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:
Same with an electrical panel, they use symbols like the ones below to note the type of equipment used in a location.
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:
Air preparation & handling:
Instrumentation and control:
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:
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.
Air… We all breathe it, we live in it, we even compress it to use it as a utility. What is it though? Well, read through the next to learn some valuable points that aren’t easy to see with your eyes, just like air molecules.
Air is mostly a gas.
Comprised of roughly 78% Nitrogen and 21% Oxygen. Air also contains a lot of other gases in minute amounts. Those gases include carbon dioxide, neon, and hydrogen.
Air is more than just gas.
While the vast majority is gas, air also holds lots of microscopic particulate.
These range from pollen, soot, dust, salt, and debris.
All of these items that are not Nitrogen or Oxygen contribute to pollution.
Not all the Carbon Dioxide in the air is bad.
Carbon Dioxide as mentioned above is what humans and most animals exhale when they breathe. This gas is taken in by plants and vegetation to convert their off gas which is oxygen.
Think back to elementary school now. Remember photosynthesis?
If you don’t remember that, maybe you remember Billy Madison, “Chlorophyll, more like Bore-a-fil.”
Carbon dioxide is however one of the leading causes of global warming.
Air holds water.
That’s right, high quality H2O gets suspended within the air molecules causing humidity. This humidity ultimately reaches a point where the air can simply not hold anymore and it starts to rain. The lack of humidity in the air leads to static, while lots of moisture in the air when it gets compressed causes moisture in compressed air systems.
Air changes relative to altitude.
Air all pushes down on the Earth’s surface. This is known as atmospheric pressure.
The closer you are to sea level the higher the level of pressure because the air molecules are more densely placed.
The higher you are from sea level the lower the density of air molecules. This causes the pressure to be less. This is also why people say the air is getting a little thin.
Hopefully this helps to better explain what air is and give some insight into the gas that is being compressed by an air compressor and then turned into a working utility within a production environment. If you would like to discuss how any of these items effects the compressed air quality within a facility please reach out to any Application Engineer at EXAIR.
The supply side of a compressed air system has many critical parts that factor in to how well the system operates and how easily it can be maintained. Dryers for the compressed air play a key role within the supply side are available in many form factors and fitments. Today we will discuss heat of compression-type dryers.
Heat of compression-type dryers are a regenerative desiccant dryer that take the heat from the act of compression to regenerate the desiccant. By using this cycle they are grouped as a heat reactivated dryer rather than membrane technology, deliquescent type, or refrigerant type dryers. They are also manufactured into two separate types.
The single vessel-type heat of compression-type dryer offers a no cycling action in order to provide continuous drying of throughput air. The drying process is performed within a single pressure vessel with a rotating desiccant drum. The vessel is divided into two air streams, one is a portion of air taken straight off the hot air exhaust from the air compressor which is used to provide the heat to dry the desiccant. The second air stream is the remainder of the air compressor output after it has been processed through the after-cooler. This same air stream passes through the drying section within the rotating desiccant drum where the air is then dried. The hot air stream that was used for regeneration passes through a cooler just before it gets reintroduced to the main air stream all before entering the desiccant bed. The air exits from the desiccant bed and is passed on to the next point in the supply side before distribution to the demand side of the system.
The twin tower heat of compression-type dryer operates on the same theory and has a slightly different process. This system divides the air process into two separate towers. There is a saturated tower (vessel) that holds all of the desiccant. This desiccant is regenerated by all of the hot air leaving the compressor discharge. The total flow of compressed air then flows through an after-cooler before entering the second tower (vessel) which dries the air and then passes the air flow to the next stage within the supply side to then be distributed to the demand side of the system.
The heat of compression-type dryers do require a large amount of heat and escalated temperatures in order to successfully perform the regeneration of the desiccant. Due to this they are mainly observed being used on systems which are based on a lubricant-free rotary screw compressor or a centrifugal compressor.
No matter the type of dryer your system has in place, EXAIR still recommends to place a redundant point of use filter on the demand side of the system. This helps to reduce contamination from piping, collection during dryer down time, and acts as a fail safe to protect your process. If you would like to discuss supply side or demand side factors of your compressed air system please contact us.
All atmospheric air contains some amount of water vapor. When air is then cooled to saturation point, the vapor will begin to condense into liquid water. The saturation point is the condition where the the air can hold no more water vapor. The temperature at which this occurs is knows as the dew point.
When ambient air is compressed, heat is generated and the air becomes warmer. In industrial compressed air systems, the air is then routed to an aftercooler, and condensation begins to take place. To remove the condensation, the air then goes into separator which traps the liquid water. The air leaving the aftercooler is typically saturated at the temperature of the discharge, and any additional cooling that occurs as the air is piped further downstream will cause more liquid to condense out of the air. To address this condensation, compressed air dryers are used.
It is important to dry the air and prevent condensation in the air. Many usages of the compressed air are impacted by liquid water being present. Rust and corrosion can occur in the compressed air piping, leading to scale and contamination at point -of -use processes. Processes such as drying operations and painting would see lower quality if water was deposited onto the parts.
There are many types of dryers – (see recent blogs for more information)
Refrigerant Dryer – most commonly used type, air is cooled in an air-to-refrigerant heat exchanger.
Regenerative-Desiccant Type – use a porous desiccant that adsorbs (adsorb means the moisture adheres to the desiccant, the desiccant does not change, and the moisture can then be driven off during a regeneration process).
Deliquescent Type – use a hygroscopic desiccant medium that absorbs (as opposed to adsorbs) moisture. The desiccant is dissolved into the liquid that is drawn out. Desiccant is used up, and needs to be replaced periodically.
Heat of Compression Type – are regenerative desiccant dryers that use the heat generated during compression to accomplish the desiccant regeneration.
