To understand what diagrams are used in the design of automation tools for technological processes, let’s see the valid regulatory documents. Currently, this is GOST 21.408-2013 «RULES OF INDUSTRIAL PROCESS AUTOMATION WORKING DOCUMENTATION EXECUTION». According to GOST 21.408-2013, there are following diagrams:

  • automation diagrams;
  • circuit (electrical, pneumatic) diagrams;
  • diagrams (tables) of hookups and external wiring connection
  • equipment and external wiring layout drawings
  • automation equipment drawings

Let’s consider symbol designation of instruments in the diagrams following the above sequence

1. Instrumentation symbols in automation diagrams (functional diagrams)

To designate instruments in the diagrams, it is necessary to be guided by the currently valid GOST 21.208-2013 «Instrumentation symbols for use in diagrams«. In international projects, functional diagrams are called «Piping and instrumentation diagram» (PID), however, it is rather difficult to read and understand the entire GOST. Let me try to interpret instrument symbol explanation. For many years, design has had no limitations. Therefore, when designing in international practice, «International standards ISO 14617-6» is used.  The symbols adopted in GOST 21.208-2013 are also similar to ISO 14617-6, so that they would be understandable to specialists, regardless of the country, and the language used in different countries. For many devices, the symbols were taken from the first letters of the word in English, denoting this device.  The first letter of instrument symbol according to GOST 21.208-2013 indicates the type of the measured value.

  • А— Analysis — analysis meters (composition, concentration). According to the «Attachment B» to GOST, these can be moisture analyzers, instruments for measuring acidity, oxygen content in flue gases, viscometers, etc.
  • В –Burner – flame monitor instruments, burner firing.
  • D— Differential – differential pressure instruments.
  • F—  Flow – flowmeters
  • Н— Hand — instruments for manual operation (manual call point)
  • I – Indicating – Secondary indicating instruments
  • J— Power (Сила) – мощность
  • K-Time (Время) — время
  • L— Level–level instruments
  • Р-Pressure – instruments for measuring pressure, discharge.
  • Q— Quantity – instruments that measure the amount of a substance in any medium. Usually this letter is used to designate gas analyzer, because it measures the amount of harmful or hazardous substances in the air..
  • R— Radiation – instruments that measure radiation
  • S— Speed – speed measurement instruments
  • T— Temperature – temperature measuring instruments.
  • U— Multivariable / Several mixed measured values (for example, ESD panel controllers)
  • V— Vibration – instruments for measuring the vibration level (for example of a pump)
  • W-Weight – instruments for weight, mass measurement (for example, electronic scales)
  • Z— movement, position instruments (for example, limit switches)

But there may be some differences in international projects. So, the first letter D-Density according to ISO 14617-6 — denotes instruments for measuring the density of the pumped liquid (for example, flow densitometer).U-Shutoff valve.  The symbol of UV shut-off valve also corresponds to GOST 21.208-2013 because the shut-off valve is usually triggered when the permissible values of various parameters of the technological process are exceeded. Therefore, the letter U is used — several heterogeneous measured values

These are the letters denoting the instrument stand first in the instrument symbol. The second letter in the instrument symbol according to GOST 21.208-2013 can be D, F, J, Q, S and Z. 

  • D— Differential — as noted above. For instance, PDT symbol, where the second letter D denotes a drop, in this particular case is a pressure drop.
  • F— Fractional part, Ratio – instruments that measure the ratio of any parameters. It can be, for instance, an instrument that measures flow rate ratio and hydrogen sulfide to the cyclone furnace of the sulfur treatment plant.
  • J— Multiplexed scanning — an instrument that collects information from several transducers, and transmits it to the control system as a digital signal.
  • Q – Integrated, Totalize — an instrument that accrues the measured value. For example, FQ is a water counter.
  • S – Safety — an instrument that ensures safety when technological parameters are exceeded. For example, PSV is a safety valve. Например PSV- предохранительный клапан.Z — Z axis state (состояние относительно оси Z) – приборы продольного перемещения, например прибор осевого сдвига вала насоса.
  • Z — Z axis state — longitudinal displacement instruments, for example, a pump shaft axial shift instrument

