Hopper Dryer

Image source Caibeitech

Hopper dryers are types of machinery and installations used in plastic processing to dry the polymeric raw materials which will eventually be used in the making of the plastics. The device is designed to eliminate moisture elements from the plastic raw materials during the processing phase of plastic production.

A typical hopper dryer comprises different key components that ensure it does it job perfectly. For example, it features a temperature controller that allows users to determine the level of drying that you would like to achieve.

The primary reason behind the use of hooper dryers is to enable manufacturers achieve fine and refined plastic products. The presence of moisture is likely to compromise the quality of the final products.

Hopper dryers come in different sizes and capacities. You are free to choose one that will meet your production needs. They also come in different technical specifications, a factor that will eventually affect the functionality and performance levels.

Keep reading as we explore everything you should know about hopper dryers.

Function of hopper dryer

As we have mentioned the main function of a hopper dryer is to completely remove moisture from the plastic resin materials during the production phase of plastic production.

The polymeric materials, which are used in the manufacturing of plastics tend to have low hygroscopic index. On the surface, they require minimal drying. Polypropylene and polyethylene materials also tend to have the same low index.

However, various factors such as poor storage can affect the moisture content in these materials. They will end up absorbing significant amount of moisture, which will eventually affect their product quality.

The presence of moisture can lead to issues such as discoloration and bubbles when the final product is being molded. The moisture elements in the plastics can also weaken the structural property of the plastic products that are being produced.

This is where the importance of a hopper dryer comes in. It is able to dry plastic materials using a stream of hot air. The plastic materials are loaded into this machine which utilizes its components and working mechanisms to get rid of every moisture element.

Hopper dryers have internal mechanisms to ensure that the drying process is done fast and with utmost precision. It also has internal features and mechanisms that protect the plastic raw materials from the heat damage.

At the end of the process, you will have completely dry plastic raw materials and pellets which also means that the quality of the final plastic product is likely to be high. Also, we cannot ignore the effectiveness and efficiency of hopper dryers when they are incorporated into the manufacturing process.

Key features of hopper dryer

Let’s look at the key features that characterized the operation and functionality of a hopper dryer.

Drying hopper

This is considered the main component of a hopper dryer as it is where the actual drying of the plastic material takes place. You will place the material that you want to dry in this hopper.

Drying hoppers come in different capacities. The larger the hopper, the more capacity it will have to accommodate more raw materials. The capacity that you choose will often depend on your production requirement.

Drying hoppers are made of stainless material or any other similar metal material that can withstand high temperatures and constant movement of the materials.

Since the actual drying takes place in the hopper the hopper is embedded with a heating system that facilitates the distribution of heat which will lead to even drying. All the plastic materials must dry up at the same rate.

Heating system

It is called a dryer because it has the ability to dry the plastic pellets and materials that are fed into the hopper. It heats up the air inside the hopper and this air will eventually be responsible for removing moisture from the plastic material.

Different types of hopper dryers have different forms of heating systems. While the electric heating system seems to be the most common one, a gas system can also do a good job when it comes to heating up the air. The choice of the heating system to use usually depends on the application area of the hoper dryer.

Electric heating systems are popular because of their simplicity. They are easy to use and even incorporate into the production line of plastic products. We cannot ignore the safety and reliability of electric heating systems.

The heating systems are installed inside the hopper where the plastic pellets will be dried. The arrangement of these heating elements is in such a way that they should distribute heat throughout the hopper equally.


Working closely with the heating system is a fan. Its work is to facilitate even distribution of hot air inside the hopper. The fan also blows away the steam or moisture that is being expelled from the hopper during the drying process.

The fan system in a hopper dryer comes in two design options, axial fan and centrifugal fan. Your choice will always depend on the overall design of the hopper dryer.

Usually, the fan of a hopper dryer works in conjunction with other critical components such as the temperature sensor and controllers. Such conjunction ensures that the speed and behavior of the fan are always automated.

Temperature control

This is another key feature of the hopper dryer. It has a temperature control system that ensures the polymeric raw materials are dried at the right temperature. This is done while keeping in mind that different materials have a tolerance to different temperature ranges.

The temperature control system has a thermostat that detects the temperature inside the hopper. The values recorded will determine whether you should reduce or increase the heating.

The temperature control system can also serve as a safety device. For example, some have alarms that will alert users in case the temperature goes beyond the expected range.

Safety Components

The best hopper dryers have modern safety features that guarantee safe operation. A timer is one of the basic safety features as it allows the machine to shut off automatically once the drying process is complete.

There are also safety buttons that you can press to shut off the whole system in case of an emergency.

Alarms are good at alerting people in case of an abnormality in the drying system.

