Compressors, Water and Ruined Paint Jobs

 2) Spray Booth Maintenance  Comments Off on Compressors, Water and Ruined Paint Jobs
Feb 272013

Using properly fitted and maintained high quality paint booth filters will undoubtedly improve the finishes coming out of your paint booth.  But proper maintenance doesn’t stop with filters.  Other areas of your operation must be continually maintained and monitored.  One often overlooks areas is the quality of your compressed air.  More specifically is your compressed air free of water and water vapor?

One cannot overemphasize the importance of clean, dry compressed air.  When minuscule particles of water find their way from your compressor through your air lines and into the nozzle of your paint gun, blemishes and fish eyes will develop in your paint job.

So what do you need to know to ensure your compressed air is moisture-free?

The first step involves a brief review of how an air compressor operates.  In an air compressor, there are two major parts – a compressing system and a power source.  The compressing mechanism will most likely be either a piston or screw.  Power is supplied by an electric or natural gas motor.  The basic air compressor takes atmospheric (i.e., normal) air and draws it through the compressing mechanism which causes the air’s volume to decrease / compress.  The now compressed air is either used immediately or contained in a vessel to maintain its pressurized state until needed.

Moisture is even more pronounced in compressed air.  Why?  Because you are taking say 5 cubit feet or atmospheric air and compressing it to 1 cubit foot of compressed air; however, the process of compressing the air also compressed the water in the air.  Moreover, as you may recall from basic physics, using energy generates heat and this heat is imparted into the compressed air.  As hot air cools when it moves from your compressor throughout your shop via air lines and hoses, compressed air has a tendency to condensate creating water in your air lines.

So now you know that compressed air will naturally contain moisture.  To eliminate moisture, you must make one of the single most valuable purchase for your shop to ensure the delivery of moisture free compressed air — refrigerated dryers or desiccant air dryers.

  • Refrigerated Air Dryers are the most economical type of dryer.  Warm and saturated air from the air compressor is cooled to a temperature of 35°F to 50°F.  At these temperatures, the water condenses and can be mechanically separated and discharged from the system.  Air, now free of liquid moisture, can be reheated and discharged into the compressed air system.  This air now has a 35°F to 50°F pressure dew point, which means the air temperature has to drop below this temperature before further condensation occurs.
  • Desiccant Air Dryers are dryers are used in applications that require compressed air at dew points as low as -100°F.  Through two identical drying towers, each containing a desiccant bed, air flows alternately.  While one tower is on-stream drying, the other is off-stream being regenerated.  Purge air is used to regenerate the desiccant.  Diameter and length of desiccant beds determine drying efficiency.

Air drying systems (and frequent maintenance thereof) are the single most important factor to achieving moisture-free air.  And when your air is dry, you’ll eliminate many of those paint imperfections, leading to a lower total cost of ownership for your shop combined with raving customer reviews of your work.

 Posted by at 11:41 AM

Do You Believe in Spontaneous Filter Combustion?

 2) Spray Booth Maintenance  Comments Off on Do You Believe in Spontaneous Filter Combustion?
Feb 252013

You work in a collision repair facility. You clean up and go home, but when you return the next morning, you find a storage drum smoldering.  Did you know used paint booth filters can spontaneously combust?  Some folks have even observed used filters catching fire right after being removed from their paint booth.

In an effort to find an answer, several organizations have conducted research to identify the cause of spontaneous combustion in filters.  The research generated several recommendations as noted below.

  • Do not dispose of used filters in a dumpster where the filters can be smashed / compressed
  • Do not store used filters in trash bags

  • Use a leak-proof, tightly sealed metal drum to store

    the used filters because this cuts off oxygen

  • Do not store with other trash or hazardous materials

  • Keep the storage containers with the used filters in a

    cool environment

  • Dry used filters before disposal and storage

Simply put, the key to preventing combustion of paint booth filters is to prevent them from being compressed or stored with other waste where heat and oxygen is present.  Storing and compressing filters results in spontaneous combustion because there is enough oxygen to permit oxidation at a steady rate.  For example, just think about the heat that gets generated from a compost pile.

We all know that  filter maintenance is important, but how you dispose of your filters is also significant.  And you should also concern yourself with whether or not a used filter is considered hazardous waste. There are only two ways of knowing this.

  • Written documentation showing that the paint used contained non-toxic materials / metals.  A current Material Safety Data Sheets (MSDS), will assist in this determination.  Remember, while the filter is not considered hazardous waste, it can become hazardous once is contains hazardous materials.
  • Conducts a Toxicity Characteristic Leaching Procedure (TCLP), effectively a third-party / independent test.  If the filters come back hazardous, you must manage them as you do other hazardous waste in your shop.

