Drying Hoppers for Plastic Resins
By Mark Haynie and Joshua Belisle · Edited by Dana Gardner
Published August 8, 2024 · Reviewed by Mark Haynie · August 10, 2026
Summary
How do I size a resin drying hopper?
A drying hopper is usually sized to hold about four times the hourly throughput of the dryer it serves. Sizes run up to 18,000 lb capacity in stainless or carbon steel depending on size. Heated air circulates through the resin in the hopper and absorbs moisture. Full insulation, at least 2 inches thick and covering the cone as well as the sides, matters most for energy efficiency.
Drying hoppers are part of most drying systems. They are usually sized to hold about four times the hourly throughput of the dryer they serve.
The operation of a resin drying hopper involves heating the air inside the hopper to a specified temperature and circulating it through the resin. The heated air absorbs moisture from the resin, drying it to the desired level. The hopper is typically equipped with a heater, a blower, and temperature and moisture sensors to monitor and control the drying process.
Resin drying hoppers are available in a range of sizes and capacities to meet the needs of different applications. They are typically made of stainless steel or other durable materials to withstand the harsh conditions found in industrial environments. Additionally, some resin drying hoppers are equipped with additional features, such as digital controls and alarms, to make the drying process more efficient and reliable.
Basic features you should look for in a resin drying hopper:
- Sizes range up to 18,000 lb. capacity
- Stainless Steel or Carbon Steel Construction – Depending on Size
- Insulation
- Elongated Sight Glass
- Large Access Door
- Slide-gate Shutoff and Drain
- Return Air Pellet Screen
- Mounting Bracket for Heater/Blower
Full insulation is the most important feature to ensure energy efficiency. The insulation should be at least 2” thick and should be included in the cone area as well as the sides of the hopper.
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Frequently Asked Questions
What features should a resin drying hopper have?
Look for full insulation, an elongated sight glass, a large access door, a slide-gate shutoff and drain, a return air pellet screen, and a mounting bracket for the heater and blower. Construction is stainless or carbon steel depending on size, with capacities up to 18,000 lb. Some hoppers add digital controls and alarms to make drying more efficient and reliable.
Why does insulation matter on a drying hopper?
Full insulation is the most important feature for energy efficiency in a drying hopper, which works by heating the air inside and circulating it through the resin. The insulation should be at least 2 inches thick and should cover the cone area as well as the sides.
How does a resin drying hopper work?
Air inside the hopper is heated to a set temperature and circulated through the resin, where it absorbs moisture and dries the material to the desired level. The hopper is typically equipped with a heater, a blower, and temperature and moisture sensors that monitor and control the process. Hoppers are usually stainless steel or other durable material to stand up to industrial conditions.
About the Authors
Vice President of Moisture & Drying Technologies, Novatec
Mark Haynie has designed and installed resin drying systems for more than 40 years, working in thousands of plastics plants across the industry. As Novatec’s Vice President of Moisture & Drying Technologies, he leads the company’s drying technology group, including its work on moisture measurement and predictive drying. He also serves as a technical reviewer for Novatec’s Drying Knowledge Center and has authored numerous technical articles and whitepapers on resin drying and moisture.
Mark earned a Bachelor of Science in Chemical Engineering from Virginia Tech.
Through Novatec’s Ask the Expert program, Mark regularly helps processors troubleshoot drying performance and resin-moisture challenges.
Technology Manager, Novatec
Joshua Belisle is Technology Manager at Novatec, where his work focuses on simulation and technology development for resin drying. He earned a B.S. in Mechanical Engineering with a minor in Engineering Business from the University of Virginia in 2023 and joined Novatec that same year. Joshua uses simulation tools to investigate previously difficult-to-measure aspects of the drying process, helping Novatec better understand airflow, heat transfer and other variables that influence resin-drying performance.
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Ask the Plastic Drying Expert
Author Profile:
Mark has designed and installed resin drying systems for more than 40 years, working in thousands of plastics plants across the industry. He leads Novatec’s drying technology group, including its work on moisture measurement and predictive drying, and serves as the technical reviewer for the drying articles in the Knowledge Center. He has authored numerous technical articles and whitepapers on resin drying and moisture, including How to Optimize Resin Drying in Humid Weather, and answers processors’ drying questions through the Knowledge Center’s Ask the Expert program.