Fundamentals of Compressed Air Solutions

What does a compressed air system look like?

The air compressor “pump” can be oil lubricated, or “dry”, (oil free).

Reciprocating piston, rotary vane, scroll and rotary screw pump options are all readily available in North America.

Your pump of choice will most likely be driven by an electric motor, a turbine, or a Diesel or Gas engine.

Each method has its own features, advantages, and benefits.

Because ambient air will be ingested by the compressor pump for compression, we must consider the ambient conditions, such as temperature, dust, humidity, altitude, hydrocarbons etc..

Positioning your compressor station on the outside wall of a building is preferable, as ventilation is easily accessible, and so too is the removal of large items of plant in the case of a rebuild or replacement.

Ample fresh air into the room for cooling and ducted hot air discharge will provide long term service life expectancy of the equipment and enhance performance of every item.

The aftercooler and oil cooler are an essential stage in the compression cycle. Air Cooled Compressor coolers can be air blast types, using Squirrel cage fans, or in modern day compressors they may also be Radial type fans. 

Ambient air is passed over the cooler to exchange cooler ambient air with the heat of compression, and/or oil.

Liquid cooled compressors can include water, or liquid cooling mixtures, such as Glycol and water. The liquids are exchanged with oil/heat of compression to reduce temperatures.

The aftercooler will reduce the compressed air discharge temperatures, by approximately 100°F, assuming that the compressor is located in a well-ventilated air cooled ambient, or cooling water and liquid is sufficiently maintained to exchange cool liquids with hot compressed air/oil efficiently. 

Dropping temperatures of compressed air rapidly will encourage the condensing of air born humidity into liquid water condensate. The installation of a cyclonic moisture separator, and a well positioned condensate drain trap are highly recommended, along with a wet air receiver storage tank.  All of the aforementioned will be up stream of any clean air treatment equipment, such as filters, and dryers.

Air receiver storage tanks are often overlooked when compressed air systems are designed, despite them providing several important features, advantages, and benefits. These F,A,B’s include the ability to create cyclonic motion, due to the shape of the tank itself, which encourages moisture to be transported to the internal surface of the tank. Gravity condenses this moisture in a coalescing effect towards the bottom of the tank, where an automatic condensate drain trap, or manual drain valve removes unwanted oil and water condensate contamination.

Because the compressor is ingesting ambient air, and many of the internal components and piping in the system may be metallic and corrode, a particulate removing in line filter assembly is a worthwhile investment. Protecting the air dryers heat exchangers and your downstream cylinders, and valves from carbon deposits, rust particles, and other solid contaminants will ensure a trouble free system for years to come.

Mark your calendar, or maintenance schedule to remind you to change the pre filter element at least once per year.

If the compressed air piping is situated inside the building, and kept at a fairly consistent, and stable ambient temperature, most facilities can function well with a refrigerated style air dryer. A fridge dryer will produce a +3°C, (+37°F) Pressure dewpoint, “PDP”. 

For points of use that cannot tolerate any risk of moisture carryover, a point of use desiccant style air dryer may be required. Similarly, if the compressed air piping is run outside the building and exposed to temperatures lower than a +3°C PDP, a desiccant dryer is almost certainly required to prevent the pipes freezing and moisture reaching the points of use outdoors. Desiccant dryers are manufactured in a multitude of design formats with varying regeneration methods and PDP’s available for your consideration. We strongly suggest that you seek professional assistance when selecting desiccant dryers. The biggest expense associated with this type of dryer will be the cost of ownership, and experts can help to select the best make and model for your application(s).

Removing liquid oil is also a must, in every type of application. The list of potential failures, which can result from oil contamination within a compressed air system, is very comprehensive. But trust us when we say that oil removal is vitally important. The market place is flooded with cheap imported filters today, and your focus should be on the efficiency % that manufacturers state that their filters will remove contaminants, and not the price tag. As a rule of thumb, you will get what you pay for, and it’s a case of “pay me now, or pay me much more later”. When installing or replacing filters, mark your calendar, or maintenance schedule to remind you to change the filter element at least once per year.

A large “dry” air receiver storage tank vessel is a one time investment, that will assist in saving Hydro, slowing the velocity of compressed air speed, and flow, while maintaining a stable system pressure, when tanks and piping are engineered and sized correctly. The minimum compressed air storage vessel will be 3 gallons of storage for every 1 cfm of compressed air volume. In a 1,000 cfm system, the storage tanks should equate to at least 3,000 gallons of storage volume.

Flow meters, Master controllers, Sequencers, Sigma Air Managers, (SAM), Air Main Charging Valves and many other devices are available to optimize the efficiency of the compressed air system at your facility.

Some great considerations for why you might invest in this type of accessory might include:

• Data collection, after all - you can’t improve what you don’t measure.
• Hydro cost analysis from the data collected.
• Sequencing the run times and lead/lag/stand by compressor fleet to ensure equal run times per year.
• System pressure control and sustainability.
•  Remote system monitoring of alarms and maintenance prompts, or annunciations.
• Protecting filters and dryers from overload and downstream equipment from contaminants.

The removal of unwanted contaminants is relatively simplistic and requires little or no attention from one year to the next if things are monitored and maintained correctly.

Compressed air oil/water condensate discharge, however, creates a slightly more complex challenge, due to the liquid oil content that will be discharged from an oil lubricated air compressor system.

If the drains and sewers at your facility are treated on site, you may choose to treat your own compressed air effluent on site. Its important to understand that 95% of the oil/water condensate will be water, only 5% will be oil. This still exceeds most municipal limits, and therefore an oil/water condensate management separator system is required. Often abbreviated to CMS, or OWS, the condensate manager requires no electricity, and only annual service. Kaeser’s newly designed KCF range exceeds all of the Ontario discharge limits, purifying condensate discharge to exemplary levels, suitable for discharge directly to a floor drain, or City sewer. 

Final considerations will be the distribution pipework, and to help you make the correct selection, here are a few pointers to consider:

• Pipe materials.
• The majority of pipe installations we install today are Blue Aluminum Smart Pipe Plus. This product is powder coated Blue, so its easily identified, in the ceiling space, as compressed air pipe.
• It never corrodes internally.
• Its as light as a feather, so there is no major weight load added to the roof structure.
• Should you relocate a pipe run, or your entire operation, Smart Pipe + can be disassembled and everything can be re purposed in a new location.
• Pipe diameter. Avoid under sizing pipe diameters in an attempt to save money. The compressor motor energy exerted to overcome the piping pressure drop will far exceed any cost cutting exercise, at the front end, in the long run.
• Ensure your installer has TSSA approval. The system maybe shutdown if it is installed without the correct TSSA approvals and CRN document and test criteria in place.
• Create a pipe loop, or ring main, to ensure that all of the users and points of use receive equal and stable pressure, wherever they are located in the pipe network.