Tag: oil containment

Air Quality Classes: ISO 8573-1

Published on by John BallLeave a comment

Airborne particles surround us everywhere.   In a general work environment, nearly four million particles per cubic foot are floating around us at any given time.  When an air compressor brings in this air, the concentration increases substantially.  So, compressed air is not only expensive to make, but very dirty.  As the air exits your air compressor and travels into your pneumatic system, there is so much contamination, that the International Standard Organization, ISO, created an Air Quality chart with Purity Classes.

This chart is easy to follow and can be found on the International Organization for Standardization; ISO 8573-1 for Air Quality.  It is used to select a cleanliness level for your compressed air system. Contamination is categorized into three areas; Particles, Water, and Oil (reference above).  Each class is associated with a number for each category ranging from 0 (most stringent) to 9 (most relaxed).  As an example, the Air Quality value of ISO 8573-1:2010 [1.2.4] has Class 1 for Particles, Class 2 for Water, and Class 4 for Oil.  These class values will show the maximum value in each category.

To define the categories in more detail, I will separate the three to discuss the origins and solutions.

Per the descriptions above, here are the criteria by which compressed air purity is classified.

Particles: For solid particles, this part comes from many different areas.  The surrounding ambient air that is being drawn into the air compressor is filtered, but the intake filter will only remove large diameter particles.  The smaller diameter particles will go through the filter and into the compressed air system.  Another part is rust particles that come from steel air pipes and receiver tanks.  Over time, rust will flake off and create particles that can affect pneumatic equipment.  Other particles can come from components inside the air compressor, valves, etc., that wear and breakdown.  In the ISO column for Particles, it is separated into three different micron ranges and concentrations.  The removal of particles from the compressed air is done by traps and compressed air filters.  EXAIR offers two types; Filter Separators with 5-micron filtration and Oil Removal Filters with 0.03-micron filtration.  There are other types of filtration systems depending on your ISO requirement.

Water:  Humidity is a natural occurrence.  It can be measured as a dew point temperature.  This is the temperature at which water will condense and make rain.  Inside an air compressor, the air is ‘squeezed”, and the amount of space for water vapor is reduced.  So, it will condense into liquid form as “rain” inside the pipes.  Air that comes out from an air compressor will always be saturated with water.  To remove liquid water, a mechanical device can be used.  Inside a Filter Separator, a centrifugal separator will spin the air and remove the liquid water.  To remove water vapor, a compressed air dryer is required, like a refrigerant, desiccant, deliquescent, or membrane type.  Each type will have a maximum dew point range that they can reach.  As an example, a refrigerant type will reduce the dew point to 37oF (3oC).  That means that water will not condense until the temperature reaches below 37oF (3oC).

Oil: This category can be found as a liquid, aerosol or vapor, and it includes more than just oil. It contains small hydrocarbons like CO, CO2, SO2, and NOX.  Oil mainly comes from inside an oil-flooded air compressor.  As the air passes through the compressor, it will pick up remnants of oil aerosols and carry them downstream.  With high temperatures inside the air compressor, some of the oil will vaporize.  Even with oil-less type air compressors, carbon vapor can still be an issue.  Small hydrocarbons can come through the air intake and condense inside the system like water vapor above.  To remove the liquid and aerosol type of oil, Oil Removal Filters can be used.  They are designed to “coalesce” the small particles into larger particles for gravity to remove.  Oil vapor requires activated carbon to remove it.  These types of filter units will adsorb the vapor.  This helps to remove odors as well as dangerous chemical vapors that may be in the compressed air line.

There are a variety of pneumatic systems that use the ISO 8573-1 standard.  This will include breathing air operations, food and beverage, pharmaceutical, and the electronics industry.  If you need stringent requirements for your compressed air system, the Air Quality standard should be used by referring to the class numbers above.  This helps to dictate the types of filtration and air dryers that should be used within your pneumatic system.  If you have any questions about your compressed air system, an Application Engineer at EXAIR will be happy to help you.

John Ball
Application Engineer
Email: johnball@exair.com
Twitter: @EXAIR_jb

What Size Pipe Should I Use?

Published on by Dave WoernerLeave a comment

Yesterday, I had a customer with a tough application for a Standard Air Knife. The customer was quenching individual 11″ x 11″ steel plates in oil after they had been heated to over 1,200° Celsius. Following quenching, the plate is pulled out of the oil with a fair amount of excess oil still attached. This excess oil is relatively hot and could be dangerous, if it drips from the plates as they are conveyed to the next process. The oil removed from the tank is also lost, so the tank needed to be refilled regularly. This oil added up to quite a large expense every year for this company. The customer installed (2) 12″ Standard Air Knives above the oil quenching tank to blow the oil off of the plate back into the oil quenching tank as the plate is raised out of the tank and in between the two air knives.

How the Standard Air Knife Works
How the Standard Air Knife Works

The customer called to express some disappointment about the air knife performance, I asked him a few questions about his application.

Q:What pressure is supplied to the air knife?
A: 100 PSI
Q: Where are you measuring this pressure?
A: That is our shop pressure and the pressure I’m measuring at the regulator.
Q: How are you connecting the regulator to the air knife?
A: We are using 10 feet of 3/8″ ID tubing.

At this point I suspected that the problem was in the compressed air supply line. To confirm this, I asked the customer to install a pressure gauge in the unused air inlet of the air knife. This pressure gauge read only 52 PSIG. The customer had a pressure drop of 48 PSI through the 10 foot of 3/8″ tubing, fittings, and valves that connected the regulator to the air knife.  The 12 inch Standard Air Knife utilizes 41 SCFM of compressed air when fed with 80 PSIG. In order to determine what to expect for a reasonable pressure drop, you could use EXAIR’s Air Data charts. According to EXAIR’s air data chart, for 1/8″ schedule 40 iron pipe, which has around 1/4″ ID (Which is very similar to the Inside Diameter of the 3/8″ tube) at 8 SCFM of flow the line will create a 18.6 PSIG pressure drop. When you try and shove more than 8 SCFM through the 3/8″ OD (1/4″ ID) tubing, you create a higher pressure drop. In this customer’s case it created a 48 PSI drop across the air line. This 48 PSI pressure drop was caused by the supply line as well as the fittings or valves used to connect valve to the regulator. This pressure drop limited the air knife to only 52% of its performance. In an application with a viscous fluid like oil , this drop in pressure led to lower force upon the steel plate and disappointing performance.

After getting the proper plumbing in place, the pressure drop was eliminated and the the Air Knives were operating at peak performance to remove the oil from the plates.

During the course of our troubleshooting, the customer also discovered Russ Bowman’s excellent video Proper Supply Plumbing for Compressed Air Products. In the video, our customer discovered the impact both the cross sectional area and overall length of compressed air piping can have on the performance of an air operated device.

The customer wanted to use a 12″ Air Knife to blow off the oil from the plates, which is a great application for the air knife. By properly plumbing the supply of an Air Knife, the customer contained hot oil, reclaimed quenching oil for future use, and maintained a clean shop floor. This installation was well worth the time and effort of installing the air knife properly. If the customer would like, we also have a Super Air Knife which will only use 35 SCFM and could help to save more compressed air. This savings of 7 SCFM may not seem like much, but it will have a significant impact on the energy cost of running his air compressor.

Dave Woerner
Application Engineer
@EXAIR_DW
DaveWoerner@EXAIR.com