Why should you be concerned about condensate management in your paint booth, curing oven, exhaust blowers, ductwork, or pollution control device? The primary reasons for this concern is condensates can affect the quality of your product, affect the indoor air quality of your facility, ruin equipment, create safety concerns, and, lastly, affect your bottom line. Volatile Organic Compound (VOC) based condensation can and will catch on fire, both in your production line and at your pollution control device. That’s something will definitely ruin your day. For all these reasons, you need to be concerned -- very concerned.
Anyone who paints, coats a web, or adds VOCs that are driven off the product during manufacturing has some level of condensate in their processing equipment, most likely in the exhaust blowers and the ducting that either leads outside to the atmosphere or to a pollution control device. The level of condensate directly relates to the amount of coating applied and evaporated in the production process, as well as the actual process exhaust temperature.
Typically, heavier/longer chain hydrocarbon molecules (e.g. magie oils or resin based coatings) or anything in excess of 12-15 carbons has a high propensity to form condensation. This starts in the paint booth, oven, or other processing equipment. Once the process is exhausted, that air starts to cool, and condensation starts to form on every surface it touches.
Tips for Blowers
Process exhaust blowers are typically one of the first areas to collect condensation. The bad news is that these process exhausters are usually mounted high in the air, above the spray booth or oven, and they are often difficult to access for maintenance. For processes where large size vapor droplets are entering the exhaust, such as spray paint or resin applications, it is ideal to knock them out of the airstream before they reach any fans or blowers. Impingement type devices, such as a chain filter, allow large condensate/particulate particles to be knocked out of the airstream, keeping them from coating your blower and downstream ducting.
Making the impingement device easy to maintain is key to the design. Once the airstream reaches the blower, condensate will start to accumulate. Buildup on the wheel and housing is not only flammable, but has a tendency to cause the fan to go out of balance. This can cause fans to literally shake themselves (and any equipment they are attached to) apart.
If you have a production line with an existing blower that’s mounted on top of the process line, what can you do?
- First and foremost, you want to make sure the fan is insulated, even if your process temperature is only 150-200° F. The insulation will keep the fan housing from acting as a condenser.
- Next, ensure you have an access door on the fan housing, so you can inspect buildup on both the wheel and housing. These can always be added without too much trouble.
- Isolate the fans from both the ducting and the structure they sit on. This will stop an unbalanced fan from affecting the surrounding equipment if it does get out of balance.
- Utilize rounds and readings. Somebody should regularly (monthly) actually go up and check the vibration level of the housing. It’s far easier to schedule to clean and balance a fan before it tears itself up.
Tips for Ducting
The next big issue is the ducting. Condensate builds up in the ducts and on the dampers downstream of the process. It’s even worse if the ducting runs up on the roof, thanks to mother nature, whose temperatures are out of your control. Condensate builds up on every surface it touches. If dampers suddenly don’t seal and make their limit switches, condensate builds up inside the duct, especially on elbows or impaction points.
How can you manage condensation in ducting?
- If it’s a new installation, minimize the duct lengths. Locate all the equipment as close to the process as possible. The longer the ducts run, the more heat loss you will experience, leading to more condensation.
- Size the ducting to maintain high transport velocities, which will keep vapor droplets entrained in the exhaust stream.
- Insulate the ductwork. Keep the metal temperature as close to the process temperature as possible. Insulate the duct both inside and outside the building.
Tips for Dampers
Check your dampers! Leaky dampers are one of the most overlooked areas in the process, and they can greatly contribute to condensation. Dampers located on the roof often fall into the category of “out of sight, out of mind” and don’t receive any preventative maintenance unless they fail to make their limit switches.
Typically, the process exhaust has bypass t-dampers that allow the process to either go to the atmosphere or to a control device. These dampers divert the flow in one direction or the other. Fresh air purge/idle dampers are another source for cold air infiltration. The problem is that all of these dampers are on the negative suction side of the control device. Any leakage of damper seals allows cold air to be pulled into the exhaust stream. This cools the stream and adds to the formation of condensation, not to mention adding additional air that now you have to pay to treat.
What are the best ways to manage condensation in dampers?
- Inspect your dampers regularly. Check their ability to seal in both directions. Start with adding access doors before or after your T-dampers so you can inspect, clean, and replace the seals without having to remove the damper itself. If you have to remove the damper to complete these routine tasks, they will never get done on a regular basis.
- Insulate the damper body. It costs more to insulate a damper, but it pays for itself by helping to minimize condensate formation on the damper seats.
- Adjust the damper stroke in both directions to ensure it compresses the seals.
We hope this look at condensate management has helped you as you plan your oxidizer maintenance. If you have any questions, please contact us.