How to read P&ID (Piping and instrument diagram) & PFD (Process flow diagram).

P&ID: – Schematic illustration of instruments and their interconnection is called P&ID.
– Sơ đồ minh họa thể hiện các thiết bị đo và những đường ống, kết nối liên kết với nó gọi là bản vẽ P&ID

PFD: Process flow diagram. PFD gives an overview of the plant process. PFD is a simplified version of P&ID.
– Mô tả tổng thể quá trình, nguyên lý hệ thống, PFD là một phiên bản đơn giản của P&ID

Identification Letters/Ký hiệu thiết bị đo

The following letters are used to describe the control devices involved in a process. Each device is labeled with two letters. The first letter describes the parameter the device is intended to control. The second letter describes the type of control device.

Các chử cái sau được ký hiệu để miêu tả các thiết bị đo trong hệ thống, nhà máy, Mổi thiết bị được biểu diển bằng 2 chử cái. Chử đầu tiên thể hiện thông số cần điều khiển. Chử thứ hai thể hiện chủng loại của thiết bị đo.

Typical Letter Combinations

For example, the symbol “PI,” is a “pressure indicator.”

General Instrument or Function Symbols
Instruments can have various locations, accessibilities, and functionalities in the field for certain processes. It is important to describe this clearly in a P&ID. Below is a table of these symbols commonly used in P&IDs.

Các thiết bị đo khác nhau có các vị trí, phạm vi và chức năng khác nhau tại field một hệ thống bất kỳ và là yếu tố quan trọng để mô tả cụ thể trong bản vẽ P&ID.

FunctionSymbols

In the chart above, it is necessary to know where the instrument is located and its function in order to draw it correctly on a P&ID. A primary instrument is an instrument that functions by itself and doesn’t depend on another instrument. A field mounted instrument is an instrument that is physically in the field, or the plant. Field mounted instruments are not accessible to an operator in a control room. An auxiliary instrument is an instrument that aids another primary or auxiliary instrument. Primary and auxiliary instruments are accessible to operators in a control room.

Piping and connection symbols:

These symbols are used to identify how the instruments in the process connect to each other.And what type of singnal is being used.

Line_types

Each and every line has a different meaning kindly observe the differences keenly

the “main process” refers to a pipe carrying a chemical. “Insulated” is straightforward, showing that the pipe has insulation. “Trace heated” shows that the pipe has wiring wrapped around it to keep the contents heated. “Lagged” indicates on a P&ID that the pipe is wrapped in a cloth or fiberglass wrap as an alternative to painting to improve the appearance of the pipe see here for more information. The last column in Table 1 shows pipes that are controlled by a controller. “Electrical impulse” shows that the manner in which information is sent from the controller to the the pipe is by an electrical signal, whereas “pneumatic impulse” indicates information sent by a gas.

In addition to line symbols, there are also line labels that are short codes that convey further properties of that line. These short codes consist of: diameter of pipe, service, material, and insulation. The diameter of the pipe is presented in inches. The service is what is being carried in the pipe, and is usually the major component in the stream. The material tells you what the that section of pipe is made out of. Examples are CS for carbon steel or SS for stainless steel. Finally a ‘Y’ designates a line with insulation and an ‘N’ designates one without it. Examples of line short codes on a P&ID are found below in Figure A.

Figure A: Line Labels

Figure A: Line Labels

This is useful for providing you more practical information on a given pipe segment.
For example in stream 39 in Figure A, the pipe has a 4″ diameter, services/carries the chemical denoted ‘N’, is made of carbon steel, and has no insulation.

Valve Symbols
The following symbols are used to represent valves and valve actuators in a chemical engineering process. Actuators are the mechanisms that activate process control equipment.

Valves

Valve Symbols

Valve Actuator Symbols

Valve Actuator Symbols

Transmitter Symbols
Transmitters play an important role in P&IDs by allowing the control objectives to be accomplished in a process. The following are commonly used symbols to represent transmitters.

Below are three examples of flow transmitters. The first is using an orifice meter, the second is using a turbine meter, and the third is using an undefined type of meter.

Transmitter Symbols

Transmitter Symbols

The location of the transmitter depends on the application. The level transmitter in a storage tank is a good example. For instance, if a company is interested in when a tank is full, it would be important for the level transmitter to be placed at the top of the tank rather than the middle. If the transmitter was misplaced in the middle because a P&ID was misinterpreted then the tank would not be properly filled. If it is necessary for the transmitter to be in a specific location, then it will be clearly labeled.

Miscellaneous Symbols
The following symbols are used to represent other miscellaneous pieces of process and piping equipment.

Process Equipment

Process Equipment

Process Equipment

Process Equipment

Process Equipment

Process Equipment

Fittings

Pipe supports

Pipe supports

For the detail Instrumentation symbols, and Identifications, please download the ISA S5.1:

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