Piping and Instrumentation diagrams (P&ID)

When it comes to drawings and diagrams to map out a process system, the piping and instrumentation diagrams (P&ID) are a great way to situate and find components.  They use different symbols to represent the type of products, the layout in the system, installation, and process flow.  These standard symbols are created by ANSI or ISO.  They are used in electrical, hydraulic, and pneumatic processes.  Since EXAIR has been manufacturing Intelligent Compressed Air Products since 1983, I will cover some pneumatic symbols and the process flow in this blog.

A colleague, Russ Bowman, wrote an article about “Knowing Your Symbols Is Key To Understanding Your Drawings”.  As a reference, air compressors are the start of your pneumatic system, and there are different types as represented by the symbols below.

The one on the left can be used for any air compressor. The others denote specific types of air compressor (from left:) Centrifugal, Diaphragm, Piston, Rotary, and Screw.

Air compressors are considered the fourth utility in industries because they use so much electricity; and they are inefficient.  So, you need to use the compressed air as efficiently as possible.  As a typical pneumatic system, the air compressors, receiver tanks and compressed air dryers would be on the supply side.  The distribution system, or piping, connects the supply side to the demand side.  This symbol is represented by a simple line.  The demand side will have many different types of pneumatic devices.  Since there are so many, ANSI or ISO has created some common types of equipment.  But if there isn’t a symbol created to represent that part, the idea is to draw a basic shape and mark it.

From top left, and then down: Automatic Drain Filter Separator, Pressure Regulator, and Super Air Knife

As an example, if I were to do a P&ID diagram of the EXAIR Super Air Knife Kit; it would look like the above diagram.  The kit will include the Super Air Knife with an Automatic Drain Filter Separator and a Pressure Regulator.  The Filter Separator is a diamond shape and since it has an Automatic Drain, a triangle is placed at the bottom.  Filter Separators are used to clean the compressed air and keep the Super Air Knife clean.  The Automatic Drain will discard water and oil from the filter bowl when it accumulates over a float.  The next item is the pressure regulator which is represented by a rectangle with an adjustment knob to “dial in” the desired blowing force.  And at the end, we drew a rectangle, which does represent a Super Air Knife, as marked.

Using the P&ID diagram for the process flow is also important.  You noticed that the Filter Separator will come before the Pressure Regulator.  This is significant when installing this system.  Remember the statement above about “using your compressed air as efficiently as possible”?  Inefficiencies come from two basic areas; pressure drop and overusing your compressed air.  Pressure drop is based on velocity.  The lower the velocity, the lower the pressure drop.  If the Filter Separator is placed after the Pressure Regulator, the lower pressure will increase the velocity.  Since air expands at lower pressure, the volume of air will increase.  And since the area of the compressed air pipe is the same, the velocity will have to increase.   For the second part with overusing compressed air, the Pressure Regulator will help.  You want to use the lowest amount of air pressure as possible for the Super Air Knife to “do the job”.  The lower air pressure will use less compressed air in your operation.

EXAIR products are engineered to be safe, efficient, and effective in your compressed air system.  If you need help to place them in your P&ID diagrams, an Application Engineer can help you.  It is important to have the pneumatic devices in the proper place, and if you want to efficiently use your compressed air, you can use EXAIR products for your blow-off devices.

John Ball
Application Engineer

Email: johnball@exair.com
Twitter: @EXAIR_jb

Common Compressed Air Symbols

When any product / system is designed drawings are made to assist in the production of the designed product. For example if a mechanical part is being machined you may see symbols like these to verify the part is made correctly:

GD&T
GD&T Symbol Examples

Same with an electrical panel, they use symbols like the ones below to note the type of equipment used in a location.

electronic.JPG
Electrical Symbol Examples

 

Then there’s the Piping & Instrumentation Diagram (P&ID)…it depicts an overall view of a system, showing the flow (usually fluid or electricity) through that system’s components, giving the viewer an understanding of the operation, and expected results from said operation.

Some examples of symbols you might find in a compressed air system are:

Compressors:

all-compressor
The one on the left can be used for any air compressor. The others denote specific types of air compressor (from left:) Centrifugal, Diaphragm, Piston, Rotary, and Screw.

 

Air preparation & handling:

filters-and-regulator-symbols-and-pic.jpg
The symbols on the left denote the EXAIR products on the right: Automatic Drain Filter Separator, Oil Removal Filter, and Pressure Regulator

Instrumentation and control:

instrumentation-and-controls1.jpg
The symbols on top denote the EXAIR products below (left to right): Flowmeter, Pressure Gauge, and Solenoid Valve

Occasionally, we’re asked if there are standard ANSI or ISO symbols for any of our  engineered Intelligent Compressed Air Products…and there aren’t.  Perhaps one day they might make the cut, but for now, their standard convention is to choose a shape and call it out by name.  It might look something like this:

sak-pid1
From top left, and then down: Automatic Drain Filter Separator, Oil Removal Filter, Pressure Regulator, and Super Air Knife

If you have questions about any of the quiet EXAIR Intelligent Compressed Air® Products, feel free to contact EXAIR and myself or one of our Application Engineers can help you determine the best solution.

Jordan Shouse
Application Engineer
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Knowing Your Symbols Is Key To Understanding Your Drawings

There are all kinds of engineering drawings, used for all kinds of purposes:

  • Pipe fitters and millwrights use Plan & Elevation drawings to make sure fluid system flanges, elbows, tees, etc., line up with each other, and don’t run into anything.
  • Exploded view drawings help maintenance folks identify parts, and, when they need replaced, make sure the new ones go in the same way the old ones came out.
  • Fabrication and machining drawings (usually to scale) are used to ensure the part being made is the right size & shape, that mounting holes are in the right place, and that critical surfaces are as flat & smooth as they need to be.
  • Then there’s the Piping & Instrumentation Diagram (P&ID)…it depicts an overall view of a system, showing the flow (usually fluid or electricity) through that system’s components, giving the viewer an understanding of the operation, and expected results from said operation.  It should not be confused with its simpler cousin, the flow chart that is so dreaded by OTE-types (“Other Than Engineer”…you know who you are,) of which these are my favorite examples:
There’s a lot of “life lesson” in these two graphics.

The big difference between a flow chart and a P&ID is the symbols.  In fact, you can find ISO & ANSI standard symbols for many components you’ll find in fluid & electrical P&ID’s.  Some examples of symbols you might find in a compressed air system are:

Compressors:

The one on the left can be used for any air compressor. The others denote specific types of air compressor (from left:) Centrifugal, Diaphragm, Piston, Rotary, and Screw.

Air preparation & handling:

The symbols on the left denote the EXAIR products on the right: Automatic Drain Filter Separator, Oil Removal Filter, and Pressure Regulator

Instrumentation and control:

The symbols on top denote the EXAIR products below (left to right): Flowmeter, Pressure Gauge, and Solenoid Valve

Occasionally, we’re asked if there are standard ANSI or ISO symbols for any of our  engineered Intelligent Compressed Air Products…and there aren’t.  Perhaps one day they might make the cut, but for now, their standard convention is to choose a shape (user preference…you’re the one it’s gotta make sense to) and call it out by name.  It might look something like this:

From top left, and then down: Automatic Drain Filter Separator, Oil Removal Filter, Pressure Regulator, and Super Air Knife

Oh, and if you’ve ever got any questions about your compressed air system that you think looking at a drawing together could help us solve, you can send that drawing to us at techelp@exair.com, and one of us will be happy to help.

Russ Bowman
Application Engineer
EXAIR Corporation
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