Summer: Birds are chirping, flowers are blooming, and scrap rates are up!
It’s not just you; summer months can bring challenges when it comes to processing and handling plastic materials—specifically materials that are hygroscopic and are prone to taking on moisture. Let’s take a quick look at why that is and how you can help avoid those issues to make consistent product regardless of month.
In this blog, we will touch on 3 key considerations for drying plastics in the summer months:
- Dryer design
- Initial Moisture Content
- Dryer Maintenance
How Dryer Design Impacts Drying Plastic in the Summer:
Not all dryers are created equal, but unfortunately spotting the imposters isn’t always easy. The key to your problems may lie in the design of the system, so you’ll want to understand the differences between single blower and dual blower designs.
Single Blower Dryers: This means that the blower used to dry plastic is also used to purge the system of moisture. This loss in air from the system requires the dryer to make up the air from the surrounding room. This is typically done through a hole in the system that is located in the filter housing. In the summer, this air is very wet and humid.
Do you have a system that seems to perform great in the winter but causes you nothing but headaches in the summer? This could be due to the single blower design. This is like turning on your air conditioner and opening up the windows. It just doesn’t make sense and typically leads to less effective and much less efficient dryers.
Dual Blower Dryers: The alternative is separating the two functions to different blowers. In a dual blower design, one blower is for drying plastic, and a separate, smaller blower is for regenerating the desiccant or purging the moisture out of the system. At Conair, we use this “dual blower” design because it has the advantage where the only moisture that our dryer sees is that which is taken out of the plastic. It is a totally closed loop that is unaffected by the environment.
How Initial Moisture Content Impacts Drying Plastic in the Summer:
Dryers are designed to control four major variables in the drying process:
- Dew point
However, there is another critical variable that dryers can’t control, and that is the initial moisture content of the material you are drying.
Plastic gains moisture depending on the type of material, the environmental conditions, and the time of exposure. In the summer, your environment is more humid, so material can gain higher amounts of moisture at much faster rate.
Overcoming initial moisture content challenges:
If you think about initial moisture content like running a race, the further from the finish line you are, the longer it will take to get there and the more energy you will have to use.
To combat this issue, it is a good idea only to open the bags of material you plan you use within a few minutes or hours depending on your material and environment. Any unused materials should be put back in re-sealed bags and boxes.
If you plan to blend hygroscopic material, you may want to consider a dry air blanket to help maintain moisture while material sits idle.
How Dryer Maintenance Impacts Drying Plastic in the Summer:
Performing regular maintenance on your dryer is crucial to having it run optimally during humid summer months. Three areas should be at the top of your maintenance checklist:
Check for Air Leaks in Your Drying System
Air leaks provide a break in the system and allow ambient environment to enter into your drying system, similar to the “single blower” designs we mentioned earlier. This requires the desiccant and the dryer to do more work.
An air leak costs money and makes it hard for a dryer to maintain a stable process. In addition, the leaking air may be robbing your process of airflow needed to properly heat and dry the material.
What to do: Check your dryers to make sure hoses are secure and connections are tight. Ensure that your doors have good seals and no leaks. This will keep your system running like a top.
Check the Airflow of Your Drying System
Air restrictions such as crushed hoses or dirty filters can hamper airflow in the system and rob the process of critical air required for drying.
What to do: Inspect dryer hoses to make sure they have not been crushed, delaminated, or bent in a way that would restrict airflow.
Filters should also be cleaned frequently and changed regularly to ensure good airflow.
The actual frequency of filter maintenance depends on the quantity and quality of material that you process. If excessive fines or particulate are present in the material being dried—or in ambient plant air used in drying or regeneration—a dust collector can be added to the intake/return air circuit to reduce the burden on the filter and extend filter maintenance intervals.
Another filter-related concern comes up when drying resins that release volatiles during the drying process (e.g., PET, TPUs, flexible PVCs, TPV and others). When process air enters the aftercooler, volatiles coalesce into oily or waxy contaminants that can cause problems if they accumulate on the aftercooler heat exchanger or the surface of the desiccant wheel. Ideally, volatiles should be collected from process air using a demister filter and volatile trap (optional on most dryers) which must be regularly drained and cleaned. Otherwise, accumulated volatiles can interfere with heat transfer, clog desiccant wheels (necessitating cleaning or replacement), and even pose a flammability risk.
Inspect the Effectiveness of your Dryer’s After Cooler
After cooler effectiveness can also play a part in your dryer’s efficiency and process stability.
To work efficiently, desiccant likes cold air. The after cooler plays a big part in cooling the air down.
What to do: If you are using a water-cooled dryer, make sure you have good flow and water temperature. It may also be a good idea to pull the coil periodically for a thorough cleaning.
Unlike our competitors, all Conair Dryers come with some sort of internal after cooler. It’s not an add-on or upsell. In some cases, this after cooler is air-cooled and in other cases, it’s water-cooled depending on dryer size and customer preference.
Keeping Plastic Material Dry No Matter the Season
That’s it. Running a dryer in the summer that’s as easy as one, two, three.
These simple steps and tips noted above will keep your material dry no matter what the season or conditions.
If it seems like a lot to remember, don’t get intimidated. All Conair Plus and Premium controls come with maintenance alerts and reminders that enable the dryer to tell you when it’s time to do the work.