Membrane Type– use special membranes that allow the water vapor to pass through faster than the dry air, reducing the amount water vapor in air stream.
The air should not be dried any more than is needed for the most stringent application, to reduce the costs associated with the drying process. A pressure dew point of 35°F to 38°F (1.7°C to 3.3°C) often is adequate for many industrial applications. Lower dew points result in higher operating costs.
If you have questions about compressed air systems and dryers or any of the 15 different EXAIR Intelligent Compressed Air® Product lines, feel free to contact EXAIR and myself or any of our Application Engineers can help you determine the best solution.
Everyone knows there’s oxygen in our air – if there wasn’t oxygen in the air you’re breathing right now, reading this blog would be the least of your concerns. Most people know that oxygen, in fact, makes up about 20% of the earth’s atmosphere at sea level, and that almost all the rest is nitrogen. There’s an impressive list of other gases in the air we breathe, but what’s more impressive (to me, anyway) is the technology behind the instrumentation needed to measure some of these values:
We can consider, for practical purposes, that air is made up of five gases: nitrogen, oxygen, argon, carbon dioxide, and water vapor (more on that in a minute.) The other gases are so low in concentration that there is over 10 times as much carbon dioxide as all the others below it, combined.
About the water vapor: because it’s a variable, this table omits it, water vapor generally makes up 1-3% of atmospheric air, by volume, and can be as high as 5%. Which means that, even on a ‘dry’ day, it pushes argon out of the #3 slot.
There are numerous reasons why the volumetric concentrations of these gases are important. If oxygen level drops in the air we’re breathing, human activity is impaired. Exhaustion without physical exertion will occur at 12-15%. Your lips turn blue at 10%. Exposure to oxygen levels of 8% or below are fatal within minutes.
Likewise, too much of other gases can be bad. Carbon monoxide, for example, is a lethal poison. It’ll kill you at concentrations as low as 0.04%…about the normal amount of carbon dioxide in the atmosphere.
For the purposes of this blog, and how the makeup of our air is important to the function of EXAIR Intelligent Compressed Air Products, we’re going to stick with the top three: nitrogen, oxygen, and water vapor.
Any of our products are capable of discharging a fluid, but they’re specifically designed for use with compressed air – in basic grade school science terms, they convert the potential energy of air under compression into kinetic energy in such a way as to entrain a large amount of air from the surrounding environment. This is important to consider for a couple of reasons:
Anything that’s in your compressed air supply is going to get on the part you’re blowing off with that Super Air Nozzle, the material you’re conveying with that Line Vac, or the electronics you’re cooling with that Cabinet Cooler System. That includes water…which can condense from the water vapor at several points along the way from your compressor’s intake, through its filtration and drying systems, to the discharge from the product itself.
Sometimes, a user is interested in blowing a purge gas (commonly nitrogen or argon) – but unless it’s in a isolated environment (like a closed chamber) purged with the same gas, most of the developed flow will simply be room air.
Another consideration of air make up involves EXAIR Gen4 Static Eliminators. They work on the Corona discharge principle: a high voltage is applied to a sharp point, and any gas in the vicinity of that point is subject to ionization – loss or gain of electrons in their molecules’ outer valences, resulting in a charged particle. The charge is positive if they lose an electron, and negative if they gain one. Of the two gases that make up almost all of our air, oxygen has the lowest ionization energy in its outer valence, making it the easier of the two to ionize. You can certainly supply a Gen4 Static Eliminator with pure nitrogen if you wish, but the static dissipation rate may be hampered to a finite (although probably very small) degree.
When you have two objects and they are of different temperatures, we know from experience that the hotter object will warm up the cooler one, or conversely, the colder object will cool down the hotter one. We see this everyday, such as ice cooling a drink, or a fan cooling a person on a hot day.
The Second Law of Thermodynamics says that heat (energy) transfers from an object of a higher temperature to an object of a lower temperature. The higher temperature object has atoms with higher energy levels and they will move toward the lower energy atoms in order to establish an equilibrium. This movement of heat and energy is called heat transfer. There are three common types of heat transfer.
Heat Transfer by Conduction
When two materials are in direct contact, heat transfers by means of conduction. The atoms of higher energy vibrate against the adjacent atoms of lower energy, which transfers energy to the lower energy atoms, cooling the hotter object and warming the cooler object. Fluids and gases are less heat conductive than solids (metals are the best heat conductors) because there are larger distances between atoms. Solids have atoms that are closer together.
Heat Transfer by Convection
Convection describes heat transfer between a surface and a liquid or gas in motion. The faster the fluid or gas travels, the more convective heat transfer that occurs. There are two types of convection: natural convection and forced convection. In natural convection, the motion of the fluid results from the hot atoms in the fluid moving upwards and the cooler atoms in the air flowing down to replace it, with the fluid moving under the influence of gravity. Example, a radiator puts out warm air from the top, drawing in cool air through the bottom. In forced convection, the fluid, air or a liquid, is forced to travel over the surface by a fan or pump or some other external source. Larger amounts of heat transfer are possible utilizing forced convection.
Heat Transfer by Radiation
Radiation refers to the transfer of heat through empty space. This form of heat transfer does not require a material or even air to be between the two objects; radiation heat transfer works inside of and through a vacuum, such as space. Example, the radiation energy from the sun travels through the great distance through the vacuum of space until the transfer of heat warms the Earth.
EXAIR‘s engineered compressed air products are used every day to force air over hot surfaces to cool, as well as dry and/or blow off hot materials. Let us help you to understand and solve your heat transfer situations.
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:
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:
Air preparation & handling:
Instrumentation and control:
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:
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 email@example.com, and one of us will be happy to help.
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