Arborion Global | Process Safety & Engineering Consultancy

Technical overview

Process Flow Diagrams
(PFDs) & P&IDs

PFDs and P&IDs are the primary engineering documents that define process flows, equipment, control systems, and safety instrumentation. They form the basis for HAZOP studies, SIS design, procurement, construction, and operations — making accuracy and completeness critical to plant safety and reliability. A poorly drawn P&ID introduces errors that propagate from HAZOP through SIS design into field installation. Arborion Global designs P&IDs from first principles, checks them against every discipline input, and maintains them as living documents through the plant lifecycle.

Engineering process

Process Flow Diagrams (PFDs) & P&IDs workflow

Data Gathering & Basis

Review existing PFDs, equipment lists, line lists, HAZOP scope, and relevant process licensor documentation.

Symbology & Convention Alignment

Agree ISA-5.1 / ISO 10628 symbol library, tag-numbering format, line designation, and revision control protocol.

PFD Development

Develop process flow diagrams with stream tables, heat/material balances, and major control loops per system.

P&ID Development

Detail all pipework, instrumentation, interlocks, relief devices, and utility connections per ISA-5.1 convention.

Review & Reconciliation

Cross-check P&IDs against HAZOP requirements, equipment datasheets, and line schedules; resolve all discrepancies.

Controlled Issue & As-Built

Issue for construction with revision register; conduct as-built field survey and update documents to reflect installation.

Process Flow Diagrams (PFDs) & P&IDs — Scope

Scope of work

Every deliverable — from basis to handover

Complete Process Flow Diagrams (PFDs) & P&IDs scope — every calculation, drawing, specification, and construction support activity.

PFD development: stream tables, heat/material balances, major equipment, and control loops

P&ID design covering all pipework, equipment, instrumentation, interlocks, and relief devices

Instrumentation and control loop designation per ISA-5.1 / ISA-5.3

Safety-critical interlock, ESD trip, and SIS boundary representation

Relief device, vent, drain, and utility connection representation

Line list, instrument index, and equipment list generated from P&ID

Systematic P&ID review against PFD, datasheets, HAZOP requirements, and equipment schedule

As-built field survey, mark-up, and controlled document update

Engineering outcomes

Outcomes of Process Flow Diagrams (PFDs) & P&IDs

P&ID & PFD Engineering Quality

Accurate P&IDs are the foundation of HAZOP and process safety studies
Correctly represented safeguards support LOPA IPL credit
SIS interlocks correctly documented for IEC 61511 compliance
Relief device representation supports pressure protection review

ISA-5.1 / API / ASME P&ID Defence

HAZOP baseline document — errors in P&IDs propagate to HAZOP findings
OSHA PSM process safety information — P&IDs required at operating level
ASME and API code compliance via correct equipment representation
SIS design basis requires correct P&ID representation of logic

Operability & Commissioning Clarity

Operators and maintenance technicians rely on accurate P&IDs daily
Commissioning and startup require correctly issued P&IDs
MOC basis — all changes must be reflected in updated P&IDs
Training resource for new operators understanding the process

P&ID Revision & Construction Cost Efficiency

P&ID errors found in FEED are far cheaper to fix than in construction
Accurate P&IDs reduce commissioning rework and delays
Prevent costly field changes from misunderstood design intent
As-built P&IDs prevent unsafe field workarounds over plant life

Process Flow Diagrams (PFDs) & P&IDs

Process Flow Diagrams(PFDs) & P&IDs

Process Flow Diagrams (PFDs) & P&IDs workflow

Every deliverable — from basis to handover

Outcomes of Process Flow Diagrams (PFDs) & P&IDs

Ready to start your project?

Process Flow Diagrams
(PFDs) & P&IDs