Typical Control System Design Document/Guideline
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This document outlines the typical design process for a control system, including measurement and control device design, control system hardware design, control system wiring installation design, process control design, and on-site services. It describes key design elements such as instrument specifications, control panel arrangements, loop drawings, I/O definitions, software configuration, and commissioning assistance. The purpose is to provide comprehensive documentation and design of all aspects of an industrial control system.
Typical Control System Design Document/Guideline
- 1. Typical Control System Design Document/Guideline : 1.0 Measurement and Control Devices Design : 1.1 Instrument List The Instrument List tabulates instrument numbers, description, service and P&ID numbers in addition to other information on individual devices that might be required for a given project. 1.2 Instrument Specifications Specifications for commonly used instrumentation are prepared in standard ISA data sheet format and contain information from P&ID's, vendor catalogs, calculations, and piping drawings. Special instrumentation such as analyzer systems may require a complete specification document. 1.3 Local Enclosures Panels or racks mounted near the process equipment which contain field devices such as transducers, solenoids, and I/P or P/I converters. They are normally NEMA 4 design with many devices pre-wired to industrial terminal strips. 1.4 Local Control Panels Operator interface panels with controllers, pushbutton and indication needed for process local startup or local control of a specific operation. 1.5 Instrument Air Piping These drawings indicate the general location of all instrumentation that require field piping, air connections, or pneumatic signals. They are made to scale so that a reasonable estimate of material quantities can be made for construction and they are a scope document for subcontract work. 1.6 Construction Specifications Specifications that describe the work required to install instrumentation by field contractor. Typical specifications include calibration and commissioning, installation work scope, instrument wiring, and control pnael fabrication. 1.7 Instrument Systems Wiring Diagrams Drawings produced to provide connection information for complicated systems such as analyzers, halon, L.E.L., and chromatograms. 1.8 Instrument Installation Details The Instrument Installation Detail shows the piping arrangement for the mounting and connection of field instrumentation items. These drawings contain a complete Bill of Material for piping requirements and a reference to the instrument tag numbers.
- 2. 1.9 Purchase Requisitions All work necessary to complete purchasing on instrumentation including requisition preparation, bid tabs, and purchasing assistance. 2.0 Control Systems Hardware Design : 2.1 Systems Specification Formal Document generated to obtain competitive bids on process control systems, both DCS and PLC based. The specification should include scope of control systems, I/O requirements, system architecture sketch, functionality requirements, performance criteria, and vendor responsibilities. 2.2 System Equipment List Supplement to the specification to detail deliverables from the selected vendor. In some projects with a pre-selected vendory, only the equipment list is prepared. 2.3 Cabinet Arrangements Arrangement of I/O and controllers in the DCS system cabinets, or PLC cabinets/panels. Can be formal drawings or sketches given to the selected vendor who prepares the formal drawings and documentation. 2.4 Console/Panel Arrangement Design of control room console based on standard offering from vendor, or custom consoles required for integrating operator interface equipment from various vendors. Usually a desk type arrangement without a vertical section, however, large control room panels are also included in this group. 2.5 Power Distribution Design of the power feed to the control system and to each cabinet or controller requiring power. Includes distribution panel and details for connection to the individual devices. 2.6 Grounding Design of a system grounding system to comply with the vendors requirements and the NEC. Includes ground connection to cabinets, consoles, and cabling to the gorund bus. 2.7 Control Room Arrangement Details the location of all control equipment in a control room. Can be a formal drawing or included as part of an architectural drawing. 2.8 Loop Drawings
- 3. Drawings detailing all components of a single control loop including all information necessary to understand, test, and operate the loop. Loops can include both analog and digital components. 2.9 I/O Schematics Drawings that functionally detail electrical connections to control components used in digital control such as process switches, limit switches and solenoids. These are normally directly connected to I/O modules. 2.10 Motor Control Schematics Drawings that functionally detail electrical connections to motors that are controlled from the process control system through I/O modules. 2.11 Transducer/Interface Panels Control room mounted panels that contain components required to interface field devices with the control system. They can contain signal conditioning or isolating equipment suchas relays. 3.0 Control System Wiring Installation Design: 3.1 Wiring Block Diagram Identifies all the main components in a control system such as panels, computers PLC's, operator consoles, etc... These drawings show the general interconnection between components and the wiring strategy to be used. 3.2 Field Device Connection Details Details specifying conduit and fitting requirements and standard hook-up of instrumentation and control devices. 3.3 Field Terminal Panels Panels used as a central termination for multiple device cables from the main control room location. Individual device wiring is run from these panels normally in conduit to the field mounted device. 3.4 Conduit and Cable Schedules Schedule or listing of cables defining the connection location at each end, conduit number, type of cable, and wiring in the cable. 3.5 Control Device Location and Conduit Plans Plan drawings of the process area that indicate the location of all control devices and diagrams the conduit connection and routing to the devices from the control panels and terminal panels.