A paint booth is a critical tool for a shop, and when used properly, it can help create a beautiful paint finish.  However, a shop that does not follow industry standards in maintaining its spray booth is placing its workers and its business at great risk. OSHA and EPA fines can be financially devastating . Importantly, the steps to maintaining a safe spray booths are straightforward and easily achievable without significant cost or disruption to a shop’s operation.


 Posted by at 5:32 PM
Oct 242012

Over the past couple of months, we’ve gotten request after request for sets of those small rubber tips — you know the ones that are placed on the metal ends of  filter grids allowing the filter grid to be held into place within the holding frame.  These are small, little parts but without the exhaust side of you booth is rendered unusable.

We now offer these rubber tips at!  They come in sets of 48 and can be purchased for 11 gauge wire (RT-SM-48) and 9 gauge wire (RT-LG-48).  Another simply way we at are responding to the needs of our customers and keeping paint booths across the nation running.

 Posted by at 1:22 PM
Sep 062012

We constantly get asked, “Why should I change my filters?”  Here are a few thoughts for consideration:

  • Changing filters regularly ensures a balanced air flow as well as a clean and safe operating environment.  We all know that employee safety is the single most important issue for all operators of paint spray booths, regardless of the size of your business.
  • Create and then stick to a routine maintenance schedule based upon your production level.  As a general rule of thumb, paint arrestors should be changed every 2-3 weeks, cross draft intake filters should be changed every 3 months and down draft intake filters should be changed every 9-12 months.  Proper use of prefilters in a down draft operating environment will ensure the costly down draft intake filters operate to their fullest operating potential.
  • Remember that regardless of where you purchase your filters, they will not arrive yesterday.  Putting things off to the last minute will lead to operating disruptions, which means lost revenue and profits.  You wouldn’t hold off on changing the oil in your car, so why wait on changing your filters.  Plus just like a proper routine oil change, a filter change for your paint booth will result in better performance, less stress on components and, in general, longer equipment life.
  • Proper filter maintenance means your booth will have proper paint booth pressurization.  Over-pressurization causes overspray to become dirt in your finish; under-pressurization can result in poor overspray removal.  Balancing a booth to near zero pressurization will ensure the best result.
  • Just remember that changing your filters will extend the life of your paint booth.  And you paint booth is most likely one of the costliest investments in your business.
  • Lastly, it is important to take a step back every year to evaluate your airflow.  Start at the point where the air enters your system and follow it all the way through until it exits.  Is you manometer proper set?  Are there places where bypass reduces performance?  Basically, you’re working day-in and day-out.  You need a vacation to refresh your batteries; an annual air flow evaluation of your paint booth is needed to refresh its operating performance.
 Posted by at 9:39 AM

What is a Manometer & How Does it Work?

 2) Spray Booth Maintenance  Comments Off on What is a Manometer & How Does it Work?
Jun 132011

Air movement is critical inside a paint spray booth if a perfect finish is to be achieved.  With proper air flow, paint overspray is pulled away from the object being painted and drawn into filters to be trapped.  Such a process ensures the paint chamber remains free from overspray particles that would otherwise damage a finish. Paint spray booths require a lot of air, typically a minimum of 100 feet per minute.

So if air flow is critical, how to you know you’re reaching the aforementioned recommended levels – through the use of a manometer.

In a paint spray booth, fan blades cause air to move in a desired direction.  The force of the air movement is known as velocity pressure.  A second pressure is always present, independent of air movement, and is called static pressure.  Both velocity pressure and static pressure are measured in inches of water column (wc).

A manometer is an instrument designed to measure the difference between velocity pressure and static pressure to determine the force of the air, which in turn can be translated air velocity (distance traveled per unit of time, typically expressed in feet per minute, or fpm).

In its simplest form, a manometer is a u-shaped tube filled with a liquid.  The earliest manometers likely used water, hence the measurement nomenclature known as “inches of water column”.  Modern manometers now use mercury due to chemical properties which increase the accuracy of measurement.

Figure 2-1 depicts a situation when static pressure is equal on both tubes, so the manometer measures zero or environment can be thought of as being “at rest”.  Figure 2-2 depicts pressure being exerted on one tube, forcing the liquid to move up the opposite side tube.  Figure 2-3 is the opposite of Figure 2-2, whereby a vacuum is created on one tube, causing the liquid to retreat up the same tube.

So turning to a paint spray booth, to most accurate measure airflow, a manometer should be mounted on the side of your booth.  One tube is positioned inside the paint booth and thus absorbs the force of the air being moved by the fans.  The other tube is positioned outside the paint booth to monitor the static pressure.  The result is the measurement of the pressure difference, which using a rather inexpensive digital manometer will determine air velocity.

 Posted by at 11:30 AM