed /activated and most preferably, startup overrides should be auto disarmed when the process variable is back within the normal operating bounds. If you like, you can have a summary list of these SOS in the PCN and PSFM also in an appendix if that helps.

Development of these critical documents is mainly the task of the plant process engineer and some input from the plant DCS / PLC controls engineer is also required. In many cases, a great deal of time, sweat and tears involved.