Pipe Dimension And Piping Information

Piping and Instrumentation Diagram (P&ID) Of Fuel Gas System

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Introduction

A Fuel Gas System supplies clean, pressurized gas to fired equipment such as gas turbines, heaters, boilers, and process furnaces.
The Piping and Instrumentation Diagram (P&ID) shows the essential flow of gas from the source through treatment, pressure control, heating, and distribution — along with key instrumentation, valves, and safety features.

Understanding this P&ID helps engineers design, operate, and maintain a safe and reliable fuel supply network.

1. Process Overview

Typical flow sequence:

Fuel Gas Source → Filter/Separator → Pressure Control → Heater → Distribution Manifold → Users

The system ensures:

  • Continuous and stable gas pressure

  • Filtration to remove solids/liquids

  • Temperature control to prevent condensation

  • Automatic shutdown on high/low pressure or emergency events

2. Main Equipment on the P&ID

Tag Description Function
V-101 Suction / Knockout Drum Removes entrained liquids before downstream use
F-201 A/B Fuel Gas Filters / Coalescers Dual (changeover) filtration for solids and aerosols
PCV-301 Pressure Control Valve Maintains stable downstream pressure to users
E-401 Fuel Gas Heater (Electric or Glycol) Prevents condensation and hydrates
SDV-501 Emergency Shutdown Valve (ESDV) Isolates supply during emergency or trip
BDV-502 Blowdown Valve Safely vents system gas to flare
V-601 Distribution Header / Manifold Feeds multiple burners or turbines
PSV-701 Pressure Safety Valve Relieves excess pressure to flare system

Optional:

  • Analyzer (AIT-801) for BTU, moisture, or H₂S content

  • Flow Transmitter (FIT-301) on main supply

  • Temperature Indicator (TIT-401) after heater

  • Dew Point Monitor (DPIT-501) for gas quality assurance

3. Key Valves and Control Loops

a) Pressure Control Loop

  • PIC-301 senses downstream pressure and adjusts PCV-301.

  • If upstream pressure fluctuates, control valve modulates to protect burners or turbines.

  • Bypass line with manual valve HV-301B allows maintenance on PCV.

b) Temperature Control

  • TIC-401 monitors gas outlet temperature from heater.

  • Modulates heating element or glycol flow via TCV-401.

  • Low temperature alarm (TAL-401) prevents cold gas supply.

c) Shutdown & Protection

  • ESDV (SDV-501) — closes automatically on high-high pressure, low pressure, or external trip.

  • BDV-502 — opens to flare for controlled depressurization.

  • PSV-701 — mechanical relief on overpressure.

  • All interlocks handled via PLC / ESD system.

4. Instruments and Typical Tags

Instrument Tag Example Function
Pressure Indicator PI-101 Local reading on header
Pressure Transmitter PIT-301 Signal to controller PIC-301
Temperature Indicator TI-401 Measures heater outlet
Flow Indicator FI-501 Indicates fuel gas consumption
Level Transmitter LIT-101 On knockout drum, with drain LV-101
Pressure Safety Valve PSV-701 Relief to flare
Solenoid Valve SV-501 Operates ESDV pneumatically

🧠 Tip: Use standardized ISA tagging in your AutoCAD legend (PT, TT, FT, LT, etc.) for clarity and automation compatibility.

5. Typical Control Philosophy

  1. Normal Operation:

    • Fuel gas flows through filters → pressure control → heater → users.

    • PCV-301 keeps downstream pressure constant.

    • TIC-401 maintains outlet temperature (~40–60°C).

  2. Startup:

    • Line-up valves open gradually; purge with nitrogen if required.

    • Heater energized when minimum flow is achieved.

  3. Shutdown:

    • On ESD: SDV-501 closes, BDV-502 opens, venting to flare.

    • Heater and analyzer isolated.

  4. Trips & Alarms:

    • High Pressure (PSH-301) → close ESDV; alarm.

    • Low Pressure (PSL-301) → trip user (turbine/furnace).

    • High Temp (TSH-401) → shutdown heater.

    • Gas Detection near skid → close ESDV, alarm control room.

6. Design and Operating Parameters (typical values)

Parameter Typical Range
Inlet Pressure 20–35 barg
Outlet Pressure 10–25 barg
Flow Rate As per burner/turbine load
Gas Temperature 30–60°C
Filter Rating 1–5 micron
Heater Type Electric / Glycol / Steam
Relief Set Pressure 110% of MAWP

7. Safety and Flare Integration

  • PSV-701, BDV-502 discharge to flare header via knockout pot and seal drum.

  • Thermal Relief Valves (TRV) on blocked segments.

  • Fire & Gas Detectors located around heater, skid, and filter section.

  • ESD Pushbutton near access point for emergency isolation.

8. Lines and Legend

Line Type Service
Solid Line Main Fuel Gas
Dashed Line Instrument / Control Air
Dotted Line Signal or Impulse
Double Line Flare / Vent Line
Dash-Dot Utility (nitrogen, drain)

Piping Material: Carbon Steel or SS316 (depending on gas quality)
Flanges: ASME Class 300 or higher as per design pressure
Instrument Air: Dry, 6–8 barg

9. Deliverables & Download

Included Files:

  • P&ID (DWG)

Conclusion

A Fuel Gas System P&ID defines every critical element of a plant’s gas supply — from filtration and pressure regulation to temperature control and safety isolation.
It ensures safe delivery of fuel gas to turbines, heaters, and boilers while meeting reliability and safety standards.

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