Standard No.:	HG/T 20637.2-1998
Chinese Name:	自控专业工程设计用图形符号和文字代号
English Name:	Symbols and identifiers for engineering design of instrumentation
Professional Classification:	P94 Metal equipment and process pipe installation engineering
Professional Classification:	HG Professional Standard - Chemistry
ICS Classification:	25.040.40 Industrial process measurement and control
Issued by:
Issued on:	1998-06-22
Implemented on:	1999-01-01
Status:	ABOLISHED
Replace By:	HG/T20637.2-2017
Replace By Date:
Language:	English
File Format:	PDF
Word Count:	22000 words
Price(USD):	660 (USD)
Delivery:	via email in 1-5 business day

1 General Provisions
1.0.1 In order to meet requirements of instrumentation engineering design and make the engineering design documents standardization and normalization, hereby this guide is compiled.
1.0.2 This guide is applicable to drawing of symbols such as instrument loop diagram, location plan of instrument, layout drawing of instrument cable bridge framework, layout drawing of instrument cable (tube bundle) and bridge framework, wiring diagram of local instrumentation, logical diagram, semi-graphic flow drawing, DCS process display and common electrical equipment of instrument for instrumentation engineering design of chemical equipments.
1.0.3 Relevant standards are as follows:
ISA 5.2 Binary logical diagram for process operation
ISA 5.4 Instrument loop diagram
ISA 5.5 Symbols for process display
IEC 617 Part 12: Binary logical unit
HG20505 "Functional identification and symbols for process measuring and controlling instrumentation"
The implementation of this Guide shall also meet the requirements of current relevant standards of the nation.
2 Symbols in Instrument Loop Diagram
2.1 General
2.1.1 Symbols in instrument loop diagram are applicable to instrument loop diagram documents for instrumentation engineering design with adoption of conventional instrument or decentralized control system in order to represent functions of the instrument for process detection and control system, installation location of connection box, connecting pipe box, terminal block and bulkhead adaptor as well as the connection of signal lines between instruments and energy line connection.
2.1.2 Double lines drawing shall be adopted in instrument loop diagram.
2.2 Symbols
2.2.1 Explanations of end connection and energy (power supply, air supply and hydraulic power) shall be included in instrument symbols.
2.2.2 Symbol size of terminal block or bulkhead adaptor etc shall be determined by designer according to demand and drawing size.
2.2.3 Ellipse in thin solid line shall be represented for instrument signal shielding wire symbols as follows: