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autoclave news on steam autoclaves by priorclave

Want to Find the Most Energy Efficient Autoclave?

As we noted in our previous post, two factors determine the energy efficiency of your autoclave:

The autoclave’s steam source and its chamber shape

Steam source is perhaps the easiest of these to tackle. While many labs favor a specific chamber shape, most research-grade autoclaves on the market can be outfitted to either rely on in-chamber steam generation or an independent steam generator—regardless of how their pressure vessel is configured. 

Many factors may lead to you preferring one steam source over the other. But, strictly in terms of energy efficiency, in-chamber heating is far more efficient. Testing side-by-side Priorclaves running the exact same cycles, we’ve found that external steam generation fairly consistently requires at least 45% more energy than using an in-chamber heater.

Chamber shape can be more of a sticking point. Many research labs are accustomed to using front-loading autoclaves with rectangular pressure vessels—the standard layout for hospital sterilizers. This style of autoclave is terrific for high-throughput settings that require 24/7 operation and must be able to run “immediate use” cycles (i.e., hospitals). But those extreme operating conditions—many daily back-to-back cycles, quick heating and cooling—make them terrible resource hogs.

Before investing in yet another rectangular-chambered autoclave, it’s worth asking: Do I absolutely have to have a hospital-style sterilizer?

Autoclave Chamber Shape Has a Massive Impact on Efficiency

If you’re running one cycle (or less) per day, only during business hours, and not taking a tray of surgical tools directly from the sterilizer to a patient etherized upon a table, then it’s very, very unlikely you need a front-loading autoclave with a rectangular chamber.

If you are looking to lower your carbon footprint, that’s excellent news. Rectangular vessels must be specially engineered to handle sterilization pressures and temperatures, in addition to the extreme stresses created by those “immediate use” cycles. As a result, they have roughly twice as much steel in them as cylindrical vessels. As you’ll recall from high school physics, there’s a linear relationship between mass and time to heat—as one goes up, so does the other. At least twice as much metal means at least twice as long to heat—unless you pour in significantly more energy in order to reduce those heating times. And that’s assuming the full mass of the metal chamber is exposed to the heat source. This is the case with a cylindrical vessel (which is single-walled)—but not with most rectangular pressure vessels. Not only do these have thicker walls, but the also have external reinforcing ribs. These act like heat sinks, cooling the pressure vessel you’re attempting to heat.

Given two like-sized autoclave chambers, you’ll find that the rectangular chamber—which has about twice as much steel in it—requires a heater rated at roughly three times that of a comparable cylindrical chamber. In practice, it takes about as much energy just to heat a rectangular chamber up to begin sterilization as it does to run an entire cycle through a cylindrical model.