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CO2 Cryogenic cleaning with dry ice or carbon snow.

1. Introduction

In this article, we will provide information about CO2 cleaning with carbon snow for plastic parts.

Currently, with increasingly strict quality requirements, there are not many systems approved by major OEMs for cleaning plastic parts. One of these is CO2 cleaning.

Throughout our experience, we have seen and gathered countless opinions on this topic, which sometimes distort the reality, and the big question always arises: does it work? The answer is not straightforward, but if I had to decide, I would say yes, as long as the system is well-chosen and other factors such as airflow and air quality are taken into account.

As an example, with a client who used a Power Wash, we installed a dual system, and after a short period of working with both systems, over 95% of the production was permanently shifted to CO2 cleaning. The hourly cost relationship between a Power Wash and CO2 is very interesting in favor of CO2.

2. What advantages does it offer?

There are several advantages it offers:

  • Effective cleaning.
  • Minimal space requirement.
  • Moderate/low implementation cost.
  • Economical operating cost.
  • Low environmental impact.

3. How it works

The answer is simple. Basically, cleaning occurs due to three factors:

  • Impact cleaning, which can be more or less energetic depending on the type of system chosen, whether snow or pellets.
  • Thermal shock cleaning on the surface of the part, generated by the sublimation of CO2. This thermal shock causes, due to the different coefficients of expansion of the materials, the dirt to separate from the substrate.
  • An airflow cleans and removes the dirt.

One of the main advantages of carbon dioxide is that, upon evaporating, it leaves no residue.

4. Which product to choose

There are primarily two types of cleaning based on the initial state of the product, both of which are carbon dioxide.

4.1 Pellets

These are small solid pellets, available in various sizes ranging from 2 to 10 mm. This type of cleaning is effective for cleaning and degreasing metals due to its high energy impact. However, it is not the most recommended for painting application lines due to the tendency to accumulate water in the nozzles. This results in microdroplets of water ending up on the part, causing other quality issues.

4.2 Carbon Snow

With less impact than pellets, it generates a gentler cleaning effect on the part. Carbon snow is stored in liquid phase in a tank and is transported in either liquid or gas phase to the application point.

This is where we find significant differences. Transporting in liquid phase requires insulation to prevent gasification, which, in extreme climates, may even require vacuum jackets. Then, in the application machine, the gas must return to the tank, and at every point of evaporation, it is susceptible to generating ice due to the product's phase change, potentially causing various issues in valves and components.

Due to all these factors, at Coapsys, we choose to integrate the gas system for simplicity, maintenance, and robustness. The gas system is transported at 15-20 bar, and once it reaches the booster or pressure releaser, it reaches 55-65 bar. This gas is cooled again to generate the snow crystals ready for application.

5. What elements make up the installation and how it is applied

The installation of a CO2 system consists of the following elements:

  • CO2 Tank: Typically supplied by the product vendor, it stores the CO2.
  • Gasifier: Installed alongside the tank and also supplied by the vendor, its purpose is to convert the liquid into gas.
  • Installation.
  • Pressure booster: This equipment is responsible for raising the transport pressure to the required application pressure.
  • CO2 Equipment: Manages the treatment of the CO2, which needs to be cooled, as well as the air, which is heated. Both are transported separately to the application point.
  • Application Nozzles: The tool responsible for dispensing the product with air onto the part. Usually mounted on a robot, but it can also be installed in a reciprocating or static manner for other applications.

The application of CO2 is another crucial factor for the success of the process; considering the application speed and angle of incidence is fundamental.

Other important points to consider relate to the painting line, such as air quality, type of booth, etc., as well as safety components. We will address this in another article.

ISO 9001: Quality Certificate.
Double painting line.

Contact information

  •   Industria 40
    08755 Castellbisbal Barcelona
    Spain
  •  +34 936766723
  •  coapsys@coapsys.com

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