Blog.
Field notes on P&ID extraction, ISA 5.1, and instrumentation engineering.
Archive.
Marshalling cabinet sizing from an I/O list. The rules that survive the fieldFebruary 2026Marshalling cabinet sizing from a structured I/O list: terminal-density rules, intrinsic-safety zoning, and the SIS/BPCS separation that drives cabinet count.PLC card sizing from a P&ID. The math, the rules, and what to bake into your bidDecember 2025PLC card sizing from a P&ID: an I/O count to a card-sizing rollup, channel-density math, vendor differences, spare-capacity rules, and bid-to-cabinet gotchas.Validating an I/O list against P&IDsNovember 2025Why I/O lists drift from drawings, what discipline keeps validation tractable, and what the MOC change report needs to contain.DCS migration. Reconstructing current scope from P&IDsOctober 2025Why DCS migration discovery work overruns, what the as-built scope actually means, and how to keep the discovery phase from blowing the schedule.Counting instruments on a P&ID without missing scopeSeptember 2025Counting instruments on a P&ID: what counts on a bid I/O count, how to handle redundant pairs, what to ignore, and tag-suffix patterns that flag missed scope.What Changed in ISA 5.1-2022 for I/O ListsAugust 2025ISA 5.1-2022 is the first major revision in a decade: clearer conventions for digital and shared-display instruments and refined panel-mounting symbology.Reading Legacy 1980s P&IDs. A Digitizing GuideJuly 2025Legacy 1980s P&IDs use conventions not always compatible with modern ISA 5.1: what the older drawings get right and where they confuse modern engineers.
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