EN 12845-2 Annex O — P&ID Flow Diagram Example

The P&ID (Piping and Instrumentation Diagram) is the core reference for designing, commissioning and maintaining a fire system. Annex O provides standard P&ID examples for ESFR and CMSA, a symbol catalogue and a tagging convention. A missing P&ID slows every insurer process down.

During an annual FM Global audit at a logistics warehouse, the P&ID was requested. What had been produced at design stage was an Excel table — a list of equipment with no flow diagram. The auditor's position was straightforward: no flow diagram, no approval. Two weeks were lost preparing a proper P&ID. A P&ID is not a spreadsheet; it is a visual flow diagram. That is precisely why the Annex O examples are useful — they give designers a standard to work from.

What Annex O contains

1. An ESFR system P&ID example (tank → pump → control valve → sprinklers)
2. A CMSA plus in-rack P&ID example with parallel branches
3. A foam-water P&ID example (deluge plus foam concentrate)
4. A symbol catalogue (ISO 14617 plus EN 12845-specific symbols)
5. Tagging conventions (V-, P-, FS-, PS-, CV-)
6. BMS and alarm connections
7. Test points (drain, flush, flow test)
8. Integration with adjacent systems (HVAC, fire alarm)

A typical ESFR P&ID flow

• Tank (T-001) → suction pipe (PS-001 suction pressure)
• Electric pump (P-001) plus diesel pump (P-002)
• Pump discharge header (PS-002 discharge pressure)
• Main → control valve set (CV-001)
• Flow switch (FS-001) plus alarm valve
• Distribution pipework → sprinklers (S-001 onwards)
• Test points: drain (D-001), flush (FL-001)
• BMS connections (flow, pressure, valve position)

Standard symbol categories

Category	Example	Tag format
Tank	T-001 (fire water tank)	T-XXX
Pump	P-001 (electric), P-002 (diesel)	P-XXX
Valve	V-001, V-002	V-XXX
Control valve set	CV-001 (zone 1)	CV-XXX
Flow switch	FS-001	FS-XXX
Pressure switch	PS-001 (suction), PS-002 (discharge)	PS-XXX
Sprinkler	S-001 onwards	S-XXX
Drain	D-001	D-XXX
Test point	TP-001	TP-XXX
Alarm	A-001 (main panel)	A-XXX

Field error — inconsistent tagging

A paper mill's P&ID was drawn by the design team in 2018. The maintenance team then applied their own numbering on site, mixing V-1, V-2, V-A and V-B. Five years later, during an emergency, the instruction was to close valve V-007 — which did not exist on site; there was a V-A and a V-7. Thirty-five minutes were lost. There was no fire at the time, but the operational exposure was real. The fix was to migrate the P&ID, the site labelling and the maintenance register onto a single tagging system. Annex O emphasises exactly this consistency.

Software for producing P&IDs

• AutoCAD MEP — professional, expensive licence
• Revit MEP — BIM integration
• SmartDraw — simple and inexpensive
• Lucidchart — browser-based, good for teams
• Dedicated sprinkler design packages — hydraulics plus automatic P&ID output
• Microsoft Visio — adequate for simple projects

When to reissue the P&ID

1. At design stage (the first issue)
2. After commissioning (the as-built issue)
3. Before each annual audit (verification against site)
4. After every modification
5. After any insurer re-approval
6. On a change of maintenance contractor (for handover training)

BMS and alarm connections

• Flow switch → BMS digital input
• Pressure switch → BMS analogue input
• Valve position → BMS limit switch
• Pump running → BMS status
• Fire alarm panel → central monitoring
• BMS → automatic HVAC shutdown
• BMS → transmission to the fire service

Test points on the P&ID

• Main drain for each zone
• Flushing connection at the most remote point
• Flow test connection
• Pump test bypass line
• Manual alarm trip
• BMS signal test input

Turkish regulation and local practice

BYKHY does not name the P&ID explicitly, but it does expect installation plans, sections and flow diagrams. Building inspection firms and insurers frequently ask for one. New buildings commonly combine a BIM model, Revit MEP and a hydraulic package. In older facilities, a missing P&ID is a recurring annual-audit finding. TS EN 12845-2:2024, including Annex O, is available in Turkish as the standard reference.

Quick check list

• Is there a real P&ID — a diagram, not a spreadsheet?
• Symbols follow ISO 14617 and EN 12845.
• Tagging follows the V-, P-, FS-, PS-, CV- convention.
• Site labels, P&ID and maintenance register share one tag system.
• Every valve, pump and sensor appears on the P&ID.
• Test point locations are shown.
• BMS connections are documented.
• The P&ID is current after the latest modification.
• The P&ID is verified against site before the annual audit.

Frequently Asked Questions

Is an equipment list enough instead of a P&ID?

No. Insurers and auditors expect a visual flow diagram showing tank, pumps, valve sets, switches and sprinkler distribution. A spreadsheet of equipment is routinely rejected.

What tagging convention does Annex O use?

Prefix-based tags: T- for tanks, P- for pumps, V- for valves, CV- for control valve sets, FS- for flow switches, PS- for pressure switches, S- for sprinklers, D- for drains.

When must the P&ID be reissued?

At design, after commissioning as an as-built, before each annual audit, after every modification, after any insurer re-approval, and on a change of maintenance contractor.

Why does tagging consistency matter so much?

Because in an emergency the instruction refers to a tag. If the P&ID, the site labels and the maintenance register disagree, the response stalls exactly when it cannot afford to.

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