Pipe Dimension And Piping Information

P&ID of Nitrogen Generation Plant (PSA N₂ Plant)

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Introduction

A PSA (Pressure Swing Adsorption) Nitrogen Generation Plant separates nitrogen from compressed air using carbon molecular sieve (CMS) adsorbers. The P&ID communicates how equipment, piping, valves, and instruments integrate to deliver the specified N₂ purity, pressure, and flow—and documents safety devices and control logic for operations and maintenance.

1) Process Overview

  • Feed Air → filtration & drying → Twin CMS Adsorbers (A/B) operating in adsorption/regeneration cycles → N₂ Buffer/Receiver → user tie-in.

  • Cycle Control via automated valves (SV/CV) with equalization steps to reduce power losses.

  • Quality Control by O₂ (or N₂) analyzer with auto-vent on off-spec.

2) Major Equipment on the P&ID

  • AC-101 Air Compressor (oil-free or oil-injected with downstream coalescer), discharge PT/TT.

  • AF-201/202 Prefilters (coalescing + particulate), ΔP indicators.

  • AD-301 Air Dryer (refrigeration or heatless desiccant), dew point monitor (DPIT-301).

  • CF-401 Carbon Tower (optional oil vapor removal), ΔP.

  • V-501 & V-502 CMS Adsorber Vessels (A/B) with manways, PSVs, blowdown lines, acoustic vent to atmosphere.

  • V-601 N₂ Buffer/Receiver with level (if condensate risk), PT, PSV.

  • N₂ Product Polisher (optional activated carbon or particulate filter).

  • Analyzer Skid: O₂ analyzer (AIT-701) or N₂ purity analyzer, sample conditioning, auto-vent.

  • Control System: PLC with local HMI, solenoid manifold, air set, E-stop.

3) Key Piping & Valves

  • Main Isolation: MOV-101 (air in), MOV-601 (N₂ out).

  • Adsorber Inlet/Outlet: CV-A-IN, CV-A-OUT, CV-B-IN, CV-B-OUT (pneumatic on/off).

  • Equalization: CV-EQ-1/2 between vessels with check valves to prevent reverse flow.

  • Purge/Regeneration: CV-PUR-A, CV-PUR-B with RO-A/B orifice plates; blowdown valves BDV-A, BDV-B to vent silencers.

  • Off-Spec Vent: CV-VNT after analyzer to stack with rain hood and dispersion height.

  • Check Valves on product header to protect purity and prevent backflow.

  • Pressure Safety Valves (PSVs) on both adsorbers, buffer, and dryer as applicable.

  • Drains/Low Points with ball valve + cap; vents/high points for commissioning.

4) Instruments & Typical Tags

  • Pressure: PIT-101 (compressor discharge), PIT-A/B (adsorbers), PIT-601 (buffer).

  • Flow: FIT-401 (feed air), FIT-701 (product N₂).

  • Temperature: TIT-101 (aftercooler), TIT-301 (dryer outlet).

  • Quality: AIT-701 (O₂ analyzer) with HI alarm & S/D setpoints; optional moisture analyzer (AIT-702).

  • Dew Point: DPIT-301 (at dryer outlet).

  • Differential Pressure: DPDT-AF-201/202, DPDT-V-501/502.

  • Valves: SV-xxx (solenoid), XV-xxx (on/off), CV-xxx (auto), PCV (if pressure control), NRV (check).

  • Switches/Alarms: PSL/PSH for safe limits; ESD pushbutton near skid.

5) Control Philosophy (Simplified)

  • Adsorption: Vessel A online, B regenerating. Inlet/Outlet CVs open on A, purge/BDV open on B.

  • Equalization: Short step to share pressure between vessels; reduces vent losses.

  • Regeneration: Depressurize → purge with dry N₂ → repressurize via equalization or product.

  • Quality Interlock: If AIT-701 O₂ > setpoint (e.g., >10, >100, or >1000 ppm per spec), CV-VNT opens to off-spec vent; MOV-601 to users closes; alarm to HMI.

  • Fail-Safe: Air/solenoid failure drives CVs to fail-closed on product, fail-open on vent/relief as per HAZOP.

  • Start/Stop: Sequenced start with dryer dew point OK, analyzer ready; orderly shutdown vents safely.

6) Typical Design/Operating Parameters (adjust per project)

  • Feed Air: 6–10 barg; Aftercooler to ≤35 °C; dew point ≤-20 °C (or per spec).

  • Product N₂: 95%–99.999% purity; Pressure 5–8 barg; Flow per nameplate (e.g., 10–1000 Nm³/h).

  • Vent Lines: Size for rapid depressurization; add silencer; route outdoors with safe dispersion.

  • Materials: Piping CS/SS; analyzer lines SS 316; elastomers oxygen-compatible on air side.

  • Electrical/ATEX: Class/Zone per site; instruments and solenoids rated accordingly.

7) Safety, Relief & ESD

  • PSVs on V-501/502 and V-601 sized for fire case & blocked-in scenarios.

  • Rupture Disc (optional) upstream of PSV for analyzer/buffer cleanliness.

  • ESD: Pushbutton trips feed isolation, opens vent route, closes product to users.

  • O₂ Monitoring in analyzer shelter; Noise Control at blowdowns; Backflow Prevention to protect analyzer and product header.

8) Lines, Specs & Legend (P&ID Notation)

  • Line Types:

    • Compressed Air: solid line; Product N₂: double solid; Purge/Blowdown: dashed; Instrument air: dotted.

  • Ratings: Class 150/300 per design; confirm at compressor discharge and dryer.

  • Typical Legend:

    • PIT = Pressure Indicator Transmitter; FIT = Flow Indicator Transmitter; AIT = Analyzer; DPDT = Differential Pressure Indicator; CV = Control Valve; XV = On/Off Valve; NRV = Check Valve; BDV = Blowdown Valve; PSV = Pressure Safety Valve.

  • Instrument Air Header with FRL set; solenoid cabinet tagged SM-701.

9) Cause & Effect (Excerpt)

  • High O₂ (AIT-701 > Hi) → Close MOV-601 (to users), Open CV-VNT (to vent), Alarm.

  • Very High O₂ (AIT-701 > Hi-Hi) → Trip unit, Depressurize current vessel, Alarm.

  • Low Dew Point Alarm (DPIT-301 not OK) → Prevent startup / switch to standby dryer.

  • Compressor Trip → Close feed, vent adsorber to safe state.

  • ESD Pushbutton → Unit shutdown, isolate feed, open vent, close product.

10) Deliverables & Download

  • P&ID Files: DWG + legend.

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