Shelves and trays are essential components in many industrial drying ovens. They determine how products are arranged inside the chamber, how much material can be processed per batch, and how effectively heated air can circulate around the products.
Choosing the right shelf and tray design is therefore not simply a matter of selecting a convenient size. The design should match the product dimensions, batch weight, operating temperature, airflow requirements, loading method, and cleaning requirements.
For example, an oven used to dry 50 kg of agricultural products may require perforated stainless steel trays, while an oven processing 300 kg of metal components may need heavy-duty shelves designed for much higher point loads.
This guide explains the key factors buyers should consider when selecting shelves and trays for an industrial drying oven.
1. What Is the Difference Between Shelves and Trays?
Although the terms are sometimes used interchangeably, shelves and trays serve slightly different purposes.
Shelves are usually fixed or removable horizontal support structures installed inside the oven chamber. Products can be placed directly on the shelves or on separate trays.
Trays are removable containers or platforms that hold the products during drying.
A typical configuration might look like this:
| Component | Example |
|---|---|
| Oven Chamber | 1,200 × 1,000 × 1,500 mm |
| Shelf Quantity | 8 |
| Tray Quantity | 8 |
| Tray Size | 800 × 600 mm |
| Tray Material | Stainless Steel |
| Maximum Load per Tray | 10 kg |
| Total Tray Load | 80 kg |
Using removable trays can make loading and unloading faster because operators can prepare products outside the oven before placing the trays inside.
2. Start With Product Size
The first consideration is the size of the material being dried.
Suppose a customer needs to dry products measuring approximately:
Length: 400 mm
Width: 250 mm
Height: 80 mm
A tray measuring 800 × 600 mm could potentially accommodate several pieces, depending on their arrangement and required spacing.
However, the available tray area should not be filled completely.
Products need sufficient spacing to allow heated air to circulate around them.
For example:
| Parameter | Example |
|---|---|
| Tray Size | 800 × 600 mm |
| Tray Area | 0.48 m² |
| Product Footprint | 400 × 250 mm |
| Theoretical Pieces/Tray | 4 |
| Practical Loading | 2–3 pieces |
The theoretical number is not necessarily the recommended production arrangement. If four pieces completely block the airflow path, drying uniformity may deteriorate.
This is why usable loading area and airflow clearance should be considered together.
3. Tray Size Should Match the Oven Chamber
A tray should not simply be made as large as possible.
For example, consider an oven chamber with internal dimensions of:
1,200 mm W × 1,000 mm D × 1,500 mm H
A possible tray configuration could be:
800 mm W × 600 mm D
This leaves space around the tray for airflow and mechanical clearance.
If the tray were increased to approximately 1,150 × 950 mm, the usable tray area would be larger, but the remaining airflow space could become very limited depending on the oven's air circulation design.
A simplified comparison:
| Tray Size | Area | Potential Benefit | Potential Concern |
|---|---|---|---|
| 600 × 400 mm | 0.24 m² | Good airflow flexibility | Lower capacity |
| 800 × 600 mm | 0.48 m² | Balanced loading | Moderate airflow space |
| 1,000 × 800 mm | 0.80 m² | Higher loading area | Requires airflow verification |
| 1,150 × 950 mm | 1.09 m² | Maximum usable area | May restrict airflow |
The optimum tray size depends on the chamber design, circulation pattern, product characteristics, and required production capacity.
4. Leave Enough Space Between Trays
Vertical spacing between trays is another important factor.
Suppose an industrial drying oven has an internal height of 1,500 mm and uses 8 trays.
The average vertical pitch could be approximately:
1,500 ÷ 8 = 187.5 mm
However, this does not mean that each tray automatically has 187.5 mm of usable product height.
Space is also needed for:
Tray thickness
Shelf structure
Product height
Airflow
Loading and unloading
Thermal expansion
For example, if the products are 100 mm high, a tray spacing of 180–200 mm may provide approximately 80–100 mm of free space above the products, depending on the actual rack structure.
The correct spacing should therefore be determined from the product height and required airflow rather than simply maximizing the number of shelves.
5. Why Airflow Matters
Industrial drying ovens commonly use forced hot-air circulation.
