EDITOR’S CHOICE
P&ID QUALITY IS A COST CONTROL MEASURE
The hidden cost of P&ID drawing errors on process plant commissioning, by Darren Fenton, Founder, Outsource CAD
A
P&ID drawing error discovered during commissioning is rarely just a documentation problem. It is a delay. And in the process plant and oil and gas sector, delays during
commissioning translate directly into significant costs – lost production revenue, extended engineering contractor time on site, and the expense of resolving the discrepancy between what the drawings show and what was actually built or specified.
The consequences of a P&ID inaccuracy depend on where in the process it is discovered. An error found during HAZOP review can be corrected with a drawing revision. An error found during pre- commissioning checks requires field verification and may delay the sequence of activities that follow. An error discovered during first start-up can require a process shutdown to resolve. Understanding where P&ID errors originate, and how to reduce their frequency, is a legitimate cost control issue for any process plant project – not just a quality management obligation. P&ID inaccuracies enter the drawing record at several stages of a project’s life. During detailed design, errors can arise from symbol inconsistencies, incorrect instrument tag assignments, missing tie-in points, and failure to capture all control loop logic. These are often the result of working to multiple symbol libraries simultaneously or applying changes to one sheet without updating related sheets. During construction, field changes are the primary source of deviation between the P&ID and the as-installed plant. Pipework re-routes, equipment substitutions, valve relocations, and instrumentation changes made during construction create a gap between the drawing and reality. When these changes are not captured in redline
markups or incorporated into the P&ID promptly, the gap widens throughout the construction period. During the plant’s operational life, process modifications made for operational reasons – adjusted setpoints, additional isolation valves, instrument replacements – create further drift between the P&ID and the actual plant configuration if the drawing record is not maintained.
The commissioning consequence Commissioning teams work from P&IDs as the authoritative reference for the plant’s process and control systems. When the drawing does not match the installed plant, the commissioning team must resolve the discrepancy before proceeding. In a simple case, this means a field walk to verify the actual configuration and a drawing correction. In a complex case, it can mean halting commissioning while the design team investigates whether the deviation is acceptable, requires a process change, or requires physical modification to the plant. On large EPC projects, where commissioning is a critical path activity with significant daily cost implications, a cluster of P&ID errors can extend the commissioning programme materially. The total cost of resolving P&ID discrepancies – in engineering time, contractor time, and schedule delay – frequently exceeds the cost of the original P&ID drawing programme several times over. For most process plant projects, P&ID drawing
production is managed as a documentation deliverable rather than a project risk. Drawing production is specified, contracted, and checked as a completeness exercise – are all sheets present, are all tags listed – rather than an accuracy exercise. A more rigorous approach treats P&ID quality control as a cost control measure. This means
independent QA checks of P&ID drawings against the design basis, the PFDs, and the instrument index at key project stages. It means a structured redline management process throughout construction to keep the drawing record current. And it means a final as-built P&ID verification check before commissioning, using field-verified data rather than just the drawing record.
The cost of this additional rigour is modest
relative to the cost of commissioning delays caused by drawing errors. A structured P&ID QA programme adds a small percentage to the drawing production budget but can eliminate a disproportionate number of the commissioning problems that generate the largest project costs. P&IDs are living documents. The most accurate P&ID at first start-up is still only accurate until the first operational modification. Process plants that maintain their P&IDs through a disciplined management of change process – requiring all modifications to be reflected in the P&ID before implementation, not after – operate with a drawing record that can be trusted by the maintenance team, the safety team, and the future modification design team. Plants that allow P&ID currency to drift
through the operational phase accumulate risk. Future HAZOP reviews, process modifications, and expansion projects are all compromised by a drawing set that does not accurately reflect the plant as it currently operates.
The P&ID is arguably the most important document on a process plant. Treating its production and maintenance as a cost item to be minimised is a false economy.
Outsource CAD
outsourcecad.com
SEPTEMBER 2026 | PROCESS & CONTROL ENGINEERING
37
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44
