Selecting a SHEL LAB Laboratory or Vacuum Oven
Given that the oven choices from SHEL LAB are diverse, we thought it would be helpful to detail the differences. Within the SHEL LAB oven series you will find forced air ovens (floor models and bench-top units), gravity convection, clean room ovens, nitrogen purge ovens, and vacuum ovens. You will often hear the terms drying oven, curing oven, or bake out oven being used in industrial applications. These are generic terms that can be represented across multiple heat processing applications.
Forced Air SHEL LAB Ovens
Forced Air lab ovens use blowers to force warm air throughout the interior chamber evenly. In SHEL LAB units this is accomplished by sending air horizontally across the chamber. SHEL LAB CE and HF ovens use smaller holes on one side of the chamber than the other side. This creates greater velocity on one side and less resistance on the other as air moves evenly over oven samples. This horizontal airflow design is found in the bench-top laboratory ovens, CE3F, and CE5F, as well as the High Performance HF series of SHEL LAB ovens. Forced air lab ovens have a constant air stream. If you are drying or baking samples that may easily be blown around in the chamber, a gravity convection oven may be a better choice. Forced air, however, provides better temperature uniformity over multiple shelf levels, and provides for uniform drying or curing in a fully loaded oven.
The FX14 and FX28 are large lab ovens that provide very cost effective drying space. They deliver ample uniformity for a wide variety of drying applications. Airflow in these units is from the back wall forward, with a vertical return to the ceiling. This works well for most applications, but if material is to be loaded in the chamber on customer-supplied cookie sheet style solid trays, the vertical component of the airflow pattern may be blocked, depending on the size of the trays. In these instances, the SHEL LAB HF Ovens should be considered. The HF models closest in size to the FX14-2 and the FX28-2 are the HF15-2 and the HF25-2. The HF models offer the advantage of horizontal side to side airflow, which passes evenly over the material on all shelf levels.
High Performance Drying, Curing and Bakeout Ovens
The HF high performance oven series is built to a stricter standard. Using thicker gauge metal, a very precise air flow pattern and higher velocity blowers the HF series is able to achieve tight uniformity over a large space. This airflow pattern increases drying and curing efficiency.
Gravity Convection Lab Ovens
The CE3G, and CE5G are the two gravity convection lab ovens offered by SHEL LAB. Using natural heat convection (hot air rising), warm air passes gently over the samples being baked, cured or dried. Air exchange and moisture loss are adjusted using a top damper. As with all oven applications, the wider the damper is open the more moisture being removed.
Clean Room Ovens
SHEL LAB offers one clean room oven, the CR1-2. To prevent any flaking or dust coming from the oven entering the clean room environment this clean room oven is constructed of 304 stainless steel (both interior and exterior) with gasketed body panels to ensure insulation particulates don't escape. The interior is equipped with a HEPA filter that screens all chamber recirculating air with an efficiency of 95% at the 0.3 micron level. The CR1-2 also has a seam welded chamber, making it possible to purge the chamber using an inert gas such as nitrogen.
Nitrogen Purge - Inert Atmoshpere Oven
If you are in need of a nitrogen purge oven (also called inert gas oven), but do not need the additional features and cost of a HEPA filtered clean room oven, SHEL LAB offers the HF2-2. The SHEL LAB HF2-2, like the CR1-2 has a seam welded chamber, but only uses stainless steel on the interior. It does not have a HEPA filter. If you aren't sure if you need an inert gas oven, it is helpful to know that purging the chamber interior with nitrogen helps create a dry oxygen-reduced environment, decreasing product oxidation. The positive pressure created by introducing a gas also inhibits the entry of contaminants.
The CR1-2, HF2-2 and the rest of the HF series from SHEL LAB come with a Watlow 24 step programmable temperature controller. This is another differentiator between this series and the CE or FX series which use a single set point controller, and a digital timer with a maximum settable span of 99 hrs, 59 min.
Vacuum Ovens - Laboratory and Industrial
Vacuum Ovens are the final category to review. Vacuum ovens could encompass a page of their own (future article), because of the variety of applications that can be addressed by adjusting the vacuum levels and temperature within the chamber. A vacuum pump is a required accessory. If you already have a vacuum pump, you can use it with your SHEL LAB vacuum oven by simply pulling the desired vacuum level, then closing the vacuum valves. The entire SHEL LAB line of vacuum ovens uses true vacuum valves, and a unique door design that delivers an extremely effective seal.
Vacuum ovens are extremely effective for decontamination and very low moisture determination studies. They have been used for years in semi-conductor production to reduce oxygen exposure. The SHEL LAB 1425, 1445, and 1465 all come with KF25 fittings at of the rear of the chamber. The large VPX9-2 vacuum oven uses a KF40 fitting. At 9 cubic feet, the VPX9-2 is the largest vacuum oven SHEL LAB offers.
We hope this article has been helpful. Please feel free to contact us with any questions you may have regarding laboratory ovens, industrial ovens, or heat treat furnaces. Engineeered Product Sales Corp.