The heated air must move around the products to transfer heat and remove moisture.
If trays are packed too tightly, several problems can occur:
Restricted airflow
Longer drying times
Uneven product temperature
Higher moisture variation
Hot and cold zones
Reduced drying efficiency
Consider a simplified example.
An oven has 10 trays, each loaded with 8 kg:
10 × 8 kg = 80 kg per batch
If operators increase the load to 12 kg per tray:
10 × 12 kg = 120 kg per batch
The production capacity increases by 50%.
However, if the additional material blocks air passages, the actual drying time may increase significantly.
Therefore, increasing tray loading does not automatically increase production efficiency.
The oven's airflow system must be capable of handling the increased product load.
6. Choosing the Right Tray Material
Tray material should be selected according to the product and operating temperature.
Common choices include:
| Tray Material | Typical Characteristics | Common Applications |
|---|---|---|
| Stainless Steel | Corrosion-resistant, easy to clean | Food, pharmaceutical, general industrial |
| Carbon Steel | Strong and economical | General industrial components |
| Galvanized Steel | Corrosion protection | Lower-temperature applications |
| Aluminum | Lightweight, good thermal conductivity | Selected drying applications |
| Perforated Stainless Steel | Allows airflow through tray | Food and agricultural products |
| Mesh Tray | High airflow | Small particles, herbs, sliced products |
For example, a fruit and vegetable drying application may benefit from a perforated or mesh tray because air can pass through and around the material.
For heavy metal components, a solid heavy-duty steel shelf may be more appropriate.
The tray material should also be compatible with the maximum operating temperature and the chemical environment inside the oven.
7. Perforated Trays vs. Solid Trays
The tray surface can significantly affect airflow.
Perforated Tray
A perforated tray contains multiple openings that allow air to pass through the material.
This can be useful for:
Fruits
Vegetables
Herbs
Small components
Granular materials
For example, a perforated tray may use openings of approximately 5–15 mm, depending on the size and shape of the product.
The exact opening size should prevent the product from falling through while still providing adequate airflow.
Solid Tray
A solid tray provides a continuous surface.
It can be useful when:
Small particles must not fall through
Liquid or residue needs to be contained
Products require full support
Cleaning and containment are priorities
The choice should therefore be based on both product characteristics and airflow requirements.
8. Check the Load Capacity of Each Shelf
Shelf load capacity is especially important when drying heavy industrial components.
For example, suppose an oven has:
6 shelves
Maximum load per shelf: 50 kg
The theoretical shelf loading capacity is:
6 × 50 kg = 300 kg
If each shelf carries 50 kg, the total product load is 300 kg.
But this does not mean every arrangement of 50 kg is safe.
The manufacturer should also consider whether the load is:
Evenly distributed
Concentrated in the center
Positioned near the shelf edge
Supported at multiple points
A 50 kg evenly distributed load may produce a very different mechanical condition from a single 50 kg component placed in the middle of the shelf.
For heavy products, both uniform load capacity and point-load capacity should be considered.
9. Numerical Case: 40–70 kg Vegetable Drying
Consider a customer who wants to dry fruits and vegetables.
The requirements are:
Batch load: 40–70 kg
Temperature: below 100°C
Loading method: manual trays
Product: sliced fruits and vegetables
Multiple batches per day
A possible configuration could be:
| Parameter | Example |
|---|---|
| Oven Chamber | 1,200 × 1,000 × 1,500 mm |
| Tray Size | 800 × 600 mm |
| Number of Trays | 8 |
| Load per Tray | 5–8 kg |
| Total Load | 40–64 kg |
| Tray Material | Stainless Steel |
| Tray Type | Perforated |
| Temperature | 40–100°C |
At 8 kg per tray, the total load would be:
8 × 8 = 64 kg per batch
This falls within the customer's target range of 40–70 kg.
The perforated tray allows air to circulate around the product while the removable design makes it easier for operators to load and unload sliced materials.
The final tray spacing and loading thickness should still be verified through drying tests because different products have different moisture contents and drying characteristics.
10. Numerical Case: Heavy Metal Components
Now consider an industrial application involving metal components.