The third letter in instrument symbol according to GOST 21.208-2013 can be E, G, I, K, S, T, X, Y. These letters indicate the type of information that is displayed on the instrument

  • E— Sensor (Primary element) — is a sensing element. These can be primary transducers of temperature (thermocouples, thermal resistances, pyrometers), flow rates (diaphragms, orifices) and other primary instruments that convert the measured parameter of the medium into an electrical or pneumatic signal for further conversion of a standard signal.
  • G— Glass, Guage, Viewing Device — the primary indicating instrument — for example, a level column with a viewing glass.
  • I— Indicated Guage — Secondary indicating instrument
  • K— is used to designate a control station that has a switch to select the type of control and a device for remote control
  • S— Switch — a contact switching instrument used to enable, disable, switch and lock. It can be either a primary instrument (for example, an electrical contact pressure gauge) or a secondary instrument with a relay output that switches when a certain value of the measured parameter is reached.
  • T— Remote Transmitter — Transducer is usually installed close to the sensing element and converts into a standard signal for transmission to the control system. Commonly, the primary instrument is combined in the same housing with the transducer.
  • X— Un classified — Auxiliary computer devices
  • Y— Y— Computer convert (signal converters) — auxiliary computing means.

The fourth letter in the instrument symbol according to GOST 21.208-2013 can be A, C, D, R.

  • A— Alarm — Warning — instruments that generate an alarm when the specified value of the measurement parameter — the setpoint is reached. It can be both a primary measuring instrument and a panel instrument, with a contact group that switches when the setpoint value is reached.
  • С-Controller (Control) — Automatic adjustment and control — instruments that control any parameter of the technological process (regulation of temperature, pressure, flow, etc.)
  • D— Differential — The deviation of function D when combined with function A (alarm) indicates that the measured variable deviated from the reference or other setpoint by more than a predefined number.
  • R— Record – registration. Recording instruments (recording the measured parameters in its memory cell or on a paper tape).

The fifth letter in the symbol of the instrument accordong to GOST 21.208-2013 can be Н, L, M.

  • H— High — The upper limit of the measured value — the instrument is set at the high point of the measured parameter. For example, high level alarm in a tank
  • L— Low — The lower limit of the measured value — the instrument is set at the lowest point of the measured parameter. For example, low level alarm in a tank.
  • М— Middle — The medium value or position.  It is used very rarely in the petrochemical industry.

There is no any reference to the digital designation of the instruments in the interstate standard GOST 21.208-2013. But in practice, it is customary for a reference designation to start with a certain digit, denoting the measured value.

  1. Temperature measuring instruments
  2. Pressure measuring instruments
  3. Flow measuring instruments
  4. Level measuring instruments
  5. Analyzers
  6. Control valves, on-off valves
  7. Manual valves, gates
  8. Electric motor control units
  9. Other instruments

The remaining digits in the reference designation are the serial number of the instrument. For small units, the reference designation consists of three digits, for larger units — four digits.

There are also digits in the beginning of the symbol (tag number) of the instruments in the deign documentation. For example, 1-RT-2001. This digit is used to indicate the number of the unit section. In other words, a large process plant is divided into sections: 100, 200, 300, etc. and the first digit of the unit section number is written in the tag number. Section number specification before the instrument tag simplifies the identification of the instrument, both on the route plan and on the functional diagrams.

There is no need to list the combinations of the instrument symbols specified in GOST 21.208-2013. Everything is clear based on the given examples. There can be some difficulties when you have to put an instrument tag number that has not been used by the design organization before. Let’s use as an example industrial controller «БАЗИС-21» . The instrument accepts analog and discrete signals. Displays information on the current parameter values on the LCD screen. Saves information in the form of trend data. Outputs a sound and light signal about exceeding the value of the measured parameters. Outputs a stop (block) signal. Let’s put letter designations in accordance with p. 5.10 of GOST 21.208-2013.

As a result, the tag number is UISAR-901

  • U-instrument that measures several heterogeneous quantities
  • I— secondary indicating instrument
  • S— blocking
  • A-alarm system
  • R— record instrument

Symbols of instruments in electrical diagrams.