The sleek design of the hopper makes it easy to handle and minimizes accidents that can occur due to the poor handling of the equipment.

Before you buy any hopper dryer, it will be prudent to inquire about its safety features.

Hopper dryer working principle

Now let’s have a look at how a typical hopper dryer works, right from the time it is loaded with the plastic resin materials to the time that you retrieve the dried materials.

Step 1: Loading

The very first stage of the hopper dryer working mechanism entails loading the plastic granules into the hopper.

The hopper has a wide opening at the top to allow easy loading of the plastic material. You can only load the hopper according to its designated capacity. This is why the size  or capacity of the hopper dryer that you choose should match your production needs.

The stainless steel material of the hopper also makes it easy to handle when it comes to the loading process.

Step 2: Heating the plastic pellets and resins

Once the plastic pellets and resin are settled in the hopper the next step is to apply some heat in the system. A hopper dryer comprises heating elements that are designed to raise temperatures in the system.

While raising the temperature in the system the heating elements also heat up the air that will be used for drying the materials. Keep in mind that this is the air that will be blown through the moisturized plastic materials.

Since the heated elements are at the bottom of the hopper, there is a functional mechanism for blowing hot air upwards.

Step 3: Circulation of hot air

Now that you have the materials and the source of heat, the next step of the working principle entails the circulation of hot air in the hoper.

But, where does this air come from? A hopper dryer has a blower that absorbs air from the outside and channels it inside the hopper. This air is cold so it will be directed towards the bottom of the hopper where it will get heated.

This hot air will then circulate around the hopper absorbing moisture content along it. The moisture-laden hot air will then be channeled outside.

Step 4: Drying of the plastic materials

Moisture that is on the resin material is eliminated by the evaporation process.  This is possible because the hot air circulating is at higher temperature than that of the plastic materials.

Also, the pressure that is used to circulate the hot air speeds up the evaporation process of the moisture which will find its way outside the hopper.

How long does it take for the material to be dried?

Well, it all depends on the temperature settings selected by the operator. The higher the settings the faster the drying process.

Also, most hopper dryers come with timers that allow operators to set the expected drying period of the material.

Step 5: Unloading the material

This is the final step of the hopper dryer working principle. Most hopper dryers have discharge valves located at the bottom end of the hopper. You simply need to open the valve and the dry plastic materials will flow out.

As you can see, combining all these processes ensures you have dry plastic materials. Also, an issue in one of these stages will compromise the quality of the product.

Hopper dryer design principle

Hopper dryer design principle

Image source Caibeitech

The design principle is all about the physical attributes of hopper dryers that make them effective when it comes to executing their functions. The design should facilitate the smooth flow of the plastic materials.

Most hoppers have cylindrical shapes though you can find some that come in rectangular shapes. As we have already mentioned the hopper is built of polished stainless steel and the design should accommodate the required volume of the plastic material.

A hopper dryer also has a control panel where an operator can dictate the expected performance of the equipment. The panel has buttons though in some it comes in the form of a touchscreen interface.

A hopper dryer has an exhaust port that allows the vaporized moisture to exit from the hopper. The design of the port also prevents this moisture from getting back into the system.

Another key aspect of the hopper dryer design is the insulation system. The hopper is well-insulated to minimize loss of heat during the drying process.

When buying a hopper dryer, it is vital to confirm the design specifications before buying. A manufacturer may even allow you to request for custom design hopper dryers.

Factors to consider when buying a hopper dryer

Here are the key things you should know when buying hopper dryers:

  • Hopper dryer capacity: This refers to the volume of the plastic material that the dryer can handle at a time. The capacity that you choose should match your production needs. Whether it is a 25kg hopper dryer or 1000kg, you should specify.
  • Temperature range: This is the maximum temperature that you can choose on the hopper dryer.  Some dryers have low range while others have a high-temperature range.
  • Speed: How long will it take for the dryer to completely dry the plastic material? Check out the estimated drying time of the equipment.
  • Design and style: You should choose a hopper dryer that has sleek design and modern style. For example, its control panel should allow you to perform an array of functions.
  • Performance and efficiency: The hopper dryer should be able to deliver excellent performance when it comes to drying plastic material. The equipment should also be energy-efficient such that you won’t have to pay high energy bills.

Choose reliable hopper dryer manufacturer in China

Where you buy a hopper dryer will always matter. If you are planning to buy a hopper dryer in China, ensure that it is from a reputable source. This is where Caibeitech comes in. We are a known manufacturer of quality hopper dryers in China.

Other than the quality equipment, we also have excellent customer support. All you need is to analyze your production and we will help you get the right hopper dryer.

4.8/5 - (169 votes)

Leave a Reply

Your email address will not be published. Required fields are marked *

Post comment