Process Safety Analysis (HAZOP)

Proof required

Submit: (1) the Process Flow Diagram (PFD) with equipment tags, stream labels, and process parameter annotations (draw.io export or equivalent); (2) a design intent statement for the system (200–300 words) covering: what the system is designed to do, the key process parameters it operates at (normal operating temperature, pressure, flow), and the key safety constraints (maximum allowable working pressure, maximum temperature, minimum flow to prevent cavitation or dry running); (3) a stream table listing all process streams with their normal operating conditions.

What gets checked

• PFD includes equipment tag numbers for all major equipment — 'HX-101 (shell-and-tube heat exchanger)' and 'P-101 (feed pump)' are valid tags; unlabelled boxes are not engineering drawings
• Stream table lists at least temperature, pressure, and flow rate for all named streams — a stream table with only stream names and no operating conditions has not captured the design intent
• Design intent statement specifies the maximum allowable working pressure (MAWP) or maximum operating temperature as a safety constraint — these are the parameters that HAZOP deviations will be assessed against

Common mistakes

• Selecting a system so simple it has fewer than five process lines — a single pipe from a tank to a pump has one process line; a HAZOP on one line cannot demonstrate the systematic deviation study methodology across multiple nodes
• Drawing a block flow diagram rather than a process flow diagram — a block flow diagram shows process steps as boxes; a PFD shows equipment symbols (heat exchanger symbols, pump symbols, vessel symbols) with stream connections and operating parameters

Resources

What a verifier looks for

• Engineering Design Triad: M1 produces a design artifact (PFD with equipment tags, stream labels, and process parameters) — this is the first of three artifact types required across M1–M3.
• PFD must use proper equipment symbols — check that heat exchangers, pumps, and vessels are drawn with standard chemical engineering symbols, not generic boxes.
• Stream table must include temperature, pressure, and flow rate for all streams — check that all named streams have entries.
• Design intent must specify at least one safety constraint with a numerical value — MAWP, maximum temperature, or minimum flow.
• Reviewer must be a chemical or process engineer — PFD accuracy and design intent completeness require discipline-specific expertise.

Proof required

Submit: (1) the completed HAZOP worksheet table covering at least three nodes — the table must include columns for: Node, Parameter, Guide Word, Deviation, Cause, Consequence, Existing Safeguards, Recommendation; (2) a brief methodology note (100 words) confirming the team composition (real or hypothetical), the node boundaries used, and any deviations that were screened out as non-credible with the reason.

What gets checked

• HAZOP worksheet covers all six guide words for Flow and Pressure at every node — a worksheet that applies only 'No Flow' and 'High Flow' has not completed the systematic guide-word study; 'Reverse Flow', 'Low Flow', 'Other Than' (wrong composition in stream), and 'As Well As' (contamination) must also appear
• Every meaningful deviation has a populated Cause, Consequence, and Safeguard column — a deviation row with 'N/A' in the Consequence column when the consequence is potentially serious indicates the study was not conducted with sufficient rigour
• Recommendations are specific and actionable — 'install a low-flow alarm on FIC-101 with setpoint at 20% of normal flow, to alert operator before pump cavitation damage occurs' is a valid recommendation; 'add more instrumentation' is not

Common mistakes

• Applying only 'High' and 'Low' deviations and omitting 'No/None', 'Reverse', 'Other Than', and 'As Well As' — a partial guide-word study is not a HAZOP; the systematic completeness of the guide-word application is the defining feature of the methodology
• Recording consequences as 'process upset' without specifying the physical mechanism — a consequence must describe what physically happens: 'pump cavitation, leading to pump damage and potential seal failure with consequent hydrocarbon release' is a valid consequence; 'process upset' is not

Resources

What a verifier looks for

• Engineering Design Triad: M2 produces an analysis artifact (HAZOP worksheet — a systematic hazard analysis) — this is the primary deliverable of the HAZOP study.
• All six guide words must appear for Flow and Pressure at each node — check that 'No/None', 'More', 'Less', 'Reverse', 'Other Than', and 'As Well As' are all represented.
• Consequences must be physically specific — check a random sample of five deviation rows; reject any consequence described as 'process upset' without a physical mechanism.
• Recommendations must be specific and actionable — check that each recommendation names a specific instrument, interlock, or procedural change.
• Reviewer must be a chemical or process engineer with HAZOP or process safety experience — HAZOP worksheet quality and recommendation completeness require discipline-specific safety engineering expertise.

Proof required

Submit: (1) the complete HAZOP report (all sections above); (2) the risk summary table (top five hazard scenarios with severity, likelihood, and risk rating from the risk matrix); (3) the recommendations register (all recommendations with priority, responsible party, and target date); (4) a written record of the reviewer's completeness challenge and your response (250 words minimum, attributing reviewer by professional role and HAZOP experience).

What gets checked

• Risk summary table uses a risk matrix with explicit severity and likelihood criteria — 'High severity: potential for fatality or serious injury; Medium severity: potential for injury requiring medical treatment; Low severity: minor injury or no injury but process disruption' are valid criteria; 'High/Medium/Low' without criteria cannot be consistently applied
• Recommendations register assigns a priority to every recommendation — 'Priority 1 (Critical — implement before next start-up)' and 'Priority 3 (Opportunity — implement at next planned shutdown)' are valid priorities; unranked recommendations leave the operating team with no guidance on what to do first
• Reviewer challenge addresses the completeness of the guide-word application — 'you identified High Flow as a credible cause but did not consider the scenario where the control valve fails open due to instrument air failure, which would also cause High Flow; this needs a separate cause entry' is a valid completeness challenge

Common mistakes

• Producing a risk matrix without defining the severity and likelihood criteria before applying it — a risk rating of 'High' applied inconsistently across the hazard scenarios is worse than no risk rating, because it gives a false sense of relative priority
• Omitting the recommendations register — the HAZOP worksheet identifies hazards; the recommendations register is what makes the HAZOP actionable; a HAZOP report without a register is a hazard identification exercise, not a safety management tool

Resources

What a verifier looks for

• Engineering Design Triad check: M1–M3 together produce a design artifact (PFD with design intent + stream table), an analysis artifact (HAZOP worksheet with systematic deviation study), and a documentation artifact (HAZOP report with risk summary table and recommendations register) — confirm all three types are present.
• Risk matrix must define severity and likelihood criteria explicitly — check that the criteria are stated in the report, not just implied.
• Recommendations register must assign priority to every recommendation — check that no recommendation is unranked.
• Reviewer challenge must address a specific node's completeness — a general approval is not a completeness challenge.
• Reviewer must be a chemical or process engineer with HAZOP experience — HAZOP completeness evaluation and risk matrix calibration require discipline-specific safety engineering expertise.
• The Proof Accessibility Rule applies — draw.io, UK HSE publications, EPA resources, IChemE free resources, and AIChE CCPS free introductory content are all accessible without payment.