- 4. 3.6 Cable Tray Layout Overall arrangement of control and instrument tray systems detailing the routing of tray between field panels and the main control area. Required on projects with extensive cable systems. 3.7 Wireway Layout Overall arrangement of control and instrument wireway systems detailing routing of wireway. Drawings can also include device locations. 3.8 Electrical Construction Specification Specifications that describe the work required to wire the instrumentation by a field contractor. Typical specifications include a work scope, wiring material description, and testing requirements. 3.9 Electrical Material Specifications Specifications of all material required for the electrical installation of the instrumentation. A material takeoff of all material so that quantities can be established and ordered for construction. 3.10 Control Room Wiring Layout Conduit, tray, or computer floor layout for wiring to control equipment. Can be a separate drawing or part of an area control plan drawing. 4.0 Process Control Design : 4.1 P&ID Input The instrumentation representation on P&ID's must include proper loop representation, tagging, and measurement and control device symbols. 4.2 Continuous Control Loops Design of the control shceme for all continuous control loops is often completed on the P&ID diagram. It can also be accomplished using SAMA control symbols for control algorithms. Control loops must be completely defined prior to devoping DCS configuration software. 4.3 Discrete Logic Design Discrete logic can be described in a structured narrative of process operation or on a diagram using symbols for logic gates. A detailed design of logic must be completed before programming can be complted on PLC projects.
- 5. 4.4 Operator Interface Design of CRT based operator interface using process graphics, alarm screens, control faceplates, trends, and text screens. The interface design is prepared in conjunction with control logic to define how the operator interacts with the process to accomplish desired control functions. 4.5 Process Control Operational Description The operational description defines how the control system functions and the operator interface for various modes of process operation. It is derived from the logic and operator interface design. 4.6 I/O Definition Definition of the I/O tagging, service description, location, range values and alarm limits. The I/O definition forms the primary database for configuration of the control system. 4.7 PLC Software and Documentation PLC code using a software development package with complete documentation capabilities. The software is based on the logic and control loop design. Also includes operator interface code for CRT displays. 4.8 DCS Software and Documentation Generation of DCS configuration by utilizing vendor forms or development system. Normally consists of an I/O point database and software connection of vaious control function blocks. Also includes operator interface code for CRT displays. These are usually graphics and faceplates supplied as part of the DCS system. 4.9 System Software/Hardware Testing Simulation of the process operation to test the software functions. Testing is done at the vendors fabrication location and can consist of test sofwtware or simple hardware I/O switches and analog inputs. Also includes testing of system hardware components. 5.0 On Site Services : 5.1 Installation Supervision Monitoring of the instrumentation contractor for installation, wiring, and testing of all I/O devices and system components. 5.2 System Commissioning Initial operation of the system from power up, to testing of I/O into the system for proper operation. On completion of this task the system is ready for process start-up.
- 6. 5.3 Start-Up Assistance Field verification of system software and standby operation during process start-up to make on-line control system modification during the intial period of process operation.
- 7. 5.3 Start-Up Assistance Field verification of system software and standby operation during process start-up to make on-line control system modification during the intial period of process operation.