According to p. 5.4.2 of GOST 21.408-2013 «Electrical diagrams are performed according to GOST 2.701 and GOST 2.702«. Circuit diagrams is according to «GOST 2.701-2008 «Diagrams. Kinds and Types. General requirements for fulfillment» this is document that defines full composition of elements and interconnections between them and, as a rule, gives a complete (detailed) understanding of the principles of product (unit) operation. There are following circuit diagrams:

  • Э — circuit electrical diagram;
  • Г — hydraulic connection diagram;
  • П — pneumatic diagram;
  • Х — gas diagram;
  • Е- structural dividing circuit;
  • К — kinematic;
  • В – vacuum;
  • Л – optical;
  • Р – energy;
  • Е – dividing;
  • С – combined;

Since when designing automation diagrams, it is necessary to combine various types of diagrams, and when denoting, the designation of the combined diagram is mainly used — С.

  • 1 — structural;
  • 2 – functional;
  • 3 – circuit;
  • 4 – connections;
  • 5 – wiring;
  • 6 – general;
  • 7 – layout;
  • 0 – combined;

A combination of letters and digits is used to designate the diagram code. As a result, the following are used to designate the diagram in the document code:

  • С3 — circuit diagram;
  • С4 – connection diagram (external wiring diagrams);
  • С7 – layout diagram (route plan);

The nomenclature, titles and codes of other diagrams must be established in the standards of the organization (GOST 2.701-2008).

Since we have considered the designations of instruments in automation diagrams above, let’s analyze circuit diagrams.

According to GOST 2.702-2011 «Rules for execution of circuit diagram» p. 5.3.1″ The circuit diagram shows all electrical elements or instruments necessary for the implementation and control of the installed electrical processes, all electrical interconnections between them, as well as electrical elements (connectors, clamps, etc.) that end input and output circuits.

5.3.2.  The diagram is allowed to depict connecting and mounting elements installed in the unit for design reasons.

When drawing up circuit diagrams, instrument code designation (tag number) assigned in the automation diagram is used to designate instruments. The automation diagram does not indicate intermediate junction boxes, marshaling elements, etc. Letter designation on electrical diagrams is done in accordance with GOST 2.710-81 (LETTER AND DIGITAL DESIGNATIONS IN ELECTRICAL DIAGRAMS)

When choosing a symbol for the electrical diagram in the GOST, we can use only some of the symbols. For example — XT — Dismountable contact joints — used to indicate terminal connections in junction boxes and marshaling cabinets. For general information, see this GOST. But in the instrumentation electrical diagrams, international rules are used more.

These rules do not contradict the requirements of GOST 2.710-81.According to p. 1.2 «GENERAL PROVISIONS» — «If necessary, it is allowed to use designations and their qualifying symbols, the types of which are not established by this standard. The content and method of recording such designations should be explained in the documentation for the facility (for example, in the diagram).»

There are usually few elements in the electrical instrumentation diagrams. There is more detailed description.

Junction boxes:

  • JB — Junction Box — 4-20mA junction box for intrinsically safe circuits.
  • JBI — Junction Box intrinsically safe — Junction box 4-20 mA for intrinsically safe circuits.
  • JBE — Junction Box ESD — 4-20 mA junction box for non-intrinsically safe ESD circuits
  • JBEI — Junction Box ESD intrinsically safe — Junction box 4-20 mA for intrinsically safe ESD circuits
  • JBFF — Junction Box Foundation Fieldbus.
  • JBD — Junction Box Digital signals- Junction box for digital signals.
  • JBED -Junction Box ESD Digital signals- Junction box for ESD discrete signals
  • JBDI — Junction Box ESD Digital signals- Junction box for intrinsically safe ESD discrete signals.
  • JBS — Junction Box Solenoid valves — Junction box for control signals of solenoid valves
  • JBES — Junction Box ESD Solenoid valves — Junction box for control signals for ESD solenoid valves.
  • GJB — Gas detector Junction Box — Junction box for analog signals of gas detection system.
  •  GJBВ — Gas detector Junction Box Digital signals — Junction box for discrete signals of gas detection system.
  • FJB — Fire systems Junction Box — Junction box for analog signals of the fire detection system.
  • FJS — Fire systems Junction Box Solenoid valves — Junction box for discrete signals of a fire detection system..
  • JBM — Junction Box MMS signals — Junction box for discrete vibration sensors
  • JBMI — Junction Box MMS signals intrinsically safe — Junction box for analog vibration sensors.
  • JBA — Junction Box 220V — Junction Box for discrete circuits 220V.
  • JBT — Junction Box Thermistor.
  • JAT — Junction Box Thermoelectric transducer — Junction box for thermocouples..
  • JP — JJunction Box Power supply — Junction box for 24V power supply.

