I have been asked, or even been told, that e-beam is “only a surface treatment and can’t get through any more than a piece of paper.” Wrong. For decades, e-beam has been used to sterilize whole cases of medical devices, such as those in the picture below. Thousands of truckloads are contract-sterilized by e-beam each year!
Today, electron beams come in a variety of different capabilities. While there are limitations to the depth of penetration of the electrons, they can penetrate most medical devices in their current packaging.
There are two key parameters for accelerators: the energy and power at which they operate. Energy, measured in million electron volts (MeV), is related to the speed of the electrons and therefore the penetration of the electrons. Power, measured in kilowatts (kW), is related to throughput. The higher the power, the more product that can be processed in an hour’s time. Another blog that talks about key parameters can be found here.
Let’s take a look at different energy e-beams and see what applications they are successfully used in.
Low energy electron beams are used for the curing of ink or coating on film lines because they only have to penetrate the film. There are a few medical device manufacturers who use these machines for surface sterilization.
Medium energy beams from 1-3 MeV are often used for crosslinking plastics and sometimes for specialized sterilization applications.
Electron beams operating at 4-5 MeV are often used when sterilizing medical devices or when crosslinking formed parts. These high power machines (150 kW) are capable of sterilizing a full truck of medical devices in only an hour or two. These beams can penetrate up to 8-10 pounds per square foot of product – – which means a high percentage of existing medical products. A detailed explanation of the calculation for pounds per square foot is found in this blog.
The highest energy beams are typically 10 MeV. These machines are capable of penetrating the large majority of medical devices, and even dense, bulk packaged products, such as bags of animal feed. These beams can penetrate up to 18 lbs per square foot of product, but they typically operate at lower power (10-20 kW), so their throughput is lower.