P&ID and PFD Drawing used various Symbols and Legend.
If you want to learn how to read P&ID and PFD, you must know the legend used in this drawings. So please watch the video till the end. You can download this presentation for free. The link is available in description.
PFD and P&ID are also known as PFS and PEFS. PFD is Process Flow Diagram. P&ID is Process or piping & Instrument Diagram. PFS means Process Flow Scheme and PEFS means Process Engineering Flow Scheme.
Here, I have tried to cover symbols that regularly used on the P&ID and PFD. There are other symbols also you can check the full list of the symbol by visiting the link this link. I advised you before you start working on actual plant or construction project you should check the project-specific symbol library which is also known as P&ID lead sheets or P&ID legend drawing.
P&ID symbols and level of information available on P&ID may change from company to company, but more or less they provide similar information.
What P&ID or PFD symbol is?
P&ID symbols are a graphical representation of physical equipment that installed on the field.
There are few ISO and British standards available that provide symbols and best practices to draw PFD and P&ID such as, ISA S5.1, BS 5070 and ISO 10628.
Pumps and Turbine P&ID Symbols
The symbols for various types of rotary equipment such as a centrifugal pump, vacuum pump and also positive displacement pumps such as gear and screw types. Last two symbols are of vertical pump and turbine.
P&ID Symbols for Compressor
The symbols for the compressor such as reciprocating, centrifugal, rotary, liquid ring and turbine driven.
Heat Exchanger P&ID symbol
These are the symbols for the heat exchanger. On drawing you can see both types of symbols are used the one on the right-hand side are more frequent than the one on the left-hand side.
Symbols for Static Equipment and Distillation column
Static equipment are straightforward. Vessel, drum, tanks, and furnace. Here you can see the symbols for dome roof tank, fixed roof tank, and internal floating roof tank. In case of the tank is only floating roof than there will be no roof on this symbol.
There are two types of the tower are shown here, one with column internal, and the other is without internals. There are different types of internals are used in the column and for that different symbols are used.
Here in the distillation tower, you can see the different types of internal, such mist mat, pipe distributor, liquid spray distributor, vortex breaker, baffle plate, packing bed and some other types of trays.
Line Symbols for PFD and P&ID
Below image shows various lines and connections that used on PFD and P&ID. Main process lines are shown as dark black line whereas minor lines are shown as thin black lines. You can see the symbols for pneumatic, hydraulic and capillary lines also.
Electric signals are shown as a dotted line, and Electromagnetic signals are shown as a wave on the solid line.
P&ID Symbols for Piping Valves
This is the trickiest part of reading P&ID and PFD. Here you can see the various types of valve symbols. If you remember that I have mentioned that P&ID symbols vary from company to company, valves symbols are the one that changes most of the time. So, if you are moving from one company to other, don’t rely on your memory and refer the lead sheets for symbols. Lead sheets are the one that contains all the project or plant-specific symbols.
Symbols for instruments
Now back to our symbols. Here you can see the various instrument bubble. In a process plant, more than 90 percent of instrument measured either pressure, temperature, flow or level. You can see the small table on the side which shows the first letter of the instrument. Now the function of these instruments are either indicate, record, control or transmit the measured value.
Here on this table, you can see the meaning of the first letter and subsequent letters. You can hold the video to read all the letters and their meaning. In next slide, I will tell you the meaning of the horizontal line on the instrument bubble.
|Measured or Initiating variable||Modifier||Readout function||Output|
- If there is a single horizontal line that means the instrument is located on the main control panel and accessible to panel operator.
- No horizontal line means the instrument is installed in the field, near the process and it is accessible to field operator.
- If there is a double horizontal line that means the instrument is installed on some secondary satellite local panel in the field.
- The last type is instrument bubble with a single dashed horizontal line. This symbol is used for instruments that are inaccessible in field or hidden or password protected on the control system.
Check this link if you want to learn P&ID Symbology in extreme depth. Download the Presentation by subscribing.
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