The requirements are:
Product weight: 20 kg per component
Number of components: 15
Total load: 300 kg
Operating temperature: 180°C
Loading method: removable shelves
A possible arrangement could be:
| Parameter | Example |
|---|---|
| Number of Shelves | 6 |
| Load per Shelf | 50 kg |
| Total Load | 300 kg |
| Product Weight | 20 kg each |
| Temperature | 180°C |
| Shelf Material | Heavy-Duty Steel |
| Loading | Manual / Cart |
For example, each shelf could hold approximately 2–3 components, depending on their dimensions.
The key consideration is not simply whether the shelf can support 50 kg. The shelf structure should also provide sufficient stiffness and clearance for the components and maintain adequate air circulation.
11. Fixed Shelves or Removable Shelves?
Both configurations have advantages.
Fixed Shelves
Fixed shelves remain permanently installed inside the chamber.
Advantages include:
Simple construction
Stable positioning
Lower handling requirements
Suitable for repetitive production
They can work well when the product and loading method remain relatively consistent.
Removable Shelves
Removable shelves can be taken out of the oven.
Advantages include:
Easier loading
Flexible shelf spacing
Easier cleaning
Easier handling of different products
For example, one production batch may require:
8 shelves × 8 kg = 64 kg
while another product may require fewer shelves with heavier loads.
Removable shelving allows the chamber configuration to be changed according to the product.
12. How Many Trays Do You Need?
The required tray quantity can be estimated from the batch load.
Suppose the customer needs:
60 kg per batch
and each tray can safely hold:
7.5 kg
Then:
60 ÷ 7.5 = 8 trays
Therefore, approximately 8 trays are required.
If the customer increases the target batch load to 90 kg while maintaining 7.5 kg per tray:
90 ÷ 7.5 = 12 trays
However, simply adding four more trays is only possible if the oven chamber has sufficient vertical space and airflow capacity.
This is why tray quantity must be considered together with chamber dimensions and airflow.
13. Tray Loading Thickness Also Matters
The weight on a tray is not the only factor.
For moisture-sensitive products, the thickness of the material layer can affect drying performance.
For example, suppose a tray contains sliced vegetables.
Case A
Product layer thickness: 20 mm
Case B
Product layer thickness: 60 mm
Even if both trays contain the same total weight, the thicker product layer may require more time for moisture to travel from the interior of the material to the surface.
For this reason, drying performance should be evaluated based on:
Product moisture content
Product thickness
Product density
Air temperature
Air velocity
Relative humidity
Drying time
Tray design should support the required product layer rather than simply maximize weight per tray.
14. How to Choose the Right Shelf and Tray Design
Before specifying shelves and trays for an industrial drying oven, buyers should provide the following information:
Product Information
Product name
Product dimensions
Product weight
Moisture content
Maximum product height
Whether the product is solid, liquid, granular, or sliced
Production Requirements
Required batch capacity
Number of batches per day
Required drying temperature
Target drying time
Required final moisture content
Loading Information
Manual loading
Tray loading
Cart loading
Forklift loading
Crane loading
Oven Information
Chamber dimensions
Number of shelves
Shelf spacing
Maximum shelf load
Tray dimensions
Tray material
Tray surface type
Providing these details allows the oven manufacturer to design the shelves and trays around the actual process rather than using a standard configuration that may not fit the application.
Conclusion
Shelves and trays play an important role in the performance and usability of an industrial drying oven.
The right design should balance loading capacity, product dimensions, airflow, tray spacing, material selection, operating temperature, and handling efficiency.
For a 40–70 kg agricultural drying application, for example, eight perforated stainless steel trays carrying approximately 5–8 kg each may provide a practical starting configuration.
For a 300 kg metal-component drying application, six heavy-duty shelves carrying approximately 50 kg each could be considered, provided the shelf structure, chamber dimensions, and airflow system are designed for the load.
The most important point is that shelf and tray capacity should not be evaluated independently from the oven's airflow and thermal design. A larger tray or heavier load can increase theoretical batch capacity, but it may also change airflow and drying performance.
For a customized industrial drying oven, providing the product size, weight, temperature, batch capacity, and loading method allows the manufacturer to determine the appropriate shelf dimensions, tray material, spacing, and load capacity.