Key Documents
This set of documents establishes the foundation and detailed specifications for the instrumentation and control system.
Project Design Basis / Philosophy: Outlines the fundamental principles, codes, standards (like API, ISA, IEC), and project-specific requirements for the design of instrumentation and control systems.
Cause & Effect (C&E) Matrix: A critical safety document that defines the relationship between a cause (e.g., high pressure, low level) and its corresponding effect (e.g., trip a pump, open a valve, activate an alarm). It’s fundamental for designing the Process Shutdown (PSD) and Emergency Shutdown (ESD) systems.
Instrument Index / Database: A master list of every instrument and tagged item in the project. It contains all relevant data for each tag, including its service description, P&ID number, loop number, I/O type, range, set points, and references to other relevant documents like datasheets and loop diagrams.
Instrument Datasheets / Specification Sheets: Detailed one- or two-page documents providing all the technical specifications for a specific instrument (e.g., pressure transmitter, control valve). This includes process data, materials of construction, performance requirements, and electrical ratings.
I/O List (Input/Output List): A list detailing all the inputs and outputs connected to the control system (DCS/PLC). It specifies the tag number, description, signal type (e.g., 4-20mA, HART, Digital Input), and termination details.
Control & Shutdown Narratives: A descriptive document explaining the logic and philosophy of the control and safety systems in plain language, complementing the C&E Matrix and Logic Diagrams.
System Architecture Diagram: A high-level block diagram showing the overall structure of the control and safety systems, including servers, workstations, controllers, and network connections.
Functional Design Specification (FDS): A detailed document describing the functionality and operational requirements of the control system software and hardware.
Factory Acceptance Test (FAT) & Site Acceptance Test (SAT) Procedures: Documents outlining the procedures, steps, and criteria for testing the control system at the vendor’s factory (FAT) and after installation on-site (SAT).
Key Drawings
These drawings provide a visual representation of the instrumentation systems, from a process overview to detailed wiring.
Piping & Instrumentation Diagrams (P&IDs): The most fundamental drawing. It shows the process piping, equipment, and how the instruments are connected to the process. Each instrument is shown with its unique tag number.
Instrument Loop Diagrams: A detailed wiring schematic for a single control loop (e.g., a pressure control loop). It shows all components from the field instrument to the control system I/O card, including junction boxes, marshalling cabinets, wiring, and power supplies. It’s essential for construction, commissioning, and maintenance.
Logic Diagrams / Function Block Diagrams: Visual representation of the control and shutdown logic defined in the C&E Matrix and Control Narrative. They show how inputs are processed through logic gates (AND, OR, timers) to produce outputs.
Instrument Layout Drawings: Plan view drawings showing the physical location of instruments, junction boxes, and control panels within the plant or on a specific piece of equipment.
Junction Box (JB) Wiring Diagrams: Shows the internal wiring of a junction box, detailing how field instrument cables are terminated on one side and how the multicore cable to the control room is connected on the other.
Marshalling Cabinet / System Cabinet Layout & Wiring Drawings: Details the layout and wiring inside the control system cabinets, showing the arrangement of I/O cards, power supplies, terminals, and intrinsic safety barriers.
Instrument Installation Details / Hook-up Drawings: Standardized drawings that show the exact method for mounting and connecting an instrument to the process piping or vessel. This includes details on tubing, valves, and fittings required for a correct and safe installation (e.g., a 5-valve manifold for a differential pressure transmitter).
Cable Tray / Conduit Layouts & Schedules: Drawings showing the routing of instrument cable trays and conduits throughout the facility. The cable schedule is a list of all cables with details on their type, size, origin, and destination.
Advanced & Detailed Engineering Documents
These documents provide a deeper level of detail and cover specific subsystems and calculations.
Instrument Sizing & Selection Calculations: Detailed calculations to justify the selection of specific instruments. This includes:
Control Valve Sizing: Calculations for Cv, noise prediction, and cavitation analysis.
Flow Element Sizing: Calculations for orifice plates, venturi meters, or Coriolis meters based on process conditions.
Thermowell Wake Frequency Calculations: To ensure the thermowell’s mechanical integrity and prevent failure due to vortex-induced vibrations.
Pressure Relief Valve (PRV) Sizing: Calculations to determine the required relief capacity for overpressure protection scenarios.
Specialized System Philosophies:
Fire & Gas (F&G) Philosophy: Outlines the design principles for the F&G detection and protection system, including detector types, coverage philosophy, and response actions.
Machine Monitoring System (MMS) Philosophy: Details the requirements for monitoring rotating equipment like compressors and turbines, including vibration, temperature, and speed monitoring.
Tank Gauging System Philosophy: Describes the system for measuring level, temperature, and pressure in storage tanks for inventory management.
Power & Earthing Philosophy for Instrumentation: Defines the requirements for instrument power supplies, including Uninterruptible Power Supply (UPS) systems, cable types, and grounding/earthing requirements to prevent signal noise.
Hazardous Area Classification Schedule & Drawings: A list and corresponding drawings that classify all areas of the plant based on the potential presence of flammable gases or dusts (e.g., Zone 0, 1, 2). This is critical for selecting appropriately rated (e.g., Ex d, Ex i) electrical equipment.
Instrument Cable Schedule: A comprehensive list of every single instrument cable in the project, detailing its unique tag number, type, size, core count, origin, destination, and routing information.
System Control and Data Acquisition (SCADA) / Telecom Interface Register: A list specifying all the data points and signals to be exchanged between the main process control system and other systems like SCADA, PLCs from package units, or telecommunication networks.
Construction & Commissioning Specific Documents
These documents are crucial for the construction, testing, and startup phases of the project.
Installation Scope of Work (SOW): A detailed document for the construction contractor outlining the specific tasks, responsibilities, and standards for installing all instrumentation and control equipment.
Pre-commissioning & Commissioning Procedures: Step-by-step procedures for checking and verifying the integrity and functionality of the installed systems before introducing hydrocarbons. This includes:
Loop Check Folders: A package of documents for each individual loop (loop diagram, datasheet, calibration certificate) used by technicians to perform loop checks from the field device to the control system graphic.
Function Test Procedures: Detailed procedures for testing the logic defined in the Cause & Effect matrix and logic diagrams.
Punch Lists: A formal list used during walk-downs and testing to record any items that are incomplete, incorrect, or non-conforming.
Material Take-Off (MTO) / Bill of Materials (BOM): A detailed list of all the materials required for installation, including cables, glands, tubing, fittings, junction boxes, and instrument stands.
Vendor & As-Built Documentation
This documentation is provided by equipment suppliers and is updated at the end of the project for the final handover.
Vendor Documentation: A critical set of documents provided by the manufacturers of the equipment.
Vendor Manuals: Installation, Operation, and Maintenance (IOM) manuals for every instrument and control system component.
Vendor-Specific Drawings: Drawings for skid-mounted “package units” (e.g., a compressor package), showing the internal instrumentation and control system provided by the vendor.
Calibration Certificates: Certificates from the factory for each instrument, verifying its accuracy against a known standard.
As-Built Drawings & Documents: All the key engineering drawings and documents (P&IDs, Loop Diagrams, Wiring Diagrams, etc.) are revised and updated at the end of the project to reflect the “as-installed” condition. These are the final records used by the operations and maintenance teams for the life of the plant.
Red-Line Mark-ups: The on-site drawings that have been marked up in red ink by construction and commissioning teams to show any changes or deviations from the original design. These are used to create the final “As-Built” drawings.
Spares & Special Tools List: A recommended list of spare parts and any special tools required for the maintenance of the instrumentation and control systems.