Have a Plan and Stick to It: Common Compressed Air Drawing Symbols

Mike Tyson once said “everyone has a plan ‘til they get punched in the mouth”. I do believe it’s always important to have a plan, but hopefully your line of work does not involve anyone punching you in the mouth. If this plan is a Piping & Instrumentation Diagram (or P&ID), you’d be best served to follow it to the exact letter (or symbol). Otherwise, you might end up finding some facility or maintenance manager that is of the same mindset as good ol’ Mike.

The Piping & Instrumentation Diagram is a great way to illustrate the layout of your complete system. Different symbols, created by ANSI or ISO, are used to identify the specific items in the diagram and lays out the entire system, installation, and process flow.

Air compressors are the heart of the pneumatic system and have a variety of different types of symbols that can be used based on the style of compressor that you have. Below are some examples of the symbols used to denote an air compressor on a P&ID:

On the left is a generic symbol that can be used for any style of compressor. Moving towards the right we have specific, unique symbols for each: centrifugal, diaphragm, piston, rotary, and screw compressors. As the 4th utility in any industrial environment, air compressors are a critical piece of equipment in the facility. From the compressor there will be a line drawn to denote the distribution system or piping that connects the supply side (air compressors) to the demand side.

On the demand side are a variety of different available symbols for each type of equipment. EXAIR recommends installing filters and regulators at the point-of-use to keep air clean and dry as well as operating at the minimal pressure for compressed air conservation. The symbols below are used for particulate filters, oil removal filters, and pressure regulators:

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

They’re laid out in this order for a reason which is why it’s important to follow the drawing exactly as shown when installing the equipment. The particulate filter must come before the coalescing filter in the supply line. Since we can experience pressure drop across filters, it makes the most sense to include the pressure regulator AFTER the air exits the particulate and oil removal filters for the most accurate representation of point-of-use line pressure.

Oftentimes, you may encounter a situation where the product you’re looking to use doesn’t have a specified ANSI or ISO symbol. In those cases, what is recommended is to choose any shape you wish and call it out specifically by name. For our Super Air Knives, this would look something like this:

Having a plan is one thing, but it’s important to make sure this plan has been well-thought-out prior to doing any installation work. It’s not that Mike Tyson is going to come around throwing haymakers or biting off ears if you don’t, but you run the risk of wasting quite a bit of time (and money!) by not adhering to the original plan.

If your plan includes using some of EXAIR’s Intelligent Compressed Air Products, give us a call. We have a variety of products ready to ship same-day from stock to help you get the most out of your compressed air system.

Tyler Daniel, CCASS

Application Engineer

E-mail: TylerDaniel@EXAIR.com

Twitter: @EXAIR_TD

Mike Tyson photo courtesy of Abelito Roldan via Flickr Creative Commons License

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