P&ID
Review Checklist
Piping & Instrumentation Diagram — Systematic Review Tool
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General
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Ensure P&IDs are not crowded — normally no more than 4 pieces of equipment per drawing.
Verify the P&ID matches Process Flow Diagram (PFD) connectivity.
Verify spec breaks over valves/PSVs, steam tracing, and electrical tracing are shown.
Verify all equipment numbers and specs agree with process data sheets, specifications, and equipment list.
Verify insulation requirements for piping, equipment, and instruments are shown where required.
Verify piping, valve, equipment, and instrument symbology and numbering against the standard legend and instrument interface.
Include notes for any items rotated for access (e.g. handwheels) — confirm rotation angle is feasible given bolt-hole count per
ASME B16.5
.
Verify revision, purpose of revisions, numbering, and P&ID title are correct.
Show notes whenever items must be within sight of each other (e.g. level gauge visible from manual valve).
Verify notes for reference drawings, including Decommissioning/Removal P&IDs.
Verify all Notes/Holds are relevant, clearly referenced, correctly spelled, and that standard project notes and holds are included on each drawing.
Verify utility P&IDs tie in correctly to main drawings and show connection to utility stations and analysers.
Verify all mark-ups were applied by drafters correctly with correct spelling.
Check the drafting process did not introduce random new errors away from revised/marked-up areas.
Verify revision triangles, clouds, and other revision markings are added or removed as required.
Verify provisions for future expansion are shown, if anticipated.
Check company document/drawing number is present.
Check client document number is present.
Check licensor/vendor document number is present.
Verify title block By/Approved/Checked fields are filled and signed; date, revision, all company logos, and client signoff blocks are shown.
Conduct pre-HAZOP review of processes shown on the P&ID and related P&IDs.
Conduct pre-Constructability review.
Clear all HOLDs before final issue.
Process Lines
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Verify line numbers and cross-check with line schedule and sizing. Verify all pipe specs are shown and correct.
Verify flow direction arrows are on each turn of a line and point in the correct direction.
Verify lines connecting to a main flare line connect from above — including detours if needed — to ensure proper drainage.
Show tie points at all old/new line interfaces and ensure the tie-in schedule revision agrees with the P&ID revision.
Verify branching or reducing lines connect according to the project piping branch table.
Verify header line numbers include all header block valves so they are installed with the header, not with branch lines.
When process lines cross: vertical lines break for horizontal lines. Instrumentation lines break for process lines (unless specified otherwise).
Verify reference to other P&IDs and line continuity through off-page connectors (OPCs). Alignment of OPCs is correct.
Stream tags include the fluid and drawing number; note the equipment name and the stream origin/destination.
Where applicable, verify streams enter from the left side and exit from the right side of P&IDs.
Show slopes and elevations where required.
Verify all battery limits are clearly marked.
Instrumentation Lines
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Verify instrumentation signal lines are the correct line type; local/DCS code is correct.
Verify complete instrumentation and control loops are shown on the P&IDs.
Instrumentation
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Instruments are the right type; local/transmitted and control type are correct; block and bypass valves are shown.
Verify instrumentation details match job specification (isolation valve size and spec, vent & drain requirements, etc.).
Verify Cause-and-Effect / Safe Chart requirements are clearly represented.
Valves
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Verify control valve type, failure mode, block/bypass valves, and reducers — confirm sizes are the latest from the controls department.
Verify Pressure Relief Valves are correct: set pressure,
PSV size
, inlet/discharge size and pipe spec match latest calculations; outlet lines are Car Sealed Open or have no valves (if to atmosphere); relief outlet goes to drain/flare/atmosphere.
Verify block valves indicate if they are normally open/closed or car sealed open/closed.
Verify drain valves are present, shown with smaller gate valve symbol, and placed between checks/gates/etc.
Verify minor valves are placed logically (check valve near pump discharge, swing blind near gate valve).
Verify spectacle blinds are correctly shown normally open/closed and positioned on the side facing the hazard source (pressure or contamination).
Verify double-block valves are shown (with
¾″ drain
between) where required — i.e. ≥600 psig or hazardous fluids such as acids.
Verify consistency of double-block-and-bleed arrangements.
Verify proper valving for drain and relief valves.
Verify all valve sizes are indicated and match process calculations (control valves, relief valves, bypass valves).
Verify low-temperature impact if expansion occurs across control valve, relief valve, or during depressurization.
Verify operability for start-up and valve opening under high differential pressure (especially riser valves).
Verify whether the working range of the control valve is adequate or requires split-range configuration.
Verify failure position of shutdown and control valves is shown.
Verify bypass requirements and appropriate valving are shown.
Verify full bore and reduced bore ball valves are indicated where appropriate.
Equipment & Vessels
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Verify all equipment tags and titles above equipment have correct spelling.
Verify stream tags include the fluid and drawing number; note the equipment name and stream origin/destination.
Verify equipment names match other documents: PFD, equipment list, datasheet, etc.
Verify isolation of equipment (spectacle blind, double-block-and-bleed) complies with job standard.
Verify equipment data and level diagrams are filled in and match process calculations.
Verify all equipment numbers and specs agree with data sheets, specifications, and equipment list.
Verify all nozzles are shown including drains, vents, and manholes.
Vessels
— show: size, design temperature/pressure, full vacuum rating, internals/levels, and skirt height to grade.
Verify all set points are indicated.
Heat exchangers
— show: area, design T/P, duty, motor horsepower (air coolers); condenser/reboiler elevation; motor controls.
Heaters
— show: size, duty, design T/P, coil arrangement; utilities on a separate page.
Boilers
— show: size, design T/P, superheater outlet temperature; utilities on their own page.
Tanks
— show: size, capacity, type; heaters and agitators shown.
Pumps
— show: rated flow, horsepower, differential head; temporary strainers, drains, motor with controls.
Turbines
— show: inlet/outlet temperature and pressure, horsepower, strainers.
Compressors
— show:
ACFM
at inlet, discharge pressure, driver type, horsepower, strainer, lube/seal oil.
Verify steam-out/steam connections are shown where required; full vacuum rating is shown on equipment when required.
Verify limit of package and limit of supply / vendor scope are clearly indicated.
Verify all
SP items
are indicated.
Verify all installation requirements are shown (no slope, high point, min. straight length, no pocket, min. length, etc.).