How to read a P&ID?In this article, we will learn how to read a Piping & Instrumentation Diagram which is something that engineers encounter on a daily basis.
In many of our RealPars articles, we discuss control system and instrumentation devices in great detail so you can understand exactly how they work. In this article, we will learn how to read a P&ID on a daily basis.
P&IDs, or Piping and Instrumentation Diagrams to give them their full name, are schematic representations of pipelines, equipment, instrumentation, and control systems found in process environments such as Oil Refineries, Chemical Plants, Paper Mills, and Cement Plants, etc.
P&ID Symbols and Codes
The symbols contained in P&IDs represent the equipment in the process such as actuators, sensors, and controllers.
Process equipment such as valves, instruments, and pipelines are identified by codes and symbols.
As well as devices and pipelines, a P&ID will commonly contain information on vents, drains, and sampling lines as well as flow directions, control I/O and Interconnection References.
P&ID Code Format
The Instrumentation codes listed in P&IDs follow a standard format, after some practice in reading P&IDs you will know these codes by heart, but in the meantime, there are many resources on the web where you can download these tables for reference.
The first letter of the code identifies the parameters that are being controlled or monitored for example Flow, Temperature, Level or Pressure.
The next letter is used to define the type of control device being used, for example, Transmitter, Valve or Controller.
The number refers to the logical numerator.
For example, we may have a system with 4 temperature transmitters, it makes sense to identify these as TT01, TT02, TT03, and TT04.
Let’s consider for a moment an instrument on a P&ID named FV01.
Looking up the code for this we could tell this is a Flow Valve numbered 01.
Symbols, circles, and lines are used to represent instruments and to show how they are connected to the rest of the system.
P&ID Instruments Location
Now that we know our device FV01 is represented by a circle, we can also tell from the P&ID where the instrument or device is located.
The presence or absence of a line in the circle determines the location of the physical device. Let’s take a look at how these are commonly represented.
– NO LINE: The instrument is located in the field near the process & operator.
– DOTTED LINE: The instrument is located in a control room (accessible to the operator).
– SOLID LINE: The instrument is not directly accessible.
P&ID Piping and Connections
The piping or connection lines on the P&ID also tell us about the instrument, for example, a solid line would indicate the interconnection is via pipework whereas a dotted line would indicate an electrical connection.
It is worth familiarising yourself with the different types of connection symbols as this can give you an insight into the function of an instrument even before you know its code.
In this article, we have looked at the basic interpretation of a P&ID or Piping and Instrumentation Diagram.
We learned that each instrument involved in the process appears on the P&ID and is represented by a symbol and a code.
We also learned that using this code and symbol we can understand what type of device it is, its location and how it is connected to the rest of the process.
To read a P&ID effectively one must be familiar with standard instrument symbols and standard identification letter codes.
We hope you enjoyed this short article on reading P&IDs, here at RealPars our team of experts is on hand to answer your questions and respond to your feedback.
We’d love to hear your suggestions for topics you want our team to cover.
Want to Learn More?
By downloading the RealPars app, you can have access to a wealth of practical knowledge as an automation engineer right in your pocket and you will also receive new fresh out of the oven videos each and every week.
Got a friend, client, or colleague who could use some of this information? Please share this article.
5 ACTIONABLE TIPS FOR GETTING A PLC PROGRAMMING JOB WITH NO EXPERIENCE The mindset that helped me find my ideal job as a PLC programmer with NO experience. Working as a PLC Programmer is one of the most attractive and highest paying jobs in the engineering industry....
With this article, we will continue with where our previous article, What are the leading Industrial Automation Job types?, closed with beginning the discussion on Automation Job Interview questions. So now that we have learned about the Automation Job types let's...
RealPars is the world's largest online learning platform for automation engineers.
+31 10 316 6400
Mon - Fri 8:30 am to 5:30 pm (CET)
Rotterdam Science Tower, Marconistraat 16,
3029AK Rotterdam, The Netherlands
© 2020 RealPras B.V. All rights reserved.
Created with coffee and tea in Rotterdam.