Various local control panels:

LP— Local Panel (local control panel)

Therefore, designations of various production safety systems have been added in the symbols of junction boxes. There are production following safety systems:

  • GDS — Gas detection system — a system for the detection of flammable and toxic gases, vapors of flammable liquids
  • FDS — FDS — Fire detection system
  • PAGA —  Public address / general alarm — two-way loudspeaker communication system
  • CCTV —  Closed Circuit television
  • TPS — Telephone system
  • ACS — Access control system – СКУД.
  • SMIS — Structured system of monitoring and management of engineering systems – СМИС
  • PRS— Process radio system — Technological system of wireless radio communication
  • MMS— Machinery monitoring system — (vibration diagnostics system for pumping and compressor equipment)
  • HVAC — Heating, Ventilation and Air Conditioning

The design of the above systems is carried out in separate parts of the project. Since the elements of these systems are not always indicated in the process automation diagrams, the symbols of equipment for various systems in the electrical diagrams are used in accordance with the purpose of the system.

Instruments symbols in connection diagrams (external wiring)

Instruments designation in the connection diagrams (external wiring) does not differ from the designation in the circuit diagrams.Let’s consider external wiring cable tagging in this section. External wiring diagrams is carried out in accordance with GOST 2.702-2011 «RULES FOR EXECUTION OF CIRCUIT DIAGRAM», part 5.4 «Rules for the execution of connection diagrams.»

There is no need to give various excerpts from this GOST. I just recommend viewing it for a general understanding. According to p. 5.4.19 «On the diagram, using a literal (letter-digit) designation, it is allowed to determine the functional belonging of a wire, bundle or cable (multicore cable, electrical cord) to a specific complex, building or functional circuit. UGO — conventional graphic designations». There are no other requirements for the cable symbol. In this case, let’s again refer to the generally accepted rules applied in international standards.

Single cables from instruments to junction boxes (local panels) shall have the same identification number as the instrument

To distinguish a cable from a harness, it is necessary to put the letter C — Cable (prefix) before the tag number.

To designate several cables suitable for one instrument, letters A, B, C …(postfix) is placed at the end of the tag number.

To indicate instrumentation power cable, the letter Р is placed at the end of the tag number (postfix).

Examples of cable tagging:

C-1111-1-FT-3001-A- Unit 1111, Section 1, control cable between FT-3001 flowmeter and junction box — first cable.

C-1111-1-FT-3001-A-Unit 1111, Section 1, control cable between FT-3001 flow meter and junction box-the second cable.

C-1111-1-FT-3001-A- Unit 1111, Section 1, FT-3001 flowmeter external power cable and junction box

Main cables are identified in the same way as the equipment where the cable is connected — junction boxes, local panels. The letter C is also placed before the tag number. If there are several cables connected to the equipment, the letter A, B, C is placed at the end of the tag number.

C-1111-1-JB-001 — Unit 1111, Section 1, cable between JB-001 junction box and instruments installed in the building.

Symbols of instruments in layout diagrams (route plans)

Letter-digit designation of instruments is sufficient in the layouts of instrumentation equipment (route plans) in the above information. It remains only to consider the designation of cable trays. There are no requirements for the designation of cable trays either in GOST 2.702-2011 «RULES FOR EXECUTION OF CIRCUIT DIAGRAM» or in GOST 21.210-2014 «SYMBOLS OF ELECTRICAL EQUIPMENT AND WIRES ON PLANS». When designing a small project, such as pump station, compressor station, tank storage plant, etc. you can limit yourself to the numbering of cable trays — No.1, 2, 3 … It is too difficult to apply this designation when designing a project for a large unit, with long main cable tray route and a large number of junctions from main trays in different sections

Let’s consider designation of cable trays used in international projects.

