INSTRUMENTATION & CONTROL DESIGN

1. Instrumentation Layout Drawing

• A 2D/3D plan showing the physical location of all instruments within a process unit.

• Key Details Include:

• Field instruments (transmitters, gauges, control valves) with tag numbers (e.g., PT-101, FV-203)

• Mounting details (elevation, orientation, access requirements)

• Proximity to process equipment (nozzles, vessels, piping)

• Hazardous area classification (Zone 0/1/2 per IEC 60079)

• Purpose:

  • Ensures instruments are accessible for maintenance

  • Avoids clashes with piping/structural elements

  • Complies with ergonomic and safety standards

2. Loop Diagram (Loop Sheet)

• A detailed schematic of an instrument loop, showing electrical/ pneumatic connections from field to control system.

• Key Components:

• Field device (e.g., pressure transmitter)

• Junction box (JB) termination points

• Cable/wiring details (wire numbers, colors)

• Control system I/O card (PLC/DCS address)

• Power supply (24V DC, 120V AC)

• Intrinsic safety barriers (for hazardous areas)

3. Hookup Tubing Diagram

• Shows pneumatic/ hydraulic connections for instruments (e.g., pressure gauges, control valves).

• Details Shown:

• Tubing material (SS316, PVC) and size (1/4", 1/2")

• Fittings (compression, Swagelok)

4. Connection List / Termination Diagram

• A tabular/wiring diagram of all electrical terminations between instruments and control systems.

• Key Data:

  • Field Device Cable No. JB Terminal DCS Terminal Wire Type

  • PT-101 CBL-204 JB-12 (TB3-5) DCS-AI-204 18AWG SHIELDED

• Purpose:

  • Ensures correct wiring during installation

  • Reduces commissioning errors

  • Air supply headers and regulators

  • Root valves and bleed ports

• Typical Applications:

  • Control valve air supply (3-15 psi)

  • Pressure transmitter impulse lines

5. Cable & Cable Drum Schedule

• A comprehensive list of all instrumentation cables with routing and drum management data.

• Cable Schedule Columns:

  • Cable Number (e.g., CBL-204)

  • Type (MI, PVC, LSZH)

  • From-To (PT-101 → JB-12)

  • Length (+10% spare)

  • Drum ID (for tracking during installation)

• Drum Schedule Fields:

  • Drum ID

  • Cable Reel Length

  • Test Certificates (Megger test results)

• Critical For:

  • Material handling during construction

  • Traceability for QA/QC

6. Instrument Index (Master List)

• Definition:

• A master database of all instruments in a project.

• Typical Columns:

• Tag Description P&ID Spec Signal Type Manufacturer

• FT-301 Coriolis Flow Meter P-102 ROSEMOUNT 8732E 4-20mA HART Emerson

• Purpose:

  • Single source of truth for procurement and tracking

7. Instrument Datasheet

• Definition:

  • Technical specifications for each instrument.

• Key Sections:

  • Process conditions (pressure, temperature, fluid)

  • Materials of construction (wetted parts)

  • Electrical requirements (24V DC, Ex-d certification)

  • Communication protocol (HART, Foundation Fieldbus)

Workflow Integration

• Design Phase:

  • Layout Drawings → Loop Diagrams → Hookup Diagrams

• Procurement Phase:

  • Instrument Index → Datasheets → Requisitions

• Construction Phase:

  • Cable Schedule → Termination Diagrams → Loop Testing