## Common ground
All options are types of drying cylinders, used for drying materials in industrial processes like papermaking or textile production.
## Options at a glance
**3926.90 – Made of plastic material**
- **Defining trait:** Resistant to corrosion and lightweight, but limited to low-temperature applications.
- **Typical examples:** Polyethylene or polypropylene cylinders in chemical processing.
- **Best fit when:** Operating with corrosive substances or where weight matters (e.g., mobile units).
**6903 – Made of refractory ceramic**
- **Defining trait:** High heat resistance and durability at extreme temperatures.
- **Typical examples:** Kiln drying cylinders in cement or ceramics manufacturing.
- **Best fit when:** Used in high-temperature industrial drying (above 800°C).
**6909.1X – Made of ceramic**
- **Defining trait:** Hard, non-porous surface; used for precision or hygiene-sensitive processes.
- **Typical examples:** Ceramic rollers in pharmaceutical or food processing.
- **Best fit when:** Need chemical inertness and smooth surface finish (e.g., sanitary applications).
**7017 – Made of glass**
- **Defining trait:** Transparent, chemically inert, and ideal for visual monitoring.
- **Typical examples:** Glass cylinders in lab-scale drying or chemical synthesis.
- **Best fit when:** Monitoring process visually or handling highly reactive chemicals.
## Key differences
| Feature | Plastic (3926.90) | Refractory Ceramic (6903) | Ceramic (6909.1X) | Glass (7017) |
|---------------------|-------------------|----------------------------|--------------------|--------------|
| Max temperature | Low (<150°C) | Very high (>1000°C) | Medium-high (~800°C)| Moderate (~400°C) |
| Chemical resistance | Good (some) | Excellent | Excellent | Exceptional |
| Transparency | No | No | No | Yes |
| Mechanical strength | Low | High | High | Low (brittle)|
## How to choose
- Does it operate at very high temperatures (>800°C)? → 6903
- Is visual monitoring needed? → 7017
- Is chemical inertness critical and surface smoothness required? → 6909.1X
- Is weight or corrosion resistance the priority? → 3926.90
## Overlaps & pitfalls
- A ceramic cylinder (6909.1X) may also be refractory, but 6903 is specifically for extreme heat.
- Glass (7017) can be used in high-purity processes, but not for high heat or heavy use.
- If multiple traits apply (e.g., chemical resistance + transparency), prioritize the **main function**: process monitoring vs. durability vs. temperature.
- Do not assume "ceramic" means refractory—6903 is a subset of ceramic materials for extreme conditions