PIPING DESIGN

A piping and instrumentation diagram/drawing (P&ID) is a diagram in the process industry which shows the piping of the process flow together with the installed equipment and instrumentation.

Contents and Function

An example of a P&ID.

A piping and instrumentation diagram/drawing (P&ID) is defined by the Institute of Instrumentation and Control as follows:

1. A diagram which shows the interconnection of process equipment and the instrumentation used to control the process. In the process industry, a standard set of symbols is used to prepare drawings of processes. The instrument symbols used in these drawings are generally based on Instrumentation, Systems, and Automation Society (ISA) Standard S5. 1.
2. The primary schematic drawing used for laying out a process control installation.

P&IDs play a significant role in the maintenance and modification of the process that it describes. It is critical to demonstrate the physical sequence of equipment and systems, as well as how these systems connect. During the design stage, the diagram also provides the basis for the development of system control schemes, allowing for further safety and operational investigations, such as the hazard and operability study (HAZOP).

For processing facilities, it is a pictorial representation of

• Key piping and instrument details
• Control and shutdown schemes
• Safety and regulatory requirements and
• Basic start up and operational information

List of P&ID items

• Instrumentation and designations
• Mechanical equipment with names and numbers
• All valves and their identifications
• Process piping, sizes and identification
• Miscellanea - vents, drains, special fittings, sampling lines, reducers, increasers and swagers
• Permanent start-up and flush lines
• Flow directions
• Interconnections references
• Control inputs and outputs, interlocks
• Interfaces for class changes
• Computer control system input
• Identification of components and subsystems delivered by others

Identification and Reference Designation

The P&ID is used for the identification of measurements within the process. Identification letters for measurements are based on Standard S5. 1 and ISO 14617-6:

For reference designation of any equipment in industrial systems the standard IEC 61346 (Industrial systems, installations and equipment and industrial products — Structuring principles and reference designations) can be applied. For the function Measurement the reference designator B is used, followed by the above listet letter for the measured variable.

For reference designation of any equipment in power station the KKS Power Plant Classification System can be applied.

Symbols of chemical apparatus and instrumentation

Below are listed some symbols of chemical apparatus and instrumentation normally used in a P&ID, according to DIN 30600 and ISO 14617.

Symbols of chemical apparatus and instrumentation

	Pipe		Thermally insulated pipe		Jacketed pipe		Cooled or heated pipe
	Jacketed mixing vessel (autoclave)		Half pipe mixing vessel		Pressurized horizontal vessel		Pressurized vertical vessel
	Pump		Vacuum pump or compressor		Bag		Gas bottle
	Fan		Axial fan		Radial fan		Dryer
	Packing column		Tray column		Furnace		Cooling tower
	Heat exchanger		Heat exchanger		Cooler		Plate & frame heat exchanger
	Double pipe heat exchanger		Fixed straight tubes heat exchanger		U shaped tubes heat exchanger		Spiral heat exchanger
	Covered gas vent		Curved gas vent		Dust trap		Funnel
	Steam trap		Viewing glass		Pressure reducing valve		Flexible pipe
	Valve		Control valve		Manual valve		Back draft damper
	Needle valve		Butterfly valve		Diaphragm valve		Ball valve