  •  IS — Intrinsically safe – cable trays for intrinsically safe circuits. ESD, DCS, PLC and MMS system cables are laid inside IS cable trays. 
  • NIS — Not intrinsically safe — cable trays for non-intrinsically safe circuits. NIS cable trays are used to lay ESD, DCS cables, electric solenoid valves control cables, gas control system cables, 24V DC power cables.
  • FF — Foundation Fieldbus — digital system of two-way data transmission — cable trays for the system of digital FF communication of the controller with instruments.
  • P- Public address / general alarm — cable trays for two-way communication system up to 110 V. Cables for two-way intercom system, public address loudspeaker system, as well as for the fire alarm and fire extinguishing system are laid inside P cable trays.
  • PA — Public address / general alarm — cable trays for two-way communication system above 110 V. Cables for two-way intercom system, as well as cables of light and sound alarms are laid inside РА cable trays.
  • IE- Instrument Electrical Interface — power supply of instrumentation- cable trays for power supply of instruments and communication tools with a voltage of ~ 220 V.
  • S — Communication system — cable trays for data transmission systems, including fiber-optic communication lines.

The complete cable tray designation consists of a letter symbol and a digital symbol. Digital symbol consists of 3 digits. The first number of the digital symbol indicates cable gallery level.

  • 0 — The lowest level of the cable gallery
  • 1 — The second level of the cable gallery
  • 2 — The third level of the cable gallery.

For example:

IS-001 — cable tray for intrinsically safe circuits located on the ground level of the cable gallery.

NIS-101-1 — cable tray for non-intrinsically safe circuits located on the second level of the cable gallery — junction from the cable tray No. 1.

Symbols of instruments in the drawings of automation equipment units

«SYMBOLS OF ELECTRICAL EQUIPMENT AND WIRES ON PLANS» are made in accordance with GOST 21.210-2014. Graphic images of the equipment are presented in this GOST. There is no letter designation for equipment that has not been indicated in the functional and circuit diagrams.

There is a need for an identifying code of equipment not specified in the above diagrams.  Let’s consider some options according to international standards.To understand instruments decoding, we first consider the abbreviation of some automation system symbols.

  • APCS — Automation Process Control System — АСУТП: 
  • PLC:  Process Logic Controller — ПЛК
  • DCS-  Distributed Control System — РСУ.
  • ESD- Emergency shut-down- Аварийное отключение — ПАЗ
  • PIMS- Process Infrormation Management System
  • ECS — Electrical Control System
  • UPS — Uninterruptable Power Supply — ИБП
  • OWS — Operator Workstation
  • EWS —  Engineering Workstation — АРМ 

Symbols for equipment and control cabinets depend on system appliance of such equipment. Examples are given below

  • ESD- Emergency shut-down Cabinet
  • ESM- ESD Marshaling Cabinet
  • DCS- Distributed Control System Cabinet
  • DCM- Distributed Control System Marshaling Cabinet
  • CFA  — Cabinet Fire Alarm System 
  • CFS — Cabinet Fire Extinguishing
  • SRC — Server Cabinet
  • FOC —  Fiber Optic Patch Panels Cabinet
  • PDC — Power Distribution Cabinet
  • IEI — Instrument Electrical Interface
  • IMC — Interconnecting Marshaling Cabinet
  • MC — Maintenance Console
  • OC — Operating Console
  • SC — Supervision Console

The complete equipment symbol consists of the unit number, the equipment designation and the serial number. For example, 1111-DCM-01

According to GOST 2.710-81 p. 1.1. letter-digit designations (hereinafter — designations) are intended:

  • for a definitive record in abbreviated form of information about elements, devices and functional groups (hereinafter referred to as parts of the facility) in the documentation for the facility;
  • for reference to the corresponding parts of the facility in text documents;
  • for application directly to the object, if provided in its design.